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Synthesis, Characterization and Applications of Natural Polymers

A special issue of Polymers (ISSN 2073-4360). This special issue belongs to the section "Biobased and Biodegradable Polymers".

Deadline for manuscript submissions: closed (5 August 2024) | Viewed by 12546

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Faculdade de Engenharia, Universidade Federal da Grande Dourados—UFGD, Rodovia Dourados-Itahum, Km 12, Dourados 79804-970, MS, Brazil
Interests: natural polymers; antimicrobials; edible films; edible coatings
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Department of Materials Science and Engineering, Universitat Politècnica de Catalunya (UPC BarcelonaTech), 08222 Terrassa, Spain
Interests: edible packaging; edible coatings; food packaging; starch
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

This Special Issue of Polymers on the “Synthesis, Characterization, and Applications of Natural Polymers” is dedicated to the dissemination of relevant research articles that demonstrate advances in the area in this broad field. The production, characterization, and use of natural polymers have increased in recent years, and they are widely used in various fields of the pharmaceutical, food, medical, and cosmetic industries and in everyday life. To obtain these polymers, several modifications are carried out, to obtain the desired properties, in addition to being considered from renewable sources. It is my pleasure to invite you to submit your manuscript and contribute significantly to this edition.

Prof. Dr. Vitor Augusto dos Santos Garcia
Dr. Silvia Maria Martelli
Prof. Dr. Farayde Matta Fakhouri
Guest Editors

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Keywords

  • natural polymers
  • applications
  • polymer synthesis
  • films
  • delivery system
  • oral films

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Related Special Issue

Published Papers (7 papers)

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Research

19 pages, 24483 KiB  
Article
Oral Films Printed with Green Propolis Ethanolic Extract
by Leandro Neodini Remedio, Vitor Augusto dos Santos Garcia, Arina Lazaro Rochetti, Andresa Aparecida Berretta, Julieta Adriana Ferreira, Heidge Fukumasu, Fernanda Maria Vanin, Cristiana Maria Pedroso Yoshida and Rosemary Aparecida de Carvalho
Polymers 2024, 16(13), 1811; https://doi.org/10.3390/polym16131811 - 26 Jun 2024
Viewed by 1461
Abstract
Oral film (OF) research has intensified due to the effortless administration and advantages related to absorption in systemic circulation. Chitosan is one of the polymers widely used in the production of OFs; however, studies evaluating the maintenance of the active principles’ activity are [...] Read more.
Oral film (OF) research has intensified due to the effortless administration and advantages related to absorption in systemic circulation. Chitosan is one of the polymers widely used in the production of OFs; however, studies evaluating the maintenance of the active principles’ activity are incipient. Propolis has been widely used as an active compound due to its different actions. Printing techniques to incorporate propolis in OFs prove to be efficient. The objective of the present study is to develop and characterize oral films based on chitosan and propolis using printing techniques and to evaluate the main activities of the extract incorporated into the polymeric matrix. The OFs were characterized in relation to the structure using scanning and atomic force electron microscopy; the mechanical properties, disintegration time, wettability, and stability of antioxidant activity were evaluated. The ethanolic extract of green propolis (GPEE) concentration influenced the properties of the OFs. The stability (phenolic compounds and antioxidant activity) was reduced in the first 20 days, and after this period, it remained constant. Full article
(This article belongs to the Special Issue Synthesis, Characterization and Applications of Natural Polymers)
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Graphical abstract

Graphical abstract
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<p>Chitosan-based oral films with and without printing of green propolis ethanolic extract (GPEE): (<b>a</b>) without printing (control); (<b>b</b>) number of print layers = 1; (<b>c</b>) number of print layers = 2; (<b>d</b>) number of print layers = 3 (<b>e</b>) number of print layers = 4; (<b>f</b>) color parameters (chroma a*, chroma b* and luminosity); and (<b>g</b>) color difference (ΔE*). Note: NGPEE = number of GPEE-printed layers.</p>
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<p>Tensile strength (TS) and elongation (E) of chitosan-based oral films with and without the printing of green propolis ethanolic extract (GPEE). Note: NGPEE = number of GPEE-printed layers. Different letters indicate significant differences between the means (Tukey’s test, <span class="html-italic">p</span> &lt; 0.05).</p>
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<p>Effect of time on the contact angle of oral films based on chitosan-based oral films with and without printing of green propolis ethanolic extract (GPEE): (▼) without printing (control); (●) number of print layers = 1; (▲) number of print layers = 2; (????) number of print layers = 3 (⬟) number of print layers = 4.</p>
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<p>(<b>a</b>) Fourier transform infrared absorbance spectra of chitosan-based oral films and GPEE; (<b>b</b>) analytical deconvolution curves of chitosan-based oral films with four printed layers of GPEE (some deconvoluted analytical curves of GPEE and chitosan bands are highlighted in different colors under the FTIR absorption spectrum); (<b>c</b>) FTIR absorption spectra of chitosan-based oral films with and without green propolis ethanolic extract (GPEE) printing. Note: NGPEE = number of GPEE-printed layers.</p>
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<p>Stability over time of chitosan-based oral films with and without printing of green propolis ethanolic extract (GPEE): (<b>a</b>) concentration of total phenolic compounds (CTF); (<b>b</b>) antioxidant activity determined using the method of FRAP (AAFRAP) and (<b>c</b>) antioxidant activity determined using the oxygen radical absorbance capacity (AAORAC). Note: NGPEE = number of GPEE-printed layers. Different letters indicate significant differences between the means (Tukey’s test, <span class="html-italic">p</span> &lt; 0.05).</p>
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15 pages, 2106 KiB  
Article
Identification of Oil-Loving Cupriavidus necator BM3-1 for Polyhydroxyalkanoate Production and Assessing Contribution of Exopolysaccharide for Vegetable Oil Utilization
by Yuni Shin, Hyun Joong Kim, Tae-Rim Choi, Suk Jin Oh, Suwon Kim, Yeda Lee, Suhye Choi, Jinok Oh, So Yeon Kim, Young Sik Lee, Young Heon Choi, Shashi Kant Bhatia and Yung-Hun Yang
Polymers 2024, 16(12), 1639; https://doi.org/10.3390/polym16121639 - 10 Jun 2024
Cited by 2 | Viewed by 1004
Abstract
Polyhydroxyalkanoates (PHA) have received attention owing to their biodegradability and biocompatibility, with studies exploring PHA-producing bacterial strains. As vegetable oil provides carbon and monomer precursors for poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (P(3HB-co-3HHx)), oil-utilizing strains may facilitate PHA production. Herein, Cupriavidus necator BM3-1, which [...] Read more.
Polyhydroxyalkanoates (PHA) have received attention owing to their biodegradability and biocompatibility, with studies exploring PHA-producing bacterial strains. As vegetable oil provides carbon and monomer precursors for poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (P(3HB-co-3HHx)), oil-utilizing strains may facilitate PHA production. Herein, Cupriavidus necator BM3-1, which produces 11.1 g/L of PHB with 5% vegetable oil, was selected among various novel Cupriavidus necator strains. This strain exhibited higher preference for vegetable oils over sugars, with soybean oil and tryptone determined to be optimal sources for PHA production. BM3-1 produced 33.9 g/L of exopolysaccharides (EPS), which was three-fold higher than the amount produced by H16 (10.1 g/L). EPS exhibited 59.7% of emulsification activity (EI24), higher than that of SDS and of EPS from H16 with soybean oil. To evaluate P(3HB-co-3HHx) production from soybean oil, BM3-1 was engineered with P(3HB-co-3HHx) biosynthetic genes (phaCRa, phaARe, and phaJPa). BM3-1/pPhaCJ produced 3.5 mol% of 3HHx and 37.1 g/L PHA. BM3-1/pCB81 (phaCAJ) produced 32.8 g/L PHA, including 5.9 mol% 3HHx. Physical and thermal analyses revealed that P(3HB-co-5.9 mol% 3HHx) was better than PHB. Collectively, we identified a novel strain with high vegetable oil utilization capacity for the production of EPS, with the option to engineer the strain for P(3HB-co-3HHx). Full article
(This article belongs to the Special Issue Synthesis, Characterization and Applications of Natural Polymers)
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Figure 1
<p>Crude EPS extraction method. Simple scheme of crude EPS extraction method.</p>
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<p>Screening and identification of PHA-producing <span class="html-italic">Cupriavidus necator</span> strains. (<b>a</b>) Comparison of DCW and PHA production by nine <span class="html-italic">Cupriavidus necator</span> strains via GC analysis. Strains were cultured in <span class="html-italic">Ralstonia</span> minimal medium, with 1% fructose and 5% soybean oil. (<b>b</b>) Phylogenetic tree generated via 16S rRNA sequencing of <span class="html-italic">Cupriavidus necator</span> BM3-1.</p>
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<p>Optimal culture conditions for cell growth and PHA production. (<b>a</b>) Effects on cell growth and PHA production in carbon sources ranging from sugars to oils (glucose, fructose, sucrose, xylose, galactose, lactose, glycerol, soybean oil, and corn oil). (<b>b</b>) Comparison of growth and PHA production with different types of inorganic nitrogen sources (urea, NH<sub>4</sub>Cl, and (NH<sub>4</sub>)<sub>2</sub>SO<sub>4</sub>) and organic (beef extract, yeast extract, tryptone, and peptone) nitrogen sources.</p>
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<p>EPS composition analysis using GC-MS. Monosaccharide analysis using GC-MS through MSTFA derivatization.</p>
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<p>Characterization of crude EPS properties of BM3-1. (<b>a</b>) Emulsification activity of EPS. The 1% SDS and 1% EPS from H16 were used as controls. (<b>b</b>) Comparison of flocculation efficiency according to pH (pH 3 to 9).</p>
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<p>Fed-batch fermentation for P(3HB-co-3HHx) production using (<b>a</b>) BM3-1/pPhaCJ and (<b>b</b>) BM3-1/pCB81.</p>
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19 pages, 3738 KiB  
Article
Green Foaming of Biologically Extracted Chitin Hydrogels Using Supercritical Carbon Dioxide for Scaffolding of Human Osteoblasts
by Mariana Quintana-Quirino, Adriana Hernández-Rangel, Phaedra Silva-Bermudez, Julieta García-López, Víctor Manuel Domínguez-Hernández, Victor Manuel Araujo Monsalvo, Miquel Gimeno and Keiko Shirai
Polymers 2024, 16(11), 1569; https://doi.org/10.3390/polym16111569 - 1 Jun 2024
Viewed by 741
Abstract
Chitin is a structural polysaccharide abundant in the biosphere. Chitin possesses a highly ordered crystalline structure that makes its processing a challenge. In this study, chitin hydrogels and methanogels, prepared by dissolution in calcium chloride/methanol, were subjected to supercritical carbon dioxide (scCO2 [...] Read more.
Chitin is a structural polysaccharide abundant in the biosphere. Chitin possesses a highly ordered crystalline structure that makes its processing a challenge. In this study, chitin hydrogels and methanogels, prepared by dissolution in calcium chloride/methanol, were subjected to supercritical carbon dioxide (scCO2) to produce porous materials for use as scaffolds for osteoblasts. The control of the morphology, porosity, and physicochemical properties of the produced materials was performed according to the operational conditions, as well as the co-solvent addition. The dissolution of CO2 in methanol co-solvent improved the sorption of the compressed fluid into the hydrogel, rendering highly porous chitin scaffolds. The chitin crystallinity index significantly decreased after processing the hydrogel in supercritical conditions, with a significant effect on its swelling capacity. The use of scCO2 with methanol co-solvent resulted in chitin scaffolds with characteristics adequate to the adhesion and proliferation of osteoblasts. Full article
(This article belongs to the Special Issue Synthesis, Characterization and Applications of Natural Polymers)
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Figure 1
<p>Representative desorption curves for S<sub>A</sub> and S<sub>M</sub> (<b>A</b>,<b>B</b>) and mass loss of both materials due to CO<sub>2</sub> desorption (<b>C</b>,<b>D</b>) at 353 K and 175 bar. The dotted lines represent the fitted data.</p>
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<p>X-ray diffraction patterns of native chitin and chitin treated with scCO<sub>2</sub> (<b>A</b>) at 175 bar and 353 K using water (S<sub>A</sub>) and methanol (S<sub>M</sub>) as co-solvents, and (<b>B</b>) S<sub>M</sub> scaffolds obtained at different temperatures and pressures.</p>
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<p>Number of pores (<b>A</b>), average diameter (<b>B</b>), pore distribution (<b>C</b>), swelling (<b>D</b>) and erosion (<b>E</b>) for SCF-treated S<sub>A</sub> and S<sub>M</sub> samples at 353 K and 175 bar. Different letters mean statistically different results (Tukey–Kramer <span class="html-italic">p</span> ≤ 0.05).</p>
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<p>SEM micrographs of S<sub>M</sub> after scCO<sub>2</sub> (S: surface, T: transverse) (<b>A</b>). Average diameter (<b>B</b>) and distribution of the pores (<b>C</b>) at different temperatures and constant pressure (175 bar). The different letters in the histograms mean that they are statistically different (Tukey–Kramer <span class="html-italic">p</span> ≤ 0.05).</p>
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<p>SEM micrographs of S<sub>M</sub> after scCO<sub>2</sub> (S: surface, T: transverse) (<b>A</b>), average diameter (<b>B</b>), and distribution of the pores (<b>C</b>) at different pressures and constant temperature (353 K). The different letters in the histogram mean that they are statistically different (Tukey–Kramer <span class="html-italic">p</span> ≤ 0.05).</p>
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<p>Stress–strain curves for SCF-treated S<sub>A</sub> and S<sub>M</sub> samples at 353 K and 175 bar (<b>A</b>) and for S<sub>M</sub> samples at different temperature (<b>B</b>) and pressure (<b>C</b>) conditions.</p>
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<p>Proliferation of human osteoblasts cultured in scCO<sub>2</sub>-mediated porous chitin S<sub>M</sub> and S<sub>A</sub> scaffolds. Different letters in the histogram at the same days of cell culture mean that they were statistically different (Tukey–Kramer <span class="html-italic">p</span> ≤ 0.05).</p>
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<p>Cell viability of human osteoblasts cultured for 14 days in scCO<sub>2</sub>-mediated porous chitin S<sub>M</sub> and S<sub>A</sub> scaffolds. Shown from front (surface) and side (cell penetration) views (<b>A</b>). Viable cells are shown in green, while non-viable cells are shown in red. SEM micrographs of human osteoblasts (white arrows) cultured on scCO<sub>2</sub>-mediated porous chitin S<sub>A</sub> (<b>B</b>) and S<sub>M</sub> (<b>C</b>) scaffolds after 21 days of cell culture. Representative H&amp;E staining micrographs showing the cell nuclei (white arrows) of human osteoblasts monolayers on scCO<sub>2</sub>-mediated porous chitin S<sub>A</sub> (<b>D</b>) and S<sub>M</sub> (<b>E</b>) scaffolds after 14 days of cell culture.</p>
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22 pages, 5929 KiB  
Article
Development of Polylactic Acid Films with Alkali- and Acetylation-Treated Flax and Hemp Fillers via Solution Casting Technique
by Anamol Pokharel, Kehinde James Falua, Amin Babaei-Ghazvini, Mostafa Nikkhah Dafchahi, Lope G. Tabil, Venkatesh Meda and Bishnu Acharya
Polymers 2024, 16(7), 996; https://doi.org/10.3390/polym16070996 - 5 Apr 2024
Cited by 1 | Viewed by 1682
Abstract
This study aims to enhance value addition to agricultural byproducts to produce composites by the solution casting technique. It is well known that PLA is moisture-sensitive and deforms at high temperatures, which limits its use in some applications. When blending with plant-based fibers, [...] Read more.
This study aims to enhance value addition to agricultural byproducts to produce composites by the solution casting technique. It is well known that PLA is moisture-sensitive and deforms at high temperatures, which limits its use in some applications. When blending with plant-based fibers, the weak point is the poor filler–matrix interface. For this reason, surface modification was carried out on hemp and flax fibers via acetylation and alkaline treatments. The fibers were milled to obtain two particle sizes of <75 μm and 149–210 μm and were blended with poly (lactic) acid at different loadings (0, 2.5%, 5%, 10%, 20%, and 30%) to form a composite film The films were characterized for their spectroscopy, physical, and mechanical properties. All the film specimens showed C–O/O–H groups and the π–π interaction in untreated flax fillers showed lignin phenolic rings in the films. It was noticed that the maximum degradation temperature occurred at 362.5 °C. The highest WVPs for untreated, alkali-treated, and acetylation-treated composites were 20 × 10−7 g·m/m2 Pa·s (PLA/hemp30), 7.0 × 10−7 g·m/m2 Pa·s (PLA/hemp30), and 22 × 10−7 g·m/m2 Pa·s (PLA/hemp30), respectively. Increasing the filler content caused an increase in the color difference of the composite film compared with that of the neat PLA. Alkali-treated PLA/flax composites showed significant improvement in their tensile strength, elongation at break, and Young’s modulus at a 2.5 or 5% filler loading. An increase in the filler loadings caused a significant increase in the moisture absorbed, whereas the water contact angle decreased with an increasing filler concentration. Flax- and hemp-induced PLA-based composite films with 5 wt.% loadings showed a more stable compromise in all the examined properties and are expected to provide unique industrial applications with satisfactory performance. Full article
(This article belongs to the Special Issue Synthesis, Characterization and Applications of Natural Polymers)
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Figure 1

Figure 1
<p>(<b>a</b>) Flax and (<b>b</b>) hemp (adapted from [<a href="#B5-polymers-16-00996" class="html-bibr">5</a>]). Scalebar: 1 cm.</p>
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<p>FTIR spectra of fillers and films. Flax fiber and hemp fiber (<b>a</b>–<b>d</b>). Control and composites containing treated and untreated fibers (<b>e</b>–<b>j</b>).</p>
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<p>High-resolution XPS spectra. Signal assessments of different binding energies of (<b>a</b>) untreated flax, (<b>b</b>) untreated hemp, (<b>c</b>) alkali-treated flax, (<b>d</b>) alkali-treated hemp, (<b>e</b>) acetylated flax, and (<b>f</b>) acetylated hemp.</p>
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<p>TGA and DTG of PLA/flax and PLA/hemp films with (<b>a1</b>,<b>a2</b>) alkali treatment and (<b>b1</b>,<b>b2</b>) acetylation treatment.</p>
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<p>Color of PLA/flax and PLA/hemp films. Red dashed line was the neat PLA as the control sample.</p>
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<p>Water contact angle: (<b>a</b>) untreated flax/PLA, (<b>b</b>) alkali-treated flax/PLA, (<b>c</b>) acetylation-treated flax/PLA (green dashed line), (<b>d</b>) untreated hemp/PLA, (<b>e</b>) alkali-treated hemp/PLA, and (<b>f</b>) acetylation-treated hemp/PLA (green dashed line).</p>
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<p>Moisture absorption of PLA/flax (<b>a</b>,<b>b</b>) and of PLA/hemp (<b>c</b>,<b>d</b>) films. The bar chart represents the difference between untreated, alkali-treated, and acetylation-treated fibers loaded into the PLA films.</p>
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<p>WVP of PLA/flax and PLA/hemp films. (<b>a</b>) PLA/Flax Particle size &lt; 75 μm, (<b>b</b>) Particle size 149–210 μm, (<b>c</b>) PLA/Hemp Particle size &lt; 75 μm, (<b>d</b>) Particle size 149-210 μm.</p>
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<p>Mechanical characteristics of PLA/flax films. Particle size &lt; 75 μm: (<b>a</b>) tensile strength, (<b>c</b>) elongation at break, and (<b>e</b>) Young’s modulus. Particle size 149–210 μm: (<b>b</b>) tensile strength, (<b>d</b>) elongation at break, and (<b>f</b>) Young’s modulus. Particle size &lt; 75 μm: (<b>g</b>) stress–strain curves of PLA/flax films.</p>
Full article ">Figure 9 Cont.
<p>Mechanical characteristics of PLA/flax films. Particle size &lt; 75 μm: (<b>a</b>) tensile strength, (<b>c</b>) elongation at break, and (<b>e</b>) Young’s modulus. Particle size 149–210 μm: (<b>b</b>) tensile strength, (<b>d</b>) elongation at break, and (<b>f</b>) Young’s modulus. Particle size &lt; 75 μm: (<b>g</b>) stress–strain curves of PLA/flax films.</p>
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<p>Mechanical characteristics of PLA/hemp films. Particle size &lt; 75 μm: (<b>a</b>) tensile strength, (<b>c</b>) elongation at break, (<b>e</b>) Young’s modulus. Particle size &lt; 149–210 μm: (<b>b</b>) tensile strength, (<b>d</b>) elongation at break, (<b>f</b>) Young’s modulus. Particle size &lt; 75 μm: (<b>g</b>) stress–strain curves of PLA/hemp films.</p>
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<p>A chart displaying the properties of natural and synthetic materials is presented, with Young’s modulus plotted (adapted and modified from [<a href="#B4-polymers-16-00996" class="html-bibr">4</a>]). Values obtained in this study are denoted by stars.</p>
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21 pages, 5304 KiB  
Article
Influence of Alkali Treatment of Jatropha Curcas L. Filler on the Service Life of Hybrid Adhesive Bonds under Low Cycle Loading
by Viktor Kolář, Petr Hrabě, Miroslav Müller, Monika Hromasová, David Herák and Hadi Sutanto
Polymers 2023, 15(2), 395; https://doi.org/10.3390/polym15020395 - 12 Jan 2023
Cited by 2 | Viewed by 1707
Abstract
The aim of this research was to evaluate the effect of untreated and 5% aqueous NaOH solution-treated filler of the plant Jatropha Curcas L. on the mechanical properties of adhesive bonds, especially in terms of their service life at different amplitudes of cyclic [...] Read more.
The aim of this research was to evaluate the effect of untreated and 5% aqueous NaOH solution-treated filler of the plant Jatropha Curcas L. on the mechanical properties of adhesive bonds, especially in terms of their service life at different amplitudes of cyclic loading. As a result of the presence of phorbol ester, which is toxic, Jatropha oilseed cake cannot be used as livestock feed. The secondary aim was to find other possibilities for the utilization of natural waste materials. Another use is as a filler in polymer composites, that is, in composite adhesive layers. The cyclic loading of the adhesive bonds was carried out for 1000 cycles in two amplitudes, that is, 5–30% of the maximum force and 5–50% of the maximum force, which was obtained by the static tensile testing of the adhesive bonds with unmodified filler. The static tensile test showed an increase in the shear strength of the adhesive bonds with alkali-treated filler compared to the untreated filler by 3–41%. The cyclic test results did not show a statistically significant effect of the alkaline treatment of the filler surface on the service life of the adhesive bonds. Positive changes in the strain value between adhesive bonds with treated and untreated filler were demonstrated at cyclic stress amplitudes of 5–50%. SEM analysis showed the presence of interlayer defects in the layers of the tested materials, which are related to the oil-based filler used. Full article
(This article belongs to the Special Issue Synthesis, Characterization and Applications of Natural Polymers)
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<p>Soxhlet apparatus.</p>
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<p>Oilseed cakes from Jatropha Curcas L. (filler) before and after alkaline surface treatment.</p>
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<p>Scheme of adhesive bond according to EN 1465 [<a href="#B52-polymers-15-00395" class="html-bibr">52</a>].</p>
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<p>Jaws of LABTest 5.50 ST: (<b>A</b>): detailed view of the sample; (<b>B</b>): distance sheet to compensate for the bending moment of the adherend.</p>
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<p>Principle of low cycle loading of adhesive bonds.</p>
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<p>Static tensile test—shear tensile strength.</p>
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<p>Static tensile test—strain.</p>
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<p>Strength results after cyclic loading of adhesive bonds with a composite adhesive layer.</p>
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<p>Strain results after cyclic loading of adhesive bonds with a composite adhesive layer.</p>
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<p>Quasi-static curves of the J_NaOH adhesive bond at a cyclic loading amplitude of 5–30% and 5–50%.</p>
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<p>SEM analysis of a cross-section of a hybrid adhesive layer with C-filler (SE detector Oxford): (<b>A</b>): Cross-section of a hybrid adhesive bond with C-filler (MAG 250×), (<b>B</b>): Interaction between hybrid adhesive layer and adherend (MAG 3000×), (<b>C</b>): Interaction between C-filler and resin (MAG 3000×), (<b>D</b>): Cross-section of hybrid adhesive bond with filler C_NaOH (MAG 250×), (<b>E</b>): Interaction between hybrid adhesive layer and adherend (MAG 3000×), (<b>F</b>): Interaction between filler C_NaOH and resin (MAG 3000×).</p>
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<p>SEM analysis of a cross-section of a hybrid adhesive layer with S-filler (SE detector Oxford): (<b>A</b>): Cross-section of a hybrid adhesive layer with S-filler (MAG 250×), (<b>B</b>): Interaction between S-filler and resin (MAG 1500×), (<b>C</b>): Interaction between hybrid adhesive layer and adherend (MAG 1000×), (<b>D</b>): Cross section of a hybrid adhesive bond with S_NaOH (MAG 250×), (<b>E</b>): Interaction between S_NaOH (MAG 1500×), (<b>F</b>): Interaction between hybrid adhesive layer and adherend (MAG 1000×).</p>
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<p>SEM analysis of the cross-section of the hybrid adhesive layer with J filler (SE detector Oxford): (<b>A</b>): Cross section of the hybrid adhesive layer with filler J (MAG 250×), (<b>B</b>): Interaction between J filler and resin (MAG 1000×), (<b>C</b>): Interaction between hybrid adhesive layer and adherend (MAG 3000×), (<b>D</b>): Cross-section of hybrid adhesive bond with filler J_NaOH (MAG 250×), (<b>E</b>): Interaction between filler J_NaOH and resin (MAG 1000×), (<b>F</b>): Interaction between hybrid adhesive layer and adherend (MAG 3000×).</p>
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<p>SEM analysis of a cross section of a hybrid J-filler adhesive layer after 1000 cycles at a load cycle test of 5–50% (Oxford SE detector): (<b>A</b>): Cross-section of hybrid adhesive bond with J-based filler (MAG 250×), (<b>B</b>): Interaction between adherend and hybrid adhesive layer (MAG 1000×), (<b>C</b>): Detail of the interaction between the hybrid adhesive layer and the adherend (MAG 3000×), (<b>D</b>): Cross-section of hybrid adhesive bond with filler J_NaOH (MAG 250×), (<b>E</b>): Interaction between adherend and hybrid adhesive layer (filler J_NaOH and resin) (MAG 1000×), (<b>F</b>): Detail of the interaction between the hybrid adhesive layer and adherend (MAG 3000×).</p>
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12 pages, 4332 KiB  
Article
Comparison of the Degree of Acetylation of Chitin Nanocrystals Measured by Various Analysis Methods
by Murat Yanat, Ivanna Colijn, Kieke de Boer and Karin Schroën
Polymers 2023, 15(2), 294; https://doi.org/10.3390/polym15020294 - 6 Jan 2023
Cited by 10 | Viewed by 2958
Abstract
Chitin and its derivate chitosan have versatile properties and have been used in various applications. One key parameter determining the functionality of chitin-based materials is the degree of acetylation (DA). For DA determination, NMR and FTIR spectroscopy are often considered to be the [...] Read more.
Chitin and its derivate chitosan have versatile properties and have been used in various applications. One key parameter determining the functionality of chitin-based materials is the degree of acetylation (DA). For DA determination, NMR and FTIR spectroscopy are often considered to be the gold standard, but these techniques may not always be available and are rather time-consuming and costly. The first derivative UV method has been suggested, although accurate measurements can be challenging for materials with high degrees of acetylation, due to hydroxymethylfurfural (HMF) formation and other side reactions occurring. In this paper, we re-evaluated the first derivate UV method for chitin and chitosan powder, chitin nanocrystals, and deacetylated chitin nanocrystals. Our results showed that the first derivative UV method is capable of measuring DA with high accuracy (>0.9), leading to values comparable to those obtained by 1H NMR, 13C NMR, and FTIR. Moreover, by-product formation could either be suppressed by selecting the proper experimental conditions, or be compensated. For chitin nanocrystals, DA calculation deviations up to 20% due to by-product formation can be avoided with the correction that we propose. We conclude that the first derivative UV method is an accessible method for DA quantification, provided that sample solubility is warranted. Full article
(This article belongs to the Special Issue Synthesis, Characterization and Applications of Natural Polymers)
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<p>Background absorbance at λ = 310 nm for chitin and chitosan powder, chitin nanocrystals (ChNC), and deacetylated chitin nanocrystals (D-ChNC); measured (<b>A</b>) during solubilization (no incubation), (<b>B</b>) after 24 h incubation at 20 °C; and (<b>C</b>) after 24 h incubation at 55 °C. (UV-vis spectra of samples can be found in <a href="#app1-polymers-15-00294" class="html-app">Appendix</a> <a href="#polymers-15-00294-f0A6" class="html-fig">Figure A6</a>, <a href="#polymers-15-00294-f0A7" class="html-fig">Figure A7</a> and <a href="#polymers-15-00294-f0A8" class="html-fig">Figure A8</a>).</p>
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<p>Pictures of chitin powder dispersed in 85% phosphoric acid at different times. After 30 min of solubilization, the sample still looked turbid, but after 60 min the sample seems completely dissolved and no particles could be observed with the naked eye, although there was a background signal.</p>
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<p>HMF formation upon solubilization of ChNC and its effect on the measured degree of acetylation (samples incubated for 24 h).</p>
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<p>Chemical reaction for chitin deacetylation.</p>
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<p>Calibration curve first derivative UV method; the average of three measurements is shown; error bars are indicated but mostly fall within the data points.</p>
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<p><sup>13</sup>C NMR spectra for chitin powder, chitosan powder, chitin nanocrystals (ChNC), and deacetylated chitin nanocrystals (D-ChNC).</p>
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<p>FTIR spectra for chitin powder, chitosan powder, chitin nanocrystals (ChNC) and deacetylated chitin nanocrystals (D-ChNC).</p>
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<p>The measured DA of samples during solubilization (no incubation).</p>
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<p>The UV-Vis spectra of samples during solubilization (no incubation). (<b>A</b>); chitin powder, (<b>B</b>); chitosan powder, (<b>C</b>); chitin nanocrystals (ChNC), (<b>D</b>); deacetylated chitin nanocrystals (D-ChNC).</p>
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<p>The UV-Vis spectra of samples during solubilization (no incubation). (<b>A</b>); chitin powder, (<b>B</b>); chitosan powder, (<b>C</b>); chitin nanocrystals (ChNC), (<b>D</b>); deacetylated chitin nanocrystals (D-ChNC).</p>
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<p>The UV-Vis spectra of samples after 24 h incubation at 20 °C. (<b>A</b>) chitin powder, (<b>B</b>); chitosan powder, (<b>C</b>) chitin nanocrystals (ChNC), (<b>D</b>) deacetylated chitin nanocrystals (D-ChNC).</p>
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<p>The UV-Vis spectra of samples after 24 h incubation at 55 °C. (<b>A</b>) chitin powder, (<b>B</b>) chitosan powder, (<b>C</b>) chitin nanocrystals (ChNC), (<b>D</b>) deacetylated chitin nanocrystals (D-ChNC).</p>
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10 pages, 2585 KiB  
Article
Assessment of Acute Oral Toxicity of Thiolated Gum Ghatti in Rats
by Vivek Puri, Ameya Sharma, Pradeep Kumar, Kamal Dua, Kampanart Huanbutta, Inderbir Singh and Tanikan Sangnim
Polymers 2022, 14(18), 3836; https://doi.org/10.3390/polym14183836 - 14 Sep 2022
Cited by 5 | Viewed by 2075
Abstract
Various drug delivery systems were developed using a modified form of gum ghatti. Modifying gum ghatti using thioglycolic acid improves its mucoadhesive property, and hence, it is a suitable approach for the fabrication and development of controlled drug delivery systems. In accordance with [...] Read more.
Various drug delivery systems were developed using a modified form of gum ghatti. Modifying gum ghatti using thioglycolic acid improves its mucoadhesive property, and hence, it is a suitable approach for the fabrication and development of controlled drug delivery systems. In accordance with regulatory guidelines, namely, the Organization for Economic Co-operation and Development’s (OECD) 423 guidelines, an acute oral dose toxicity study was performed to examine the toxicological effects of gum ghattiin an animal (Wistar rat) after a single oral dose administration of pure gum ghatti and thiolated gum ghatti. Orally administered pure and thiolated gum ghatti do not reveal any considerable change in the behavioral pattern, food intake, body weight, hematology, or clinical symptoms of treated animals. Furthermore, histopathological studies showed no pathological mutations in the vital organs of Wistar rats after the oral administration of single doses of both types of gumghatti (i.e., 300 mg/kg and 2000 mg/kg body weight). Whole blood clotting studies showed the low absorbance value of the modified gum (thiolated gum ghatti) in contrast to the pure gum and control, hence demonstrating its excellent clotting capability. The aforementioned toxicological study suggested that the oral administration of a single dose of pure and thiolated gum ghatti did not produce any toxicological effects in Wistar rats. Consequently, it could be a suitable and safe candidate for formulating various drug delivery systems. Full article
(This article belongs to the Special Issue Synthesis, Characterization and Applications of Natural Polymers)
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<p>Diagrammatic representation of synthesis of thiolated gum ghatti using thioglycolic acid.</p>
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<p>Treatment schedule procedure, as per the OECD’s 423 guidelines, with a starting dose of 300 mg/kg body weight; 0, 1, 2, 3 represents the number of moribund or dead animals at each step.</p>
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<p>Photomicrographs of the histopathological examination of small, transverse portions of Wistar rat tissues, including the brain, heart, intestine, kidney, lungs, liver, pancreas, spleen, and stomach. Column 1: Control; Column 2: Pure gum ghatti (300 mg/kg body weight); Column 3: Thiolated gum ghatti (300 mg/kg body weight); Column 4: Pure gum ghatti (2000 mg/kg body weight); Column 5: Thiolated gum ghatti (2000 mg/kg body weight).</p>
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<p>Bar graphic representation of the hemoglobin absorbance of whole blood with respect to pure polymers and thiolated polymers; ‘a’ represents <span class="html-italic">p</span> &lt; 0.05 vs. whole blood. Data were analyzed using student’s <span class="html-italic">t</span>-Test.</p>
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