Preparation And Properties Of Modified Bamboo Fiber/polyethylene Composite

Wood plastic composite prepared by thermoplastic resin such as polyethylene and polypropylene as matrix and wood fiber as reinforcement has the advantages of natural beauty of wood and easy processing and molding of polymer materials,has broad application prospects.In order to prepare wood plastic composites with excellent performance,the surface polarity and chemical element composition of the xylem and bark fiber of the three kinds of softwood wood includes Pinus massoniana,fir and cedar as well as moso bamboo were analyzed.The performance of wood plastic composites prepared by different fibers and polyethylene(PE)was compared,and it was found that composite prepared with bamboo fiber had the best comprehensive performance among the composites studied.On this basis,in order to further improve the properties of bamboo plastic composites,the bamboo fiber was treated with heat treatment,coupling agent treatment and biological enzyme treatment,and the modified bamboo plastic composites was prepared.The modification mechanism of bamboo fiber surface properties and the influence of the three treatment on the physical and mechanical properties and mildew resistance properties of bamboo plastic composites was investigated.The main findings of this paper are as follows:(1)The polarity component and O/C ratio of xylem fibers was higher than those of bark fibers of the three studied softwood.The water absorption of bark fiber/PE composites was lower than that of xylem fiber/PE composites.The thermal stability,static flexural strength,impact strength and the mildew proof effect of xylem fiber/PE composites were generally better than those of bark fiber/PE composites.In general,among the seven wood plastic composites prepared by the different wood fibers,the bamboo fiber/PE composite had the best water resistance,the 24 h water absorption and 24 h water absorption thickness was 1.838%and 1.427%,respectively.Besides,the bamboo fiber/PE composite has the best thermal stability.In addition,the static flexural strength,elastic modulus and impact strength of the bamboo plastic composite were also the highest,which was 41.31 MPa,3.82 GPa and 10.24 KJ/m~2,respectively.Furthermore,fir fiber/PE composite has the best mildew proof capability,and its damage value was the lowest,which was 0.50.(2)At suitable temperatures,vacuum heat treatment and MAPE synergistic could improve the water resistance,bending performance and mildew resistance of bamboo plastic composites,but reduced the impact strength of composite.When the temperature was 160℃,the water absorption rate of composite was the lowest,which was 72.84%lower than that of the control group,and when the temperature was180℃,the absorbing water thickness expansion rate of composite reached the lowest,which was reduced by 65.80%compared with the control group.In addition,when the temperature was 180℃,the static flexural strength and elastic modulus of the composites reached the maximum,which increased by 39.91%and 21.77%compared with the control group,respectively.When the temperature was 200℃,the mildew proof effect of the composite was the highest,which was 60%.(3)Silane coupling agents KH550,KH570,A171 as well as polydopamine treatment could improve the water resistance,bending performance and mildew resistance of bamboo plastic composites,but reduced the thermal and impact properties of composite.Among them,the water absorption rate and the 24-h absorbing water thickness expansion rate of composite prepared by bamboo fiber treated with KH550 were the lowest,which were 44.87%and 61.93%lower than those of the control group,respectively.The static flexural strength and elastic modulus of composite modified with KH550 were the highest,which increased by10.76%and 23.57%compared with the unmodified group.In addition,the mildew proof effect of composite modified with KH550 was also the best,and the anti-mildew effectiveness was increased to 73.33%.(4)The water resistance,bending performance and mildew resistance of bamboo plastic composites were improved by biological enzymes treatment,including xylanase,lipase,laccase,pectinase,hemicellulase and amylase,but reduced the thermal stability and impact strength of composite in general.Among them,the water absorption rate of the composite prepared by hemicellulase was the lowest,which was 66.67%lower than that of the control group.The 24-h absorbing water thickness expansion rate of the composites modified by xylanase was the lowest,which decreased by 71.55%compared with the control group.The static flexural strength and elastic modulus of the compounds modified by pectinase were the highest,which were 13.39%and 11.74%higher than those of the unmodified group,respectively.The composite modified by xylanase had the best mildew proof effect,and the anti-mildew effectiveness was 74.67%.