Surface Modification Of Kevlar Nanofibers And Its Effect On The Performances Of Rubber Composites

Recently,the preparation of high-performance rubber products has become a hot topic both in industry and academia,and the research on nanomaterials as reinforcing fillers for rubber composites has attracted much attention.Kevlar nanofibers?KNFs?,due to their ultra-strong strength,high modulus,as well as superior heat resistance,have been developed gradually in nanocomposite films.In this study,we chose the simple epichlorohydrin as the modifying agent for KNFs,and the modified Kevlar nanofibers?m-KNFs?were incorporated into rubber in order to prepare high performance rubber nanocomposites.The main research contents were as follows:Aiming at the problem of poor water dispersibility of KNFs during the process of latex blending,epichlorohydrin was exploited to modify KNFs,and the water-dispersible m-KNFs were obtained by further centrifugation and ultrasonic.m-KNFs basically maintained one-dimensional morphology of the nanofiber structure,with a length of about 5mm and a diameter of about 5 nm.Through the latex blending method,m-KNFs were filled into non-polar styrene butadiene rubber?SBR?to prepare the m-KNFs/SBR composites,and the effects of m-KNFs on the curing characteristics,mechanical properties,dielectric properties and thermal stability of composites were investigated.The results showed that strong?-?interaction existed between m-KNFs and SBR matrix,and the addition of m-KNFs can greatly enhance the crosslinking density,mechanical properties,dielectric constant and thermal stability of SBR.When the content of m-KNFs was 7 phr?parts per hundred rubber?,the tensile strength,tear strength and the maximum heat decomposition temperature(T_max)of the composites were incrased by 576%,202%and 13.1?,compared with unfilled SBR.The m-KNFs/carboxylated acrylonitrile butadiene rubber?XNBR?composites were prepared by filling m-KNFs into polar XNBR by latex blending method,and the effects of m-KNFs on the mechanical properties,dielectric properties,thermal stability and solvent resistance of composites were studied.The results showed that covalent bonding interactions might be existed between m-KNFs and XNBR.When the m-KNFs content were 5 phr,the tensile strength and tear strength of composites were increased by 182%and 101%,in contrast to neat XNBR;T_max were improved by21.6?,and higher dielectric constant as well as solvent resistance of XNBR composites were also obtained.The effects of m-KNFs on the compatibility and reinforcement of SBR/XNBR blends were investigated.It was found that SBR can adsorb m-KNFs to its surface by means of?-?conjugation interactions,and meanwhile m-KNFs can form covalent bonding with XNBR,thus m-KNFs can effectively improve the compatibility of blends.When the m-KNFs content were only 0.3 phr,the tensile strength and tear strength of blends were increased by 87%and 195%.Beyond this,the addition of m-KNFs also can strongly strengthen the thermal stability and solvent resistance of blends.