Study On Improving The Decay Resistance And Color Of Poplar Wood By Heat-treated Wood Extract And Its Mechanisms

The contradiction between wood supply and demand was alleviated by the application of artificial fast-growing tree species.However,the application of fast-growing tree species such as poplar wood was limited by their poor color and lower durability.Wood preservatives and dyes were common methods used to improve the decay resistance and color of wood.The improvement of environmental protection concept of public had promoted the development of natural and eco-friendly wood preservatives and dyes.Plant-derived extracts with eco-friendly and widely sourced was gradually being attracted our attention.However,the extracts were often easily leached making them less attractive for long-term wood protection.In this study,extracts from heat-treated wood were used to improve the decay resistance and color of wood,and enzymatic grafting methods were used to improve its leaching resistance,and its mechanism of action was explored.The heat-treated spruce(Picea asperata Masters)and larch(Larix gmelinii(Rupr.)Kuzeneva)extracts combined with the main components of poplar(Populus tomentosa Carrière)by chemical bonding under the catalysis of laccase to improve the leaching resistance of the extracts.The effect of extracts on the physiological and biochemical indexes of Trametes versicolor(L.)Quel and Gloephyllum trabeum(Pers.)Murrill.was used to analyze its antifungal mechanism.The compounds with antifungal activity,reactivity and color in heat-treated wood extracts were analyzed.The reaction of extracts with wood and the anti-ultraviolet aging mechanism of modified poplar were characterized and analyzed.A technology of grafting heat-treated wood extracts to improve the decay resistance and color of wood was developed in this study,which improved the anti-leaching property of the extracts in the wood,and the grafting mechanism was analyzed.The research results were as follows:(1)The acetone extracts of heat-treated wood have better antifungal activity against wood decay fungi.The heat-treated poplar and spruce acetone extract had a positive effect on the color and decay resistance of heat-treated wood.The color of the wood will become lighter and the decay resistance will be reduced because the removal of the extract and it has significant effect on wood heat-treated at 180℃.Heat-treated acetone extracts at180℃,200℃,and 220℃ showed strong antifungal activity against wood decay fungal.Heat-treated wood extracts have the potential to be used as wood preservative.(2)The content of phenolic acids and phenolic compounds easily catalyzed by laccase in acetone extracts of heat-treated and larch were higher than that of poplar,which had strong reactivity.The compounds with relatively high content,lower price,and good antifungal activity were isovanillic acid and vanillin.The acetone extracts of heat-treated spruce and larch have strong antifungal and reactive activity and were used for the next step of grafting reaction.(3)Acetone extracts of heat-treated spruce and larch might be graft with wood to improve the stability through chemical bond under the catalysis of laccase.The strong antifungal activity of extract grafted xylan and D-(+)-cellobiose against wood decay fungi indicated that the extract might be grafted onto main components of wood.FTIR and XPS of the xylan,D-(+)-cellobiose and poplar wood grafted by the extract or its representative compound indicated that the extract might be grafted with poplar.(4)The leaching resistance of heat-treated wood extracts in wood was improved by the method of enzymatic grafting.The decay resistance against wood decay of the heat-treated larch acetone extracts and the two active compounds of isovanillic acid and vanillin grafted poplar wood after the leaching test or UV irradiation test reached Class I(the mass loss was less than 10%).Heat-treated acetone extract of larch can inhibit the activities of cellulose and lignin enzyme(white-rot fungus)of wood decay fungi,destroy the cell membrane permeability of two kinds of wood rot fungus,and inhibit the respiratory metabolism of two kinds of wood decay fungi to play the role of antifungi activity.(5)Heat-treated larch acetone extract has a good application prospect in the field of wood dyeing.The extract grafted with poplar wood showed a natural and mild color,and showed stronger color stability to water,abrasion UV irradiation than traditional dyeing methods.The color difference,color intensity reduction percentage of the extract grafted poplar before and after water boiling,UV irradiation and outdoor exposure were lower than those of the extract dyed poplar and AGR dyed poplar,while the color fastness was higher than that of poplar dyed with extract or AGR.(6)Colored compounds such as isovanillic acid,methyl vanillic acid,and UV absorber BP-6 in the extract had positive effects on dyeing.Grafting of extract with strong UV absorption onto wood results in stronger color stability of the extracts grafted onto wood.The change of chromophore and chromophore such as C=C or benzene ring,C=O,C-O and C=O conjugated,and hydroxyl was the main reason for color change.The results indicated that the heat-treated wood extract was a promising preservative and dye,and the laccase catalyzed grafting was a promising technology.The grafted wood had stable decay resistance and color.This study provided a new thinking and theoretical basis for the reuse of wood processing residues and the development and utilization of natural environment-friendly wood modifiers.