Property changes of wood-fiber/HDPE composites colored by iron oxide pigments after accelerated UV weathering

Abstract

Four kinds of iron oxide pigments were added into wood-fiber/high-density-polyethylene composites (WF/HDPE) at three different concentrations, to determine the effects of pigments on the changes in the color and mechanical properties of the composites before and after UV accelerated weathering. HDPE, wood fibers, pigments and other processing additives were dry-mixed in a high-speed mixer. The mixtures were extruded by two-step extrusion process with a self-designed twin-screw/single-screw extruder system. Color of the samples was determined according to CIE 1976 L*a*b* system by a spectrophotometer and the bending properties were tested to evaluate the mechanical properties before and after accelerated UV weathering. The result shows that the modulus of elasticity of WF/HDPE did not obviously changed after incorporating with the pigments, but the bending strength increased. After accelerated aging for 2000 h, both color and mechanical properties significantly changed. Iron oxide red and black performed better than the other two pigments, and the pigments dosage of 2.28% in the composites is favourable.

Keywords

wood-plastic composite / pigments / weathering / color / flexural property