Effect of thermal modification on mechanical, physical and biological properties of Picea abies (L.) H.Karst.

Abstract

Background: Wood modification by heat treatment has become more commercially important over the years. Thermal modification is predominant among all modifications in the market. Heat treatment alters structural compositions of the chief polymeric constituents of wood (cellulose, hemicellulose and lignin) and significantly improves its performance in service.

Methods: In the present study, thermal modification of Picea abies was attempted at temperatures of 180^oC, 210^oC and 240^oC to examine changes in mechanical strength, dimensional stability, aesthetic appearance of wood and resistance to contamination by staining fungi.

Results: Samples treated at 180^oC showed a 0.62% reduction in MOE in comparison to untreated wood sample controls. 2.85% and 9.88% reductions were observed in samples treated at 210^oC and 240^oC respectively. Similar trends were observed for MOR values with samples treated at 180oC exhibiting a reduction of 4.6% in MOR values, and 22.99% and 39.09% reductions were observed in samples treated at 210^oC and 240^oC compared to the controls. Heat treatment also imparted dimensional stability to the wood species chosen for the study which is evident from ASE (Anti swelling efficiency) values of 34.52 %, 45.44% and 63.26% treated at 180^oC, 210^oC and 240^oC respectively. The overall colour change (ΔE*) and bio resistance to staining fungi increased gradually with increasing treatment temperature. Samples treated at 240^oC showed the highest resistance whereas the lowest resistance was exhibited by controls.

Conclusions: The study established the efficacy of thermal modification as an alternative to conventional treatment methods for improving properties of Norway spruce wood for specific end uses.