Biodegradation and appearance of plastic treated solid wood

Abstract

The biodegradation of plastics and wood with different susceptibility to fungal attack have in this study been compared in order to show the biodegradability in relation to the properties of plastic and solid wood. Wood blocks of Scots pine and English Oak were treated with biodegradable aliphatic polyester, polycaprolactone, and a non-biodegradable aromatic thermoplastic, polystyrene. The plastics were applied to the wood samples dissolved in an organic solvent and thereafter the treated wood samples were exposed to brown rot decay ( Postia placenta) in an agar plate test for 8 weeks. The polycaprolactone treatments did not result in wood protection, whereas polystyrene treatments provided a protection from fungal attack. Both plastics are transparent and after treatment the solid wood blocks retained their natural wood appearance with a somewhat darker shinier surface. Scientific relevance Usually commercial wood-plastic composites are made using wood derived lignocellulose-fibers melt-blended in a screw extruder with a plastic matrix, and then the resulting material is mainly a plastic (in terms of properties and appearance) which contain some lignocellulose. We have instead used solid wood to which we have added transparent plastics, which preserve the unique and precious esthetic value of natural wood. This study describes the biodegradation of two (a more and a less resistant) wood species in combination with a biodegradable and a non-biodegradable plastic. The purpose was to study any synergetic effect in the biodegradation property between solid wood and plastic since there is a socio-environmental desire to use biodegradable plastics of renewable raw material for e.g. composite material. We show that both the wood and the plastic influence the biodegradation, for example by using an easily degraded European wood specie in combination with a biodegradable plastic (polycarolactone) no protection of the wood is obtained, whereas a relative small amount recalcitrant plastic (polystyrene) can somewhat protect both Scots pine and Oak wood without significantly compromising their appearance.