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 d ifferent types of fibres were used: An exclusively mechanically treated fib re (MEC) and a fibre refined by steam explosion (STE). The mechanical prope rties of STE fibres are 30% lower than those of MEC frbres, nevertheless th e same reinforcing effect was obtained. This is mainly due to the higher as pect ratio of STE and the better fibre distribution in the STE composites. A maximal reinforcement was not achieved, because of a too weak fibre matri x adhesion in combination with an insufficient fibre length caused by fibre damage in the extrusion and injection moulding process.