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2010
Conference Paper
Titel
Properties of extruded wood-plastic composites (WPC) based on refiner wood fibers and hemp fibres
Abstract
Refiner fibres (TMP/MDF fibers) are an interesting raw material alternative to the currently used wood flour in wood-plastic composites (WPCs) from a technological, logistical, and economical point of view. Today, refiner fibres have not been used on an industrial scale due to challenges of fibre feeding into extruders. In this research project, a compounding process for refiner fibres using a thermokinetic mixer was developed. The resulting compound displays little fiber damage and can easily be fed and processed in a commercial twin-screw, conical, counter-rotating extruder using a crammer feeder. It was determined that strength properties of WPCs with black locust (Robinia pseudoacacia L.) refiner fibers were improved compared to WPCs with Scots pine (Pinus sylvestris L.) refiner fibers. As pine fibers are longer than black locust fiber (4,5 vs. 1 mm), it is evident that fiber length does not have an influence on the strength properties of WPCs. However, the influence of fiber aspect ratio is not know yet. Extractives (e.g., tannins) in black locust appear to improve interfacial bonding between wood refiner fibers and polypropylene fibers. It is likely that black fibers were coated with extractives and lignin during the refining process. Further investigations are planned to determine the influence of refiner fiber surface characteristics to interfacial adhesion of WPCs, and to obain information on the effect of fiber aspect ratio and on improved processing conditions so that the full potential for matrix reinforcement using this type of fiber can be exploited.