Effect of Silane Coupling Agents on Crystallization Behaviors and Mechanical Properties of Low-Content Basic Magnesium Sulfate Whisker/Polypropylene Composites
Firstly,three different silane coupling agents(hexadecyl,amino,and epoxy)were selected to treat the surface of basic magnesium sulfate whiskers(MOSw),then polypropylene(PP)was modified by melt blending with MOSw.Combined with the coupling agent treatment,processing technology and resin co-compounding technology,the MOSw/PP composite material with a low MOSw content(3%mass fraction)was prepared.The effects of three silane coupling agents on the infrared spectrum and microstructures of MOSw,as well as the crystallization behaviors and mechanical properties of MOSw/PP composites were investigated by means of field emission scanning electron microscopy,infrared spectroscopy and differential scanning calorimetry.The variation rules and mechanism were also analyzed.The results show as follows:among the three silane coupling agents,cetylsilane has the best dispersion effect for MOSw due to the longest carbon chain and low polarity of—C16 H33 group,followed by epoxide silane and amino silane;The addition of MOSw hinders the crystallization of PP.The dispersion of MOSw is improved after being modified by silane coupling agents,which further hinders the crystallization of PP.The crystallinity of the composite with hexadecylsilane-modified whiskers is the lowest(only 39.3%),which decreases by 14.4%compared with that of pure PP.The crystallization rate of the composite is accelerated by adding cetylsilane and epoxy-silane modified MOSw.cetylsilane-modified MOSw have the best binding force with PP,and the properties of the composite material containing this MOSw with a mass-fraction of 3%are greatly improved,the density is only0.963 g/cm3.Compared with the mechanical properties of pure PP,thebendingmodulusisincreasedby116%,reaching2 323 MPa,the tensile strength is increased by 7.8%,the notch impact strength is increased by 2.5%.This kind of material with good performances and low density can be used to prepare lightweight products.