High temperature drying effect against resin exudation for maritime pine wood used as outdoor siding
Résumé
The effect of temperature during the wood drying process was studied in order to prevent resin exudation on the surface of maritime pine wood boards used as outdoor siding. Resin exudation is a crucial concern for the maritime pine industry, as it may strongly decrease the wood aesthetics during outdoor exposure. In a previous study, it was observed that the thermal history of rosin can change the softening point temperature of its compounds. Using heat treatment, this temperature can shift from about 40 °C–60 °C, which corresponds to the maximal surface temperature of an unpainted wood siding in a temperate climatic zone. In the present study, green wood boards from various trees were dried at various temperatures (60 °C, 90 °C, 120 °C and 150 °C) and directly evaluated after drying regarding their resistance to exudation. To perform this test, an infrared radiative system was developed in order to recreate summer outdoor conditions. The results show the absence of exudation for boards dried at high-temperature (150 °C). In order to better understand the effects of a heat treatment on resin compounds inside wood, they were studied using HPLC after extraction. The analysis was compared to a standard rosin used in a previous study showing strong similarity. These results highlight some new effects of high temperature drying which may offer new strategies for reducing resin exudation on outdoor wood siding by fixing the resin compounds inside the wood.