Analysis of Pine Resin Properties as a Way to Understand and Prevent Exudation from Wood Material

A major function of resin is to provide defense against external attacks by releasing the resin flow on the attacked or damaged area. Nonetheless, the leakage of the resin on the surface can have a negative aesthetic and economic impact on wood material. The aim of this study is to investigate which treatments affect the chemo-physical properties of the resin in order to hinder the exudation on wood surface during service. To achieve a thickening of the resin, it is necessary to remove the volatile turpentine, and several studies have been carried out in this direction, providing useful information about this process. The heat treatment at different temperatures, 60°C, 100°C and 150°C, respectively, gives different mass losses, thus confirming that the turpentine can remain for long time in the resin, and the changes in structural, morphological, and chemical properties are affected by the temperature. FTIR spectroscopy, before and after thermal treatment, does not show major changes in chemical structures. However, from the samples analyzed with UHPLC-DAD-MS significant differences of the ratios of 20 compounds were observed, which characterize possible chemical reactions, such as decomposition, dehydrogenation, oxidation and isomerization. After heat treatment, the glass transition temperature of resin increased. Color changes are evident: resin becomes darker with increasing the temperature of treatment, apart from the resin heated at 100°C. The chemical changes in the composition of the resin caused by heat treatment need further investigation.