A study of the physico-chemical properties of dried maritime pine resin to better understand the exudation process

The aim of this study was to have a better understanding of the phenomenon of resin exudation on pinewood boards due to the liquefaction of the resin caused by the heat of solar radiation. Resin exudation is a crucial problem for the maritime pine industry, as it may strongly decrease the wood’s aesthetics submitted to outdoor exposure. The softening temperature of dried pine resin was analyzed and the results were examined relative to its physico-chemical properties. To achieve this, resin samples were dried under different conditions (60°C, 120°C during 16 h and at 150°C during 24 h). After 3 months of post-drying at ambient temperature, their softening temperatures were measured by thermomechanical analysis. These same samples were subsequently studied to determine their chemical, structural and morphological properties. Samples with a low drying temperature (60°C) had high opacity attributed to crystallinity and porosity. These elements partially explained a higher softening temperature than for the other samples. Different chemical modifications of resin were also observed due to temperature, with a significant amount of oxidized derivatives for samples dried at low temperature and dehydrogenated compounds for samples dried at high temperature.