Measuring interactions between rosin and turpentine during the drying process for a better understanding of exudation in maritime pine wood used as outdoor siding

Abstract

The interactions between rosin and turpentine during the drying process were studied to better understand wood pine resin exudation in outdoor use under solar heat. Resin exudation is an important concern for industrials, as it may strongly decrease the wood’s aesthetic value. Resin viscosity change with temperature variations induced an alteration in the resin’s appearance from 65 °C. Resin, which is opaque at ambient temperature, becomes translucent above 65 °C. Resin samples were dried at temperatures respectively lower and higher (60 °C and 90 °C for 16 h) than the threshold. For all measurements, eight resins from different trees were harvested using an isolation technique developed by Biogemme®. After drying, samples were kept at room temperature, and the softening point temperature and the remaining turpentine amount were measured over time using Thermomechanical Analysis (TMA) and Thermogravimetric Analysis (TGA) respectively. After three months, the results show that a majority of samples dried at 90 °C have a softening temperature under 25 °C, while all the samples dried at 60 °C have a softening temperature above 60 °C. These results can be explained by a modification of the physical properties of the samples dried at 90 °C: they start to behave like gels, preventing the evaporation of their liquid phases. These new results highlight some properties of resin that may be interesting to develop a new strategy for reducing resin exudation on outdoor wood siding, by fixing the resin inside the wood during the industrial drying process.