Post-process hot-pressing of wood-polymer composites: Effects on physical properties

Replacing plastic with wood fibres in polymer-based products, such as facade panels, makes building more sustainable. One such bio-based material is Wood-Plastic Composites (WPC) made of wood fibres and a thermoplastic matrix. The latter enables post-process thermal forming of WPC semi-finished components. As an additive industrial manufacturing process, three-dimensional elements can be prefabricated using hot pressing technology. This could promote new building applications. However, knowledge about which essential characteristics change physical parameters to what extent is so far scarce. This study revealed that, in contrast to heating time and pressing force, the temperature causes the most significant and strongest physical changes. Extreme hot-pressing temperature resulted in 37% higher water absorption, and this was least dependent on the compound formulation. Colour, density and wettability changed differently depending on WPC composition and hot-pressing parameters. Apart from density, monitoring of colour, wettability and water absorption are suitable measures for production control as they respond most sensitively to the process. As a practical implication, product developments from hot-pressed WPC elements should consider lower temperatures and shorter heating times, whereas the pressing force hardly plays a role.