Sustainable composites from agricultural waste: The use of steam explosion and surface modification to potentialize the use of wheat straw fibers for wood plastic composite industry

Wood plastic polymer composites (WPC) have been used in the past few years in different fields such as building, furniture and automotive. Lignocellulosic fibers derived from agricultural waste can perform as low cost and more environmentally friendly replacement for wood in WPC. In this work, cellulose fibers obtained from wheat straw fibers via steam explosion were chemically modified with hexadecyltrimetoxy-silane (HDS) and [3-(2-aminoethylamino) propyl] trimethoxysilane (AEAPS) for polypropylene (PP) reinforcement. The thermo-mechanical properties of the composites were compared to wood-powder reinforced polypropylene. The thermal stability of wheat straw fibers increased after steam explosion by 5% and after surface modification by 7% and 9%, with both HDS and AEAPS, respectively, enabling higher processing temperatures. Wheat straw fibers modified with AEAPS enhanced the stiffness of PP by 55%, while wood powder showed an increase of 41%. The toughness of the composite material was also considerably improved by 51% and 42% using HDS- and AEAPS-treated wheat straw fibers. Tensile and flexural strength increased in the presence of coupling agents due to an optimized stress transfer. This work demonstrates that agricultural waste can perform as an economically sustainable reinforcement for polypropylene, promoting the replacement of wood in WPC applications. POLYM. COMPOS., 40:E53–E61, 2019.