Graft polymerization onto nano-sized SiO2 surface and its application to the modification of PBT

Nano-silica was used to modify thermoplastics polybutylene terephthalate (PBT) in order to improve the properties. Before being filled into PBT, nano-silica was subjected to graft modification. The graft polymerization of PBT prepolymer was performed onto the surface of the nano-particles and the grafted nano-silica was characterized with Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, thermal gravimetric analysis, sedimentation experiment, transmission electron microscopy, and atomic force microscope. It demonstrated that there was a chemical linkage between the nano-silica and the grafting prepolymer. Vacuum played an important role in determining the grafting amount and the length of the grafting chains. The lower the vacuum, the longer the grafting chains, and thus, the more the weight loss. The grafted nano-particles had a typical core-shell structure. The grafted version had better compatibility with the resin matrix compared to the original version and could disperse homogeneously in PBT and no aggregation occurred. Hence, interfacial adhesion between nano-silica and PBT was largely enhanced. The properties of the resultant nanocomposite including thermal stability, tensile strength, and notched impact strength were greatly improved.