Change in key mechanical properties from postprocess hot pressing of commercial wood-plastic composites with different fibre contents

Wood-plastic composites contain a high proportion of wood fibres with a reduced dependence on mineral oil. In addition to decking boards, linear facade panels are also frequently produced. The thermoplastic matrix enables subsequent forming under heat for the creation of three-dimensional facades, which offers new design options. To date, in previous studies, effects from the extrusion process itself on essential product properties have been reported; e.g. the maximum extrusion temperature must not exceed 210 degrees C to protect the wood fibre, and higher compound compaction increases material strength. However, the conditions and effects from later reheating for the purpose of reshaping existing profiles into curved elements have rarely been addressed. This study investigates how intensively decisive application-specific mechanical properties change after postprocess hot pressing under different combinations of temperature, heating duration and pressing force. Comparative tests were carried out on two commercially available WPCs with different wood contents. The flexural strength of both sample types reacted most sensitively to heat, followed by the stiffness modulus, which was significant only for the high-fibre type. A longer heating time at a lower temperature, on the other hand, counteracted the loss of strength. The impact resistance hardly changed, and the Brinell hardness was not affected at all. With regard to fastener withdrawal, both WPC types showed contrasting behaviour. Overall, the results indicate an effective use of postprocess hot pressing of WPCs in facades with partwise significant but calculable changes in WPC properties.

Automated summary

Wood-plastic composites with high wood fiber content and reduced dependence on mineral oil offer new design options for three-dimensional facades. This study investigates the effects of postprocess hot pressing on the mechanical properties of WPCs and finds that heating time and temperature have an impact on flexural strength and stiffness modulus.