The effect of heat treatment method and process temperature on the glossiness of polyurethane varnishes applied to wood material surfaces

Abstract

In this study, the glossiness properties of polyurethane varnishes applied to the surfaces of heat-treated wood materials with different methods and at different temperature levels were investigated. Beech (Fagus Sylvatica L.) and Scots pine (Pinus Silvestris L.) wood samples were heat treated by applying three different methods (ThermoWood, oil treatment and hot air) and three different temperatures (170 °C, 190 °C and 210 °C). Then, the sample surfaces were coated with polyurethane (PU) varnish according to industrial applications. Surface gloss measurements of unvarnished and varnished wood samples were carried out in accordance with TS EN ISO 2813 principles. According to the results of the study, the effect of the heat treatment method was found to be significant on the gloss values for the unvarnished samples. Lower gloss values were determined in oily heat-treated samples. The gloss values were found to be similar in the samples treated with ThermoWood and hot air methods, and in these samples, the gloss values increased after the heat treatment at low temperature (170 °C) compared to the control (non-heat treated) samples. For the varnished samples, the effect of the heat treatment method was found to be insignificant on the gloss values. On the other hand, surface gloss values decreased due to the increase in heat treatment temperature in both unvarnished and varnished samples.