Relationship between decay resistance and moisture properties in wood modified with phenol formaldehyde and sorbitol-citric acid

Abstract

AbstractImpregnation modifications improve the decay resistance of wood, but the mechanisms behind improved resistance are not yet fully understood. In this study, Scots pine sapwood samples were impregnation modified to investigate the relationship between moisture properties, decay resistance and chemical changes caused by decay. The samples were modified with phenol formaldehyde (PF) and sorbitol-citric acid (SCA) at different solids contents to study the effects of two different types of resins. The anti-swelling efficiency (ASE) and moisture exclusion efficiency (MEE) of the samples were measured, after which they were exposed to the brown rot fungi Coniophora puteana and Rhodonia placenta to determine their mass losses, moisture contents and chemical changes due to decay. The results showed that both modifications were able to increase ASE, MEE and decay resistance, and that neither modification was appreciably degraded by the fungi. However, no uniform relationship was found between mass loss and ASE or MEE for the two modifications, and there was a clear increase in the moisture contents of the decayed samples and sterile controls under decay test conditions with increasing modification degree. Overall, the results showed that modification with PF and SCA increases decay resistance, but the relationship between resistance and moisture properties requires further investigation.