This study assesses the decay resistance properties of bio-resin modified wood against decay fungi of the Basidiomycota according to the EN 113 protocol. A bio-resin system was developed by ozonolysis process from cashew nut shell liquid (CNSL), a naturally occurring mixture of phenolics. Small wood blocks from sapwood of Scots pine (Pinus sylvestris), Obeche (Triplochiton scleroxylon) and Gmelina (Gmelina arborea) were vacuum impregnated with methanolic solutions containing CNSL resin and tested for decay resistance against the brown rot fungi Coniophora puteana and Postia placenta, and white rot fungi Trametes versicolor and Pleurotus ostreatus. The relationship of fungal species, extent of resin treatment (WPG) and mass loss (ML) induced by decay were examined. The ML caused by the decay fungi, however decreased with the increasing WPG in all of the wood species against all of the fungi tested but at the highest loading of resin the protection threshold was not reached. The increased decay resistance is attributed to polymerization of the CNSL resin either in the wood cell wall or in the cell lumen providing a barrier decay fungi. The effects of ML by decay fungi and level of resin modification (WPG) on the final moisture content of resin modified wood at the end of the decay test were also examined. The moisture content at the end of the decay test was influenced by the decay fungi and the extent of resin modification. All the wood species modified with CNSL resin enhanced the hydrophobic nature of wood. As the protection threshold was not reached higher treatment levels for CNSL resin are required for full protection.

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