Creep behavior and manufacturing parameters of wood flour filled polypropylene composites

The influence of wood flour content, coupling agent and stress loading level on the creep behavior of wood flour-polypropylene composites was investigated. Maleated polypropylene (MAPP; Epolene G-3003(TM)) was used as the coupling agent to treat the wood flour used as reinforcing filler for polypropylene composite. The tensile strength and modulus of various wood flour polypropylene composites (WPCs), manufactured using the melt blending, extrusion, and palletizing methods, were measured before performing the creep test. The residual tensile strength, creep strain, and fractional deflection of the resultant wood flour-polypropylene composites were measured by means of the creep test. It was shown that the tensile strength decreased with increasing wood flour level in the composites. The creep strain also decreased as the wood flour level increased. The presence of the coupling agent increased the tensile strength of the wood flour-polypropylene composites, compared with the specimens made of pure polypropylene. For those composites containing the coupling agent, the creep deflection was significantly lower than those made without any coupling agent. The creep strains of the WPC specimens observed during the creep test fitted perfectly with the four-element burger creep model. Further investigation is required of the effects of combined mechanical and environmental loading in varying proportions. (C) 2004 Elsevier Ltd. All rights reserved.