Preparation and properties of cotton stalk bundles and high-density polyethylene composites using hot-press molding

Compared to extrusion and injection, hot-press molding can produce natural fiber plastic composites with many advantages. In this study, large cotton stalk bundles and HDPE composites were fabricated using hot-press molding. The effects of fiber size and drying temperature on the mechanical properties and thickness swelling of these composites were investigated. Cotton stalk bundles of three different sizes were oven-dried at 100°C 120°C, 140°C, and 170°C for 24 h. MAPE (5%) and phenol formaldehyde resin (5%) were added to enhance the interfacial bonding between the bundles and HDPE. Results showed that the mechanical properties of composites increased with the size of the cotton stalk bundles. The best mechanical properties were created at drying temperatures of 100°C and 140°C, with an obvious drop at drying temperatures of 120°C and 170°C. Thickness swelling of the composites was greatly improved and below 5%. The composites showed the lowest thickness swelling at a drying temperature of 170°C, and the highest at 120°C. Good bonding was found between cotton stalk fibers and HDPE, due to the addition of MAPE.