Comparison of termite resistance of wood modified with lignin cleavage products-phenol-formaldehyde and phenol-formaldehyde resins against subterranean and drywood termites

Abstract Wood modification with phenol-formaldehyde (PF) impregnation resins increases the resistance against fungal decay and subterranean termite attacks. However, phenol is obtained from non-renewable resources. Prior research explored partially replacing phenol with lignin cleavage products (LCP), and the good fungal decay resistance remains. However, the influence on termite resistance has not been studied. In this study, 30 % (w/w) of phenol in PF resins was replaced with LCP (LPF resin). Pinus sylvestris sapwood was treated with PF and LPF resins, and its resistance against European subterranean termites ( Reticulitermes flavipes ) and tropical drywood termites ( Cryptotermes dudleyi ) was evaluated by non-choice screening tests. Additionally, choice tests were carried out to confirm that the modifications were non-biocidal. The PF and LPF resin treatments improved termite resistance (reducing the mass loss) against both termite species. Low termite survival rates were observed after the non-choice test against subterranean termites. The choice tests confirmed that both treatments were non-biocidal. Visual evaluation (EN 117 (2023)) led to worse resistance ratings of treated specimens against tropical drywood termites, compared to European subterranean termites, due to different mode of actions of the termites’ attacks. Thus, new standards (or appendixes) could be useful to evaluate treated woods resistance against different termite species.