Optimization of the process of heat treatment of cut-helled veneer for the production of plywood with increased consumer properties

Abstract

The article presents the results of a comparative analysis of the properties of plywood products based on ureaformaldehyde resins using heat-treated birch shelled veneer. The conducted full–factor experiments have shown that high water resistance and strength indicators of plywood based on heat-treated veneer are provided at a processing temperature of 160 ºC and a duration of 240 minutes, for combined plywood with outer layers of heat-treated veneer – at a temperature of 200 ºC and a heating duration of 180 minutes. The use of recommended veneer heat treatment modes that do not lead to a decrease in the strength of plywood leads to a decrease in water absorption and swelling rates for combined plywood by up to 9 and 44 %, respectively. It has been established that plywood with outer layers of thermomodified veneer has higher strength characteristics in comparison with plywood based on thermomodified veneer and is slightly inferior to it in water resistance. The use of thermomodified veneer only for the outer layers of plywood products does not lead to a significant decrease in the strength indicators of plywood, however, it can significantly reduce its hygroscopicity and increase water resistance, which expands the scope of its application.