The Effect of Heat Treatment on the Pull-off Strength of Optionally Varnished Surfaces of Five Wood Materials

Abstract

This study investigated the effects of heat treatment, following optional treatment with synthetic, water-based, and alkyd varnishes, on the pull-off strength of wooden materials sampled from oriental beech (Fagus orientalis L.), oak (Quercus petraea Liebl.), black poplar (Populus nigra L.), pine (Pinus sylvestris L.), and fir (Abies bornmulleriana M.). The test samples were subjected to heat treatment at temperatures of 165 °C and 175 °C for periods of 2 and 4 h with a total of 4 variations. With respect to the wood type, the samples of beech wood yielded the highest results for pull-off strength, while fir wood yielded the lowest. With respect to the varnish types, the highest pull-off strength was found in the samples of synthetic varnished beech (5,452 with a 37.2% improvement) at 175 °C heat treatment for 4 h, while the lowest results were obtained in the samples of fir (0.991 with a 48.5% decrease) at 175 °C heat treatment for 4 h. In conclusion, heat treatment significantly decreased the pull-off strength of the woods.