Influence of Separation and Processing Systems on Morphology and Mechanical Properties of Hemp and Wood Fibre Reinforced Polypropylene Composites

Abstract

ABSTRACT The separation processes of natural fibres and the technique of composite processing influence the fibre degradation, length and herewith the composites properties in a wide range. Different separation processes (mechanical, refiner and enzymatic separation) were investigated with hemp and partially with flax and wheat straw. Selected fibres were mixed with PP in a cascade mixer (heat-cooling mixer system) or compounded in a twin screw extruder and formed into test specimens by injection moulding with 40 wt.% fibre content. Thermomechanical processed hemp fibre-PP composites showed higher mechanical properties in cascade mixer process compared to twin-screw extruder or agglomerated process. Wood fibre reinforced polypropylene composites containing hard wood fibre were prepared by extrusion-injection moulding, mixer-injection moulding, compression moulding and direct extrusion (profile) process with 30 wt.% and 50 wt.% fibre contents. It is seen that extrusion-injection moulding process showed best properties compared to other processes in maximum cases.