Extrusion specialist Berstorff (Hanover / Germany; www.berstorff.de) has teamed up with the bioprocess engineering department of Hanover University of Applied Sciences (Germany; www.fh-hannover.de) to develop a new twin-screw extruder concept for the production of natural fibre compounds. Compounds reinforced with natural fibres are a cheap, light-weight and ecologically sound alternative to conventional compounds. The natural fibres can be directly processed without any energy-intensive pre-drying and Berstorff’s patented “multi-process-elements” (MPEs) ensure gentle and cost-effective incorporation of natural fibres into compounds. In addition, the MPEs allow the line to be tailored to the moisture content of the material to be processed – from wood flour or wood fibres up to flax and hemp.

The polymer, along with additives, is introduced to the feed zone by gravimetric metering and melted in the plasticising section. The natural fibres are then introduced through downstream side feeders and gently incorporated into the melt by means of the MPEs. Several openings arranged along the processing section then remove the moisture released from the natural fibres. After the natural fibres have been mixed in, the melt is degassed under vacuum to completely eliminate any moisture or low-molecular components.