Preparation Of Linseed Oil-Based Emulsion And The Waterproofing And Moisture Resistance Of Its Modified Wood

The dimensional stability,biological degradation,photo-degradation and other properties of wood are closely related to water.Wood will crack and deform after absorbing liquid water,then causing decay and discoloration.Therefore,the waterproof modification of wood is indispensable in production and application.The current methods of wood modified with vegetable oil are mostly concentrated on pure oil modification.However,the amount of vegetable oil used is large,and insufficient polymerization will overflow from the wood.Besides,the high surface energy of vegetable oil is not conducive to the hydrophobicity of wood.Based on the above drawbacks,epoxidized linseed oil,carnauba wax and complex emulsions were prepared to impregnate poplar wood.In this study,the particle size and centrifuge stability of emulsions,as well as water absorption,moisture adsorption and dimensional stability of emulsions-treated wood,were determined.The influence of emulsions modification to the microstructure and chemical components were characterized.Meanwhile,water contact angle and adsorption model fitting were used for investigating modification mechanism.Besides,the decay resistance,mold resistance,termite resistance and photoaging resistance of emulsions-treated wood were evaluated.The main conclusions of this study are listed as below.(1)The epoxidized linseed oil emulsions,carnauba wax emulsions and complex emulsions,with good centrifuge stability,were of an average particle size about 200 nm.Emulsion penetrated easily into the interior of the wood through vessel,wood fibers,and wood rays and formed continue and discontinue films on wood surface after demulsification.After epoxidized linseed oil opened its epoxy ring under the catalysis of acetic acid,the inter-and intra-molecular crosslinking results in a tighten combination between polymerized oil and wood.(2)Only oil or wax emulsion and complex emulsion modification were all able to improve waterproofing and moisture adsorption resistance of wood,as well as dimensional stability.Wax emulsions showed a short-term efficacy while oil or complex emulsion a long-term,and complex emulsions-treated wood showed the best properties.The addition of acetic acid in the oil emulsion enhanced the modification effect of these system,and the properties of complex emulsions-treated wood further strengthened by the synergistic effect of epoxidized linseed oil and carnauba wax.(3)Water contact angle results represented that a small number of 2%-6% carnauba wax could largely improve hydrophobicity of wood,that the contact angle of epoxidized linseed oil emulsion-treated wood rapidly decreased from 100° to 0° within 6s while complex emulsion-treated wood(E20/C4)was over 100° within 80 s.Although epoxidized linseed oil had no reaction with hydroxyl groups of wood,the modification covered the accessible hydroxyl groups,which reduced the moisture content of monolayer and polymolecular layer under low humidity.(4)The oil or wax film on wood surface obstructed the damage of ultraviolet light and moisture to wood surface,thereby reducing the change of the color,composition and microstructure of wood.Although oil and wax do not contain bactericidal ingredients,they inhibited the growth of decay fungi by mechanical barrier to weaken the moisture interaction with wood,especially to white rot decay fungi.However,oil was used as a nutrient itself,the emulsions modification only had a slight delay effect on the blue stains and molds.Moreover,the inhibitory effect on termites mainly reflected in the reduction of the degree of decay.