Hardness and contact angle of thermo-treated poplar plywood for bio-building

Abstract

Abstract: The interest towards poplar cultivation and its wood has recently been growing in Italy, where the use of timber and wood-based materials in construction is increasing as well. Poplar plywood, with a national production of around 270.000 m3 in 2017, is a key product for the Italian wood sector, and currently is destined for several applications as component for furniture and motorhomes. Previous research has shown that thermal treatment can be effectively applied to poplar plywood in order to make it suitable to the requirements of new end-uses. The present study aims to widen the knowledge of the effects of thermal treatment on poplar plywood. With this purpose, 7-layered, 12-mm thick plywood bonded with urea-melamine-formaldehyde (UMF) resin was thermally treated for 2 h at 170, 190 and 210 °C through the Termovuoto® process. The treatment aimed to improve the dimensional stability and durability against fungal decay. The process was set at lower temperature and shorter time than those of many thermal treatments commonly used in practice in order to limit the reduction in mechanical properties and to maintain an adequate bonding quality. The above properties were already verified by previous research, whereas in this study Brinell hardness and contact angle of treated panels were investigated as relevant for several end-uses that can be prospected in building and in outdoor environments. Brinell hardness decreased from 10.8 to 8.3 N mm-2 and contact angle increased from 75.8° to 103.6°. Overall, treatment at 190 °C seems the most suitable to induce balanced modifications in the panels. From a technical point of view, these appear ready to enter the market, for instance for use in exterior claddings, partitions and outdoor flooring.