Physical and chemical properties of Castanopsis fargesii wood after heat treatment in sand or vacuum media

Abstract

Castanopsis fargesii is among the most prevalent hardwood species in South China. To improve the poor dimensional stability of C. fargesii wood, heat treatments were performed using vacuum or sand as the medium at four temperatures from 170 degrees C to 215 degrees C for 4 h. As a medium, vacuum or sand can create a low oxygen environment. The results showed that, as the temperature increased, the oven-dry density decreased, whereas the dimensional stability and the total color change (Delta E*) increased with both media, two different changing patterns of a* and b* were observed, the lignin content increased, and the holocellulose content decreased. The oven-dry density decreased 9.4% and 25.5%, volume shrinkage ratio decreased 27.8% and 37.7%, and the Delta E* was 19.63 and 45.52, the lignin contents increased from 17.62% to 28.62% and 42.87%, and the holocellulose contents decreased from 80.49% to 69.43% and 51.04% when C. fargesii wood was heated under vacuum and with sand at 215 degrees C, respectively. Overall, sand heat treatment affected wood physical and chemical properties more than vacuum heat treatment. The analysis of functional groups and crystallinity also showed that there were severe changes in C. fargesii wood under sand heat treatment.