Study On Preparation Of Polypropylene-Polystyrene Copolymer And Its Blend With Polypropylene

Macromolecule peroxide of polypropylene (PP) was prepared by β ray pre-irradiation method. The grafting of polystyrene (PS) onto PP was carried out with macromolecular peroxide of PP as an initiator by suspending grafting. The effects of graft temperature, ratio of monomer and initiator content on degree of grafting were studied. PP-g-PS/PP blends were prepared using Haake twin screw extruder by molten blend, properties of PP-g-PS/PP blends were investigated.The structure of graft copolymer was characterized by means of Fourier transform infrared spectroscopy (FTIR),’H nuclear magnetic resonance (’H-NMR), X-ray photoelectron spectroscopy (XPS) and wide angle X-ray diffraction (WAXD). The FTIR spectra of PP-g-PS showed some new peaks at3027cm-1、1601cm-1and1493cm-1, which are attributed to C-H bond and C=C double bond of benzene ring. The1H-NMR spectra of PP-g-PS showed new chemical shift peaks at2.0ppm,1.4ppm,1.2ppm,7.2ppm and7.1ppm, which were attributed to the H from benzene ring in PS. These results indicated that PS has been successfully grafted onto PP molecular chains.Properties of PP-g-PS and PP-g-PS/PP blends were characterized by means of differential scanning calorimety (DSC), impact apparatus and rotational rheometer. In the heating curves of PP-g-PS/PP blends, with increasing of the content of PP-g-PS, melting temperature (Tm) and molten enthalpy (ΔHm) decreased gradually. In the cooling curves, with increasing of the content of PP-g-PS, crystallization temperature (Tc) increased and crystallization enthalpy (ΔHC) decreased gradually. Impact properties of PP-g-PS/PP blends were determined. The impact results indicated that the impact strength of PP-g-PS/PP blend was highest, when the content of PP-g-PS was20%. Rheological properties of PP-g-PS/PP blends were investigated with a rotational rheometer. It was showed that the complex viscosities of PP-g-PS/PP blends are slightly higher than that of PP under the same shear frequency. Morphologies of PP-g-PS/PP blends were investigated by using scanning electron microscope (SEM). It was showed that the size of PS phase in blends decreased (<2μm) and well-distributed with increasing of the content of PP-g-PS.