Materials
The natural touch
4 Sustainably sourced fibre reinforcements – ranging from banana fibres to wood flour – can boost the properties of plastics and reduce carbon footprint. Lou Reade reports.
4 Des renforcements en fibres de sources durables, allant des fibres de banane à la poudre de bois, peuvent stimuler les propriétés des plastiques et réduire l’empreinte carbone. Lou Reade témoigne.
4 Nachhaltig bezogene Faserverstärkungen – von Bananenfasern bis zu Holzmehl – können die Eigenschaften von Kunststoff stärken und den Ausstoß an Kohlenstoffen reduzieren. Lou Reade berichtet.
F
ibre reinforcement helps engineering plastics to replace metals in a host of applications by boosting mechanical properties like stiffness and strength. Many
of the most demanding automotive and electronics applications would still have to be made in metal, if it were not for the use of fibre reinforced plastics. Glass fibre continues to dominate but
there is also increasing use of carbon fibre reinforced parts, especially for structural parts in the automotive sector.
Green Revolution
The whole field of fillers and reinforcements for plastics is undergoing change, in the face of the green revolution. While there is no end in sight for the use of conventional fibres, a new generation of naturally derived materials is finding use in a variety of industries. Some of these, like wood plastic composites
(WPCs), are fully commercialised. WPCs usually comprise a commodity plastic like PVC or polyethylene (PE), with added wood flour or wood fibres. This creates a new type of material that can be cut and shaped just like wood - but is far more durable and weather resistant.
The material was popularised in North America - where it was used as a replacement for wood in fencing and decking panels - and has now spread to Europe. In fact, WPC decking panels were used in London’s Olympic Stadium, as one of its many examples of sustainable construction. The 4000 sq m O2 VIP platform was made
of WPC panels from Vannplastic, based near Chester in the UK. Its Ecodek panels are a blend of recycled
high density polyethylene (HDPE), wood fibres and compatibilising additives. The main ingredient (HDPE, 55 per cent)
is mainly derived from recycled milk bottles. This material costs about 75 per cent of the price of virgin material, but is of high quality. Wood fibres - from post-industrial beech hardwood from a sawmill in northern France - account for 40 per cent of the mix. The remaining 5 per cent is the pigments, UV stabilisers and coupling agents needed to hold everything together. “Lots of companies skimp on the additives,
but we invest a lot in them,” says Alex Collins, technical director at the company. Although the formulation for the boards
was quite standard, he says the testing was very rigorous.
Fig. 1. HDPE, which comprises 55 per cent of the final product, is derived mainly from recycled milk bottles.
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