Profile extrusion and mechanical properties of crosslinked wood-thermoplastic composites

Challenges for wood-thermoplastic composites to be utilized in structural applications are to lower product weight and to improve the long-term load performance. Silane crosslinking of the composites is one way to reduce the creep during long-term loading and to improve the mechanical properties. In this study, silane crosslinked wood-polyethylene composites were produced by reactive extrusion and subsequently manufactured into rectangular profiles. The silane crosslinked composites were stored in a sauna at 90 degrees C to increase the degree of crosslinking. The toughness of the silane crosslinked composites was significantly higher than for the non-crosslinked composites. Improved adhesion between the wood and polyethylene phases is most likely the reason for the improved toughness of the crosslinked composites. There was no significant difference in flexural modulus between the crosslinked and non-crosslinked composites. In addition, impact testing showed that the impact strength of the crosslinked composites was considerable higher (at least double) than the non-crosslinked. The effect of temperature on the impact strength of the composites indicated slightly higher impact strength at -30 degrees C than at 0 degrees and at 25 degrees C, and then an incrase in impact strength at 60 degrees C. Crosslinking also reduced the creep response during short-term loading. Moreover, scanning electron microscopy on the fracture surface of the crosslinked composites revealed good adhesion between the polyethylene and wood phases.