Effect of heat treatment at mild temperatures on the composition and physico-chemical properties of Scots pine resin

A major function of resin in trees is to provide defense against external attacks by releasing the resin flow in the attacked or damaged area. Nonetheless, leakage of resin on the surface can have negative aesthetic and economic impacts on wood materials. The aim of this study was to investigate how heat treatment affects the physico-chemical properties of the resin of Pinus sylvestris L. to hinder exudation on wood surfaces during service. To reduce the fluidity of the resin, it is necessary to remove the volatile fraction of resin, and several studies have been carried out in this direction, providing useful information about this process. The results from thermal analyses (DSC, TGA) confirmed that heat treatment at mild temperatures, 80 °C, 90 °C and 100 °C had a positive effect on increasing the glass transition temperature T_g and that the T_g and the residual volatile content were strongly correlated. FTIR spectroscopy, before and after heat treatment, did not reveal major changes in chemical structure, while UHPLC-DAD-MS analysis revealed significant differences in the ratios of compounds, which are the result of possible chemical reactions, such as dehydrogenation, oxidation and isomerization.