Search Results (152)

This study investigated Coffee arabica husk (CAH) as a reinforcing filler to create sustainable biocomposites from agro-industrial waste. The research explored the relationship between processing, structure, and properties using two matrices: polylactic acid (LA) and a bio-based epoxy resin (BER). We found that CAH incorporation increased the elastic modulus in all composites, with the stiffening effect being more significant in BER-based systems. However, filler inclusion dramatically reduced composite toughness. Our analysis showed that melt processing significantly reduced the CAH aspect ratio, with BER causing a more pronounced reduction than LA. Conversely, LA showed a greater tendency to fill the porous voids of the CAH particles. This work demonstrates the crucial interaction of filler, matrix, and processing on a composite’s final performance. These materials have shown promises for sustainable packaging and other technical applications. Full article

Epoxy resin coatings are widely employed for steel protection owing to their excellent adhesion, chemical stability, mechanical strength, and barrier properties. However, conventional bisphenol A-based resins and organic solvents may pose risks to reproductive, developmental, and immune systems, as well as contribute to atmospheric pollution. This mini-review critically evaluates recent advancements in fully waterborne bio-based epoxy nanocomposites as sustainable alternatives, with particular emphasis on their enhanced antibacterial and corrosion-resistant performance in tropical marine environments. A central focus is the role of chitosan-grafted graphene oxide (Chi-GO) as a multifunctional nanofiller that significantly enhances both antibacterial efficacy and barrier capabilities. For instance, coatings reinforced with Chi-GO exhibit up to two orders of magnitude lower corrosion current density than pristine epoxy coatings, and achieve over 95% bacterial inhibition against Escherichia coli and Staphylococcus aureus at a 1 wt.% loading. The review summarizes key synthesis methods, functional modification techniques, and commonly adopted evaluation approaches. Emerging research further underscores environmental performance metrics, including reduced volatile organic compound (VOC) emissions and improved life-cycle assessments. By integrating bio-based polymer matrices with Chi-GO, these composite systems present a promising pathway toward environmentally benign and durable protective coatings. Nevertheless, critical challenges concerning scalability and long-term stability under real-world operating conditions remain insufficiently addressed. Future research should emphasize scalable manufacturing strategies, such as roll-to-roll processing, and conduct extended tropical exposure testing (e.g., salt spray tests beyond 2000 h). Additionally, developing comprehensive life-cycle assessment (LCA) frameworks will be crucial for sustainable industrial implementation. Full article

Epoxidized soybean oil (ESO) is the oxidation product of soybean oil with hydrogen peroxide and either acetic or formic acid obtained by converting the double bonds into epoxy groups, which is non-toxic and of higher chemical reactivity. Oxidized soybean oil (ESO) has gained significant attention as a renewable and environmentally friendly alternative to petroleum-based epoxy resins. Derived from soybean oil through epoxidation of its unsaturated fatty acids, ESO offers a bio-based platform with inherent flexibility, low toxicity, and excellent chemical resistance. When used as a reactive diluent or primary component in epoxy formulations, ESO enhances the sustainability profile of coatings, adhesives, and composite materials. This study explores the mechanical properties of ESO-based epoxy systems, with particular attention to formulation strategies, crosslinking agents, and performance trade-offs compared to conventional epoxies. The incorporation of ESO not only reduces the reliance on fossil resources but also imparts tunable thermal and mechanical properties, making it suitable for a range of industrial and eco-friendly applications. The results underscore the potential of ESO as a viable component in next-generation green materials, contributing to circular economy and low-impact manufacturing. For the application of these materials in pultrusion and FW technologies, the Taguchi method is used to determine the most influential process parameters. Full article

Growing environmental concerns and the depletion of fossil-based resources have accelerated the demand for sustainable alternatives in engineering and construction materials. Among these, bio-based composites have gained attention for their use of renewable and eco-friendly resources. Macadamia nutshells, typically treated as agricultural waste, possess high strength, brittleness, heat resistance, and fracture toughness, making them attractive candidates for structural applications. Australia alone contributes nearly 40% of global macadamia production, generating significant shell by-products that could be repurposed into high-value composites. This study investigates the development of novel composite cores and sandwich structures using macadamia nutshell particles reinforced in an epoxy polymer matrix. Two weight ratios (10% and 15%) and two particle sizes (200–600 µm and 1–1.18 mm) were employed, combined with laminating epoxy resin and hardener to fabricate composite cores. These cores were further processed into sandwich specimens with carbon fabric skins. Flexural and short beam shear (SBS) tests were conducted to evaluate the mechanical behaviour of the composites. The results demonstrate that higher filler content with fine particles achieved up to 15% higher flexural strength and 18% higher stiffness compared to coarser particle composites. Sandwich structures exhibited markedly improved interlaminar shear strength (8–15 MPa), confirming superior load transfer and durability. The results demonstrate that higher filler content and finer particles provided the most favourable mechanical performance, showing higher flexural strength, stiffness, and shear resistance compared to coarser particle formulations. Sandwich structures significantly outperformed core-only composites due to improved load transfer and resistance to bending and shear stresses, with the 15% fine-particle configuration emerging as the optimal formulation. By transforming macadamia nutshells into value-added composites, this research highlights an innovative pathway for waste utilisation, reduced environmental impact, and sustainable material development. The findings suggest that such composites hold strong potential for structural applications in construction and related engineering fields, especially in regions with abundant macadamia production. This study reinforces the role of agricultural by-products as practical solutions for advancing green composites and contributing to circular economy principles. Full article

Developing high-performance bio-based epoxy resins as sustainable alternatives to petroleum-derived bisphenol A (BPA) epoxies for recyclable carbon fiber-reinforced polymers (CFRPs) is pivotal in materials research. Herein, the bio-based bisphenol monomer BDEF was synthesized from the lignin derivative 4-propylguaiacol. The derived epoxy monomer BDEF-EP was cured with adipic acid to form a bio-based vitrimer. Stress relaxation synergistically accelerates through intrinsic dynamic carboxylic acid ester exchange and enhanced chain mobility from the flexible propyl structure. At 220 °C, this vitrimer shows rapid stress relaxation (τ* < 30 s) and repairs ~90% of surface scratches in 30 min. It exhibits tensile and flexural strengths of 69 MPa and 105 MPa, respectively. BDEF-EP’s low viscosity reduces diluent needs in composite fabrication, lowering costs and improving efficiency. The resulting bio-based CFRP achieves tensile and flexural strengths of 543 MPa and 414 MPa, respectively, which are comparable to commercially available petroleum-derived CFRP. In addition, CFRP containing dynamic crosslinked networks demonstrates degradable recyclability in ethylene glycol solvent, preserving the surface morphology and chemical structure of recovered carbon fibers. The results demonstrate that this bio-based epoxy vitrimer has promising potential for developing sustainable, degradable, and recyclable CFRP composites. Full article

Fiber-reinforced composites (FRCs) have emerged as transformative alternatives to traditional marine construction materials, owing to their superior corrosion resistance, design flexibility, and strength-to-weight ratio. This review comprehensively examines the current state of FRC technologies in marine deck and underwater applications, with a focus on manufacturing methods, durability challenges, and future innovations. Thermoset polymer composites, particularly those with epoxy and vinyl ester matrices, continue to dominate marine applications due to their mechanical robustness and processing maturity. In contrast, thermoplastic composites such as Polyether Ether Ketone (PEEK) and Polyether Ketone Ketone (PEKK) offer advantages in recyclability and hydrothermal performance but are hindered by higher processing costs. The review evaluates the performance of various fiber types, including glass, carbon, basalt, and aramid, highlighting the trade-offs between cost, mechanical properties, and environmental resistance. Manufacturing processes such as vacuum-assisted resin transfer molding (VARTM) and automated fiber placement (AFP) enable efficient production but face limitations in scalability and in-field repair. Key durability concerns include seawater-induced degradation, moisture absorption, interfacial debonding, galvanic corrosion in FRP–metal hybrids, and biofouling. The paper also explores emerging strategies such as self-healing polymers, nano-enhanced coatings, and hybrid fiber architectures that aim to improve long-term reliability. Finally, it outlines future research directions, including the development of smart composites with embedded structural health monitoring (SHM), bio-based resin systems, and standardized certification protocols to support broader industry adoption. This review aims to guide ongoing research and development efforts toward more sustainable, high-performance marine composite systems. Full article

This systematic literature review explores recent advancements in polymer-based composite materials designed for thermal insulation in automotive applications, with a particular focus on sustainability, performance optimization, and scalability. The methodology follows PRISMA 2020 guidelines and includes a comprehensive bibliometric and thematic analysis of 229 peer-reviewed articles published over the past 15 years across major databases (Scopus, Web of Science, ScienceDirect, MDPI). The findings are structured around four central research questions addressing (1) the functional role of insulation in automotive systems; (2) criteria for selecting suitable polymer systems; (3) optimization strategies involving nanostructuring, self-healing, and additive manufacturing; and (4) future research directions involving smart polymers, bioinspired architectures, and AI-driven design. Results show that epoxy resins, polyurethane, silicones, and polymeric foams offer distinct advantages depending on the specific application, yet each presents trade-offs between thermal resistance, recyclability, processing complexity, and ecological impact. Comparative evaluation tables and bibliometric mapping (VOSviewer) reveal an emerging research trend toward hybrid systems that combine bio-based matrices with functional nanofillers. The study concludes that no single material system is universally optimal, but rather that tailored solutions integrating performance, sustainability, and cost-effectiveness are essential for next-generation automotive thermal insulation. Full article

Tidal seashell waste represents an abundant, underutilized marine resource that poses environmental disposal challenges but offers potential as a sustainable bio-filler in epoxy composites. This study investigates its incorporation into bio-based epoxy systems to reduce reliance on non-renewable materials and promote circular economy objectives. Processed seashell powder was blended into epoxy formulations, and response surface methodology was applied to optimize filler loading and resin composition. Comprehensive characterization included tensile strength, impact resistance, hardness, density, and thermal conductivity testing, along with microscopy analysis to evaluate filler dispersion and interfacial bonding. The optimized composites demonstrated improved hardness, density, and thermal stability while maintaining acceptable tensile and impact strength. Microscopy confirmed uniform filler distribution at optimal loadings but revealed agglomeration and void formation at higher contents, which can reduce interfacial bonding efficiency. These findings highlight the feasibility of valorizing marine waste as a reinforcing filler in sustainable composite production, supporting environmental goals and offering a scalable approach for the development of durable, lightweight materials suitable for structural, coating, and industrial applications. Full article

The composite materials industry is increasingly seeking sustainable alternatives to mitigate the environmental impact of end-of-life materials. As a result, many sectors are transitioning toward bio-based or partially bio-based matrices (e.g., epoxy resins) to preserve material properties while improving sustainability. The transportation sector, in particular, demands materials that meet stringent mechanical and fire resistance standards. In this study, various epoxy systems with bio-based and/or recyclable content were investigated, along with renewable additives designed to enhance fire resistance through their functional groups and chemical structure. The research focused on developing formulations compatible with Sheet Moulding Compound (SMC) technology, which is widely used in transportation applications. Through extensive testing, materials with high bio-based content were successfully developed, exhibiting competitive mechanical properties and compliance with key fire safety requirements of the railway sector, as per the EN 45545-2 standard. Full article

There has been a growing interest in polymer-based materials in recent years, and current research is focused on reducing fossil-derived epoxy compounds. This review examines the potential of epoxidised vegetable oils (EVOs) as sustainable alternatives to these systems. Epoxidation processes have been systematically analysed and their influence on chemical, thermal, and mechanical properties has been assessed. Results indicate that basic, low-toxicity epoxidation methods resulted in resins with comparable performance to those obtained through more complex common/commercial procedures. In total, 5–7% oxirane oxygen content (OOC) was found to be optimal to achieve a balanced crosslink density, thus enhancing tensile strength. Furthermore, mechanical properties have been insufficiently studied, as less than half of the studies were conducted at least tensile or flexural strength. Reinforcement strategies were also explored, with nano-reinforcing carbon nanotubes (CBNTs) showing the best mechanical and thermal results. Natural fibres reported better mechanical performance when mixed with EVOs than conventional systems. On the other hand, one of the main constraints observed is the lack of consistency in reporting key chemical and mechanical parameters across studies. Environmental properties and end-of-life use are significant challenges to be addressed in future studies, as there remains a significant gap in understanding the end-of-life of these materials. Future research should focus on the exploration of eco-friendly epoxidation reagents and standardise protocols to compare and measure oil properties before and after being epoxidised. Full article

The increasing demand for sustainable materials has intensified the interest in natural fiber-reinforced composites (NFRCs) as environmentally friendly alternatives to synthetic composites. However, NFRCs often face limitations in thermal stability, restricting their use in high-temperature environments. To address this, the present study explores the hybridization of cellulosic flax fibers with protein-based wool fibers to improve thermal stability without compromising mechanical integrity. Wool–flax hybrid composites were fabricated using a bio-based epoxy resin through a resin infusion technique with different fiber proportions. The flexural properties of these composites were evaluated under varying temperature conditions to assess the influence of fiber composition and thermal conditions. This study specifically examined the impact of wool fiber content on the flexural performance of the composites under thermal conditions, including behavior near and above the matrix’s glass transition temperature. The results showed that the flexural properties of the hybrid biocomposites were significantly affected by temperature. Compared with specimens tested at room temperature, the flexural modulus of all variants decreased by 85–94%, while the flexural strength declined by 79–85% at 120 °C, depending on the variant. The composite variant with a higher wool content (variant 3W) exhibited enhanced flexural performance, demonstrating an average of 15% greater flexural strength than other variants at 60 °C and 5% higher at 120 °C. These findings suggest that incorporating wool fibers into flax-based composites can effectively improve thermal stability while maintaining flexural properties, supporting the development of sustainable biocomposites for structural applications. Full article

The dependence of conventional epoxy resins on fossil fuels and the environmental and health hazards associated with bisphenol A (BPA) demand the creation of sustainable alternatives. Because lignin is a natural resource and has an aromatic ring skeleton structure, it could be used as an alternative to fossil fuels. This study effectively resolved this challenge by utilizing a sustainable one-step epoxidation process to transform lignin into a bio-based epoxy resin. The results verified the successful synthesis of epoxidized bamboo lignin through systematic characterization employing Fourier transform infrared spectroscopy, hydrogen spectroscopy/two-dimensional heteronuclear single-quantum coherent nuclear magnetic resonance, quantitative phosphorus spectroscopy, and gel permeation chromatography. Lignin-based epoxy resins had an epoxy equivalent value of 350–400 g/mol and a weight-average molecular weight of 4853 g/mol. Studies on the curing kinetics revealed that polyetheramine (PEA-230) demonstrated the lowest apparent activation energy (46.2 kJ/mol), signifying its enhanced curing efficiency and potential for energy conservation. Mechanical testing indicated that the PEA-230 cured network demonstrated the maximum tensile strength (>25 MPa), whereas high-molecular-weight polyetheramine (PEA-2000) imparted enhanced elongation to the material. Lignin-based epoxy resins demonstrated superior heat stability. This study demonstrates the conversion of bamboo lignin into bio-based epoxy resins using a simple, environmentally friendly synthesis process, demonstrating the potential to reduce fossil resource use, efficiently use waste, develop sustainable thermosetting materials, and promote a circular bioeconomy. Full article

A biobased flame retardant, trieugenylphosphate (TEP), was synthesized from eugenol and incorporated at concentrations of 10 and 30 wt.% into the epoxy matrix. Flammability and thermal stability were investigated using the UL-94 test, pyrolysis–combustion flow calorimetry (PCFC), and thermogravimetric analysis (TGA). Thermal and thermomechanical properties were examined by differential scanning calorimetry (DSC) and dynamical mechanical thermal analysis (DMTA). The modified resin with TEP content showed self-extinguishing properties and acceptable thermal and thermomechanical properties. Furthermore, the microcalorimetric method proved that the introduction of the TEP additive to the epoxy matrix reduced the values of p_cHRR (414.4 ± 5.5 W/g), THR (29.1 ± 0.6 kJ/g), and HRC (446 ± 7 J/g·K) for the sample tested compared to the unmodified resin. Full article

The use of natural fibers in hydro turbine rotors promotes sustainability by offering biodegradable, renewable materials with a lower carbon footprint. This study compares the hydrodynamic performance of two rotors in a gravitational vortex turbine: Rotor 1, 3D-printed with polylactic acid (PLA), and Rotor 2, made from fique fiber and epoxy resin using manual molding. To compare the rotors, experimental tests were conducted on a laboratory-scale setup, where the behavior of both rotors was evaluated under different flow regimes. Rotor 1 achieved 61.01% efficiency at an angular velocity ($\omega$) 160 RPM, while Rotor 2 reached only 19.03% at $\omega$ of 165 RPM. The lower performance of Rotor 2 was due to dynamic imbalances and mechanical vibrations, leading to energy losses. These challenges highlight the limitations of manual molding in achieving precise rotor geometry and balance. To improve natural fiber rotor viability, optimizing manufacturing techniques is crucial to enhance dynamic balance and minimize vibrations. Advancements in fabrication could bridge the performance gap between natural and synthetic materials, making bio-based rotors more competitive. This study emphasizes the potential of natural fibers in sustainable energy and the need to refine production methods to maximize efficiency and reliability. Addressing these challenges will help integrate eco-friendly rotors into hydro turbine technologies. Full article

This research work focuses on the chemical recycling of a Carbon Fiber-Reinforced Composite (CFRC) manufactured through a vacuum-assisted resin infusion (VARI) process, characterized by a high Young’s modulus of approximately 7640 MPa. The recycling reaction was performed using a mixture of eco-sustainable solvents, composed of acetic acid and hydrogen peroxide, and was conducted at three different temperatures (70, 80, and 90 °C). The reaction yield values, evaluated with an innovative approach that involved the use of thermogravimetric analysis (TGA), confirmed the importance to recycle at a temperature corresponding to the glass transition temperature (Tg = 90.3 °C) of the resin. Spectroscopic investigations highlighted that the chemical bond cleavage occurred through the selective breaking of the C-N bonds of the cross-linked matrix structure, allowing the recovery of both the reinforcing phase of the epoxy matrix and the initial oligomers/monomers of the epoxy matrix. The morphological and electrical investigations carried out on the recovered fibers further confirmed the efficiency of the recycling process conducted at the highest explored temperature, allowing the recovery of cleaner fibers with an electrical conductivity value (8.04 × 10² S/m) closer to that of virgin fibers (2.20 × 10³ S/m). The proposed strategy is a true challenge in terms of saving energy, solving waste disposal problems, preserving the earth, and preventing the depletion of planet resources. Full article