Comparative Study on Dimensional Stability and Biological Durability of Poplar Wood Modified by Chemical and Heat Treatment

Abstract

The fast-growing species of Populus deltoides is of significant commercial importance to the Indian wood merchants. Despite its abundant availability and better treatability, the use of P. deltoides is limited due to its perishable nature. Heat treated and chemically modified Populus deltoides L. was thus explored for dimensional stability and biological durability to commercialise its use. Chemical modification was performed using a combination of citric acid and sodium hypophosphite. Heat treatment was done in a laboratory oven in air at 140 °C for 8h. Both chemically modified and heat-treated samples exhibited improvements in dimensional stability and biological durability in comparison to the untreated control sets. Chemical modification resulted in better dimensional stability. Anti-swelling efficiency of Populus deltoides was 2-2.5 times more for the chemically modified set compared to heat treatment in both radial and tangential directions. Chemically modified set became significantly more resistant to biodeterioration showing 5 times less mass loss by termites, whereas controls and heat-treated sets returned loss percentages which were comparable. Soil block bioassay with Trametes versicolor (TV) exhibited mass loss of 9.46 % for chemically modified samples, 40.26 % for heat treated samples and 50.02 % for the untreated controls, respectively. Rhodonia placenta (OP) followed a similar trend with mass loss of chemically modified set being 5.72 % and heat-treated set being 37 %, respectively, with the controls showing 43.85 % mass loss. Mass loss exhibited by the heat-treated samples were less than the controls, but the values suggested that heat treatment at 140 °C for 8 h failed to impart any substantial resistance against rotting fungi and termites.