Hemp fibre reinforced biodegradable polyesters - effect of fibre refinement by steam explosion

A biodegradable copolyester was compounded in a twin-screw extruder with 25 wt.-% hemp fibres and then injection moulded into tensile test bars. Two different types of fibres were used: An exclusively mechanically treated fibre (MEC) and a fibre refined by steam explosion (STE). The mechanical properties of STE fibres are 30% lower than those of MEC frbres, nevertheless the same reinforcing effect was obtained. This is mainly due to the higher aspect ratio of STE and the better fibre distribution in the STE composites. A maximal reinforcement was not achieved, because of a too weak fibre matrix adhesion in combination with an insufficient fibre length caused by fibre damage in the extrusion and injection moulding process.