Wood-plastic composites: processing simulation, optimizing tooling and property correlations in extruded profiles and injection molded components

Abstract

There is a growing interest for applications of wood plastic composites in extruded profiles and injection molded components using traditional thermoplastic commodities suca as PVC and polyolefins. Applications are mostly related to building products such as deckings and balcony railings, fences, window and door linings,etc and in the motorcar industry, their lightness is an advantage if compared to conventional wood or mineral filled thermoplastic composites.In wpc, the flow properties are strongly influenced by the type and the amount of the filler. The melt viscosity is a function of the shear rate, temperature, pressure gradient and tool geometry (Mold and die). The cooling rate and the need of high working pressure for profile compactation at the extrusion die are critical processing conditions and requires careful design tooling preferably optimized by computer simulation. Usually, die design for extrusion of bulky and complex geometries requires information on processing parameters: fluid velocity profile at the die; apparent shear rate; residence time; flow properties (consistency and power index n) and die geometry. Pressure drop at the die depend upon the combination of such factors being the key factor for the profile compactation at the die and consequently the profile linear output and specific rigidity. The present work intends to investigate the effects of flow conditions within the die using the softwares Nextrucad® and Profilecad® from the Canadian company Polydynamics Inc. The mold design for inection molding of wpc components will be performed using the software MoldFlow for cavity filling, cooling rate conditions and residual stress analysis. (AU)