Search Results (302)

In response to growing global concerns about plastic waste, the development of efficient recycling technologies for thermoplastics has become increasingly important. Polypropylene (PP), a widely used commodity resin, is of particular interest because of the urgent need to establish sustainable material circulation. However, conventional mechanical property evaluations of injection-molded products typically require dedicated specimens, which involve additional material and energy costs. As described herein, we propose a simplified mechanical model to derive Poisson’s ratio and critical expansion stress directly from standard uniaxial tensile tests of molded thermoplastics. The method based on the true stress–true strain relationship in the small deformation region was validated using various thermoplastics (PP, POM, PC, and ABS), with results showing good agreement with those of the existing literature. The model was applied further to assess changes in mechanical properties of Homo-PP and Block-PP subjected to repeated extrusion. Both materials exhibited reductions in elastic modulus and critical expansion stress with increasing extrusion cycles, whereas Block-PP showed a slower degradation rate because of thermo-crosslinking in its ethylene–propylene rubber (EPR) phase. DSC and chemiluminescence analyses suggested changes in stereoregularity and radical formation as key factors. This method offers a practical approach for evaluating recycled PP and contributes to high-quality recycling and material design. Full article

This article presents a review on the applications of basalt fibers and their composites in infrastructures. The characteristics and advantages of high-performance basalt fibers and their composites are firstly introduced. Then, the article discusses strengthening using basalt fiber sheets and BFRP bars or grids, followed by concrete structures reinforced with BFRP bars, asphalt pavements, and cementitious composites reinforced with chopped basalt fibers in terms of mechanical behaviors and application examples. The load-bearing capacity of the strengthened structures can be increased by up to 60%, compared with those without strengthening. The lifespan of the concrete structures reinforced with BFRP can be extended by up to 50 years at least in harsh environments, which is much longer than that of ordinary reinforced concrete structures. In addition, the fatigue cracking resistance of asphalt can be increased by up to 600% with basalt fiber. The newly developed technologies including anchor bolts using BFRPs, self-sensing BFRPs, and BFRP–concrete composite structures are introduced in detail. Furthermore, suggestions are proposed for the forward-looking technologies, such as long-span bridges with BFRP cables, BFRP truss structures, BFRP with thermoplastic resin matrix, and BFRP composite piles. Full article

This research paper employed the recently developed Elium thermoplastic resin and basalt fabrics as an alternative to thermoset/synthetic fibre composites to reduce their environmental impact. Elium^® 191 XO/SA and Epoxy Prime^TM 37 resin were reinforced with mineral-based semi-unidirectional basalt fibre (BF). Physical, chemical, tensile, and flexural performance was investigated under the effect of hydrothermal seawater ageing at 45 °C for 45 and 90 days. The results show that the BF/Elium composite exhibited superior tensile and flexural strength, as well as good stiffness, compared with the BF/Epoxy composite. Digital images and scanning electron microscope images were used to describe the fracture and failure mechanisms. The tensile and flexural strength values of the BF/Elium composite were 1165 MPa and 1128 MPa, greater than those of the BF/Epoxy composite by 33% and 71%, respectively. The tensile and flexural modulus values of the BF/Elium composite were 44.1 GPa and 38.2 GPa, which are 30% and 12% greater than those of the BF/Epoxy composite. The result values for both composites were normalised with respect to the density of each composite laminate. Both composites exhibited signs of resin decomposition and fibre surface degradation under the influence of seawater ageing, resulting in a more recognisable reduction in flexural properties than in tensile properties. Full article

A fabric orientation angle has a significant influence on the failure mechanisms at the lamina level. Any change in this angle can lead to a sudden reduction in strength, potentially resulting in catastrophic failures due to variations in load-carrying capacity. This study examined the impact of off-axis fabric orientation angles (0°, 15°, 30°, 45°, 60°, and 90°) on the flexural properties of non-crimp basalt-fibre-reinforced acrylic thermoplastic composites. The basalt/Elium^® composite panels were manufactured using a vacuum-assisted resin transfer moulding technique. The results show that the on-axis (0°) composite specimens exhibited linear stress–strain behaviour and quasi-brittle failure characterised by fibre dominance, achieving superior strength and failure strain values of 1128 MPa and 3.85%, respectively. In contrast, the off-axis specimens exhibited highly nonlinear ductile behaviour. They failed at lower load values due to matrix dominance, with strength and failure strain values of 144 MPa and 6.0%, respectively, observed at a fabric orientation angle of 45°. The in-plane shear stress associated with off-axis angles influenced the flexural properties. Additionally, the degree of deformation and the fracture mechanisms were analysed. Full article

Objective: To evaluate the cytotoxicity and endocrine-disrupting potential of materials used in removable orthodontic retainers. Methods: A literature search (2015–2025) covered in vitro cytotoxicity, estrogenicity, in vivo tissue responses, and clinical biomarkers in PMMA plates, thermoplastic foils, 3D-printed resins, PEEK, and fiber-reinforced composites. Results: Thirty-eight in vitro and ten clinical studies met inclusion criteria, identified via a structured literature search of electronic databases (2015–2025). Photopolymer resins demonstrated the highest cytotoxicity, whereas thermoplastics and PMMA exhibited predominantly mild effects, which diminished further following 24 h water storage. Bisphenol-type compound release was reported, but systemic exposure remained below regulatory limits. No statistically significant mucosal alterations or endocrine-related effects were reported in clinical studies. Conclusions: Retainer materials are generally biocompatible, though data on long-term endocrine effects are limited. Standardized biocompatibility assessment protocols are necessary to enable comparative evaluation across diverse orthodontic materials. Single-use thermoplastics contribute to microplastic release and pose end-of-life management challenges, raising concerns regarding environmental sustainability. Full article

The functionalisation of lignin-derived phenolics (guaiacol, 4-propylguaiacol, eugenol, isoeugenol, phenol, m-cresol, catechol, syringol, syringaldehyde, and vanillin) for the synthesis of thermoplastic polyurethanes (PUs) and polyester (PE) resins is herein described. Diols were synthesised from phenolics in a one-step reaction using either glycerol carbonate or ethylene carbonate as a greener, solvent-free synthetic route. Nine of the diols were selected for the synthesis of Pus, and two of the diols were used for the synthesis of PE resins, with their physical and thermal properties characterised. Analysis of the PUs by differential scanning calorimetry (DSC) confirmed their amorphous nature, while thermogravimetric analysis (TGA) suggested improved thermal stability for all PUs with the addition of an alkyl or aldehyde substituent on the benzene ring regardless of the diisocyanate used. However, lower PU thermal stabilities were observed with the use of an aliphatic diisocyanate over an aromatic diisocyanate in the absence of an additional substituent. Analysis of the PEs by DSC also confirmed that the clear resins were all amorphous, and gel permeation chromatography (GPC) revealed significantly higher molecular weights and dispersities when an aliphatic diacid was utilised over an aromatic diacid. Full article

The effects of benzoyl peroxide (BPO) and dimethylaniline (DMA) composition on the induction time and the tensile strength of thermoplastic acrylic (PMMA) resins have been investigated in this study. Eighteen resin formulations were prepared with different BPO/DMA ratios (2.0–9.5) and DMA contents (0.28–0.65 mol%), and it was observed that tensile strengths reached up to 66 MPa, and induction times (ITs) ranged from 100 to 207 min. Higher BPO/DMA ratios improved tensile strength but shortened IT, while greater DMA content accelerated curing. Polynomial regression models were successfully established, i.e., a third-order equation for the strength and a second-order equation for the IT, based on the BPO/DMA ratio and DMA content to identify the optimal formulation to balance the strength and the IT time. Two selected formulations, P-4-0.5 and P-3-0.3, were applied in vacuum-assisted resin infusion of glass fiber composites. The best-performing unidirectional (UD) laminate achieved a tensile strength of 1244 MPa. As regards ±45° biaxial (BX45) laminates, they exhibited a tensile strength of 124 MPa and a failure strain of 9.02%, which, while lower than that of epoxy, indicates competitive performance. These results demonstrate that the resin was well infused, resulting in 64% higher fiber volume fraction than typical infused glass/epoxy composites, and compositionally optimized PMMA resins can deliver epoxy-comparable strength and enhance damage tolerance in structural composite applications. Full article

This work provides a comprehensive review of the recent advancements in the toughening modification methods for epoxy resins. The study explores a variety of approaches, including the incorporation of liquid rubbers, core–shell rubber particles, thermoplastic resins, hyperbranched polymers, and the nanoparticle toughening method, each of which contributes to improving the mechanical properties and fracture toughness of epoxy resins. Special attention is given to the mechanisms underlying these toughening methods, such as reaction-induced phase separation, crack pinning, and energy dissipation through particle deformation. The paper also examines the synergistic effects achieved by combining different toughening agents, such as phenoxy thermoplastic rubber and core–shell rubber particles, which significantly enhance the critical fracture energy and impact strength of epoxy composites. Additionally, the challenges associated with each method, such as the potential reduction in mechanical properties and the influence of phase separation on material performance, are discussed. Through a detailed analysis of experimental studies, this paper highlights the effectiveness of various toughening strategies and suggests future research directions aimed at further optimizing epoxy resin toughening techniques for diverse industrial applications. Emerging computational modeling and machine learning applications in epoxy resin development are also systematically reviewed to highlight their potential in advancing predictive design frameworks. Full article

To improve the issue of the decreased toughness and electrical performance of epoxy resin (EP) in thermal shock environments, we prepared thermoplastic polyurethane elastomer (TPU)-filled modified EP composites. We also studied the mechanical and electrical performance of these composites, which had different TPU filling contents, under thermal shock conditions. The results indicated that after 240 h of thermal cycling between −15 °C and 100 °C, the TPU/epoxy composites, when compared to unmodified EP, exhibited a 10.1% enhancement in their elastic modulus, a 15.3% increase in their elongation at break, a 22.3% improvement in their tensile strength, and a 47.8% increase in their impact strength. Moreover, their volume resistivity increased by 10.5% and their AC breakdown strength improved by 52.1%. In contrast, their dielectric constant and dielectric loss experienced reductions of 40.2% and 7.5%, respectively. This study demonstrates that introducing flexible TPU molecular chains into the resin significantly enhances the toughness of EP structures. Additionally, the new cross-linked structures formed within the TPU/EP composites improve their insulation performance under thermal shock conditions. Full article

Polycarbonate (PC) is a highly recyclable thermoplastic with high impact strength that bodes well to re-melting extrusion and shredding for positive environmental impact. For the goal of improving impact strength further, layered carbon fiber (CF) reinforcement has been added between PC sheets by hot pressing at 6.0 MPa and 537 K for 8 min. An addition of cross-weave CF layer reinforcement to PC increased Charpy impact value, a_uc of the untreated [PC]₄[CF]₃ composite over that of untreated PC resin reported at all accumulative probabilities, P_f. At medial-P_f of 0.50, a_uc was increased 3.13 times (213%), while statistically lowest impact value a_s at P_f = 0 calculated by 3-parameter Weibull equation was boosted 2.64 times (164%). To optimize a_uc, effect of homogeneous electron beam irradiation (HLEBI) treatment of 43.2, 129, 216, 302, or 432 kGy at 170 kV acceleration voltage to the CF plies before assembly with PC then hot press was also investigated. The 216 kGy HLEBI dose appears to be optimum, raising a_s at P_f = 0 about 6.5% over that of untreated [PC]₄[CF]₃ and agrees with a previous study that showed 216 kGy to be optimum for static 3-point bending strength, when quality can be controlled. Electron spin resonance (ESR) data confirms 216 kGy HLEBI generates strong peaks in CF and PC indicating dangling bond (DB) generation. Bending strength increase was higher than that of impact due to lower test velocity and higher deformation area spreading along specimen length, allowing more DBs to take on the load. X-ray photoelectron spectroscopy (XPS) data of CF top ~10 nm surface layer in the sizing confirms C–O–H, C–H, and C–O peak height from 216 kGy exhibited little or no change compared with untreated. However, 432 kGy increased the peak heights indicating enhanced adhesion to PC. However, 432 kGy degraded a_s at P_f = 0 of the [PC]₄[CF]₃, and is reported to decrease impact strength of PC itself by excess dangling bond formation. Thus, the 432 kGy created increased PC/CF adhesion, but degraded the PC resin. Therefore, 216 kGy of 170 kV-HLEBI appeared to be a well-balanced condition between the PC-cohesive force and PC/CF interface adhesive force when fabricating [PC]₄[CF]₃. Full article

This paper review deals with frequent technologies of the production of materials based on Wood Plastic Composite, their brief definition, and description of components. The choice of processing technology depends on the polymer applied and the shape required of the part or the component. In the case of thermoplastic matrices, the dominant are extrusion and injection molding. In the case of thermosets application, the following technologies can be used: Resin Transfer Molding and Sheet Molding Compound. Currently, the research is also widely focused on composites with a matrix made of biodegradable thermoplastics—polylactide, which also brings to the forefront 3D printing technology of Fused Deposition Modeling. Each of these technologies is—to a certain extent—limited and impacts on the final characteristics of the composite material and its use. Full article

In this study, we developed lithium–sulfur rechargeable batteries using chemically modified thermoplastic sulfur polymers as cathode active materials, aiming to effectively utilize surplus sulfur resources. The resulting high-sulfur-content resins exhibited self-healing properties, extensibility, and adhesiveness. By leveraging its high solubility in specific organic solvents, we successfully introduced sulfur-based compounds into porous carbon via vacuum impregnation using a solution, rather than conventional thermal impregnation. Charge–discharge measurements of lithium–sulfur (Li-S) secondary batteries assembled with this more uniform composite cathode, compared to those using elemental sulfur, demonstrated an increased discharge capacity in the initial cycles and at higher rates. Full article

For a solar-powered unmanned aerial system (UAS), the performance and integration of the solar panel are of paramount importance. This paper examines the safety aspects of solar panels in electrical power systems, with a particular focus on the installation of solar cells onto an aircraft’s carbon fiber wing. Three distinct installation techniques are evaluated, and their respective advantages and disadvantages are discussed. A preliminary test is conducted to assess the viability of adhering commercial solar panels intended for boats using a bio-adhesive layer placed underneath the series of encapsulated solar panels. To ensure adhesion, the piece is placed under a vacuum. The subsequent test evaluates the lamination of the solar cells onto the carbon fiber skin with a resin as a component of the laminate. Finally, as a definitive solution, the adhesion of the solar panels onto the entire polymer layer used to seal the solar cells themselves was evaluated. This solution offers objective advantages in terms of adhesion, lightness and whiteness. Adhesion is guaranteed by the bond of the thermoplastic polymer used to seal the photovoltaic cells and the epoxy resin of the laminate. The bond is created through the autoclave process, which involves placing the laminate and solar cells in an oven at a specific temperature and pressure for a defined period of time. This solution results in a weight reduction of approximately three times compared to a solution not specifically designed for these materials and a reduction in thickness of approximately two times. Full article

Epoxy asphalt, as a thermosetting and thermoplastic polymer composite material, has been widely used for steel bridge decks and specialty pavements due to its road performance, thermal stability, rutting resistance, and durability. However, the poor compatibility between epoxy resin binder and asphalt, due to the difference in chemical structure, polarity, and solubleness, severely restricts their practical applications in the construction of bridges and roads. Herein, we proposed a facial method to strengthen their compatibility by blending the poly(styrene-butadiene-styrene)-modified carbon nanotubes (SBS-CNTs) in the composite. The SBS-CNTs were found to evenly disperse in epoxy asphalt matrix with the epoxy resin contents of 10%–30% and could form the three-dimensional bi-continuous cross-linked structure at 30%. Moreover, the addition of epoxy resin increased the glass transition temperature (Tg) and enhanced the high-temperature shear capacity and tensile strength (over an order of magnitudes) of SBS-CNT-modified asphalt, which showed high potential for applications in the construction of bridges and roads, providing an alternative approach for improving the performance of epoxy asphalt. Full article

This study focuses on reducing the weight of oxygen respirators in firefighters’ personal protective equipment (PPE), which currently accounts for about 56% of the total weight. The heavy PPE, weighing between 20 and 25 kg, restricts movement and can lead to musculoskeletal injuries. To address this, the study investigates using a carbon fiber-reinforced composite for the backrest of the oxygen respirator to reduce weight while maintaining strength. The backrest was fabricated using a long-fiber thermoplastic (LFT) composite made with PA66 resin and 30wt.% carbon fiber content. Initially, the injection-molding process conditions were identified to achieve a tensile strength of 85 MPa or higher. Additionally, flame retardants were added to improve fire resistance, with AF-480 at 5 wt.% found to be the best option. Subsequently, optimal injection conditions were set by fabricating the back rest with the composite by applying the Taguchi method to satisfy the required tensile strength. As a result, the composite material achieved a 12.8% weight reduction while maintaining the required strength. This development is expected to significantly improve firefighter safety, leading to more effective firefighting and reduced human and property damage. Full article