Rheology and Processing of HDPE/Wood Flour Composites

Abstract Rheological and mechanical properties of extruded wood plastic composites have been investigated for the purpose of providing a better understanding of processing conditions in profile extrusion for this novel class of thermoplastics composites. The basic formulations prepared for the study were comprised of 60 wt.% HDPE, with or without LLDPE-MAH as coupling agent, compounded with up to 40 wt.% of wood flour and lubricant. Capillary and rotational rheometers were employed to measure the rheological properties of the melt composite. A cooled die at the end of a single screw extruder was used for the extrusion of rectangular profiles having smooth surfaces and edges. Finite element flow simulation was used for the interpretation of the experimental data. Once extrusion steady conditions were achieved in the die, linear output was monitored and profile samples were cut for determination of flexural modulus and strength. The results showed that flexural properties can be influenced by many factors such as, coupling agents, lubricants, processing conditions, die pressure drop and cooling at the die. Linear speed of HDPE wood-plastic profile extrusion and end-use properties are strongly influenced by combination of these factors.