Compatibility of softwood flour and commercial biopolymers in injection molding

This study is focused on wood flour-reinforced biopolymers for injection molding. Eight commercial biopolymers were compounded with 30 and 50% wood flour and injection molded. Thermal processability via extrusion was evaluated by use of the resulting melt pressure, melt temperature, and machine load, during injection molding the injection pressure was taken. Clear increases of melt- and injection pressures could be determined at rising fiber load and better shaping of the molded parts was observed. The mechanical performance of the composites and the neat polymers was evaluated by tensile-, bending-, and impact properties. To study the effects of different fiber concentrations, multiple comparison tests were calculated. High variations in the mechanical properties and in hygroscopic behavior were found between the different biopolymers. Through incorporation of wood flour, the E-modules of all polymers were significantly improved. The strength values of the various biopolymers offered different trends because of the reinforcement. The polylactic acid (PLA) and the cellulose-based polymer Biograde showed significant decreases in strength by addition of wood flour. Scanning electron micrographs of a 50% filled PLA compound revealed low fiber matrix adhesion. Impact strength and elongation at yield of all investigated polymers dropped dramatically with rising fiber content. POLYM. COMPOS., 31:443-451, 2010. (C) 2009 Society of Plastics Engineers