A COMPARISON OF COMPOUNDING PROCESSES FOR WOOD-FIBER THERMOPLASTIC COMPOSITES/

This study was carried out to investigate the feasibility of developin g a continuous compounding process for wood-fiber/thermoplastic compos ites using the Szego mill, a unique, high speed planetary ring-roller grinding mill. Prior to compounding, air-dried sawdust was ground to e valuate the grinding effect in the mill. As the feed rate and the mill speed increased, the particle size increased and decreased, respectiv ely. Sawdust particles were successfully compounded in linear low-dens ity polyethylene using the Szego mill without any major heat applicati on. A Gelimat mixer, used for the compounding of wood fiber through a high-shear thermokinetic mixing process, was also employed for compari son. Composites with 30 wt% wood fiber were prepared by both compoundi ng processes, and their mechanical properties were evaluated. The use of a compatibilizer in compounding improved the mechanical properties of the composites regardless of the compounding process. The composite s prepared by Szego mill compounding showed comparable strength proper ties with their counterparts from the Gelimat mixer. Power consumption during mill compounding was in the range of twin-screw extruder proce ssing.