Study On Decay Resistance Of Poplar Wood Based On Nano AgCu Alloy Fungicide/Resin Inhibition Pathway

In the context of China’s"double carbon"and the beginning of the 14th Five-Year Plan,it is urgent to protect green and renewable wood resources by preserving them to extend their service life and increase their utilization value.At present,two effective strategies to improve the decay resistance of wood are the preservative-based poisoning route and the barrier-based bacterial inhibition route.However,the sterilization route usually suffers from bottlenecks such as high dosage of preservatives and easy loss of active ingredients,while the inhibition route still has key problems such as low inhibition rate and unknown inhibition mechanism.Therefore,this study focused on two pathways respectively,using silver-copper nano-alloys as preservatives to investigate their alloy antimicrobial effect and loss resistance and reveal the action law of alloy nanomaterials as representatives of the bactericidal pathway;using four different hydrophobic resin protective layers as bacterial inhibition barriers to investigate the barrier inhibition effect of each resin and its bacterial inhibition action law.The conclusions of the study are as follows:（1）The influence law of the drug loading of nano-silver-copper alloy on the corrosion resistance was explored;the high bactericidal effect of nano-silver-copper alloy with low drug loading was realized;the bactericidal effect of nano-silver-copper alloy was revealed;the change law of the attrition of nano-silver-copper alloy with the attrition time was clarified.（1）The fungicidal effect of Ag Cu NPs on both Coriolus versicolor and Geloeophyllum trabeum was enhanced with the increase of Ag Cu NPs loading;when the loading was0.18±0.02 kg/m³and 0.60±0.06 kg/m³,the mass loss rate of Ag Cu NPs treated samples against Coriolus versicolor and Geloeophyllum trabeum infestation for 12 weeks was4.8±1.3%and 3.2±1.3%,respectively,both of which reached the strong decay resistance level and achieved high decay resistance under low loading.（2）The inhibition effects of Ag Cu NPs,Ag Cu NPs relied on the combined effect of nano-effect and ion release and ions played the main bactericidal role.Ag⁺-Cu²⁺composite system,Ag⁺and Cu²⁺on Coriolus versicolor and Geloeophyllum trabeum were in the order of Ag⁺-Cu²⁺composite system>Ag Cu NPs>Ag⁺>Cu²⁺>Cu²⁺;the antibacterial rate of Ag Cu NPs was slightly lower than that of Ag⁺-Cu²⁺composite system and slightly higher than that of Ag⁺alone.（3）The loss of Ag Cu NPs gradually increased with the extension of the loss time,but the loss rate slowed down;when the drug loading was 0.18±0.02 kg/m³and 0.60±0.06 kg/m³,the loss rates of Ag Cu NPs were 5.1%and 13.8%,respectively;and the mass loss rates of the specimens after 12 weeks of infestation by Coriolus versicolor and Geloeophyllum trabeum after the loss treatment were 7.1±1.3%and 7.9±1.7%respectively after 12 weeks of attrition treatment,all of which maintained strong decay resistance grade and showed a much better decay resistance durability than the traditional mainstream waterborne preservatives（ACQ,Boric acid）.（2）The influence law of resin type and weight gain rate on decay resistance and moisture barrier was clarified,and the moisture threshold of wood decaying wood by wood decaying fungi was explored to reveal the resin barrier effect.（1）In the liquid water environment,the resin improves wood decay resistance by blocking the effective contact between wood decay fungus and wood components.The decay resistance grade was achieved after 12 weeks of infestation by Coriolus versicolor for water-based silicone protectant-1（ZM）,water-based silicone protectant-2（AH）,water-based fluorine resin protectant（SF）and water-based wood polyurethane paint emulsion（WD）treatment samples at weight gain rates of 7-8%;for SF treatment samples at weight gain rates of 7-8%and for AH,ZM and WD treatment samples at weight gain rates of 14-17%,the All the treated samples reached the decay resistance grade after 12 weeks of infestation by Geloeophyllum trabeum;the order of decay resistance of the four resins was SF>AH>ZM>WD.（2）In the humidity environment,the resins improved the decay resistance of wood by both moisture barrier and blocking the effective contact between wood decay fungus and wood components,and the four resins were effective against Coriolus versicolor and Geloeophyllum trabeum at 7-8%weight gain in both 100%（moisture content:36.4%）and96%（moisture content:33.9%）environments.The order of moisture barrier effect in the two humidity environments was AH>ZM>WD>SF;the order of corrosion resistance was SF>AH>ZM>WD,and the moisture barrier and corrosion resistance gradually increased with the increase of the weight gain rate of the treated samples.（3）In the environment where liquid water and humidity coexisted,the moisture threshold for decay of Coriolus versicolor was determined to be 25%,and the moisture threshold for decay of Geloeophyllum trabeum was 30%.When the moisture content of the treated samples was above the threshold,the resin was mainly relied on to block the effective contact between wood decay fungus and wood components,thus improving the decay resistance of wood;when the moisture content of the treated samples was below the threshold,the resin was mainly relied on to improve the decay resistance of wood by moisture barrier effect.The order of resin moisture barrier effect is AH>ZM>WD>SF,and the order of decay resistance effect is SF>AH>ZM>WD.