Preparation and recycling of polymer eco-composites i. Comparison of the conventional molding techniques for preparation of polymer eco-composites

The interest in natural fiber-reinforced polymer composites is growing rapidly due to their high performance in terms of mechanical properties, significant processing advantages, excellent chemical resistance, low cost and low density. In this study, the compression and injection molding of polypropylene (PP) and polylactic acid (PLA) based composites reinforced with rice hulls or kenaf fibers was carried out and their basic properties were examined. Rice hulls from rice processing plants and natural lignocellulosic kenaf fibers from the bast of the plant Hibiscus Cannabinus represent renewable sources that could be utilized for composites. Maleic anhydride grafted PP (MAPP) and maleic anhydride grafted PLA (MAPLA) were used as coupling agents (CA) to improve the compatibility and adhesion between the fibers and the matrix. Composites containing 30 wt % reinforcement were manufactured by compression and injection molding, and their mechanical and thermal properties were compared. It was found that the techniques applied for manufacturing of the eco-composites under certain processing conditions did not induce significant changes of the mechanical properties. The flexural strength of the compressed composite sample based on PP and kenaf is 51. 3 MPa in comparison with 46.7 MPa for the same composite produced by injection molding technique. Particularly, PP-based composites were less sensitive to processing cycles than PLA-based composites. The experimental results suggest that the compression and injection molding are promising techniques for processing of eco-composites. Moreover, the PP-based composites and PLA-based composites can be processed by compression and injection molding. Both composites are suitable for applications as construction materials