Flow Study of Wood Plastic Composite Through a Circular Die in an Extrusion Process

Abstract

This paper presents a theoretical study on wood plastic composite's (WPC's) flow, based on empirical data provided by a twin screw extruder and experimental data from a rotational rheometer. Four circular extrusion dies were designed and manufactured to produce rod shaped products with various diameters (D) and length-to-diameter ratios (L/D). Also other parameters such as screw speed (N), polymer matrix type, polymer viscosity (m) and percentage of wood content (W) were selected as the process or material factors to investigate the relationship between the flow characteristics and the above mentioned factors. Moreover, frequency sweep experiments were performed on the selected composites using rotational plate rheometer. The results from these experiments have been studied by using power law and Bingham plastic models which are believed as proper models for WPC in the literature. The results show that Bingham plastic model can explain the flow characteristics of this composite much better. Moreover, although the results of a frequency sweep test can give the required values for parameters in the Bingham plastic model, these quantities will be different with those from empirical experiments.