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Polymers, Volume 16, Issue 24 (December-2 2024) – 65 articles

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24 pages, 5010 KiB  
Article
Residual Stress Analysis at the Conductor–Insulator Interface During the Curing Process of Hair-Pin Motors
by Mingze Ma, Hongyi Gan, Xiao Shang, Linsen Song, Yiwen Zhang, Jingru Liu, Chunbai Liu, Yanzhong Hao and Xinming Zhang
Polymers 2024, 16(24), 3514; https://doi.org/10.3390/polym16243514 - 17 Dec 2024
Abstract
The curing process of hair-pin motor stator insulation is critical, as residual stress increases the risk of partial discharge and shortens a motor’s lifespan. However, studies on the stress-induced defects during insulation varnish curing remain limited. This research integrates three-dimensional numerical simulations and [...] Read more.
The curing process of hair-pin motor stator insulation is critical, as residual stress increases the risk of partial discharge and shortens a motor’s lifespan. However, studies on the stress-induced defects during insulation varnish curing remain limited. This research integrates three-dimensional numerical simulations and experimental analysis to develop a curing model based on unsaturated polyester imide resin, aiming to explore the mechanisms of residual stress formation and optimization strategies. A dual fiber Bragg grating (FBG) sensor system is employed for simultaneous temperature and strain monitoring, while curing kinetics tests confirm the self-catalytic nature of the process and yield the corresponding kinetic equations. The multi-physics simulation model demonstrates strong agreement with the experimental data. The results show that optimizing the curing process reduces the maximum stress from 45.1 MPa to 38.6 MPa, effectively alleviating the stress concentration. These findings highlight the significant influence of the post-curing temperature phase on residual stress. The proposed model offers a reliable tool for stress prediction and process optimization in various insulating materials, providing valuable insights for motor insulation system design. Full article
(This article belongs to the Special Issue Application and Characterization of Polymer Composites)
11 pages, 3403 KiB  
Article
Synergistic Effect of CNT and N-Doped Graphene Foam on Improving the Corrosion Resistance of Zn Reinforced Epoxy Composite Coatings
by Yana Mao, Shufu Liu, Shizhong Liu, Guodong Wu, Qi Liu and Xusheng Du
Polymers 2024, 16(24), 3513; https://doi.org/10.3390/polym16243513 - 17 Dec 2024
Abstract
The synergistic effect of CNT and three-dimensional N-doped graphene foam (3DNG) on improving corrosion resistance of zinc-reinforced epoxy (ZRE) composite coatings was studied in this work. Although CNT itself was demonstrated to be effective to promote the anti-corrosion performance of the ZRE coating, [...] Read more.
The synergistic effect of CNT and three-dimensional N-doped graphene foam (3DNG) on improving corrosion resistance of zinc-reinforced epoxy (ZRE) composite coatings was studied in this work. Although CNT itself was demonstrated to be effective to promote the anti-corrosion performance of the ZRE coating, the incorporation of additional 3DNG leads to further enhancement of its corrosion resistance under the synergistic effect of the hybrid carbon nanofillers with different dimensions. Both the content of the carbonaceous fillers and the ratio between them affected the performance of the coating. The optimal content of hybrid filler in the coating was determined to be only 0.1% with 3DNG:CNT = 1:3. With the modification of hybrid fillers, the corrosion current of the coating could be reduced by more than six orders of magnitude. Additionally, the immersion test of the pre-scratched coating directly demonstrated the evident contribution of the hybrid fillers to the sacrificial anode-based surface protection mechanism of the coating. These results confirmed the synergistic effect of the hybrid 1D and 3D carbonaceous fillers on promoting the corrosion inhibition of their coating, which could be promising for application in other functional composites. Full article
(This article belongs to the Special Issue A Commemorative Issue in Honor of Professor Jose M. Kenny: Advances in Polymer Composites and Nanocomposites)
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Figure 1
<p>(<b>a</b>) Tafel curves and (<b>b</b>) Bode plots of neat ZRE and hybrid filler-modified ZRE coatings.</p> Full article ">Figure 2
<p>Tafel curves of nanocarbon-modified ZRE-coated Q235 samples.</p> Full article ">Figure 3
<p>The dependence of |Z|<sub>0.01Hz</sub> of neat ZRE and 01_3DNG-CNT ZRE coatings on the immersion time.</p> Full article ">Figure 4
<p>Tafel curves of neat ZRE and 01_3DNG-CNT ZRE coatings after 300 h immersion in 3.5 wt% NaCl solution.</p> Full article ">Figure 5
<p>(<b>a</b>) Nyquist plots of 01_3DNG-CNT ZRE coating on Q235 sample immersed in NaCl solution at 25 h, 100 h and 300 h and (<b>b</b>) schematic diagrams of equivalent analog circuits for EIS analysis of the hybrid nanocarbon-modified ZRE.</p> Full article ">Figure 6
<p>Images of scratched area of neat ZRE soaked in 3.5 wt% NaCl solution for 12 h: (<b>a</b>) SEM image and inset digital photo; the element mapping of (<b>b</b>) Fe, (<b>c</b>) O, (<b>d</b>) Zn, (<b>e</b>) Cl and (<b>f</b>) C.</p> Full article ">Figure 7
<p>Images of scratched area of the hybrid filler-modified ZRE-coated steel sample soaked in 3.5 wt% NaCl solution for 12 h: (<b>a</b>) SEM image and inset digital photo and the element mapping of (<b>b</b>) Fe, (<b>c</b>) O, (<b>d</b>) Zn, (<b>e</b>) Cl and (<b>f</b>) C.</p> Full article ">Figure 8
<p>Schematic diagram of the anti-corrosive mechanism of 3DNG-CNT ZRE coating on steel in simulated seawater.</p> Full article ">
15 pages, 8205 KiB  
Article
Antifungal Activity of Newly Formed Polymethylmethacrylate (PMMA) Modification by Zinc Oxide and Zinc Oxide–Silver Hybrid Nanoparticles
by Marek Witold Mazur, Anna Grudniak, Urszula Szałaj, Marcin Szerszeń, Jan Mizeracki, Mariusz Cierech, Elżbieta Mierzwińska-Nastalska and Jolanta Kostrzewa-Janicka
Polymers 2024, 16(24), 3512; https://doi.org/10.3390/polym16243512 - 17 Dec 2024
Abstract
Incorporating nanoparticles into denture materials shows promise for the prevention of denture-associated fungal infections. This study investigates the antifungal properties of acrylic modified with microwave-sintered ZnO-Ag nanoparticles. ZnO-Ag nanoparticles (1% and 2.5% wt.) were synthesized via microwave solvothermal synthesis (MSS). Nanoparticles were characterized [...] Read more.
Incorporating nanoparticles into denture materials shows promise for the prevention of denture-associated fungal infections. This study investigates the antifungal properties of acrylic modified with microwave-sintered ZnO-Ag nanoparticles. ZnO-Ag nanoparticles (1% and 2.5% wt.) were synthesized via microwave solvothermal synthesis (MSS). Nanoparticles were characterized for phase purity, specific surface area (SSA), density, morphology, and elemental composition. ZnO and ZnO-Ag nanoparticles were added to acrylic material (PMMA) at concentrations of 1% and 2.5% and polymerized. Pure PMMA (control) and obtained PMMA-nanocomposites were cut into homogeneous 10 × 10 mm samples. Antifungal activity of nanoparticles and PMMA-nanocomposites against C. albicans was tested using minimal inhibitory concentration (MIC) determination, and biofilm formation was assessed using crystal violet staining followed by absorbance measurements. Laboratory tests confirmed phase purity and uniform, spherical particle distribution. MIC results show antifungal activity of 1% Ag nanoparticles and the PMMA-2.5% (ZnO-1% Ag) nanocomposite. PMMA-1% (ZnO-1% Ag) nanocomposite and 1% ZnO-Ag nanoparticles are efficient in preventing biofilm formation. However, ZnO nanoparticles showed antibiofilm activity, and the PMMA-ZnO nanocomposite does not protect against biofilm deposition. Incorporating hybrid ZnO-Ag nanoparticles into PMMA is a promising antibiofilm method, especially with ZnO-1% Ag nanoparticles. Full article
(This article belongs to the Special Issue Polymer Composites with Reinforcement for Dental Applications)
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<p>X-ray diffraction patterns of ZnO NPs and hybrid ZnO-Ag NPs.</p> Full article ">Figure 2
<p>SEM images taken using the Angle-sensitive Backscatter (AsB) detector: (<b>A</b>) ZnO-1% H<sub>2</sub>O, (<b>B</b>) ZnO-1% Ag, and (<b>C</b>) ZnO-2.5% Ag; SEM images taken using the Immersion Lens detector (InLens): (<b>D</b>) ZnO-1% H<sub>2</sub>O, (<b>E</b>) ZnO-1% Ag, and (<b>F</b>) ZnO-2.5% Ag.</p> Full article ">Figure 3
<p>EDS images of elemental composition maps: (<b>A</b>) ZnO-1% H<sub>2</sub>O, (<b>B</b>) ZnO-1% Ag, and (<b>C</b>) ZnO-2.5% Ag.</p> Full article ">Figure 4
<p>Antibiofilm activity of ZnO and ZnO-Ag nanoparticle solutions. The red control bar is a variant of <span class="html-italic">C. albicans</span> without the addition of nanoparticles and lines indicate standard deviation.</p> Full article ">Figure 5
<p>Sample photos of Petri dishes with number of <span class="html-italic">C. albicans</span> colonies depending on tested nanocomposite.</p> Full article ">Figure 6
<p>Crystal violet biofilm staining of acrylic: 1% (ZnO), 1% (ZnO-1% Ag), and 1% (ZnO-2.5% Ag) plates. The red control bar is a variant of <span class="html-italic">C. albicans</span> without the addition of nanoparticles and lines indicate standard deviation.</p> Full article ">Figure 7
<p>Crystal violet biofilm staining of acrylic: 2.5% (ZnO), 2.5% (ZnO-1% Ag), and 2.5% (ZnO-2.5% Ag) plates. The red control bar is a variant of <span class="html-italic">C. albicans</span> without the addition of nanoparticles and lines indicate standard deviation.</p> Full article ">Figure 8
<p>Colour differences between nanocomposites: pure PMMA (<b>left</b>), PMMA-1% (ZnO-1% Ag) (<b>middle</b>), and PMMA-2.5% (ZnO-1% Ag) (<b>right</b>).</p> Full article ">
13 pages, 3940 KiB  
Article
Modification and Use of Naturally Renewable Cardanol-Type Prepolymers in One-Component Silyl-Terminated Prepolymer Sealant Systems
by Ritvars Berzins, Remo Merijs Meri, Janis Zicans, Agnese Abele, Volodymyr Sytar, Oleh Kabat, Anton Klymenko and Nataliia Mitina
Polymers 2024, 16(24), 3511; https://doi.org/10.3390/polym16243511 - 17 Dec 2024
Viewed by 66
Abstract
The current research is devoted to integrating naturally renewable cardanol derivatives into one-component silyl-terminated-polyether-based prepolymer systems to improve climatic resistance and obtain materials with versatile mechanical properties that could be significant to various sectors of the economy. Various cardanol-type products are used in [...] Read more.
The current research is devoted to integrating naturally renewable cardanol derivatives into one-component silyl-terminated-polyether-based prepolymer systems to improve climatic resistance and obtain materials with versatile mechanical properties that could be significant to various sectors of the economy. Various cardanol-type products are used in industries that require high climatic resistance, and thus combining cardanol with commercially available silyl-terminated polyether prepolymers would improve its material climatic resistance, maintaining its market and application value as well as improving material sustainability. The results obtained in this work show that depending on how the cardanol prepolymer Ultra Lite 513 is modified, it is possible to increase the elasticity (670%) or tensile strength (104%) of the material as well as significantly increase the climatic resistance of the material, thus improving the quality and sustainability of the adhesive compared to existing silyl-terminated-prepolymer-based adhesives on the market. Full article
(This article belongs to the Section Circular and Green Polymer Science)
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Figure 1
<p>Schematic (<b>a</b>) and photographic (<b>b</b>) sample for quantitative determination of shear strength of adhesion joint.</p> Full article ">Figure 2
<p>Synthesized silyl-terminated prepolymers SIL 1189 (<b>a</b>) and SIL 1122 (<b>b</b>).</p> Full article ">Figure 3
<p>Tensile strength of model systems with commercial SAX 520 and self-synthesized SIL 1189 (<b>a</b>) or SIL 1122 (<b>b</b>) silyl-terminated prepolymers.</p> Full article ">Figure 4
<p>Tensile deformation of model systems with commercial SAX 520 and self-synthesized SIL 1189 (<b>a</b>) or SIL 1122 (<b>b</b>) silyl-terminated prepolymers.</p> Full article ">Figure 5
<p>Mechanical properties of systems with SIL 1189 (<b>a</b>,<b>c</b>) and SIL 1122 (<b>b</b>,<b>d</b>) regarding tension after aging of materials for 252 and 504 h in a climatic chamber.</p> Full article ">Figure 6
<p>Tensile strength of full systems with commercial SAX 520 and self-synthesized SIL 1189 (<b>a</b>) or SIL 1122 (<b>b</b>) silyl-terminated prepolymers.</p> Full article ">Figure 7
<p>Tensile deformation of full systems with commercial SAX 520 and self-synthesized SIL 1189 (<b>a</b>) or SIL 1122 (<b>b</b>) silyl-terminated prepolymers.</p> Full article ">Figure 8
<p>System with SIL 1189 (<b>a</b>) and SIL 1122 (<b>b</b>) viscosity changes as a function of shear rate.</p> Full article ">Figure 9
<p>The shear strength (σ<sub>s</sub>) of the adhesive joint (sealant–metal substrate) depending on the content of prepolymers based on SIL 1189 (<b>a</b>) and SIL 1122 (<b>b</b>) in the commercially available SAX 520 material.</p> Full article ">Figure 10
<p>Photos of the nature of fracture of the studied adhesion joint of the samples with SIL 1189 prepolymer (<b>a</b>–<b>c</b>) and SIL 1122 (<b>d</b>–<b>f</b>) in SAX 520 with different prepolymer contents (%): (<b>a</b>–<b>d</b>) 10%; (<b>b</b>–<b>e</b>) 20%; (<b>c</b>–<b>f</b>) 30%.</p> Full article ">
18 pages, 5537 KiB  
Article
Relaxation Phenomena in Low-Density and High-Density Polyethylene
by Viktor A. Lomovskoy and Svetlana A. Shatokhina
Polymers 2024, 16(24), 3510; https://doi.org/10.3390/polym16243510 - 17 Dec 2024
Viewed by 79
Abstract
A study was conducted on the internal friction spectra and temperature dependencies of the frequency of free damped oscillatory processes excited in the investigated samples of low-density polyethylene (LDPE) and high-density polyethylene (HDPE) over a temperature range from −150 °C to +150 °C. [...] Read more.
A study was conducted on the internal friction spectra and temperature dependencies of the frequency of free damped oscillatory processes excited in the investigated samples of low-density polyethylene (LDPE) and high-density polyethylene (HDPE) over a temperature range from −150 °C to +150 °C. It was found that the internal friction spectra exhibit several local dissipative processes of varying intensity, which manifest in different temperature intervals. The structure of the internal friction spectra and the peaks of dissipative losses are complex, as evidenced by the occurrence of sharp, locally temperature-dependent jumps in the intensity of dissipative losses observed throughout the entire temperature range. A theoretical analysis was performed to explore the relationship between the anomalous change in the frequency of the oscillatory process and the defect in the shear modulus, as well as the mechanisms of internal friction for the most intense dissipative loss processes identified in the internal friction spectra. A significant difference was revealed in the structure of the internal friction spectra of LDPE and HDPE in the temperature range of −50 °C to +50 °C. A comparison of the LDPE and HDPE samples was conducted based on changes in their strength characteristics, taking into account the locally temperature-dependent changes in the shear modulus caused by local dissipative losses observed in the internal friction spectra. Full article
(This article belongs to the Section Polymer Analysis and Characterization)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Internal friction spectrum <math display="inline"><semantics> <mrow> <mi>λ</mi> <mo>=</mo> <mi>f</mi> <mfenced> <mi>T</mi> </mfenced> </mrow> </semantics></math> of HDPE.</p> Full article ">Figure 2
<p>Schematic representation of a horizontal torsional pendulum. 1—Furnace housing; 2—collet; 3—sample; 4—substrates used in the high-temperature range; 5—horizontal rod; 6—core; 7–9—photoelectric transducer; 10—inertial weights; 11—shell; 12—counterweight; 13—tension string; 14—pendulum beam; 15—weight for tension; 16—vacuum cover; 17—electromagnets; 18—base plate.</p> Full article ">Figure 3
<p>Diagrams outlining the freely damped oscillatory process induced in the studied material; (<b>a</b>) in isothermal mode <math display="inline"><semantics> <mrow> <mi>T</mi> <mo>=</mo> <mi>c</mi> <mi>o</mi> <mi>n</mi> <mi>s</mi> <mi>t</mi> </mrow> </semantics></math>; (<b>b</b>) by pulse action. Sweep of the time dependence of the twist angle <math display="inline"><semantics> <mrow> <mi>φ</mi> <mfenced> <mi>t</mi> </mfenced> </mrow> </semantics></math> relative to the longitudinal axis <math display="inline"><semantics> <mi>Z</mi> </semantics></math> of the specimen—(<b>c</b>). The deformation of the sample—<math display="inline"><semantics> <mrow> <mi>γ</mi> <mfenced> <mi>t</mi> </mfenced> </mrow> </semantics></math>—(<b>d</b>) and the corresponding shear stresses <math display="inline"><semantics> <mrow> <msub> <mi>σ</mi> <mrow> <mi>i</mi> <mi>j</mi> </mrow> </msub> </mrow> </semantics></math> occurring in the sample—(<b>e</b>). <math display="inline"><semantics> <mi>β</mi> </semantics></math>—damping coefficient of the oscillatory process; <math display="inline"><semantics> <mi>θ</mi> </semantics></math>—period of the vibration process. All other designations are defined below in the text of the article [<a href="#B21-polymers-16-03510" class="html-bibr">21</a>,<a href="#B47-polymers-16-03510" class="html-bibr">47</a>].</p> Full article ">Figure 4
<p>DSC thermograms for LDPE and HDPE.</p> Full article ">Figure 5
<p>Internal friction spectrum <math display="inline"><semantics> <mrow> <mi>λ</mi> <mo>=</mo> <mi>f</mi> <mfenced> <mi>T</mi> </mfenced> </mrow> </semantics></math> (<b>a</b>); temperature dependence of frequency <math display="inline"><semantics> <mrow> <mi>ν</mi> <mo>=</mo> <mi>f</mi> <mfenced> <mi>T</mi> </mfenced> </mrow> </semantics></math> (<b>b</b>) for LDPE (red line) and HDPE (blue line).</p> Full article ">Figure 5 Cont.
<p>Internal friction spectrum <math display="inline"><semantics> <mrow> <mi>λ</mi> <mo>=</mo> <mi>f</mi> <mfenced> <mi>T</mi> </mfenced> </mrow> </semantics></math> (<b>a</b>); temperature dependence of frequency <math display="inline"><semantics> <mrow> <mi>ν</mi> <mo>=</mo> <mi>f</mi> <mfenced> <mi>T</mi> </mfenced> </mrow> </semantics></math> (<b>b</b>) for LDPE (red line) and HDPE (blue line).</p> Full article ">Figure 6
<p>Temperature–frequency dependencies and a graphical example of determining the modulus defect <math display="inline"><semantics> <mrow> <mo>Δ</mo> <mi>G</mi> </mrow> </semantics></math> for LDPE (<b>a</b>) and HDPE (<b>b</b>).</p> Full article ">Figure 7
<p>The internal friction spectrum of LDPE and HDPE in the temperature range from −70 °C to +130 °C.</p> Full article ">Figure 8
<p>Decomposition of the <math display="inline"><semantics> <mi>α</mi> </semantics></math> peaks and the <math display="inline"><semantics> <mrow> <msub> <mi>β</mi> <mi>k</mi> </msub> </mrow> </semantics></math> peak of dissipative losses using a mathematical method based on Gaussian distribution.</p> Full article ">Figure 9
<p>The dependence of the relaxation time and activation energy of <math display="inline"><semantics> <mi>α</mi> </semantics></math> processes on temperature for LDPE is shown, with the activation energy values indicated by a red dashed line on the additional axis on the right.</p> Full article ">Figure 10
<p>The dependence of relaxation time and activation energy of the <math display="inline"><semantics> <mrow> <msub> <mi>β</mi> <mi>k</mi> </msub> </mrow> </semantics></math> processes on temperature for LDPE and HDPE is illustrated, with the activation energy values indicated by the red dashed line on the additional axis on the right.</p> Full article ">Figure 11
<p>Schematic representation of the separation of <math display="inline"><semantics> <mrow> <mi>α</mi> <mo>+</mo> <msub> <mi>β</mi> <mi>k</mi> </msub> </mrow> </semantics></math> peaks of LDPE and HDPE.</p> Full article ">Figure 11 Cont.
<p>Schematic representation of the separation of <math display="inline"><semantics> <mrow> <mi>α</mi> <mo>+</mo> <msub> <mi>β</mi> <mi>k</mi> </msub> </mrow> </semantics></math> peaks of LDPE and HDPE.</p> Full article ">
4 pages, 176 KiB  
Editorial
Polymer Analysis and Characterization
by Giulio Malucelli
Polymers 2024, 16(24), 3509; https://doi.org/10.3390/polym16243509 - 17 Dec 2024
Viewed by 99
Abstract
This editorial aims to summarize some representative research efforts provided by the authors who contributed to the Polymer Analysis and Characterization section of the Polymers journal in the year 2024. The numerous and high-quality research outputs provided so far clearly indicate that the [...] Read more.
This editorial aims to summarize some representative research efforts provided by the authors who contributed to the Polymer Analysis and Characterization section of the Polymers journal in the year 2024. The numerous and high-quality research outputs provided so far clearly indicate that the Polymer Analysis and Characterization section of the Polymers journal is rapidly and continuously growing, stimulating more and more researchers to publish their research outcomes here. Full article
(This article belongs to the Section Polymer Analysis and Characterization)
12 pages, 3262 KiB  
Article
Connecting Dynamics and Thermodynamics in Polymer–Resin Cured Systems
by Luis A. Miccio, Clemens Sill, Carsten Wehlack and Gustavo A. Schwartz
Polymers 2024, 16(24), 3508; https://doi.org/10.3390/polym16243508 - 17 Dec 2024
Viewed by 118
Abstract
This work connects the calorimetric responses of different rubber–resin blends with varying resin contents with their alpha relaxation dynamics. We used differential scanning calorimetry and broadband dielectric spectroscopy to characterize the calorimetric and dielectric responses of styrene–butadiene, polybutadiene, and polyisoprene with different resin [...] Read more.
This work connects the calorimetric responses of different rubber–resin blends with varying resin contents with their alpha relaxation dynamics. We used differential scanning calorimetry and broadband dielectric spectroscopy to characterize the calorimetric and dielectric responses of styrene–butadiene, polybutadiene, and polyisoprene with different resin contents. To model the results, we used the Gordon–Taylor equation combined with an extension of the Adam–Gibbs approach. Thus, we propose a simple and effective model that allows us to estimate the blend dynamics from the temperature dependence of the relaxation times of the pure components and the calorimetric measurement of the glass transition temperature of only one blend composition. By estimating an effective interaction parameter from calorimetry, we achieved accurate alpha relaxation dynamics predictions for different resin concentrations. Our highly predictive approach provides a realistic description of the expected dynamics. This study offers valuable insights into the dynamic properties of polymer compounds, paving the way for the fast and effective development of advanced and more sustainable materials. Full article
(This article belongs to the Special Issue Elastomers Science and Technology)
►▼ Show Figures

Figure 1

Figure 1
<p>Left column: DSC thermograms (reversible C<sub>p</sub> vs. temperature) of pure resin and neat SBR, PBD, and PI. Red lines represent the linear fittings for <math display="inline"><semantics> <mrow> <mo>∆</mo> <msub> <mrow> <mi>C</mi> </mrow> <mrow> <mi>p</mi> </mrow> </msub> <mo>(</mo> <mi>T</mi> <mo>)</mo> </mrow> </semantics></math> determination. Right column: experimental data (circles) of the temperature dependence of the relaxation time and corresponding Adam–Gibbs fittings (lines). The obtained parameters are shown in the plots.</p> Full article ">Figure 1 Cont.
<p>Left column: DSC thermograms (reversible C<sub>p</sub> vs. temperature) of pure resin and neat SBR, PBD, and PI. Red lines represent the linear fittings for <math display="inline"><semantics> <mrow> <mo>∆</mo> <msub> <mrow> <mi>C</mi> </mrow> <mrow> <mi>p</mi> </mrow> </msub> <mo>(</mo> <mi>T</mi> <mo>)</mo> </mrow> </semantics></math> determination. Right column: experimental data (circles) of the temperature dependence of the relaxation time and corresponding Adam–Gibbs fittings (lines). The obtained parameters are shown in the plots.</p> Full article ">Figure 2
<p>Gordon–Taylor fitting of the resin concentration dependence of the <span class="html-italic">T<sub>g</sub></span> for the SBR-, PBD-, and PI-based systems. <math display="inline"><semantics> <mrow> <msub> <mrow> <mi>k</mi> </mrow> <mrow> <mi>G</mi> <mi>T</mi> </mrow> </msub> </mrow> </semantics></math> stands for the GT parameter as obtained from the fitting.</p> Full article ">Figure 3
<p>Gordon–Taylor fitting of <span class="html-italic">T<sub>g</sub></span> for the SBR-, PBD-, and PI-resin blends using only a single blend composition (25% resin).</p> Full article ">Figure 4
<p>(<b>Left</b>) Imaginary part of the complex dielectric permittivity as a function of frequency at 263 K for the SBR-based system with different resin concentrations. The arrow indicates increasing resin content. (<b>Right</b>) Experimental dielectric response (circles) and the corresponding fittings (lines) for SBR–resin samples with 0 and 34% resin. The dashed line intends to show the frequency shift of each alpha relaxation (alpha relaxation peaks are indicated in the sample’s color, whereas other contributions are presented in grey), and the width at half maximum is illustrated by the black horizontal arrows.</p> Full article ">Figure 5
<p>Log τ as a function of 1000/T for SBR-, PBD-, and PI-resin based systems’ alpha relaxation. The arrow indicates increasing resin content for the compounds (the neat and the pure resin are also included in the map).</p> Full article ">Figure 6
<p>Dynamics prediction flowchart.</p> Full article ">
21 pages, 3502 KiB  
Article
Study on the Characterization of Physical, Mechanical, and Creep Properties of Masson Pine and Chinese Fir Wood Flour-Reinforced High-Density Polyethylene Composites
by Hailong Xu, Xueshan Hua, Yan Cao, Lifen Li, Baoyu Liu, Xiaohui Yang and Hua Gao
Polymers 2024, 16(24), 3507; https://doi.org/10.3390/polym16243507 - 17 Dec 2024
Viewed by 166
Abstract
Improving the physical, mechanical, and creep properties of wood fiber-reinforced polymer composites is crucial for broadening their application prospect. In this research, seven types of high-density polyethylene (HDPE) composites reinforced with different mass ratios of Masson pine (Pinus massoniana Lamb.) and Chinese [...] Read more.
Improving the physical, mechanical, and creep properties of wood fiber-reinforced polymer composites is crucial for broadening their application prospect. In this research, seven types of high-density polyethylene (HDPE) composites reinforced with different mass ratios of Masson pine (Pinus massoniana Lamb.) and Chinese fir [Cunninghamia lanceolata (Lamb.) Hook.] were prepared by a two-step extrusion molding method. The mass ratios of the two fibers were 60:0, 50:10, 40:20, 30:30, 20:40, 10:50, and 0:60, respectively. The surface color, density, dimension stability, bending, tensile, impact properties, dynamic mechanical properties, and 24 h creep properties at a 10% stress level of the seven composites were investigated. Additionally, the Rule of Mixtures (ROM), the Inverse Rule of Mixtures (IROM), the Hirsch models, and the improved model were employed to simulate the mechanical properties, while the Findley index model, the two-parameter index model, and the modified ExpAssoc model were employed to simulate the creep performance of the composites. This study revealed that as the proportion of Chinese fir wood flour increased, the mechanical properties of the composites gradually improved, the storage modulus showed an increasing trend, while the loss modulus decreased, and the overall creep strain of the composites increased. Among the various models, the modified model simulated the mechanical properties of the composites the best, while the modified ExpAssoc model simulated the creep behavior most effectively. Full article
(This article belongs to the Special Issue Advanced Polymer Materials: Synthesis, Structure, and Properties)
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Figure 1

Figure 1
<p>Production flowchart of WPCs.</p> Full article ">Figure 2
<p>Force–deformation curves for WPCs under bending stress.</p> Full article ">Figure 3
<p>Force–deformation curves for WPCs under tension stress.</p> Full article ">Figure 4
<p>Storage modulus of WPCs as a function of temperature.</p> Full article ">Figure 5
<p>Loss modulus of WPCs as a function of temperature.</p> Full article ">Figure 6
<p>Loss tangent of WPCs as a function of temperature.</p> Full article ">Figure 7
<p>Strain–time curves of WPCs at 24 h.</p> Full article ">Figure 8
<p>Creep testing and simulation curves of WPC samples.</p> Full article ">Figure 8 Cont.
<p>Creep testing and simulation curves of WPC samples.</p> Full article ">
15 pages, 3040 KiB  
Article
Impact of Citric Acid on the Structure, Barrier, and Tensile Properties of Esterified/Cross-Linked Potato Peel-Based Films and Coatings
by Katharina Miller, Corina L. Reichert, Markus Schmid and Myriam Loeffler
Polymers 2024, 16(24), 3506; https://doi.org/10.3390/polym16243506 - 17 Dec 2024
Viewed by 193
Abstract
The valorization of potato peel side streams for food packaging applications, especially for the substitution of current petrochemical-based oxygen barrier solutions such as EVOH, is becoming increasingly important. Therefore, potato peel-based films and coatings (on PLA) were developed containing 10–50% (w/ [...] Read more.
The valorization of potato peel side streams for food packaging applications, especially for the substitution of current petrochemical-based oxygen barrier solutions such as EVOH, is becoming increasingly important. Therefore, potato peel-based films and coatings (on PLA) were developed containing 10–50% (w/w potato peel) citric acid (CA). To determine the impact of CA concentration on the structure and physicochemical properties of cast films and coatings, ATR-FTIR spectroscopy, moisture adsorption isotherms, tensile properties, light transmittance, oxygen permeability, carbon dioxide transmission rate, and water vapor transmission rate measurements were performed. The results indicate that an increase in CA concentration from 10% to 30% increased esterification/cross-linking and resulted in minimal values for the oxygen permeability (0.08 cm3 m−2 d−1 bar−1) at 50% RH and water vapor transmission rate (1.6 g m−2 d−1) at 50% → 0% RH, whereas an increase from 30% to 50% increased free CA concentration and resulted in increased flexibility, indicating that CA functioned as a plasticizer within the film/coating at higher concentrations. Overall, potato peel-based coatings containing CA showed comparable barrier properties to EVOH. We assume that an extensive industrial purification or fractionation of potato peel, which was not carried out in this study, could lead to even lower transmission rates. Full article
(This article belongs to the Special Issue Polymers for Circular Packaging Materials)
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Graphical abstract
Full article ">Figure 1
<p>Cross-section of a PLA–potato peel bi-layer obtained by light microscopy.</p> Full article ">Figure 2
<p>ATR-FTIR spectra in the range of 4000 to 600 cm<sup>−1</sup> of potato peel-based films containing (top to bottom) 0%, 10%, 30%, or 50% (<span class="html-italic">w</span>/<span class="html-italic">w</span> potato peel) citric acid (CA) prior to and after immersion into 0.1 M NaOH.</p> Full article ">Figure 3
<p>Moisture adsorption isotherms of potato peel-based films containing 10–50% (<span class="html-italic">w</span>/<span class="html-italic">w</span> potato peel) citric acid as a function of 0.0–0.93 a<sub>w.</sub></p> Full article ">Figure 4
<p>Tensile properties of potato peel-based cast films containing 30% or 50% (<span class="html-italic">w</span>/<span class="html-italic">w</span> potato peel) citric acid. The average thicknesses of the cast films containing 30% or 50% (<span class="html-italic">w</span>/<span class="html-italic">w</span> potato peel) citric acid were 131 ± 8 and 132 ± 9 µm, respectively. Different letters describe significant differences (<span class="html-italic">p</span> &lt; 0.05) between measured values.</p> Full article ">Figure 5
<p>Light transmittance of PLA (25 µm) and potato peel-based coatings (7 ± 1 µm) containing 10–50% (<span class="html-italic">w</span>/<span class="html-italic">w</span> potato peel) citric acid (CA) as a function of the wavelength (right).</p> Full article ">Figure 6
<p>Oxygen- (OTR), carbon dioxide- (CO<sub>2</sub>TR), and water vapor transmission rate (WVTR) of potato peel-based coatings (7 ± 1 µm) as a function of citric acid concentration. Different letters describe significant differences (<span class="html-italic">p</span> &lt; 0.05) between measured values.</p> Full article ">Figure 7
<p>Oxygen permeability of potato peel-based coatings (7 ± 1 µm) containing 10–50% (<span class="html-italic">w</span>/<span class="html-italic">w</span> potato peel) citric acid (CA) as a function of relative humidity (<b>left</b>) and water vapor transmission rate (WVTR) of PLA and PLA–potato peel bi-layers containing 10–50% (<span class="html-italic">w</span>/<span class="html-italic">w</span> potato peel) CA (<b>right</b>). Different letters describe significant differences (<span class="html-italic">p</span> &lt; 0.05) between measured values.</p> Full article ">
20 pages, 18907 KiB  
Article
From Experimentation to Optimization: Surface Micro-Texturing for Low-Friction and Durable PTFE–Steel Interfaces Under Full Film Lubrication
by Risheng Long, Jincheng Hou, Yimin Zhang, Qingyu Shang, Chi Ma, Florian Pape and Max Marian
Polymers 2024, 16(24), 3505; https://doi.org/10.3390/polym16243505 - 17 Dec 2024
Viewed by 163
Abstract
To enhance the sliding tribological performance between PTFE and 40#steel (AISI 1040) under full film lubrication conditions, laser surface texturing (LST) technology was employed to prepare micro-dimples on the contact surfaces of 40# steel discs. The Box–Behnken design response surface methodology (BBD-RSM) was [...] Read more.
To enhance the sliding tribological performance between PTFE and 40#steel (AISI 1040) under full film lubrication conditions, laser surface texturing (LST) technology was employed to prepare micro-dimples on the contact surfaces of 40# steel discs. The Box–Behnken design response surface methodology (BBD-RSM) was applied to optimize the micro-dimple parameters. Coefficients of friction (COFs), wear losses and worn contact surfaces of the PTFE–40# steel tribo-pairs were researched through repeated wear tests, as lubricated with sufficient anti-wear hydraulic oil. The influencing mechanism of micro-dimples on the tribological behavior of tribo-pairs was also discussed. The results proved that micro-dimples can significantly improve the tribological properties of PTFE–40#steel tribo-pairs. The deviation between the final obtained average COF and the prediction by the BBD-RSM regression model was only 0.0023. Following optimization, the average COF of the PTFE–40# steel tribo-pair was reduced by 39.34% compared to the smooth reference. The wear losses of the PTFE ring and 40# steel disc decreased by 91.8% and 30.3%, respectively. This study would offer a valuable reference for the optimal design of key seals used in hydraulic cylinders. Full article
(This article belongs to the Section Polymer Applications)
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Figure 1
<p>PTFE–40# steel tribo-pair and laser marking system. (<b>a</b>) Photos of the steel disc and upper counter rings (PTFE); (<b>b</b>) Section view of the lower sample (40# steel disc); (<b>c</b>) Photo of laser marking machine; (<b>d</b>) Section view of the upper sample (PTFE ring); (<b>e</b>) Textured surface of the 40#steel disc before re-polishing and the angle between two adjacent sets of micro-dimples in circumference.</p> Full article ">Figure 2
<p>Vertical universal tribological test rig. (<b>a</b>) Photo of the MMW-1A vertical universal tribo-meter; (<b>b</b>) Photo of the fixtures used; (<b>c</b>) Section view of the fixtures: ① upper fixture; ② upper sample (PTFE ring); ③ lower sample (40# steel disc); ④ oil deflector; ⑤ lower fixture; ⑥ loading flange.</p> Full article ">Figure 3
<p>COF data of different groups as the PTFE rings were tested against the 40# steel discs: (<b>a</b>) COF curves of T1–T4; (<b>b</b>) COF curves of R1–R4; (<b>c</b>) COF curves of X1–X4; (<b>d</b>) COF curves of X5-1 to X5-5; (<b>e</b>) Average COFs of 17 groups.</p> Full article ">Figure 4
<p>Representative worn surfaces of the PTFE rings and wear losses of different groups after wear tests. (<b>a</b>) Worn surfaces of the PTFE rings after ultrasonic cleaning. (<b>b</b>) Mass losses of the PTFE rings and 40# steel discs: (<b>b1</b>) mass losses of T1–T4; (<b>b2</b>) mass losses of R1–R4; (<b>b3</b>) mass losses of X1–X4; (<b>b4</b>) mass losses of X5-1–X5-5.</p> Full article ">Figure 5
<p>Representative worn surfaces of the 40# steel discs of different groups after wear tests and the FTIR curve of the PTFE transfer film. (<b>a</b>) Worn surfaces of the 40# steel discs after ultrasonic cleaning. (<b>b</b>) Typical infrared spectral characteristics of the PTFE debris collected from the transfer film on the contact surface of the 40# steel disc. (<b>c</b>) Section view of one black spot on the worn surface of the steel disc of the CT group.</p> Full article ">Figure 6
<p>Representative 3D worn morphologies (with an enlargement of 2000% in the height direction) of the PTFE–40# steel tribo-pairs (T1, T3, T4, R1, X3, X5-4) after ultrasonic cleaning. (<b>a</b>) PTFE rings; (<b>b</b>) 40# steel discs.</p> Full article ">Figure 7
<p>Response surfaces of the interaction among three factors (<span class="html-italic">D</span>, <span class="html-italic">P</span>, <span class="html-italic">H</span>) on the average COFs of the PTFE–40# steel tribo-pairs. (<b>a</b>) Response surface among average COF, <span class="html-italic">P</span> and <span class="html-italic">H</span>; (<b>b</b>) Response surface among average COF, <span class="html-italic">D</span> and <span class="html-italic">P</span>; (<b>c</b>) Response surface among average COF, <span class="html-italic">D</span> and <span class="html-italic">H</span>.</p> Full article ">Figure 8
<p>COF curves and wear losses of three groups (OT, LT and CT). (<b>a</b>) COF curves and average COF lines of OT, LT and CT; (<b>b</b>) Wear losses of OT, LT and CT.</p> Full article ">Figure 9
<p>Representative worn surfaces and 3D morphologies of the PTFE rings of OT, LT and CT after ultrasonic cleaning. (<b>a</b>) OT; (<b>b</b>) LT; (<b>c</b>) CT.</p> Full article ">Figure 10
<p>Representative worn surfaces and 3D morphologies of the 40# steel discs of OT, LT and CT after ultrasonic cleaning. (<b>a</b>) OT; (<b>b</b>) LT; (<b>c</b>) CT.</p> Full article ">Figure 11
<p>Influence mechanism of micro-dimples on the tribological performance of the PTFE–40# steel tribo-pair as lubricated with sufficient anti-wear hydraulic oil. (<b>a</b>) PTFE–40# steel tribo-pair and transfer film: (<b>a1</b>) section view of PTFE–40# steel tribo-pair; (<b>a2</b>) top view of PTFE–40# steel tribo-pair; (<b>a3</b>) transfer film left on the surface. (<b>b</b>) Micro-eddies in micro-dimples and the debris migration: (<b>b1</b>) influence of micro-eddies on the load-carrying capacity along the circumference; (<b>b2</b>) migration of wear debris along the radius direction. (<b>c</b>) Cavitation phenomenon and its formation mechanism: (<b>c1</b>) image of black spots; (<b>c2</b>) formation mechanism of cavitation.</p> Full article ">
12 pages, 2307 KiB  
Article
Synthesis of Novel Zwitterionic Surfactants: Achieving Enhanced Water Resistance and Adhesion in Emulsion Polymer Adhesives
by Mai Toan, Jaehyouk Choi, Hang Thi Ngo, Jin-Young Bae, Seunghan Shin and Kiok Kwon
Polymers 2024, 16(24), 3504; https://doi.org/10.3390/polym16243504 - 17 Dec 2024
Viewed by 259
Abstract
Recent advancements in polymer materials have enabled the synthesis of bio-based monomers from renewable resources, promoting sustainable alternatives to fossil-based materials. This study presents a novel zwitterionic surfactant, SF, derived from 10-undecenoic acid obtained from castor oil through a four-step reaction, achieving a [...] Read more.
Recent advancements in polymer materials have enabled the synthesis of bio-based monomers from renewable resources, promoting sustainable alternatives to fossil-based materials. This study presents a novel zwitterionic surfactant, SF, derived from 10-undecenoic acid obtained from castor oil through a four-step reaction, achieving a yield of 78%. SF has a critical micelle concentration (CMC) of 1235 mg/L, slightly higher than the commercial anionic surfactant Rhodacal DS-4 (sodium dodecyl benzene sulfonate), and effectively stabilizes monomer droplets, leading to excellent conversion and stable latex formation. The zwitterionic groups in SF enhance adhesion to hydrophilic substrates (glass, stainless steel, and skin). Films produced with SF exhibit outstanding water resistance, with only 18.48% water uptake after 1800 min, compared to 81% for the control using Rhodacal DS-4. Notably, SF maintains low water uptake across various concentrations, minimizing water penetration. Thus, the synthesized SF demonstrates improved adhesive properties and excellent water resistance in emulsion polymerization applications, highlighting its potential as a sustainable, high-performance alternative to petrochemical surfactants. Full article
(This article belongs to the Section Polymer Chemistry)
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<p>1H NMR and 13C NMR spectra of SF.</p> Full article ">Figure 2
<p>Surface tension measurement of SF and Rhodacal DS-4.</p> Full article ">Figure 3
<p>(<b>a</b>) Final monomer conversion and (<b>b</b>) particle size of emulsion polymerization.</p> Full article ">Figure 4
<p>Ninety-degree peel strength of SF sample on (<b>a</b>) glass and (<b>b</b>) pig skin substrates.</p> Full article ">Figure 5
<p>(<b>a</b>) Water uptake and (<b>b</b>) water contact angles of SF latex films.</p> Full article ">Figure 6
<p>Illustrating the decease in water resistance due to the mobilization of Rhodacal DS-4 in the water phase (<b>a</b>), the penetration of SF in the polymer network (<b>b</b>), and the bonding between SF and latex (<b>c</b>).</p> Full article ">
15 pages, 3436 KiB  
Article
Assessment of Two Crosslinked Polymer Systems Including Hydrolyzed Polyacrylamide and Acrylic Acid–Hydrolyzed Polyacrylamide Co-Polymer for Carbon Dioxide and Formation Water Diversion Through Relative Permeability Reduction in Unconsolidated Sandstone Formation
by Sherif Fakher, Abdelaziz Khlaifat, Karim Mokhtar and Mariam Abdelsamei
Polymers 2024, 16(24), 3503; https://doi.org/10.3390/polym16243503 - 17 Dec 2024
Viewed by 271
Abstract
One of the most challenging aspects of manipulating the flow of fluids in subsurfaces is to control their flow direction and flow behavior. This can be especially challenging for compressible fluids, such as CO2, and for multiphase flow, including both water [...] Read more.
One of the most challenging aspects of manipulating the flow of fluids in subsurfaces is to control their flow direction and flow behavior. This can be especially challenging for compressible fluids, such as CO2, and for multiphase flow, including both water and carbon dioxide (CO2). This research studies the ability of two crosslinked polymers, including hydrolyzed polyacrylamide and acrylic acid/hydrolyzed polyacrylamide crosslinked polymers, to reduce the permeability of both CO2 and formation water using different salinities and permeability values and in the presence of crude oil under different injection rates. The result showed that both polymers managed to reduce the permeability of water effectively; however, their CO2 permeability-reduction potential was much lower, with the CO2 permeability reduction being less than 50% of the water reduction potential in the majority of the experiments. This was mainly due to the high flow rate of the CO2 compared to the water, which resulted in significant shearing of the crosslinked polymer. The crosslinked polymers’ swelling ratios were impacted differently based on the salinity, with the maximum swelling ratio being 9.8. The HPAM polymer was negatively affected by the presence of crude oil, whereas increasing salinity improved its performance greatly. All in all, both polymers had a higher permeability reduction for the formation water compared to CO2 under all conditions. This research can help improve the applicability of CO2-enhanced oil recovery and CO2 storage in depleted oil reservoirs. The ability of the crosslinked polymers to improve CO2 storage will be a main focus of future research. Full article
(This article belongs to the Special Issue Progress in Polymer Networks)
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<p>Synthesized AA/HPAM-crosslinked polymer (yellow) and HPAM-crosslinked polymer (transparent).</p> Full article ">Figure 2
<p>(<b>a</b>) Sandpack experimental setup. (<b>b</b>) Sandpack experimental setup.</p> Full article ">Figure 3
<p>CO<sub>2</sub> permeability reduction for HPAM- and AA/HPAM-crosslinked polymer after one and two injection cycles at different injection rates using 3 Darcy permeability sandpack, 1 wt% polymer, and 1 wt% NaCl.</p> Full article ">Figure 4
<p>CO<sub>2</sub> permeability reduction for HPAM- and AA/HPAM-crosslinked polymers after one and two injection cycles at different injection rates using 3 Darcy permeability sandpack, 1 wt% Polymer, and 10 wt% NaCl.</p> Full article ">Figure 5
<p>CO<sub>2</sub> permeability deduction for HPAM- and AA/HPAM-crosslinked polymers after one and two injection cycles at different injection rates using 18 Darcy permeability sandpack, 1 wt% Polymer, and 1 wt% NaCl.</p> Full article ">Figure 6
<p>CO<sub>2</sub> permeability reduction for HPAM- and AA/HPAM-crosslinked polymers after one and two injection cycles at different injection rates using 3 Darcy permeability sandpack, 1 wt% polymer, 1 wt% NaCl, and 33 cp Crude Oil.</p> Full article ">Figure 7
<p>Water permeability reduction for HPAM- and AA/HPAM-crosslinked polymers after one and two injection cycles at different injection rates using 3 Darcy permeability sandpack, 1 wt% Polymer, and 1 wt% NaCl.</p> Full article ">Figure 8
<p>Water permeability reduction for HPAM- and AA/HPAM-crosslinked polymers after one and two injection cycles at different injection rates using 3 Darcy permeability sandpack, 1 wt% Polymer, and 10 wt% NaCl.</p> Full article ">Figure 9
<p>Water permeability reduction for HPAM- and AA/HPAM-crosslinked polymers after one and two injection cycles at different injection rates using 18 Darcy permeability sandpack, 1 wt% polymer, and 1 wt% NaCl.</p> Full article ">Figure 10
<p>Water permeability reduction for HPAM- and AA/HPAM-crosslinked polymers after one and two injection cycles at different injection rates using 3 Darcy permeability sandpack, 1 wt% polymer, 1 wt% NaCl, and 33 cp crude oil.</p> Full article ">
15 pages, 6547 KiB  
Article
Green Recycling for Polypropylene Components by Material Extrusion
by Roberto Spina and Nicola Gurrado
Polymers 2024, 16(24), 3502; https://doi.org/10.3390/polym16243502 - 16 Dec 2024
Viewed by 299
Abstract
High volumetric shrinkage and rheological behavior of polypropylene (PP) are the main problems that make material extrusion (MEX) uncommon for this material. The complexity is raised when recycled materials are used. This research covered different aspects of the MEX process of virgin and [...] Read more.
High volumetric shrinkage and rheological behavior of polypropylene (PP) are the main problems that make material extrusion (MEX) uncommon for this material. The complexity is raised when recycled materials are used. This research covered different aspects of the MEX process of virgin and recycled PP, from the analysis of rough materials to the mechanical evaluation of the final products. Two types of virgin PP (one in pellet and the other in filament form) and one recycled PP were analyzed. Thermal characterization and rheological analysis of these materials were initially employed to understand the peculiar properties of all investigated PP and set filament extrusion. The 3D parts were then printed using processed filaments to check fabrication quality through visual analysis and mechanical tests. A well-structured approach was proposed to encompass the limitations of PP 3D printing by accurately evaluating the influence of the material properties on the final part performance. The results revealed that the dimensional and mechanical performances of the recycled PP were comparable with the virgin filament commonly employed in MEX, making it particularly suitable for this application. Full article
(This article belongs to the Special Issue Process and Technology for Enhancing the Sustainability, Recycling and Circularity of Polymer Composites Materials)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Study flowchart.</p> Full article ">Figure 2
<p>Thermograms of heating (<b>a</b>) and cooling (<b>b</b>) phase.</p> Full article ">Figure 3
<p>SABIC PP and LDPE spectra.</p> Full article ">Figure 4
<p>SABIC PP and rPP spectra.</p> Full article ">Figure 5
<p>Master curves at 250 °C.</p> Full article ">Figure 6
<p>3devo filament maker scheme.</p> Full article ">Figure 7
<p>Diameter variations.</p> Full article ">Figure 8
<p>Specimens (all dimensions in mm).</p> Full article ">Figure 9
<p>Specimen types.</p> Full article ">Figure 10
<p>Evaluation deviation map of the cubes (ISO view and plane view) and separation from the substrate (Side View).</p> Full article ">Figure 11
<p>Tensile test results.</p> Full article ">
13 pages, 5715 KiB  
Article
Characterization and Rheological Properties of Ultra-High Molecular Weight Polyethylenes
by Alexander Ya. Malkin, Tatyana A. Ladygina, Sergey S. Gusarov, Dmitry V. Dudka and Anton V. Mityukov
Polymers 2024, 16(24), 3501; https://doi.org/10.3390/polym16243501 - 16 Dec 2024
Viewed by 353
Abstract
The molecular characteristics and rheological properties of three UHMWPE samples were investigated. The high-temperature GPC method was used for characterizing UHMWPE samples used. The interpretation of the measurement results was based on calibration using the PS standard and the approximation of the PS [...] Read more.
The molecular characteristics and rheological properties of three UHMWPE samples were investigated. The high-temperature GPC method was used for characterizing UHMWPE samples used. The interpretation of the measurement results was based on calibration using the PS standard and the approximation of the PS data by linear and cubic polynomials, as well as on the data for linear PE. The assessment of the average MW and MWD depends on the choice of calibration method, so that different methods give different results. Only the results obtained using PS with cubic approximation are close to the characteristics offered by the manufacturer. It was also shown that the obtained MW characteristics depend on the dissolution time. The reason for this may be the presence of any processing-aid compounds or destruction of macromolecules. Measurements of the rheological properties were performed in creep modes for a wide range of shear stresses and harmonic oscillations. It was shown that even at 210 °C, UHMWPE does not flow, and the observed irreversible deformations are due to the plasticity of the polymer, i.e., UHMWPE is in an elastic–plastic state. The ultimate plastic deformations drop sharply with increasing MW of the polymer. The plasticity modulus for the highest molecular weight UHMWPE samples does not depend on stress. Measurements of viscoelastic characteristics confirmed that the terminal region of viscous flow cannot be reached under any conditions. Increasing the duration of holding the polymer at high temperature leads not to flow, but to the destruction of macromolecules. Full article
(This article belongs to the Section Polymer Analysis and Characterization)
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Graphical abstract
Full article ">Figure 1
<p>Calibration curves using PS standards and linear approximation with recalculating for PE (<b>a</b>), without recalculating (<b>b</b>), and cubic approximation without recalculating (<b>c</b>).</p> Full article ">Figure 2
<p>Results of measurements of the MWD of the studied UHMWPE samples, obtained by dissolution for 5 h.</p> Full article ">Figure 3
<p>Results of measurements of the MWD of the studied UHMWPE samples, obtained by dissolution for 2.5 h.</p> Full article ">Figure 4
<p>Shift of the MWD curves of the GUR-4120 sample depending on the duration during the preparation of the studied solutions.</p> Full article ">Figure 5
<p>Creep (at σ = 200 Pa) of and elastic recovery for the three samples at 210 °C.</p> Full article ">Figure 6
<p>Creep of UHMWPE C for samples GUR 4150 (<b>a</b>), GUR-4120 (<b>b</b>), and UTEC 6540 (<b>c</b>), at 210 °C.</p> Full article ">Figure 7
<p>Moduli of plasticity for UHMWPE samples GUR 4150 (<b>a</b>), GUR-4120 (<b>b</b>), and UTEC 6540 (<b>c</b>).</p> Full article ">Figure 8
<p>Dependence of the ultimate deformations for GUR 4150 (<b>a</b>), GUR-4120 (<b>b</b>), and UTEC 6540 (<b>c</b>), at 210 °C.</p> Full article ">Figure 9
<p>Dependence of the ultimate deformation on MW for GUR 4150, GUR-4120, and UTEC 6540 samples at 210 °C related to PE series (<b>a</b>) and related to PS-linear series (<b>b</b>).</p> Full article ">Figure 10
<p>Elastic modulus components obtained at different deformation amplitudes (temperature 170 °C, frequency 6.28 rad/s); filled symbols—G’, open symbols—G”.</p> Full article ">Figure 11
<p>Frequency dependencies of G’(ω) (filled symbols) and G”(ω) (open symbols) for samples GUR-4120 (<b>a</b>), GUR-4150 (<b>b</b>), and UTEC 6540 (<b>c</b>).</p> Full article ">Figure 12
<p>Temperature–frequency superposition of the elastic modulus (<b>a</b>) and loss modulus (<b>b</b>) for samples GUR-4120, GUR-4150, and UTEC 6540. Master curves are built for 240 °C.</p> Full article ">Figure 13
<p>Visco-elastic properties of the linear low-MW PE at 210 °C.</p> Full article ">
18 pages, 16187 KiB  
Article
Cumulative Strain and Improvement Mechanisms of Soil Reinforced by Xanthan Gum Biopolymer Under Traffic Loading
by Liu Yang, Lingshi An, Kuangyu Yan and Gaofeng Du
Polymers 2024, 16(24), 3500; https://doi.org/10.3390/polym16243500 - 16 Dec 2024
Viewed by 286
Abstract
As is widely accepted, cumulative strain and improvement mechanisms of stabilized soil are critical factors for the long-term reliable operation of expressways and high-speed railways. Based on relevant research findings, xanthan gum biopolymer is regarded as a green and environmentally friendly curing agent [...] Read more.
As is widely accepted, cumulative strain and improvement mechanisms of stabilized soil are critical factors for the long-term reliable operation of expressways and high-speed railways. Based on relevant research findings, xanthan gum biopolymer is regarded as a green and environmentally friendly curing agent in comparison to traditional stabilizers, such as cement, lime, and fly ash. However, little attention has been devoted to the cumulative strain and improvement mechanisms of soil reinforced by xanthan gum biopolymer under traffic loading. In the current study, a series of laboratory tests, including cyclic triaxial tests and scanning electron microscopy (SEM) tests, were performed to investigate this issue in more detail. The influences of xanthan gum biopolymer content, curing time, moisture content, confining pressure, and cyclic stress amplitude on cumulative strain were analyzed. In addition, the cumulative strain model was proposed to provide a good description of experimental data. Finally, the microscopic structure of soil reinforced by xanthan gum biopolymer was analyzed to discuss the improvement mechanisms. The results show that the cumulative strain is strongly influenced by xanthan gum biopolymer content. For a given number of loading cycles, the greater the confining pressure, the smaller the cumulative strain. The calculated results of the cumulative strain model show a good agreement with test data. The “flocculent” hydrogel can form a denser structure and greater bonding strength in comparison to the “branch-like” and “net-like” hydrogels. Full article
(This article belongs to the Special Issue Polymers in Civil Engineering)
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<p>The grain-size distribution curve of soil.</p> Full article ">Figure 2
<p>The molecular structure of xanthan gum biopolymer [<a href="#B40-polymers-16-03500" class="html-bibr">40</a>].</p> Full article ">Figure 3
<p>The grain-size distribution curve of xanthan gum biopolymer.</p> Full article ">Figure 4
<p>Test procedures: (<b>a</b>) Workflow of experiment; (<b>b</b>) Load-on pattern of one-way cyclic loading.</p> Full article ">Figure 5
<p>The applied stress paths of cyclic triaxial tests: (<b>a</b>) CL1-CL6, LQ1-LQ5, and HSL1-HSL4; (<b>b</b>) WY1-WY4; (<b>c</b>) FZ1-FZ3.</p> Full article ">Figure 6
<p>The effect of xanthan gum biopolymer content on the cumulative strain of stabilized soil.</p> Full article ">Figure 7
<p>The cumulative strain of stabilized soil with different xanthan gum biopolymer contents at the end of loading.</p> Full article ">Figure 8
<p>The effect of curing time on the cumulative strain of stabilized soil.</p> Full article ">Figure 9
<p>The cumulative strain of stabilized soil with different curing times at the end of loading.</p> Full article ">Figure 10
<p>The effect of moisture content on the cumulative strain of stabilized soil.</p> Full article ">Figure 11
<p>The cumulative strain of stabilized soil with different moisture contents at the end of loading.</p> Full article ">Figure 12
<p>The effect of confining pressure on the cumulative strain of stabilized soil.</p> Full article ">Figure 13
<p>The cumulative strain of stabilized soil with different confining pressures at the end of loading.</p> Full article ">Figure 14
<p>The effect of cyclic stress amplitude on the cumulative strain of stabilized soil.</p> Full article ">Figure 15
<p>The cumulative strain of stabilized soil with different cyclic stress amplitudes at the end of loading.</p> Full article ">Figure 16
<p>The comparison of the test data with the calculated results of the Barksdale model and the improved model.</p> Full article ">Figure 17
<p>The calibration of the improved model: (<b>a</b>) CL1-CL6; (<b>b</b>) LQ1-LQ5; (<b>c</b>) HSL1-HSL5; (<b>d</b>) WY1-WY4; (<b>e</b>) FZ1-FZ3.</p> Full article ">Figure 18
<p>The SEM images of xanthan gum biopolymer treated soil: the xanthan gum biopolymer contents of (<b>a</b>–<b>f</b>) are 0%, 0.5%, 1%, 1.5%, 2%, and 3%, respectively.</p> Full article ">
14 pages, 2756 KiB  
Article
Tissue Sources Influence the Morphological and Morphometric Characteristics of Collagen Membranes for Guided Bone Regeneration
by Josefa Alarcón-Apablaza, Karina Godoy-Sánchez, Marcela Jarpa-Parra, Karla Garrido-Miranda and Ramón Fuentes
Polymers 2024, 16(24), 3499; https://doi.org/10.3390/polym16243499 - 16 Dec 2024
Viewed by 265
Abstract
(1) Background: Collagen, a natural polymer, is widely used in the fabrication of membranes for guided bone regeneration (GBR). These membranes are sourced from various tissues, such as skin, pericardium, peritoneum, and tendons, which exhibit differences in regenerative outcomes. Therefore, this study aimed [...] Read more.
(1) Background: Collagen, a natural polymer, is widely used in the fabrication of membranes for guided bone regeneration (GBR). These membranes are sourced from various tissues, such as skin, pericardium, peritoneum, and tendons, which exhibit differences in regenerative outcomes. Therefore, this study aimed to evaluate the morphological and chemical properties of porcine collagen membranes from five different tissue sources: skin, pericardium, dermis, tendons, and peritoneum. (2) Methods: The membrane structure was analyzed using energy-dispersive X-ray spectrometry (EDX), variable pressure scanning electron microscopy (VP-SEM), Fourier transform infrared spectroscopy (FTIR), and thermal stability via thermogravimetric analysis (TGA). The absorption capacity of the membranes for GBR was also assessed using an analytical digital balance. (3) Results: The membranes displayed distinct microstructural features. Skin- and tendon-derived membranes had rough surfaces with nanopores (1.44 ± 1.24 µm and 0.46 ± 0.1 µm, respectively), while pericardium- and dermis-derived membranes exhibited rough surfaces with macropores (78.90 ± 75.89 µm and 64.89 ± 13.15 µm, respectively). The peritoneum-derived membrane featured a rough surface of compact longitudinal fibers with irregular macropores (9.02 ± 3.70 µm). The thickness varied significantly among the membranes, showing differences in absorption capacity. The pericardium membrane exhibited the highest absorption, increasing by more than 10 times its initial mass. In contrast, the skin-derived membrane demonstrated the lowest absorption, increasing by less than 4 times its initial mass. Chemical analysis revealed that all membranes were primarily composed of carbon, nitrogen, and oxygen. Thermogravimetric and differential scanning calorimetry analyses showed no significant compositional differences among the membranes. FTIR spectra confirmed the presence of collagen, with characteristic peaks corresponding to Amide A, B, I, II, and III. (4) Conclusions: The tissue origin of collagen membranes significantly influences their morphological characteristics, which may, in turn, affect their osteogenic properties. These findings provide valuable insights into the selection of collagen membranes for GBR applications. Full article
(This article belongs to the Section Polymer Membranes and Films)
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<p>Three-dimensional structures of membranes for guided bone regeneration observed by variable pressure scanning electron microscopy. (D) Diaderm; (J) Jason; (M) Mucoderm; (OP) OSSiX Plus; (VF) Via Flex. (1,3) Membrane surface views; (2) Membrane thickness.</p> Full article ">Figure 2
<p>Mapping elemental distribution in membranes: (D) Diaderm. (J) Jason membrane. (M) mucoderm. (V) Via Flex. (OP) OSSiX plus. (VF) Via Flex. (Mag: ×250). Blue = carbon; yellow = oxygen; pink = nitrogen; orange = sodium; green = phosphorus.</p> Full article ">Figure 3
<p>Thermogravimetric analysis TGA-DSC.</p> Full article ">Figure 4
<p>Characteristic vibrations of the chemical functional groups present in collagen by FT-IR.</p> Full article ">
14 pages, 2052 KiB  
Article
Overcoming Challenges in the Commercialization of Biopolymers: From Research to Applications—A Review
by Simon Schick, Julia Heindel, Robert Groten and Gunnar H. Seide
Polymers 2024, 16(24), 3498; https://doi.org/10.3390/polym16243498 - 16 Dec 2024
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Abstract
Biopolymers are promising sustainable alternatives to petrochemical polymers, but the recent increase in published research articles has not translated into marketable products. Here, we discuss barriers to market entry by exploring application-specific, ecological, and economic aspects, such as the utilization of biodegradable polymers [...] Read more.
Biopolymers are promising sustainable alternatives to petrochemical polymers, but the recent increase in published research articles has not translated into marketable products. Here, we discuss barriers to market entry by exploring application-specific, ecological, and economic aspects, such as the utilization of biodegradable polymers to mitigate the accumulation of microplastics. We summarize previous studies revealing how fiber surface properties and the dwell time during fiber spinning affect degradability. We show how biopolymers can be processed on existing machines and how degradability can be tailored by changing process parameters. This novel approach, known as degradation by design, will allow us to rethink product development and ensure that biopolymers are not only able to replace petrochemical polymers but also reduce the environmental harm they cause. Full article
(This article belongs to the Special Issue Advances in Plastics Industry)
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<p>Theoretical framework for the evaluation of barriers that affect the polymers market.</p> Full article ">Figure 2
<p>Detailed context of the study design.</p> Full article ">Figure 3
<p>Overview of the four major groups of polymers [<a href="#B27-polymers-16-03498" class="html-bibr">27</a>,<a href="#B28-polymers-16-03498" class="html-bibr">28</a>,<a href="#B29-polymers-16-03498" class="html-bibr">29</a>]. Non-degradable petrochemical polymers are shown in the bottom right, and non-degradable biobased polymers are shown in the top right. Degradable petrochemical polymers are shown in the bottom left side, and degradable biopolymers are shown in the top left. PCL = polycaprolactone, PE = polyethylene. For other abbreviations, see the main text.</p> Full article ">Figure 4
<p>Possible end-of-life strategies for single-use textiles.</p> Full article ">
13 pages, 4597 KiB  
Article
Analysis of Interfacial Adhesion Properties Between PBT Azide Propellant Matrix and Defective AP Fillers Using Molecular Dynamics Simulations
by Xianzhen Jia, Linjing Tang, Ruipeng Liu, Hongjun Liao, Liang Cao, Xianqiong Tang and Peng Cao
Polymers 2024, 16(24), 3497; https://doi.org/10.3390/polym16243497 - 15 Dec 2024
Viewed by 392
Abstract
Filler defects and matrix crosslinking degree are the main factors affecting the interfacial adhesion properties of propellants. Improving adhesion can significantly enhance debonding resistance. In this study, all-atom molecular dynamics (MD) simulations are employed to investigate the interfacial adsorption behavior and mechanisms between [...] Read more.
Filler defects and matrix crosslinking degree are the main factors affecting the interfacial adhesion properties of propellants. Improving adhesion can significantly enhance debonding resistance. In this study, all-atom molecular dynamics (MD) simulations are employed to investigate the interfacial adsorption behavior and mechanisms between ammonium perchlorate (AP) fillers and a poly(3,3-bis-azidomethyl oxetane)-tetrahydrofuran (PBT) matrix. This study focuses on matrix crosslinking degree (70–90%), AP defects (width 20–40 Å), and temperature effects (200–1000 K) to analyze microscopic interfacial adsorption behavior, binding energy, and radial distribution function (RDF). The simulation results indicate that higher crosslinking of the PBT matrix enhances interfacial adsorption strength, but incomplete crosslinking reduces this strength. Defects on the AP surface affect interfacial adsorption by altering the contact area, and defects of 30 Å width can enhance adsorption. The analysis of temperature effects on binding energy and interface RDF reveals that binding energy and interface RDF fluctuate as the temperature increases. This study provides a microscopic perspective on the PBT matrix–AP interfacial adsorption mechanism and provides insights into the design of PBT azide propellant fuels. Full article
(This article belongs to the Section Polymer Physics and Theory)
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<p>Molecular models of (<b>a</b>) PBT, (<b>b</b>) TDI, (<b>c</b>) TMP, and (<b>d</b>) TEG. Color scheme: grey (carbon), blue (nitrogen), red (oxygen), white (hydrogen).</p> Full article ">Figure 2
<p>Crosslinking reaction mechanism.</p> Full article ">Figure 3
<p>(<b>a</b>) Ball-and-stick model of the 90% crosslinked structure; (<b>b</b>) AP crystal unit cell stick model. Color scheme: cyan (carbon), blue (nitrogen), red (oxygen), white (hydrogen).</p> Full article ">Figure 4
<p>(<b>a</b>) Adsorption stick model of PBT matrix with crosslinking degrees of 80% and flawless AP interface; (<b>b</b>) adsorption stick model of PBT matrix with crosslinking degrees of 80% and defective AP. Color scheme: grey (carbon), blue (nitrogen), red (oxygen), white (hydrogen).</p> Full article ">Figure 5
<p>Enlarged adsorption modeling of PBT matrix and flawless AP interface with crosslinking degrees of (<b>a</b>) 70%, (<b>b</b>) 80%, and (<b>c</b>) 90%. Color scheme: grey (carbon), blue (nitrogen), red (oxygen), white (hydrogen).</p> Full article ">Figure 6
<p>Enlarged adsorption modeling of PBT matrix with 80% crosslinking degree and AP with defect widths of (<b>a</b>) 20 Å, (<b>b</b>) 30 Å, and (<b>c</b>) 40 Å. Color scheme: grey (carbon), blue (nitrogen), red (oxygen), white (hydrogen).</p> Full article ">Figure 7
<p>Magnified side-perspective cross-section views of the PBT matrix with 80% crosslinking degree adsorbed onto AP defects with varying widths (30 Å). Color scheme: red (PBT matrix), grey (AP surface).</p> Full article ">Figure 8
<p>(<b>a</b>) Relationship between interfacial binding energy and crosslinking degree at the PBT-AP flawless interface. (<b>b</b>) Relationship between interfacial binding energy and defect width at the PBT-AP interface with an 80% crosslinked PBT matrix.</p> Full article ">Figure 9
<p>RDF of atom pairs at the PBT-AP flawless interface with crosslinking degrees of (<b>a</b>) 70%, (<b>b</b>) 80%, and (<b>c</b>) 90%.</p> Full article ">Figure 10
<p>RDF of atom pairs at the PBT matrix–AP interface with defect widths of (<b>a</b>) 20 Å, (<b>b</b>) 30 Å, and (<b>c</b>) 40 Å.</p> Full article ">Figure 11
<p>(<b>a</b>) Effect of temperature on the binding energy of the PBT matrix–AP interface. (<b>b</b>) Effect of temperature on radial distribution function (RDF) of N-N atom pairs.</p> Full article ">
21 pages, 9517 KiB  
Article
Thermoplastic Composite Hot-Melt Adhesives with Metallic Nano-Particles for Reversible Bonding Techniques Utilizing Microwave Energy
by Romeo Cristian Ciobanu, Mihaela Aradoaei and George Andrei Ursan
Polymers 2024, 16(24), 3496; https://doi.org/10.3390/polym16243496 - 15 Dec 2024
Viewed by 369
Abstract
This study investigated the creation of nano-composites using recycled LDPE and added 7.5 wt% nanofillers of Al and Fe in two varying particle sizes to be used as hot-melt adhesives for reversible bonding processes with the use of microwave technology. Reversible bonding relates [...] Read more.
This study investigated the creation of nano-composites using recycled LDPE and added 7.5 wt% nanofillers of Al and Fe in two varying particle sizes to be used as hot-melt adhesives for reversible bonding processes with the use of microwave technology. Reversible bonding relates to circular economy enhancement practices, like repair, refurbishment, replacement, or renovation. The physical–chemical, mechanical, and dielectric characteristics were considered to determine the impact of particle size and metal type. Through the investigation of electromagnetic radiation absorption in the composites, it was discovered that the optimal bonding technique could potentially involve a frequency of 915 MHz and a power level of 850 × 103 W/kg, resulting in an efficient process lasting 0.5 min. It was ultimately proven that the newly created hot-melt adhesive formulas can be entirely recycled and repurposed for similar bonding needs. Full article
(This article belongs to the Special Issue Smart Polymers and Composites: Multifunctionality and Recyclability)
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<p>Assembling/disassembling process under electromagnetic field (marked in red).</p> Full article ">Figure 2
<p>The control monitor of the injection machine for composites containing (<b>a</b>) Al and (<b>b</b>) Fe.</p> Full article ">Figure 3
<p>SEM images for Al-containing composites: (<b>a</b>) M1 and (<b>b</b>) M2.</p> Full article ">Figure 4
<p>SEM images for Fe-containing composites: (<b>a</b>) M3 and (<b>b</b>) M4.</p> Full article ">Figure 5
<p>XRF spectrum for M1.</p> Full article ">Figure 6
<p>XRF spectrum for M3.</p> Full article ">Figure 7
<p>Swelling degree for water.</p> Full article ">Figure 8
<p>Swelling degree for toluene.</p> Full article ">Figure 9
<p>Thermal characteristics obtained for M1.</p> Full article ">Figure 10
<p>Thermal characteristics obtained for M2.</p> Full article ">Figure 11
<p>Thermal characteristics obtained for M3.</p> Full article ">Figure 12
<p>Thermal characteristics obtained for M4.</p> Full article ">Figure 13
<p>Dielectric properties of Al-containing composites.</p> Full article ">Figure 14
<p>Dielectric properties of Fe-containing composites.</p> Full article ">Figure 15
<p>Comparative electromagnetic radiation attenuation of M1 and M3 composites.</p> Full article ">Figure 16
<p>Images of hot-melt composite M1: (<b>a</b>) before exposure and (<b>b</b>) after exposure to microwaves.</p> Full article ">Figure 17
<p>Heating characteristics at different power values (10<sup>3</sup> W/kg) of microwave exposure for hot-melt composites (<b>a</b>) M1 and (<b>b</b>) M2.</p> Full article ">Figure 18
<p>Heating characteristics at different power values (10<sup>3</sup> W/kg) of microwave exposure for hot-melt composites (<b>a</b>) M3 and (<b>b</b>) M4.</p> Full article ">Figure 19
<p>Heating efficiency of microwave exposure for hot-melt composites (<b>a</b>) at 570 × 10<sup>3</sup> W/kg power and (<b>b</b>) at 850 × 10<sup>3</sup> W/kg power.</p> Full article ">Figure 20
<p>Examples of bonding configuration: (<b>a</b>) LDPE + LDPE/M1; (<b>b</b>) PP + PP/M3.</p> Full article ">
16 pages, 15607 KiB  
Article
Vibration Welding of PLA/PHBV Blend Composites with Nanocrystalline Cellulose
by Patrycja Bazan, Barbara Kozub, Arif Rochman, Mykola Melnychuk, Paulina Majewska and Krzysztof Mroczka
Polymers 2024, 16(24), 3495; https://doi.org/10.3390/polym16243495 - 15 Dec 2024
Viewed by 377
Abstract
Thermoplastic composites have garnered significant attention in various industries due to their exceptional properties, such as recyclability and ease of molding. In particular, biocomposites, which combine biopolymers with natural fibers, represent a promising alternative to petroleum-based materials, offering biodegradability and reduced environmental impact. [...] Read more.
Thermoplastic composites have garnered significant attention in various industries due to their exceptional properties, such as recyclability and ease of molding. In particular, biocomposites, which combine biopolymers with natural fibers, represent a promising alternative to petroleum-based materials, offering biodegradability and reduced environmental impact. However, there is limited knowledge regarding the efficacy of joining PLA/PHBV-based biocomposites modified with nanocrystalline cellulose (NCC) using vibration welding, which restricts their potential applications. This study demonstrates that vibration welding enables efficient bonding of PLA/PHBV composites with NCC, resulting in strong, biodegradable, and environmentally friendly materials. The investigation revealed that the addition of nanocrystalline cellulose (NCC) at 5, 10, and 15 wt.% significantly enhanced the strength of welded joints, with the highest strength achieved at 15% NCC content. Microstructural analysis using scanning electron microscopy (SEM) and deformation studies with digital image correlation (DIC) indicated that a higher NCC content led to greater local deformation, reducing the risk of brittle fracture. Mechanical hysteresis tests confirmed the composites’ favorable resistance to variable loads, highlighting their stability and energy dissipation capabilities. Optimization of welding parameters, such as vibration amplitude, welding time, and pressure, is crucial for achieving optimal mechanical performance. These findings suggest that PLA/PHBV composites modified with NCC can be utilized as durable and eco-friendly materials in various industries, including automotive and packaging. This research presents new opportunities for the development of biodegradable high-strength materials that can serve as alternatives to traditional plastics. Full article
(This article belongs to the Section Biobased and Biodegradable Polymers)
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<p>Diagram of the produced samples: (<b>a</b>) injection sample diagram; (<b>b</b>) diagram of samples prepared for vibration welding.</p> Full article ">Figure 2
<p>Photograph of injected samples and samples after vibration welding.</p> Full article ">Figure 3
<p>Microstructure of manufactured composites: (<b>a</b>) PLA/PHBV; (<b>b</b>) 5%NCC; (<b>c</b>) 10%NCC; (<b>d</b>) 15%NCC.</p> Full article ">Figure 3 Cont.
<p>Microstructure of manufactured composites: (<b>a</b>) PLA/PHBV; (<b>b</b>) 5%NCC; (<b>c</b>) 10%NCC; (<b>d</b>) 15%NCC.</p> Full article ">Figure 4
<p>Example tension curves for the welded specimens.</p> Full article ">Figure 5
<p>Examples of DIC deformation maps for the tested joined samples.</p> Full article ">Figure 6
<p>First and twentieth hysteresis loops for welded PLA/PHBV composites.</p> Full article ">Figure 7
<p>Differences in energy dissipation between the first and twentieth load cycles.</p> Full article ">
16 pages, 10766 KiB  
Article
Investigating the Impact of Polymers on Clay Flocculation and Residual Oil Behaviour Using a 2.5D Model
by Xianda Sun, Yuchen Wang, Qiansong Guo, Zhaozhuo Ouyang, Chengwu Xu, Yangdong Cao, Tao Liu and Wenjun Ma
Polymers 2024, 16(24), 3494; https://doi.org/10.3390/polym16243494 - 14 Dec 2024
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Abstract
In the process of oilfield development, the surfactant–polymer (SP) composite system has shown significant effects in enhancing oil recovery (EOR) due to its excellent interfacial activity and viscoelastic properties. However, with the continuous increase in the volume of composite flooding injection, a decline [...] Read more.
In the process of oilfield development, the surfactant–polymer (SP) composite system has shown significant effects in enhancing oil recovery (EOR) due to its excellent interfacial activity and viscoelastic properties. However, with the continuous increase in the volume of composite flooding injection, a decline in injection–production capacity (I/P capacity) has been observed. Through the observation of frozen core slices, it was found that during the secondary composite flooding (SCF) process, a large amount of residual oil in the form of intergranular adsorption remained in the core pores. This phenomenon suggests that the displacement efficiency of the composite flooding may be affected. Research has shown that polymers undergo flocculation reactions with clay minerals (such as kaolinite, Kln) in the reservoir, leading to the formation of high-viscosity mixtures of migrating particles and crude oil (CO). These high-viscosity mixtures accumulate in local pores, making it difficult to further displace them, which causes oil trapping and negatively affects the overall displacement efficiency of secondary composite flooding (SCF). To explore this mechanism, this study used a microscopic visualization displacement model (MVDM) and microscopy techniques to observe the migration of particles during secondary composite flooding. By using kaolinite water suspension (Kln-WS) to simulate migrating particles in the reservoir, the displacement effects of the composite flooding system on the kaolinite water suspension, crude oil, and their mixtures were observed. Experimental results showed that the polymer, acting as a flocculant, promoted the flocculation of kaolinite during the displacement process, thereby increasing the viscosity of crude oil and affecting the displacement efficiency of secondary composite flooding. Full article
(This article belongs to the Section Polymer Applications)
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<p>Inter-particle adsorption of residual oil diagram.</p> Full article ">Figure 2
<p>Inter-particle adsorption of residual oil in (<b>a</b>) CT 3D image and (<b>b</b>) fluorescence photograph.</p> Full article ">Figure 3
<p>Flocculation diagram. (<b>a</b>) Kaolinite water suspension. (<b>b</b>) Formation of flocs. (<b>c</b>) Precipitation.</p> Full article ">Figure 4
<p>Experimental apparatus diagram. 1 Micro-injection pump. 2 Injection syringe. 3 Microscope. 4 Valve. 5 Micro-visualization model holder. 6 Micro-visualization model. 7 Heating plate. 8 Parallel light source. 9 Liquid recovery collection container. 10 Image acquisition computer.</p> Full article ">Figure 5
<p>Cast thin sheet. (<b>a</b>) Laser confocal scanning injection thin sheet; (<b>b</b>) vectorized image after vectorization by software(Imagine v1.7.1).</p> Full article ">Figure 6
<p>Microscopic displacement etching model.</p> Full article ">Figure 7
<p>Kaolinite aqueous suspension (30% concentration), transmitted light photograph, temperature 46 °C.</p> Full article ">Figure 8
<p>The oil displacement effect images from Experiment 1 are as follows. (<b>a</b>) Waterflooding (10 PV) transmitted light photograph. (<b>b</b>) Binary composite flooding (10 PV) transmitted light photograph. (<b>c</b>) Waterflooding (20 PV) transmitted light photograph. (<b>d</b>) Binary composite flooding (20 PV) transmitted light photograph.</p> Full article ">Figure 9
<p>The oil displacement effect images from Experiment 2 are as follows. (<b>a</b>) Binary composite flooding (10 PV) displacement effect. (<b>b</b>) Binary composite flooding (20 PV) displacement effect. (<b>c</b>) Binary composite flooding (80 PV) displacement effect.</p> Full article ">Figure 10
<p>The oil displacement effect images from Experiment 3 are as follows. (<b>a</b>) Binary composite flooding (10 PV) displacement effect. (<b>b</b>) Binary composite flooding (20 PV) displacement effect. (<b>c</b>) Binary composite flooding (80 PV) displacement effect.</p> Full article ">Figure 11
<p>The distribution of the mixed solution is shown as follows: (<b>a</b>) transmitted light photograph and (<b>b</b>) orthogonal light photograph.</p> Full article ">Figure 12
<p>The schematic of residual oil distribution types is as follows. 1 Pore surface film-type. 2 Grain adsorption-type. 3 Corner-type. 4 Throat-type. 5 Cluster-type. 6 Intergranular adsorption-type.</p> Full article ">Figure 13
<p>The residual oil distribution types are as follows. (<b>a</b>) Cluster-type. (<b>b</b>) Throat-type. (<b>c</b>) Pore surface film-type. (<b>d</b>) Corner-type. (The arrow points to the location where the residual oil is located).</p> Full article ">
16 pages, 2715 KiB  
Article
Anionic Oligo(ethylene glycol)-Based Molecular Brushes: Thermo- and pH-Responsive Properties
by Alexey Sivokhin, Dmitry Orekhov, Oleg Kazantsev, Ksenia Otopkova, Olga Sivokhina, Ilya Chuzhaykin, Ekaterina Spitsina and Dmitry Barinov
Polymers 2024, 16(24), 3493; https://doi.org/10.3390/polym16243493 - 14 Dec 2024
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Abstract
Anionic thermo- and pH-responsive copolymers were synthesized by photoiniferter reversible addition–fragmentation chain transfer polymerization (PI-RAFT). The thermo-responsive properties were provided by oligo(ethylene glycol)-based macromonomer units containing hydrophilic and hydrophobic moieties. The pH-responsive properties were enabled by the addition of 5–20 mol% of strong [...] Read more.
Anionic thermo- and pH-responsive copolymers were synthesized by photoiniferter reversible addition–fragmentation chain transfer polymerization (PI-RAFT). The thermo-responsive properties were provided by oligo(ethylene glycol)-based macromonomer units containing hydrophilic and hydrophobic moieties. The pH-responsive properties were enabled by the addition of 5–20 mol% of strong (2-acrylamido-2-methylpropanesulfonic) and weak (methacrylic) acids. Upon initiation by visible light at 470 nm and in the absence of radical initiators, yields from the ternary copolymers reached 94% in 2.5 h when the process was carried out in continuous flow mode using 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoic acid as a light-sensitive RAFT agent. The polymers were characterized using size exclusion chromatography, IR and NMR spectroscopy, and differential scanning calorimetry. The copolymers featured a sufficiently high molecular weight (93–146 kDa) consistent with theoretical values and satisfactory dispersities in the range of 1.18–1.45. The pH-responsive properties were studied in deionized water, saline, and buffer solutions. Dramatic differences in LCST behavior were observed in strong and weak acid-based polyelectrolytes. The introduction of sulfonic acid units, even in very small amounts, completely suppressed the LCST transition in deionized water while maintaining it in the saline and buffer solutions, with a negligible LCST dependence on the pH. In contrast, the incorporation of weak methacrylic acid demonstrated a pronounced pH dependence. The peculiarities of micelle formation in aqueous solutions were investigated and critical micelle concentrations and their ability to retain pyrene, a hydrophobic drug model, were determined. It was observed that anionic molecular brushes formed small micelles with aggregation numbers of 1–2 at concentrations in the order of 10−4 mg/mL. These micelles have a high ability to entrap pyrene, which makes them a promising tool for targeted drug delivery. Full article
(This article belongs to the Section Polymer Chemistry)
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<p>Starting materials used for molecular brush preparation.</p> Full article ">Figure 2
<p>Proposed mechanism of PI-RAFT polymerization.</p> Full article ">Figure 3
<p>The NMR spectrum of the copolymer. The enlarged region contains signals of the terminal methyl group of MOEGM, the methylene group of the alkyl moiety of AOEGM, and the methylene group of the RAFT agent to establish the molecular weight.</p> Full article ">Figure 4
<p>The IR spectra of AMPSA-containing molecular brushes. Sample designations are shown in <a href="#polymers-16-03493-t001" class="html-table">Table 1</a>. The enlarged region shows the carbonyl signals of the ester and amide groups, as well as a poorly visible shoulder associated with the δNH vibrations of the AMPSA amide group.</p> Full article ">Figure 5
<p>DSC thermograms for p(MPEGMA-AOEGM-AMPSA)s. Heating rate: 10 °C/min.</p> Full article ">Figure 6
<p>Turbidity curves at different pHs for copolymers containing AMPSA (<b>A</b>) and MAA (<b>B</b>).</p> Full article ">Scheme 1
<p>Schematic diagram for molecular brush synthesis.</p> Full article ">
16 pages, 2512 KiB  
Article
The Design of a Controlled-Release Polymer of a Phytopharmaceutical Agent: A Study on the Release in Different PH Environments Using the Ultrafiltration Technique
by Oscar G. Marambio, Alejandro Muñoz, Rudy Martin-Trasancos, Julio Sánchez and Guadalupe del C. Pizarro
Polymers 2024, 16(24), 3492; https://doi.org/10.3390/polym16243492 - 14 Dec 2024
Viewed by 338
Abstract
A series of hydrophilic copolymers were prepared using 2-hydroxyethyl methacrylate (HEMA) and itaconic acid (IA) from free radical polymerization at different feed monomer ratios using ammonium persulfate (APS) initiators in water at 70 °C. The herbicide 2,4-dichlorophenoxy acetic acid (2,4-D) was grafted to [...] Read more.
A series of hydrophilic copolymers were prepared using 2-hydroxyethyl methacrylate (HEMA) and itaconic acid (IA) from free radical polymerization at different feed monomer ratios using ammonium persulfate (APS) initiators in water at 70 °C. The herbicide 2,4-dichlorophenoxy acetic acid (2,4-D) was grafted to Poly(HEMA-co-IA) by a condensation reaction. The hydrolysis of the polymeric release system, Poly(HEMA-co-IA)-2,4-D, demonstrated that the release of the herbicide in an aqueous phase depends on the polymeric system’s pH value and hydrophilic character. In addition, the swelling behavior (Wt%) was studied at different pH values using Liquid-phase Polymer Retention (LPR) in an ultrafiltration system. The acid hydrolysis of the herbicide from the conjugates follows a first-order kinetic, showing higher kinetic constants as the pH increases. The base-catalyzed hydrolysis reaction of the herbicide follows a zero-order kinetic, where the basic medium acts as a catalyst, accelerating the release rate of the herbicide and showing higher kinetic constants as the pH increases. The differences in the release rates found for the hydrogel herbicide at different pH values can be correlated with the difference in their swelling capacity, where the release rate generally increases with an increase in the swelling capacity from water solution at higher pH values. The study of the release process revealed that all samples in distilled water at a pH of 10 are representative of agricultural systems. It showed first-order swelling kinetics and an absorption capacity that conforms to the parameters for hydrogels for agricultural applications, which supports their potential for these purposes. Full article
(This article belongs to the Special Issue Advanced Polymer Materials: Synthesis, Structure, and Properties)
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Full article ">Figure 1
<p>Synthetic route of the synthesis of the Poly(HEMA-co-IA) matrix.</p> Full article ">Figure 2
<p>Synthetic route of the esterification reaction of the Poly (HEMA-co-IA) -2,4- conjugate.</p> Full article ">Figure 3
<p>(<b>a</b>) UV-Vis spectrum of 2,4-D in CHCl<sub>3</sub>. (<b>b</b>) Calibration curve of herbicide 2,4-D.</p> Full article ">Figure 4
<p>(<b>a</b>) <sup>1</sup>H NMR spectrum of Poly (HEMA-co-IA) matrix and (<b>b</b>) Poly (HEMA-co-IA)-2,4D conjugate.</p> Full article ">Figure 5
<p>(<b>a</b>) Infrared spectra of P(HEMA-co-AI) matrix and (<b>b</b>) P(HEMA-co-AI) grafted with 2.4-D for a copolymer composition of 3.0:1.0.</p> Full article ">Figure 6
<p>The swelling capacity of poly(HEMA-co-IA) hydrogel with a copolymer composition of 75:25 mol-% was studied as a function of pH in buffered solutions at pH values of 3, 5.4, and 10 at room temperature (25 °C). Inserted images (<b>a</b>–<b>c</b>) of the hydrogel dry, at pH 5.4 and 10.</p> Full article ">Figure 7
<p>Release curves of herbicide using the P(HEMA-co-IA)-2,4-D hydrogel at different pH values.</p> Full article ">
25 pages, 12316 KiB  
Article
Accounting for the Structure–Property Relationship of Hollow-Fiber Membranes in Modeling Hemodialyzer Clearance
by Anton Kozmai, Mikhail Poroznyy, Violetta Gil, Dmitrii Butylskii, Dmitry Lopatin, Aleksey Rodichenko, Igor Voroshilov, Artem Mareev and Victor Nikonenko
Polymers 2024, 16(24), 3491; https://doi.org/10.3390/polym16243491 - 14 Dec 2024
Viewed by 257
Abstract
Abstract: The relevance of the hemodialysis procedure is increasing worldwide due to the growing number of patients suffering from chronic kidney disease [...] Full article
(This article belongs to the Section Polymer Membranes and Films)
20 pages, 7164 KiB  
Article
Development of Antimicrobial Blends of Bacteria Nanocellulose Derived from Plastic Waste and Polyhydroxybutyrate Enhanced with Essential Oils
by Everton Henrique Da Silva Pereira, Marija Nicevic, Eduardo Lanzagorta Garcia, Vicente Fróes Moritz, Zeliha Ece Ozcelik, Buket Alkan Tas and Margaret Brennan Fournet
Polymers 2024, 16(24), 3490; https://doi.org/10.3390/polym16243490 - 14 Dec 2024
Viewed by 399
Abstract
The escalating global concern regarding plastic waste accumulation and its detrimental environmental impact has driven the exploration of sustainable alternatives to conventional petroleum-based plastics. This study investigates the development of antimicrobial blends of bacterial nanocellulose (BNC) derived from plastic waste and polyhydroxyalkanoates (PHB), [...] Read more.
The escalating global concern regarding plastic waste accumulation and its detrimental environmental impact has driven the exploration of sustainable alternatives to conventional petroleum-based plastics. This study investigates the development of antimicrobial blends of bacterial nanocellulose (BNC) derived from plastic waste and polyhydroxyalkanoates (PHB), further enhanced with essential oils. The antimicrobial activity of the resulting BNC/PHB blends was tested in vitro against Escherichia coli, Staphylococcus aureus, and Candida albicans. The incorporation of essential oils, particularly cinnamon oil, significantly enhanced the antimicrobial properties of the BNC/PHB blends. The BNC with 5% PHB blend exhibited the highest antifungal inhibition against C. albicans at 90.25%. Additionally, blends with 2% and 10% PHB also showed antifungal activity, inhibiting 68% of C. albicans growth. These findings highlight the potential of incorporating essential oils into BNC/PHB blends to create effective antimicrobial materials. The study concludes that enhancing the antimicrobial properties of BNC/PHB significantly broadens its potential applications across various sectors, including wound dressings, nanofiltration masks, controlled-release fertilizers, and active packaging. Full article
(This article belongs to the Special Issue Advances in Cellulose-Based Polymers and Composites, 2nd Edition)
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<p>Antimicrobial activity of essential oils against (<b>A</b>) <span class="html-italic">E. coli</span>, (<b>B</b>) <span class="html-italic">S. aureus,</span> and (<b>C</b>) <span class="html-italic">C. albicans</span> in liquid culture. The absorbance values were measured at 530 nm for <span class="html-italic">S. aureus</span> and 630 nm for <span class="html-italic">E. coli</span> and <span class="html-italic">P. aeruginosa</span> after 24 h of incubation. The dashed lines represent the positive (red) and negative (green) controls, while the dotted line represents the MIC threshold, and triangles indicate the minimum inhibitory concentration (MIC) for each essential oil.</p> Full article ">Figure 2
<p>Zones of inhibition of examined essential oils against <span class="html-italic">E. coli</span> and <span class="html-italic">S. aureus</span> in a Ø 89.42 mm standard petri dish. Arrows represent the halo’s radius.</p> Full article ">Figure 3
<p>Antimicrobial activity of essential oils against <span class="html-italic">E. coli</span> and <span class="html-italic">S. aureus</span>. (<b>A</b>) Box plot of the antimicrobial activity of the essential oils (<b>B</b>) Heatmap of the antimicrobial activity of the essential oils against <span class="html-italic">E. coli</span> and <span class="html-italic">S. aureus</span>.</p> Full article ">Figure 4
<p>Visual and Physical Characteristics of BNC Blends with PHB (<b>top</b>) and PHA-enriched biomass (<b>bottom</b>), in a Ø 89.42 mm standard petri dish.</p> Full article ">Figure 5
<p>Materials 2.5D topographic simulations at 15× magnification of BNC (<b>A</b>), BPHB2 (<b>B</b>), BPHB5 (<b>C</b>), and BPHB10 (<b>D</b>).</p> Full article ">Figure 6
<p>SEM images and pore size distribution analysis of BNC/PHB blends. (<b>A</b>) BNC, (<b>B</b>) BPHB2, (<b>C</b>) BPHB5, and (<b>D</b>) BPHB10. SNOW algorithm segmentation of (<b>E</b>) BNC, (<b>F</b>) BPHB2, (<b>G</b>) BPHB5, and (<b>H</b>) BPHB10 from same figure from (<b>A</b>–<b>D</b>), respectively, which the color gradient visualizes pore size variation within and between materials red (largest pores) to blue/purple (smallest); (<b>I</b>) Cumulative pore size distributions of BNC/PHB blends.</p> Full article ">Figure 7
<p>Examples of stress-strain tensile curves obtained, grouped by color and duplicates differentiated by dashed and dotted lines.</p> Full article ">Figure 8
<p>TGA curves of examined BNC blends: BNC/PHB blends.</p> Full article ">Figure 9
<p>FT-IR spectra of examined BNC blends.</p> Full article ">Figure 10
<p>Microbial growth graph depicting cultures of <span class="html-italic">E. coli</span> (<b>A</b>), <span class="html-italic">S. aureus</span> (<b>B</b>), and <span class="html-italic">C. albicans</span> (<b>C</b>) as positive controls, alongside cultures growing in the presence of BNC-based blends with and without the addition of Cinnamon oil. Growth percentages are calculated relative to the average growth of the positive controls, set at 100%.</p> Full article ">Figure 11
<p>Effects of Bacterial Nanocellulose and BNC-PHB Composites on Microbial Biofilms. The samples in red indicate the absence of anti-biofilm activity.</p> Full article ">Figure 12
<p>Survival analysis of <span class="html-italic">C. elegans</span> AU37 exposed to BNC/PHB materials. Kaplan–Meier survival curves for (<b>A</b>) all experimental groups and (<b>B</b>) groups with statistically significant differences.</p> Full article ">
21 pages, 1339 KiB  
Review
Advancing the Physicochemical Properties and Therapeutic Potential of Plant Extracts Through Amorphous Solid Dispersion Systems
by Arif Budiman, Nur Parida Mahdhani Hafidz, Raden Siti Salma Azzahra, Salma Amaliah, Feggy Yustika Sitinjak, Agus Rusdin, Laila Subra and Diah Lia Aulifa
Polymers 2024, 16(24), 3489; https://doi.org/10.3390/polym16243489 - 14 Dec 2024
Viewed by 328
Abstract
Plant extracts demonstrate significant potential as a rich source of active pharmaceutical ingredients, exhibiting diverse biological activities and minimal toxicity. However, the low aqueous solubility of extracts and their gastrointestinal permeability, as well as their poor oral bioavailability, limit clinical advancements due to [...] Read more.
Plant extracts demonstrate significant potential as a rich source of active pharmaceutical ingredients, exhibiting diverse biological activities and minimal toxicity. However, the low aqueous solubility of extracts and their gastrointestinal permeability, as well as their poor oral bioavailability, limit clinical advancements due to drug delivery problems. An amorphous solid dispersion (ASD) delivers drugs by changing an active pharmaceutical ingredient (API) into an amorphous state to increase the solubility and availability of the API to the body. This research aimed to analyze and summarize the successful advancements of ASD systems derived from plant extracts, emphasizing characterization and the effects on dissolution and pharmacological activity. The results show that ASD systems improve phytoconstituent dissolution, bioavailability, and stability, in addition to reducing dose and toxicity. This research demonstrates the significance of ASD in therapeutic formulations to augment the pharmacological activities and efficacy of medicinal plant extracts. The prospects indicate promising potential for therapeutic applications utilizing ASD systems, alongside medicinal plant extracts for clinical therapy. Full article
(This article belongs to the Special Issue Sustainable Polymer Composites from Renewable Resources: Functionality and Applications)
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<p>Different preparations of ASD systems.</p> Full article ">Figure 2
<p>The speculated mechanism of the improvement of the bioavailability of plant extracts in ASD systems.</p> Full article ">
21 pages, 6018 KiB  
Article
Optimization of the Filament Winding Process for Glass Fiber-Reinforced PPS and PP Composites Using Box–Behnken Design
by Sevinc Orman, Mustafa Dogu and Belma Ozbek
Polymers 2024, 16(24), 3488; https://doi.org/10.3390/polym16243488 - 14 Dec 2024
Viewed by 346
Abstract
Filament winding is a widely used out-of-autoclave manufacturing technique for producing continuous fiber-reinforced thermoplastic composites. This study focuses on optimizing key filament winding process parameters, including heater temperature, roller pressure, and winding speed, to produce thermoplastic composites. Using Box–Behnken response surface methodology (RSM), [...] Read more.
Filament winding is a widely used out-of-autoclave manufacturing technique for producing continuous fiber-reinforced thermoplastic composites. This study focuses on optimizing key filament winding process parameters, including heater temperature, roller pressure, and winding speed, to produce thermoplastic composites. Using Box–Behnken response surface methodology (RSM), the study investigates the effects of these parameters on the compressive load of glass fiber-reinforced polypropylene (GF/PP) and polyphenylene sulfide (GF/PPS) composite cylinders. Mathematical models were developed to quantify the impact of each parameter and optimal processing conditions were identified across a wide temperature range, enhancing both manufacturing efficiency and the overall quality of the composites. This study demonstrates the potential of thermoplastic filament winding as a cost-effective and time-efficient alternative to conventional methods, addressing the growing demand for lightweight, high-performance, out-of-autoclave composites in industries such as aerospace, automotive, and energy. The optimized process significantly improved the performance and reliability of filament winding for various thermoplastic applications, offering potential benefits for industrial, aerospace, and other advanced sectors. The results indicate that GF/PPS composites achieved a compressive load of 3356.99 N, whereas GF/PP composites reached 2946.04 N under optimized conditions. It was also revealed that operating at elevated temperatures and reduced pressure levels enhances the quality of GF/PPS composites, while for GF/PP composites, maintaining lower temperature and pressure values is crucial for maximizing strength. Full article
(This article belongs to the Section Polymer Composites and Nanocomposites)
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<p>A schematic illustration of the thermoplastic filament winding system used in the present study.</p> Full article ">Figure 2
<p>An illustration of the winding pattern created in CADWIND<sup>®</sup>.</p> Full article ">Figure 3
<p>Filament winding system.</p> Full article ">Figure 4
<p>Filament-wound composites.</p> Full article ">Figure 5
<p>Flowchart of the experimental methodology.</p> Full article ">Figure 6
<p>Compression test setup.</p> Full article ">Figure 7
<p>Composite structure and test sampling.</p> Full article ">Figure 8
<p>Predicted vs. actual compressive load of GF/PPS and GF/PP composites.</p> Full article ">Figure 9
<p>The effects of (<b>a</b>) pressure and temperature, (<b>b</b>) winding speed and temperature, and (<b>c</b>) pressure and winding speed on the compressive load of GF/PPS composites produced by filament winding.</p> Full article ">Figure 9 Cont.
<p>The effects of (<b>a</b>) pressure and temperature, (<b>b</b>) winding speed and temperature, and (<b>c</b>) pressure and winding speed on the compressive load of GF/PPS composites produced by filament winding.</p> Full article ">Figure 10
<p>The effects of (<b>a</b>) pressure and temperature, (<b>b</b>) winding speed and temperature, and (<b>c</b>) pressure and winding speed on the compressive load of GF/PP composites produced by filament winding.</p> Full article ">Figure 10 Cont.
<p>The effects of (<b>a</b>) pressure and temperature, (<b>b</b>) winding speed and temperature, and (<b>c</b>) pressure and winding speed on the compressive load of GF/PP composites produced by filament winding.</p> Full article ">
12 pages, 3689 KiB  
Article
Modification of Processability and Shear-Induced Crystallization of Poly(lactic acid)
by Ruiqi Feng, Daisuke Kugimoto and Masayuki Yamaguchi
Polymers 2024, 16(24), 3487; https://doi.org/10.3390/polym16243487 - 14 Dec 2024
Viewed by 279
Abstract
We studied the rheological properties under both shear and elongational flow and crystallization behaviors after shear history for binary blends of poly(lactic acid) (PLA) and ethylene–vinyl acetate copolymer (EVA) with a slightly lower shear viscosity. EVA was immiscible with PLA and dispersed in [...] Read more.
We studied the rheological properties under both shear and elongational flow and crystallization behaviors after shear history for binary blends of poly(lactic acid) (PLA) and ethylene–vinyl acetate copolymer (EVA) with a slightly lower shear viscosity. EVA was immiscible with PLA and dispersed in droplets in the blend. The addition of EVA significantly reduced the shear viscosity, which is attributed to the interfacial slippage between PLA and EVA. In contrast, under elongational flow, the addition of EVA provided strain hardening in the transient elongational viscosity. Consequently, the degree of neck-in behavior in T-die extrusion, i.e., a decrease in the film width, was reduced with the high orientation of the PLA chains. Furthermore, it was found that the addition of EVA accelerated the shear-induced crystallization of PLA, although EVA showed no nucleating ability without a flow field. Because the EVA addition can improve the mechanical toughness, this modification technique is attractive for various industrial applications of PLA. Full article
(This article belongs to the Special Issue Biodegradable Polymers: Innovations in Processing, Diverse Applications, and Sustainable Solutions)
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<p>SEM image of the fractured surface of the PLA/EVA (70/30) film prepared by compression molding.</p> Full article ">Figure 2
<p>Differential scanning calorimetry (DSC) heating and cooling curves for the sample films prepared by compression molding. (<b>a</b>) Heating at 30 °C min<sup>−1</sup>, (<b>b</b>) cooling at 30 °C min<sup>−1</sup>, and (<b>c</b>) cooling at 2 °C min<sup>−1</sup>.</p> Full article ">Figure 3
<p>Temperature dependence of (closed symbols) tensile storage modulus <span class="html-italic">E′</span> and (open symbols) loss modulus <span class="html-italic">E″</span> at 10 Hz for (circles) PLA, (triangles) EVA, and (diamonds) PLA/EVA (70/30).</p> Full article ">Figure 4
<p>Angular frequency dependence of (closed symbols) shear storage modulus <span class="html-italic">G</span>’ and (open symbols) loss modulus <span class="html-italic">G</span>″ at 180 °C for (circles) PLA, (triangles) EVA, and (diamonds) PLA/EVA (70/30).</p> Full article ">Figure 5
<p>Flow curves evaluated by the capillary rheometer at 180 °C for (circles) PLA, (triangles) EVA, and (diamonds) PLA/EVA (70/30). The photograph of an EVA strand extruded at 1000 s<sup>−1</sup> is shown on the right.</p> Full article ">Figure 6
<p>Elongational viscosity <span class="html-italic">η<sub>E</sub></span><sup>+</sup> growth curves for PLA, EVA, and PLA/EVA (70/30) at 180 °C. The numerals in the figure represent the strain rates (s<sup>−1</sup>).</p> Full article ">Figure 7
<p>Extruded films under crossed polarizers.</p> Full article ">Figure 8
<p>Depolarized light intensity (DLI) growth curves for PLA and the blend obtained during cooling at 30 °C min<sup>−1</sup>. The samples had a shear history from 190 to 160 °C at various shear rates.</p> Full article ">Figure 9
<p>POM images of PLA and PLA/EVA (70/30) under crossed polarizers at 80 °C during cooling.</p> Full article ">
4 pages, 171 KiB  
Editorial
Fiber and Polymer Composites: Processing, Simulation, Properties and Applications II
by Zina Vuluga
Polymers 2024, 16(24), 3486; https://doi.org/10.3390/polym16243486 - 14 Dec 2024
Viewed by 341
Abstract
Compliance with EU legislation on the efficient use of fossil fuels and the reduction in emissions and environmental impact has led many sectors of industry to become interested in obtaining and using more sustainable polymer composites with improved lifetime, in the recovery and [...] Read more.
Compliance with EU legislation on the efficient use of fossil fuels and the reduction in emissions and environmental impact has led many sectors of industry to become interested in obtaining and using more sustainable polymer composites with improved lifetime, in the recovery and recycling of materials at the end of their life cycle, and in the use of renewable natural resources [...] Full article
(This article belongs to the Special Issue Fiber and Polymer Composites: Processing, Simulation, Properties and Applications II)
15 pages, 4924 KiB  
Article
Folic Acid-Targeted Mixed Pluronic Micelles for Delivery of Triptolide
by Meizhen Yin, Xinying Zhang, Tongguang Zhang, Zhiqiang Bao and Zhihui He
Polymers 2024, 16(24), 3485; https://doi.org/10.3390/polym16243485 - 13 Dec 2024
Viewed by 365
Abstract
The present study aimed to explore an ideal delivery system for triptolide (TPL) by utilizing the thin-film hydration method to prepare drug-loaded, folate-modified mixed pluronic micelles (FA–F-127/F-68–TPL). Scanning electron microscopy and atomic force microscopy showed that the drug-loaded micelles had a spherical shape [...] Read more.
The present study aimed to explore an ideal delivery system for triptolide (TPL) by utilizing the thin-film hydration method to prepare drug-loaded, folate-modified mixed pluronic micelles (FA–F-127/F-68–TPL). Scanning electron microscopy and atomic force microscopy showed that the drug-loaded micelles had a spherical shape with a small particle size, with an average of 30.7 nm. Cell viability experiments showed that FA–F-127/F-68–TPL significantly reduced HepG2 cell viability, exhibiting strong cytotoxicity. Its cytotoxicity was markedly enhanced compared with bare TPL. Nile red (Nr) was used as a model drug to prepare FA–F-127/F-68–Nr to further validate its tumor-targeting and cellular uptake capability. After coincubation with HepG2 cells, a multifunctional microplate reader showed that intracellular fluorescence intensity significantly increased, indicating that FA–F-127/F-68–Nr could more effectively enter the cells. A nude mouse model of subcutaneous hepatocellular carcinoma was constructed. Following tail vein injection of FA–F-127/F-68–Nr, the fluorescence imaging system showed that FA–F127/F-68–Nr could significantly target tumor tissue, and even if entering the small-sized tumor was challenging, it could be excreted through urine. Nude mice with subcutaneous hepatocellular carcinoma were treated with tail vein injections of FA–F-127/F-68–TPL (45 µg/kg) every other day for 21 days. The results showed that the growth of the transplanted tumors was significantly slowed, with no significant difference compared with bare TPL. In summary, the FA–F-127/F-68–TPL exhibits the advantages of low cost, excellent biological properties, active/passive targeting capabilities, notable cytotoxicity against liver cancer cells, and significant inhibition of transplanted hepatocellular carcinoma growth. Significantly, the FA–F-127/F-68–TPL, despite challenges in targeting tumors with an insignificant EPR effect, can be efficiently excreted via the kidneys, thereby preventing the release of the drug during prolonged circulation and potential damage to normal tissues. Therefore, FA–F-127/F-68–TPL represents a promising antitumor drug delivery system. Full article
(This article belongs to the Special Issue Biomedical Applications of Intelligent Hydrogel 2nd Edition)
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<p>Infrared spectra of FA–F-127/F-68–TPL, FA-F127/F-68, and TPL.</p> Full article ">Figure 2
<p>Morphology of the FA–F-127/F-68–TPL drug-loaded micelles: (<b>a</b>) SEM images; (<b>b</b>) AFM images.</p> Full article ">Figure 3
<p>Size distribution of the FA–F-127/F-68–TPL drug-loaded micelles: (<b>a</b>) FA–F-127/F-68–TPL; (<b>b</b>) FA–F-127/F-68.</p> Full article ">Figure 4
<p>Cell viability of HepG2 cells treated with FA–F-127/F-68–TPL: (<b>a</b>) treatment of HepG2 cells with different concentrations of FA–F-127/F-68–TPL for 24 h; (<b>b</b>) treatment of HepG2 cells with 100 ng/mL FA–F-127/F-68–TPL for 24, 48, and 72 h. * <span class="html-italic">p</span> &lt; 0.01 indicates significant difference.</p> Full article ">Figure 5
<p>Fluorescent imaging of whole-body and isolated organs of tumor-bearing mice after tail vein injection of FA–F-127/F-68–Nr. Order of organs: heart, liver, spleen, lung, kidney, pancreas, and tumor. (<b>a</b>–<b>d</b>) Fluorescence imaging of isolated tumor tissues and organs 1 h after injection: (<b>a</b>) control group, (<b>b</b>–<b>d</b>) FA–F-127/F-68–Nr group; tumor volume of approximately (<b>b</b>) 80 mm<sup>3</sup>, (<b>c</b>) 120 mm<sup>3</sup>, and (<b>d</b>) 500 mm<sup>3</sup>. (<b>e</b>–<b>h</b>) Whole-body fluorescent imaging when the tumor volume is approximately 500 mm<sup>3</sup>, (<b>e</b>) control group, 0.5 h after injection. (<b>f</b>–<b>h</b>) FA–F-127/F-68–Nr group; (<b>f</b>) 0.5 h, (<b>g</b>) 1 h, and (<b>h</b>) 2 h after injection. (<b>i</b>) The color from top to bottom indicates the fluorescence intensity level. Red and blue indicate the strongest and weakest fluorescence, respectively.</p> Full article ">Figure 6
<p>The fluorescence intensity values of HepG2 cells in each group. (<b>a</b>,<b>b</b>) HepG2 cells coincubated for 2 h with (<b>a</b>) FA–F-127/F-68 and F-127/F-68 and (<b>b</b>) FA–F-127/F-68–Nr and F-127/F-68–Nr. (<b>c</b>) HepG2 cells coincubated with 5 μg/mL FA–F-127/F-68–Nr.</p> Full article ">Figure 7
<p>Volume change curves of transplanted tumors in each group treated for 21 days.</p> Full article ">Figure 8
<p>Pathological results of liver cancer-transplanted tumors in the treatment group and model group.</p> Full article ">
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