The Effects of adding wood flour content and curing temperature on some properties of polyurethane foam core in wood-based sandwich panel

Abstract

The objectives of this study were to examine the chemical, physical and mechanical properties of polyurethane (PU) foam produced by different wood flour contents and curing temperatures in a core layer of wood-based sandwich panels. The five conditions of wood flour in content of 2, 4, 6, 8, 10 and 12% were investigated and the curing temperature of 100, 120, 140, 160°C was studied with 10% wood flour content. The results showed that the cell size distribution and density of the PU foam were increased at the wood content above 6 %, which caused the compressive strength reduction. It was also found in PU with 10 % wood content that the curing temperature at 100 to 160 °C caused a decrease in 50 % of foam density compared with PU foam cured at the standard condition (i.e., at room temperature). SEM and cell size measurements show the anisotropy of PU foam and the increase of foam cell diameter by increasing the curing temperature from standard condition to 140 °C. Consequently, the compressive strength and specific value declined abruptly at the high curing temperatures starting from 100 °C. These results suggest that high curing temperature causes a decrease in the properties of wood-filled PU foam due to the high distribution in foam cell structure.