Quercetin-grafted modification to improve wood decay resistance

Abstract As a renewable biomass material, wood is often deteriorated by decay fungi. Quercetin was here grafted onto poplar ( Populus nigra ) using oxalic acid as a linker through vacuum-pressure treatment and esterification with various molar ratios of quercetin to oxalic acid (Q/O) to enhance the wood decay resistance. Decay resistance, flexural strength, graft mechanism, and microscopic structure of the quercetin-grafted wood were analyzed. Results indicated that the decay resistance of quercetin-grafted wood to white-rot fungi ( Trametes versicolor ) and brown-rot fungi ( Gloephyllum trabeum ) was significantly improved. The modulus of rupture (MOR) of the quercetin-grafted wood was reduced while the modulus of elasticity (MOE) was improved. Quercetin was grafted onto wood through formation of ester groups among oxalic acid, wood, and quercetin. The highest amount of ester groups in the grafted wood was achieved when Q/O was 1:2 and Q/O lower than 1:2 would severely degrade the wood. The thickness of cell walls of the quercetin-grafted wood increased and reached a maximum of 2.2 μm with Q/O of 1:2. Quercetin can be grafted on wood cell wall by oxalic acid as an environment-friendly preservative to enhance the decay resistance of wood.