Thermo-vacuum treatment of poplar (Populus spp.) plywood

Poplar cultivation is enduring a long-lasting crisis in Italy, but it is still playing a relevant role in the Italian and European wood sectors. To improve its prospects, the manufacturers of poplar plywood have recently activated various strategies to make it a distinguished panel with specific performances. In this frame, thermo-treatment could open new applications and markets. The present study investigates the physico-mechanical properties of thermo-treated poplar plywood. For this purpose, panels were manufactured with urea-melamine-formaldehyde adhesive, both in a standard mixture and added with resorcinol. They were then treated by the Termovuoto process at 170, 190 and 210°C for 2 h. Changes in density, bonding quality, bending strength, modulus of elasticity, color and durability related to the aforementioned temperatures were investigated. Overall, the bonding quality of treated panels complied with the requirements of EN 314-1 and 2; bending strength and modulus of elasticity decreased, color darkened and durability increased. The latter is particularly important, because poplar wood is not durable and this process makes it suitable for use in humid conditions, offering new prospects for poplar plywood applications.