Abstract
The effects of wood flour and plasticizer on the rheology and extrusion of polyvinyl chloride (PVC) based wood—plastic composites are investigated. The intention of the study was to determine an optimal pair of PVC based wood—plastic composites that should exhibit substantially different rheological behaviors so that patterns similar to grain of wood can be developed inside and on the surface of the product when two selected wood—plastic compounds are extruded at once. The rheological study reveals that the shear viscosity and shear thinning behavior of the composites can be controlled by varying the contents of wood flour and plasticizer. It is also found that the depression of glass transition temperature due to the addition of plasticizer is substantially reduced by the loading of wood flour. In addition, various wood—plastic composites were compounded into different colors, and several pairs of the compounds with different rheological properties were extruded in single and twin screw extruders to see whether any wood-patterns are developed. When the differences in the shear viscosity and the glass transition temperature of the two compounds were too large, the incomplete plasticization of the higher viscosity component was observed due to the premature plasticization of the lower viscosity component. It is shown that distinct wood-patterns were developed both inside and on the surface of the extruded products only for the pairs of the composites with an optimal differences in both viscosity and plasticizer content.
© 1999, Carl Hanser Verlag, Munich
