Problem definition and objectives: Currently, due to high prices and non-biodegradability of synthetic fibers, there has been a significant increase in using natural fibers as reinforcement in polymer composites. Natural fibers have been welcomed by engineers and researchers as suitable alternatives to synthetic fibers, considering their unique characteristics such as low density, low production cost, good modulus and strength, abundance, accessibility, renewability, recyclability, biodegradability, and environmental compatibility. The type and proportion of lignocellulosic materials in combination with polymer resins play a crucial role in determining the final properties of these composites and significantly influence their ultimate applications. Therefore, this study aims to explore the possibility of manufacturing and reinforcing polymer composites (epoxy resin) using different proportions of lignocellulosic materials (reed stem, roselle stem, and palm leaf) and analyze their physical and mechanical properties.
Materials and Methods: Reed stem, roselle stem, and palm leaf were obtained from the Chahnameh Nursery and Baqiyatallah Educational and Research Complex at Zabol University. The materials were dried in a laboratory oven at 103°C for 24 hours. Epoxy resin (AD-301) and epoxy hardener (HA-12) from Mokarrar Company were used in a 100:10 ratio. The study variables initially included three lignocellulosic materials: roselle stem (TS), reed stem (RS), and palm leaf (PL) at three levels: 10, 30, and 50 percent (weight ratio of lignocellulosic materials to epoxy resin). Lignocellulosic-reinforced epoxy composites were manufactured using a manual layup method with a wooden mold (300 × 300 × 50 mm) under press conditions (80°C and 6.2 MPa pressure for 3 hours). Tensile, flexural, and water absorption tests were conducted according to ASTM D3033, ASTM D790, and ASTM D570 standards, respectively. The best treatment was subsequently alkaline-treated at 5 and 10 percent levels to improve physical and mechanical properties, and the impact of alkaline treatment was evaluated.
Results: Epoxy composites reinforced with 10% roselle stem exhibited the lowest tensile strength, flexural strength, and water absorption. Mechanical properties increased with lignocellulosic material proportion up to 30%, with palm leaf composites at 30% showing the highest mechanical properties. Increasing the lignocellulosic material proportion from 30% to 50% resulted in decreased tensile and flexural strength. The highest water absorption was observed in samples with 50% roselle stem, while the lowest was found in samples with 10% palm leaf. The optimal treatment, based on physical and mechanical properties, was identified as 30% palm leaf reinforcement. Alkaline treatment at 3% and 5% improved the mechanical and physical properties of epoxy composites, with flexural strength, flexural modulus, and tensile strength increasing by 11.9%, 12.7%, and 15%, respectively, compared to untreated samples.
Conclusion: The study demonstrated that incorporating lignocellulosic materials in epoxy resin enhances the mechanical properties of hybrid epoxy-lignocellulosic composites. Utilizing these renewable resources not only reduces dependence on petroleum-based materials and costs but also contributes to natural resource conservation and environmental pollution reduction. The findings underscore the potential of these composites as lightweight, robust, and environmentally friendly materials in various industries, including automotive, construction, and packaging.