Modification Of Wheat Straw Fiber And Its Effect On Properties Of Composite Materials

Wood-Plastic Composites are used in various fields due to its high strength,light weight,zero formaldehyde and other excellent properties.However,due to different of polarities plant fibers and thermoplastic,which results in the weak adhesion at the two phase interface and leads to the poor mechanical.And surface modification of plant fibers in one of the effective methods to improve the compatibility of thermoplastic and fibers.In this paper,wheat straw fiber/high-density polyethylene composites were prepared with wheat straw fibers(WSF)and high-density polyethylene by mixing and injection molding technology.The effect of WSF loading,coupling agent modification,enzyme treatment and composite modification on the mechanical properties,thermal stability,crystallinity and moisture absorption of WSF/HDPE composites was investigated.The chemical structure of WSF and the tensile profile of WSF/HDPE composites were analyzed by Fourier Transform Infrared Spectroscopy(FTIR)and Scanning Electron Microscopy(SEM).The paper also studied the effects of aramid fiber(AF)on the properties of WSF/I-HDPE composites.The main conclusions of this paper were as follows:(1)The mechanical properties of WSF/HDPE composites decrease trend with the increase of WSF content,FTIR anslysis revealed that all three coupling agents can react with hydroxyl groups on WSF and improve the mechanical properties of WSF/HDPE composites,and the cou.pling agent A-172 has better effect.TG and DSC results show that the coupling agent could improve the thermal stability and crystallinity of WSF/HDPE.(2)The enzyme treatment methods had significant influence on the surface roughness of WSF,the xylanase and lipase compound treatment method had the best effect on the modification of WSF,and the tensile strength,flexural strength and flexural modulus of the prepared 30WPXL composite was reached 23.4 MPa?34,0 MPa and 1944.6 MPa,respectively,30WPXL composites had the lowest water absorption rate.Enzyme treatment could improve the thermal stability and crystallinity of the WSF/HDPE composites.The SEM analysis showed that the interface bonding effect of 30WPXL composites treated with xylanase and lipase was better than that of single treatment.(3)The mechanical properties of 30WPXL-A3 composites prepared by WSF,which treated with enzyme and coupling agent A-172 were significantly higher than of single treatment,and the water absorption rate was the lowest.The SEM test results showed that the combination of WSF and HDPE in the 3 0WPXL-A3 composites that compound treatment was better than other treatment methods.(4)The addition of aramid fiber(AF)can improve the mechanical properties,thermal stability and crystallinity of WSF/HDPE composites.The water absorption between the WSF/HDPE composites prepared before and after AF modification was not much different.FTIR analysis showed that the surface active groups of AF increased after NaOH treatment.SEM showed that AF treated with NaOH could make its surface become uneven,and resulting in enhanced binding ability with HDPE.