Effects Of Hyperbranched Polymers On The Properties Of Sisal Fiber Reinforced Polypropylene Composites

In this paper,sisal fiber(SF)reinforced polypropylene(PP)composites were prepared by injection molding process.The interface compatibility between PP and SF was improved by adding coupling agent,treating SF with alkali and introducing hyperbranched polymer into the composites.The effects of hyperbranched polyester(HBPE),hyperbranched epoxy resin(HBEP)and hyperbranched polyamide(HBPA)on the properties of the composites were studied.The results show that the mechanical properties of the materials increase with the increasing of the HBPE contents.Compared with the control sample of composite material,when the content of HBPE is 10 wt%,the tensile strength and impact strength increase by11.44% and 14.55%.The impact strength of the composite material treated with alkali treatment and 10 wt% hyperbranched polyester synergistic treatment can further improve,increasing by 24.25%.However,the addition of HBPE can reduce the melt flow rate(MFR)of the composite material,and the higher content of HBPE in the composite system,the lower MFR value of the composite material.The scanning electron microscope(SEM)images of the tensile section of the composite material show that the addition of HBPE is beneficial to improve the interface compatibility between the sisal fiber and the polypropylene matrix.When 10 wt% HBEP is added to the PP/SF composite,the tensile strength and impact strength increase by 15.16% and 62.59%.The mechanical properties of the composite material treated by silane coupling agent KH550 and 10 wt% HBEP can improve.Compared with PP/SF,the impact strength of the composite increases by 43.88%.However,the addition of HBEP can reduce the MFR value of the composite material.After the sisal fiber modified by KH550,it can be seen from the SEM image that the surface of the SF is covered by a layer of silane coupling agent.Fourier transform infrared spectroscopy(FTIR)shows that Si—O—Si absorption peak can be observed after the fiber modification.When the content of HBPA increase,the tensile,impact and flexural properties of the composite material can also improve significantly.When 10 wt% of HBPA content is added,the tensile,flexural and impact strengths of the composite material increase by29.05%,12.33%,and 43.88%,respectively,compared with the control sample.However,high content of HBPA will reduce the MFR of the composite material.The existence of polypropylene grafted maleic anhydride(MAPP)is extremely conducive to enhancing the tensile and flexural properties of the material and improving the melt flow rate and thermal stability of the composite material,but it reduces the impact performance of the material.With the addition of KH560 modified sisal fiber,HBPA and MAPP,the tensile,flexural and impact strengths of the composite materials increased by 39.80%,22.16%,and 12.47%,respectively.In summary,the composite material treated by the combination of HBPA and MAPP has the best comprehensive mechanical properties.