Study On Synergistic Reinforcement And Toughening System Of Rod-Shaped Bamboo Fiber/HDPE Composite

Wood plastic composite(WPC)is an environmentally friendly biomass composite material that "captures" carbon into the composite material,thereby avoiding carbon dioxide generated by landfilling or incineration.In response to the environmental concept of "carbon peak and carbon neutrality",the reuse of agricultural and forestry wastes has become partinent.However,most of the wood fibers used in traditional woodplastic composite materials are in powder form,with a small aspect ratio,and their reinforcement effect on the polymer matrix is average.In order to leverage the reinforcement advantages of long fibers,this article uses30-40 mesh rod-shaped bamboo fibers and high-density polyethylene(HDPE)as the main raw materials,polymethylhydrosiloxane(PMHS),ethylene propylene diene monomer(EPDM)as modifiers,and montmorillonite(MMT)as additives to prepare rod-shaped bamboo fiber/HDPE composite materials through extrusion granulation and injection molding;Explore the synergistic enhancement of strength and toughness of composite materials by modifiers PMHS,EPDM,and additive MMT.The research results are as follows:(1)Most of the 30-40 mesh bamboo fibers are in the shape of long rods,with a wide distribution of aspect ratios.The average aspect ratio is8,which is slightly larger than that of powdered bamboo fibers.The preparation of BF/HDPE composite materials using 30-40 mesh rodshaped bamboo fibers has better processing performance and reinforcement effect than powdered bamboo fibers.As the filling amount of 30-40 mesh bamboo fibers increases,the impact strength and elongation at break of BF/HDPE composite materials decrease significantly.(2)PMHS and EPDM were successfully grafted onto BF surface in turn by two-step method.The interface of BF/HDPE composite material modified by PMHS and EPDM is tightly bonded,and no cracks are observed.When the content of modifier PMHS is 3% and EPDM is 2%,the mechanical properties of the composite material are the best,with tensile and impact strength increased by 65.8% and 16.6%,respectively.Compared with unmodified BF/HDPE composite material,the strength and toughness have been significantly improved.This indicates that EPDM and PMHS have a synergistic reinforcing and toughening effect.(3)The high filling content unmodified BF/HDPE composite material showed the phenomenon of bamboo fiber aggregation,and the interface of the modified composite material was tightly bonded without cracks.When the content of modifier PMHS is 5% and EPDM is 2%,compared to the unmodified composite material,its tensile and impact strength are increased by 30.9% and 29.1%,respectively.This indicates that EPDM and PMHS have a synergistic strengthening and toughening effect on high filling content composite materials.Compared to unmodified composite materials,the water absorption rate and water absorption thickness expansion rate of PMHS and EPDM modified composite materials decreased by 36% and 72.8%,respectively,proving that the modified composite materials have excellent moisture expansion resistance.Under the same aging conditions of water immersion,ultraviolet radiation and salt spray treatment,the mechanical properties of the modified composite have a relatively small decline,which indicates that the modified composite has a certain anti-aging performance.The thermal stability of the modified composite material does not change much,but it can significantly improve its crystallization performance and dynamic thermal mechanical properties.(4)PMHS was successfully grafted onto the surface of MMT.The SEM results indicate that the interface of the high filled BF/HDPE composite material with PMHS modified MMT can still maintain good bonding without obvious cracks.The mechanical results indicate that when the MMT addition is 6%,the strength and toughness of the composite material are the best.Compared to the composite material without MMT addition,its tensile,bending,and impact strength increased by 17.9%,3.8%,and 11.3%,respectively.This indicates that MMT modified with PMHS not only improves the strength of BF/HDPE composite material,but also enhances the toughness of the composite material.Addition of PMHS modified MMT can improve the heat resistance and crystallinity of the composite material.