Influence of heat treatment of sycamore and spruce wood on tensile adhesion strength of transparent coatings

The aim of this study was to investigate the effect of heat treatment on adhesion strength of transparent coatings. Heat treatment is one of the processes used to modify the properties of wood. Heat-treated wood (thermowood) is considered an eco-friendly alternative to chemically impregnated wood materials. For this purpose, specimens with 150×100×20 mm3 of Sycamore and Spruce wood exposed to heat treatment at 160 and 180 °C for ٣ hours. After heat treatment, surfaces of all specimens sanded and coated with transparent coatings in two separate processes: sealer-clearer water-based coating and water-based special coating for Thermowood. The tensile adhesion strength (Pull-off) and scratch Cross-Cut was measured according to ASTM D-4541 and ASTM D 3359, respectfully. The results revealed that by increasing the temperature of heat treatment, adhesion strength was reduced. The decrease in the sealer-clearer coating was statistically significant. However, there was no significant difference observed between different temperatures for Thermowood special coating. It was also found that the adhesion strength of coating in Spruce wood was higher than Sycamore wood. The highest adhesion strength was obtained in the Thermowood special coating in heat-treated specimens at 160 °C and the least observed in sealer-clearer coating in heat-treated specimens at 180 °C.