Study On Mechanical Properties And Interfacial Compatibility Of HDPE/Wood Fiber Composites

Wood fiber or vegetable fiber can be added in thermoplastics as an inexpensive filler to form a newly developed material called Wood plastic composites(WPC).It has combined the advantages of the plastics and wood,and there are very important meanings in solving energy shortage and environmental pollution.However,a key problem in WPC is the weak compatibility between hydrophobic thermoplastic and hydrophilic wood fiber,which destroys the mechanical properties to a large content and furthermore limits applications of WPC.In this paper,much effort had been made on wood fiber/HDPE composites.Several methods such as surface modification of wood fiber,γ-irradiation on HDPE and addition of interface compatilizer prepared by ourself had been adopted to improve the mechanical performance and interfacial compatibility of wood fiber/HDPE composites.Polyethylene wax combined with maleic anhydride was grafted on the surface of poplar wood fiber,initiated with peroxide.The obvious variety of FTIR and dispersive free energy of the wood fiber before and after treatment confirmed that the grafting reaction had taken place. The grafting ratio of the reaction was calculated.The mechanical properties of grafted wood fiber filled HDPE composites are better than those of untreated ones.The tensile strength and flexural strength increased 34.9%and 29.2%respectively.The effect of Co⁶⁰γ-irradiation on the molecular structure of HDPE and mechanical properties of wood Fiber/γ-HDPE Composites were studied through FT-IR,DSC,and mechanical properties test.The experimental results show that due to the introducing polar groups into HDPE chain,the interfacial adhesion between wood Fiber and HDPE and mechanical properties of the blend are improved quite a lot,suggesting a method for improving the compatibility between the wood Fiber and HDPE.SEM micrographs further prove that surface modification of wood fiber andγ-irradiation on HDPE improved the dispersion and interfacial adhesion between wood fiber and HDPE matrix.In this paper,a series of compatilizer such as high density polyethylene grafted by maleic anhydride(HDPE-MAH),high density polyethylene grafted by vinyltrimethoxysilane(HDPE-VTMS), and high density polyethylene grafted by mix of maleic anhydride and vinyltrimethoxysilane(HDPE-MAH,VTMS)was prepared by means of initiation ofγ-irradiation on HDPE and peroxide respectively.The experiment result showed that the compatilizer had improved compatibility between wood Fiber and HDPE and the mechanical properties of WPC to a large content.Among these compatilizer,high density polyethylene grafted by mix of maleic anhydride and vinyltrimethoxysilane(HDPE-MAH,VTMS) prepared when the dose ofγ-irradiation was 30 kGy and the ratio of the mix of maleic anhydride and vinyltrimethoxysilane was 3%the most effectively enhanced mechanical properties of WPC.The kinetics of nonisothermal crystallization of HDPE and its interface compatilizer were investigated by differential scanning calorimetry(DSC).The Avrami equation,Ozawa equation and Mo method were applied to the whole non-isothermal crystallization of HDPE and its interface compatilizer.It was observed that the Avrami equation can effectively describe the beginning of crystallization;the Ozawa equation could describe the end of crystallization. However,Mo method is successful in describing the whole nonisothermal process of HDPE and its interface compatilizer.At last,the effective activation energy(â–³E)was determined through electing Kissinger method.The results showed that theâ–³E of interface compatilizer prepared by ourself is lower than those of HDPE.It indicated that the polar branch chains initiated in the grafting reaction had two roles in the crystallization process,one was hindered the motion of the molecular of HDPE,but the another one was used as nucleation agent decreasing the needed energy of nucleation.