The utilization of biochemically modified microfibers from grain by-products as reinforcement for polypropylene biocomposite

The presented research study aims to evaluate microfibers from grain by-products as a substitute for wood flour in wood-thermoplastic composites. Grain husks are an abundant and cheap source of annual, renewable raw material, which besides lignocellulose, may also contain substantial amounts of starch, proteins and fats. These grain residues may negatively affect the mechanical properties of their composites, and generate an odor when decomposition occurs at higher temperatures during plastics processing. Such odors may also be present in the end-product. In order to overcome this drawback, in this research study, a simple and effective enzymatic treatment is proposed. This environmental friendly process removed protein, starch and fats in selective manner. Treated microfibers have shown enhanced thermal stability for ca. 20 degrees C at 1% of weight loss. This correlates with lower amount of odor emission during plastics processing as well as in the final, injection molded parts (25-65% decrease). The mechanical properties of composites were either preserved, or slightly improved. All results were compared to standard injection molded softwood WPC.