Search Results (938)

Fiber reinforcement offers a promising solution to improve the mechanical performance and durability of cement-based foam backfill (CFB), addressing critical issues such as brittleness and poor crack resistance under high-stress conditions. This study investigates the effects of polypropylene and polyacrylonitrile fibers, at varying contents and lengths, on the mechanical and flow properties of CFB. A series of experiments, including slump tests, rheology analysis, uniaxial compressive strength (UCS) tests, pore structure analysis, and scanning electron microscopy (SEM), were conducted to comprehensively evaluate fiber reinforcement mechanisms. The results show that increasing fiber content and length reduced fluidity due to fiber entanglement, while significantly enhancing mechanical properties through anchoring effects and network formation. After 28 days of curing, UCS increased by 208.2% with 2 wt% polypropylene fibers and 215.3% with 1 wt% polyacrylonitrile fibers (both at 6 mm length). Fiber-reinforced CFB demonstrated improved structural integrity and crack resistance, with failure modes transitioning from brittle to ductile. These findings highlight the potential of fiber-reinforced CFB to deliver durable, crack-resistant, and efficient mine backfill solutions, contributing to enhanced safety and sustainability in underground mining operations. Full article

Reflective thermal insulation layers can offer an energy-efficient strategy for preventing temperature rises by reflecting sunlight on surfaces. Our previous study presented a novel solvent-based method to prepare porous polypropylene (PP) with high solar reflectivity. However, the stiffness and strength of the neat porous PP were insufficient for thermal insulation applications, as mechanical loads from installation and environmental factors limit the applicability of such products. This paper addresses this gap by applying our solvent-based surface modification technology to glass fiber (GF)-reinforced PP composite sheets, creating a previously unexplored system. While the enhanced modulus and strength aligned with expectations, the micro- and nano-structured porous outer layers situated below the skin layer of the sheets, the refractive index mismatch between the PP matrix and the GF, and the size of the GF delivered a notable advancement in reflective thermal insulation performance. The combined effect of 30 wt% GF, nucleating agents, and surface modification resulted in a highly porous surface layer featuring spherulite sizes of 0.5–2.0 μm. With these combined effects, we achieved a modulus value of ~4 GPa, a tensile strength of 60 MPa, and an average solar reflectance of up to 94%. Thermal insulation performance measurements demonstrated that the registered inner temperature was lower by 24.1 °C compared to neat PP sheets. These combined effects demonstrate the potential of our solvent-based surface modification technology to develop cost-effective, porous PP composite sheets for efficient reflective thermal insulation. Full article

This paper addresses the analysis of compressive stress limit values of plastic components with a thickness of no more than 3 mm used in bolted joints, especially in the automotive industry. The results of the compression tests show that the compressive stress limit values often exceed the tensile stress limit values specified in the material data sheets, which has a significant impact on the way in which reliable bolted joints are designed without the risk of plastic deformation. In addition to compression tests, stress tests involving axial force and torque (combined load typical for bolted joints) were also performed. Th results of both types of tests were compared in the final table, involving a comparison of yield strength under compression and yield strength under a combined load with yield strength and/or stress at break from material data sheets, estimated using tensile stress tests. Various plastic materials were tested, including Acrylonitrile Butadiene Styrene (ABS), Polyamide (PA), Polyoxymethylene (POM), Polypropylen (PP) and the glass fiber-reinforced materials. The tests showed that it is possible to exceed the tensile stress limit in material data sheets by 5 to 10% without plastic deformation and by approximately 50%, in some cases by 280%, when loading by pure compression. Considering the combined load, the compressive stress limit values are within the range of 95 to 224% of tensile stress limits. The results of the study contribute to the optimization of the plastic tightened components design and reduce the need for excessive testing in automotive production. Full article

In recent years, wind energy has emerged as one of the fastest-growing green technologies globally, with projections indicating that decommissioned wind turbine blades (WTBs) will accumulate to millions of tons by the 2030s. Due to their thermosetting nature and high glass/carbon fiber content, the efficient recycling of WTBs remains a challenge. In this study, we utilized solid-state shear milling (S3M) to produce a fine WTB powder, which then underwent surface modification with a silane coupling agent (KH550), and we subsequently fabricated WTB-reinforced polypropylene (PP) composites with enhanced mechanical performance through solid-state stretching. The stretching-process-induced orientation of the PP molecular chains and glass fibers led to orientation-induced crystallization of PP and significant improvements in the mechanical properties of the PP/WTB@550 composites. With 30 wt. % WTB content, the PP/WTB@550 composite achieved a tensile strength of 142.61 MPa and a Young’s modulus of 3991.19 MPa at a solid-state stretching temperature of 110 °C and a stretching ratio of 3, representing increases of 268% and 471%, respectively, compared to the unstretched sample. This work offers both theoretical insights and experimental evidence supporting the high-value recycling and reuse of WTBs through a cost-effective, environmentally friendly, and scalable approach. Due to the enhanced mechanical properties of the PP/WTB composite and the intrinsic waterproofing and corrosion resistance of PP, it is hoped that such a composite would be used in road engineering and building materials, such as geogrids, wall panels, floor boards, and floor tiles. Full article

The increasing global emphasis on sustainable construction practices has spurred significant international research into developing durable and eco-friendly concrete materials. This study investigates the potential of metakaolin and glass powder as supplementary aluminosilicate materials in slag- based geopolymer mortars, aiming to enhance their mechanical properties and durability. To further improve the performance, polypropylene fibers were incorporated at various dosages. Therefore, 13 mixtures of geopolymer mortar based on blast furnace slag have been developed. The control mix does not contain fibers or slag replacement materials, whereas in the other formulations, glass powder and metakaolin have been employed as substitutes for slag at weight percentages (relative to the weight of slag) of 5% and 10%, separately and in combination. Additionally, the fiber-containing samples are divided into two groups based on the volume percentage of polypropylene fibers, comprising 0.2% and 0.4%. The results of the investigation show that the use of glass powder, particularly at a replacement percentage of 10%, leads to an improvement in the 28-day compressive strength. Furthermore, the mixes containing glass powder demonstrated higher flexural strength compared to those containing metakaolin, irrespective of the volume percentage of fibers. The best performance in the rapid chloride permeability test is associated with the mix containing a combination of glass powder and metakaolin at a replacement percentage of 10%. Satisfactory results have been obtained when using fibers at volume percentages of 0.2% and 0.4%. Additionally, this study utilized a fuzzy inference system to predict compressive strength. The results indicate that, by considering uncertainties, the compressive strength of the mortar can be predicted with an error of less than 1% without the need for complex mathematical calculations. Full article

The use of cellulose fiber-filled polypropylene (PP) composites in combination with foam injection molding has enabled the lightweight design of injection-molded parts. The study provides achievements for the physical foam injection molding (MuCell^®) process of PP–cellulose fiber compounds by using CO₂ as the direct foaming agent, including a comparison of MuCell^® foaming with N₂ and a comparison to a chemical foaming process. Weight and density reductions, foam structure and specific mechanical properties are highly dependent on the applied processing parameters. The maximum weight reduction reached values of up to 16%, and density reduction even reached 33% in relation to the compact plates. The extent of weight and density reduction could be adjusted, among other factors, by a reduction in the shot volume. Setting the density reduction to 22% allowed for simultaneously decreasing weight while sustaining the specific flexural properties and limiting the loss of specific impact strength. By using optimized FIM parameters, the mechanical performance could be improved, with specific modulus values even outperforming the compact reference sample. This presents a significant benefit for the preparation of lightweight products and sets the basis for further optimization and modeling studies. Full article

Hernia repair is the most common surgical operation applied worldwide. Mesh prostheses are used to support weakened or damaged tissue to decrease the risk of hernia recurrence. However, the patches currently used in clinic applications have significant short-term and long-term risks. This study aimed to design, produce, and characterize a three-layered semi-resorbable composite hernia mesh using the electrospinning technique, where the upper layer (parietal side) was made of non-resorbable polypropylene (PP-Cl) fibers, the partially resorbable middle layer was made of PP-Cl and polycaprolactone (PCL) fibers, and the fully resorbable lower layer (visceral side) was made of H. perforatum oil-loaded polyethylene glycol (PEG) fibers. The extracellular matrix-like fibrous structure of the patches provided low density and high porosity, minimizing the risk of long-term foreign body reactions, and the hydrophilic/hydrophobic character of the surfaces and the detected swelling rates supported biocompatibility. The patches exhibited mechanical properties comparable to commercially available products. Controlled release of therapeutic oil could be achieved from the oil-integrated patches due to the dissolution of PEG in the acute process. In vitro cell culture studies with the L929 mouse fibroblast cell line revealed that the meshes do not have a cytotoxic nor a biomaterial-induced necrotic effect that will induce apoptosis of the cells. The visceral side of the meshes exhibited non-adherence of cell-like structures to the surface due to the dissolution of PEG. The composite hernia patches were concluded to reduce the risk of adhering to internal organs in the hernia area, have the potential to be used in in vivo biomedical applications, and will support the search for an ideal hernia mesh that can be used in the treatment of abdominal hernias. Full article

Fiber-reinforced cemented paste backfill (FR-CPB) has attracted considerable attention in modern mining applications due to its superior mechanical properties and adaptability. Despite its potential, understanding its rheological behavior remains limited, largely because of the absence of quantitative methods for assessing fiber packing behavior within CPB. This study develops a rheology-based approach to determine the maximum packing fraction of polypropylene fibers in fresh CPB, revealing that shorter fibers (3 mm) achieve a maximum packing fraction of 0.661, significantly higher than longer fibers (12 mm) with 0.534. Building on these findings, a quantitative model for the static yield stress of FR-CPB was developed, showing that under a high fiber content (0.9%) and with longer fibers (12 mm), the yield stress reached 274.34 kPa, a 40% increase compared to shorter fibers. Additionally, the study modeled the time-dependent evolution of yield stress, achieving a prediction accuracy with a correlation coefficient of 0.92. These advancements enable the optimization of FR-CPB composition, which can reduce material usage, enhance pipeline transport efficiency, and improve backfill stability in underground voids. By minimizing the risk of structural failure and optimizing resource allocation, this research provides a theoretical foundation for safer and more cost-effective mining operations. Full article

Ensuring the mechanical performance of backfill materials while reducing cementation costs is a key challenge in mine backfill research. To address this, fiber materials such as polypropylene (PP) fiber and rice straw (RS) fiber have been incorporated into cement-based mixtures for mine backfilling. This study investigates the effects of PP and RS fibers on the mechanical properties, flow characteristics, and microstructure of Tailings and Wasted Stone Mixed Backfill (TWSMB). A series of orthogonal experiments were designed to evaluate the influence of variables, including the cement–sand ratio, solid mass concentration, wasted stone mass concentration, fiber content, and fiber length on the TWSMB properties. The results indicate that the influence of cement–sand ratio and solid mass concentration have a more significant impact on strength than fibers, though the fibers show a stronger effect than the wasted stone mass concentration. Both fiber types enhanced the strength of the specimens, with PP fiber exhibiting a stronger reinforcing effect than RS fiber. Furthermore, the effect of PP fiber content was more pronounced than that of fiber length, whereas the opposite trend was observed for RS fiber. The optimum fiber parameter levels were determined for each type: PP fiber performed best at a mass concentration of 1.5% and a length of 6 mm, while RS fiber showed optimal performance at a mass concentration of 1.0% and a length of 5–10 mm. Macroscopic damage analysis indicated that the structural integrity and residual compressive strength of the TWSMB specimens were preserved even after surpassing the ultimate compressive strength, due to the crack-bridging effect of the fibers. Microstructural analysis showed that PP fiber-reinforced specimens exhibited a dense structure formed through reactions with other hydration products. In contrast, the surface of RS fibers was nearly fully encapsulated by hydration products, resulting in the formation of a physical skeleton structure. This study provides new insights into minimizing cement consumption and reducing backfilling costs in mining operations. Full article

This study was aimed at determining the hardened and fresh properties as well as the high-temperature resistance of high-strength concrete (HSC) produced by incorporating diatomaceous earth, polypropylene, and glass fibers. CDE (calcined diatomaceous earth) was employed as a 10% cement replacement, while polypropylene and glass fibers were added separately to the mixtures at 0.2, 0.4, 0.6, 0.8, and 1.0% volumetric contents. Moreover, the mixtures without using CDE and fibers were used as references. The concrete mixtures were fabricated, followed by the determination of the fresh concrete flow, the absorption capacity, and the flexural, compressive, and splitting tensile strengths of hardened concrete. Furthermore, the specimens fabricated for the hardened concrete were exposed to temperatures of 400 °C, 500 °C, and 600 °C, and the remaining compressive strength was examined. The findings suggested that the incorporation of polypropylene and glass fibers in HSC with CDE enhanced the compressive, flexural, and splitting tensile strengths by 23.4 and 32.6%, 70.0 and 83.5%, and 18.9 and 17.9%, respectively. Moreover, the inclusion of polypropylene and glass fibers reduced the absorption of hardened concrete. Meanwhile, the inclusion of CDE lowered the strengths and increased the absorption. It was further identified that the incorporation of CDE enhanced the resistance of HSC to high temperatures, while polypropylene and glass fibers lowered the resistance. The incorporation of CDE, polypropylene, and glass fibers also lowered the flow of fresh concrete. Full article

Wood plastic composites (WPCs) offer a means to reduce the carbon footprint by incorporating natural fibers to enhance the mechanical properties. However, there is limited information on the mechanical properties of these materials under hostile conditions. This study evaluated composites of polypropylene (PP), polystyrene (PS), and polylactic acid (PLA) processed via extrusion and injection molding. Tests were conducted on tensile and flexural strength and modulus, heat deflection temperature (HDT), and creep analysis under varying relative humidity conditions (10% and 90%) and water immersion, followed by freeze—thaw cycles. The addition of fibers generally improved the mechanical properties but increased water absorption. HDT and creep were dependent on the crystallinity of the composites. PLA and PS demonstrated a superior overall performance, except for their impact properties, where PP was slightly better than PLA. Full article

This article systematically investigated the improvement effect of polypropylene fiber (PPF) on the mechanical and freeze–thaw properties of alkali-activated fly ash slag concrete (AAFSC) with high fly ash content and cured at room temperature. Fly ash and slag were used as precursors, with fly ash accounting for 80% of the total mass. A mixed solution of sodium hydroxide and sodium silicate was used as alkali activator, and short-cut PPF was added to improve the performance of AAFSC. Firstly, the strength characteristics of AAFSC at different curing ages were studied. Then, key indicators such as morphology, residual compressive strength, weight loss, relative dynamic modulus of elasticity (RDME), and pore characteristics of AAFSC after different freeze–thaw cycles were tested and analyzed. The strength performance analysis showed that the optimal dosage of PPF was 0.90%. When the alkali equivalent of the alkali activator was increased from 4% to 6%, the frost resistance of AAFSC could be improved. Furthermore, adding 0.90% PPF could increase the freeze–thaw cycle number of AAFSC by about 50 times (measured by RDME). With the increase in freeze–thaw cycles, the porosity of AAFSC increased, the fractal dimension decreased, and the proportion of harmless and less harmful pores decreased, while the proportion of harmful and multiple harmful pores increased. The relationship model between the porosity and compressive strength of AAFSC after freeze–thaw cycles was established. Full article

This study investigates the impact of carding and blending recycled carbon fibers (rCF) with crimped thermoplastic polypropylene (PP) fibers on the mechanical properties of rCF, using a Weibull statistical approach. Tensile properties of rCF were evaluated before and after carding with varying rCF/PP blend ratios (100/0%, 85/15%, 70/30%, and 50/50%). A comparison between the two-parameter and three-parameter Weibull models showed that the two-parameter model provided a better fit for rCF properties before carding. The results show that adding crimped PP fibers during carding helps to decrease the stress-at-break disparity and move their distribution to higher values. Furthermore, a slight increase in tensile modulus was observed in carded rCF, with higher PP ratios associated with smaller scatter modulus distributions. Elongation at break remained consistent, with the Weibull modulus increasing slightly with carding and the inclusion of PP fibers, indicating improved consistency. Overall, carding rCF with PP fibers helped in the mechanical property uniformity of the resulting carded webs without compromising tensile performance. This work shows the potential of the carding process with or without thermoplastic fibers to efficiently realign and give continuity to discontinuous recycled carbon fibers. Full article

Oyster farming plays a crucial role in sustainable food production due to its high nutritional value and relatively low environmental impact. However, in a scenario of increasing production, it is necessary to consider the issue of plastic use as a limitation to be addressed. A life cycle assessment (LCA) was conducted on oyster farming in La Spezia (Italy) as a case study, utilizing 1 kg of packaged oysters as the functional unit. Fossil-based plastics and wooden packaging were identified as the primary environmental concerns. To analyze potential strategies for reducing the environmental impact of oyster farming, alternative scenarios were considered wherein fossil-based materials were replaced with bio-based materials. Specifically, this study examined the substitution of the current packaging, consisting of a wooden box and a polypropylene (PP) film, with a fully recyclable PP net. Additionally, polylactic acid (PLA), polyhydroxyalkanoates (PHAs), and bio-based polyethylene terephthalate (Bio-PET) were proposed as alternatives to virgin high-density polyethylene (HDPE) and PP for buoys, oyster bags, and boxes. Among the scenarios analyzed, the sole effective strategy to reduce the impact of plastics on the process is to replace them with PHA. In the other cases, the high energy consumption of their non-optimized production renders them disadvantageous options. However, the assessment must include the effects of degradation that traditional plastics can have in the marine environment, an aspect that potentially renders natural fibers more advantageous. The use of PP net packaging has demonstrated high efficacy in reducing impacts and provides a foundation for considering the need to combine sustainability and marketing with current legislation regarding food packaging. Full article

Fibers from milkweed, which grows in Quebec (Canada), offer a distinct and outstanding advantage compared to other natural fibers: their ultra-lightweight hollow structure provides excellent acoustic and thermal insulation properties for the automobile industry. To highlight the properties of milkweed fibers and reduce the use of synthetic materials in vehicles, nonwoven carpeting made from a blend of milkweed fibers and polylactic acid (PLA) fibers was produced using the air-laid process. Some of the nonwovens were compressed to investigate the effects of increased mass per unit area on their thermal, acoustic, and mechanical properties. The nonwovens’ mass per unit area, thermal insulation, sound absorption coefficient, airflow resistivity, compression, and resistance to moisture were evaluated and compared to other carpets made of natural and synthetic fibers. The findings indicate that milkweed and PLA carpets have lower thermal conductivity values of 37.45 (mW/m·K), (mW/m·K) less than carpets made from cotton and polypropylene. At low frequencies, none of the carpets absorbed sound. At high frequencies, milkweed and PLA carpets showed sound absorption values of at least 0.6, which provide better acoustic insulation than nonwoven materials made from jute and polyethylene (PE) fibers. Milkweed and PLA carpets exhibited better compression values than polypropylene (PP) carpets. Full article