Injection Molding of Wood-Plastics Composites using Powder Technology

Abstract

In this work, wood plastics composites (WPC) were produced by injection molding and characterized in terms of density, hardness, morphology and mechanical properties (impact, flexural and tensile). In particular, the initial material used (linear low density polyethylene as the matrix and maple wood flour as reinforcement) was dry-blended in a powder form and no preliminary compounding step (like extrusion) was performed before molding to save on processing time/cost and to limit material degradation. As a first step, no coupling agent or surface treatment was performed and only the effect of wood content between 0 and 40% wt. was studied after optimization of the molding conditions. The results show that adding up to 40% wt. of wood flour increased the tensile modulus of LLDPE by 145% (from 210 to 515 MPa), without losing much on tensile strength (15.2 to 14.2 MPa). Similarly, a substantial improvement in flexural modulus was obtained with an increase of 281% (577 to 2204 MPa). On the other hand, density increased from 930 to 1091 kg/m3, while notched Charpy impact strength decreased from 219 to 19 J/m, as well as tensile elongation at break dropping from 1567 to 20%.