Study On Ultraviolet Aging Resistance And Hydrolysis Behavior Of PLA/PBAT/Salix Composites

Wood-plastic composite（WPC）has been mainly based on non-degradable resin since its emergence.With the introduction of plastic restriction policies in various countries around the world,degradable WPC has become a research hotspot in the wood-plastic industry in recent years.In this study,the biodegradable resin polylactic acid（PLA）with excellent mechanical properties and degradability and the fastest development speed was selected as the matrix raw material.Based on solving the problems of poor toughness,poor heat resistance and high cost,Butylene Adipate-co-Terephthalate（PBAT）and Salix powder were used as modified resins and fillers to prepare ternary degradable WPC.On the basis of optimizing the mechanical properties,the thermal stability,UV aging resistance and degradation behavior of WPC were studied to provide reference for expanding the application field of WPC and waste treatment.The main contents and conclusions are as follows:1.Adding PBAT with flexible chain structure and appropriate amount of wood powder to PLA/PBAT/Salix composites can improve the toughness and heat resistance of PLA-based WPC and reduce production costs.Appropriate amount of wood powder can significantly improve the stiffness of WPC,but PBAT will reduce the strength and stiffness of the composite system.Appropriate amount of coupling agent KH550 can improve the interfacial compatibility between wood and plastic and enhance the performance of WPC.When the ratio of wood to plastic is 1:1,PBAT accounts for 50%of the total resin,and the coupling agent is added to 3%,the properties of WPC are relatively good.2.Adding appropriate particle size and amount of Ti O₂ to the composite system,the particles are evenly distributed inside the material and are closely combined with each component,which can significantly improve the mechanical properties,thermal stability and UV aging resistance of PLA/PBAT/Salix composites.When the particle size of Ti O₂ is100nm and the addition amount is 2%,the reinforcing effect on WPC is the best,and the static bending strength,elastic modulus,tensile strength and impact strength are 41.88MPa,3760MPa,20.03MPa and 5.38k J/m²,respectively.After 240 hours of UV aging,the properties of WPC decreased slightly.Compared with no Ti O₂,the retention rates of the above mechanical properties increased by 7.3%,12.6%,0.6%and 24.7%,respectively.With the extension of UV irradiation time,Ti O₂ was gradually consumed,and the ability of WPC to reflect and absorb ultraviolet light was weakened,and the performance was greatly reduced.3.When the degradation time was 48h,the degradation rate of WPC in alkaline（p H=11.0）degradation solution was higher than that in acidic and neutral and the decrease of mechanical properties,water absorption and mass loss rate were the largest.The properties of WPC decreased significantly with the extension of degradation time.When the hydrolysis time was 384h,compared with the hydrolysis time of 0h,the mechanical properties of WPC decreased greatly,and the mass loss rate and water absorption rate were6.1%and 22.4%,respectively.The p H value of the hydrolysate decreased to 5.86.Under alkaline hydrolysis conditions,the ester bonds of PLA and PBAT molecular chains were broken to produce lactic acid and other acidic substances,which reacted with OH^-in the solution to promote the positive hydrolysis reaction,and the material was further degraded.