The Study On Preparation, Structure And Properties Of High Performance Polyethylene-Polystyrene Copolymer

High performance polyethylene-polystyrene graft copolymer (LLDPE-g-PS) was perpeared by using pre-irradiation linear low density polyethylene (LLDPE) and styrene (St) as the main starting materials via suspension graft copolymerization. The effects of monomer concentration, reaction temperature, reaction time and ratio of materials on degree of grafting were studied. Chemical structures of graft copolymer were characterized by means of Fourier transform infrared (FTIR) spectroscopy,1H nuclear magnetic resonance (1H-NMR) and X-ray photoelectron spectroscopy (XPS). Comparing with the FTIR spectrum of LLDPE. the LLDPE-g-PS showed three new peaks at 3060 cm-1,3026 cm-1 and 1602 cm-1, which are attributed to C-H bond and C=C double bond of benzene ring:1H-NMR of LLDPE-g-PS showed chemical shift peaks at 1.5 ppm.1.6 ppm and 6.5-6.7 ppm, which are attributed to chemical shift of 1H in -CH2- and -CH- of vinyl group and benzene ring; the XPS of LLDPE-g-PS showed bind energy peaks at 285 eV and 533.5 eV, which are attributed to bind energy of C 1s in C-O and O 1s in C-O. This indicated that PS has been grafted onto LLDPE molecular. The structure and properties of LLDPE-g-PS were studied by using wide angle X-ray diffraction (WAXD) and differential scanning calorimety (DSC). It was found the melt temperature (Tm) decreased a little, the crystallization temperature (Tc) increased. Because of grafted PS onto LLDPE molecular chains, the perfection of LLDPE molecular chains were asymmetry, which would lead to the reduction of surface-potential barrier. The crystallization rate of LLDPE-g-PS was higher than that of LLDPE. The tensile properties of LLDPE-g-PS were determined. No obvious changes could be found for the tensile strength and elongation at break of LLDPE-g-PS. Morphologies of LLDPE-g-PS were investigated by using scanning electron microscope (SEM). It was found that the PS in LLDPE could graft copolymerization forming ball shape. Rheological properties of LLDPE and LLDP-g-PS were investigater with a rotational rheometer. It was found that complex viscosity, storage modulus and loss modulus are lower for LLDPE-g-PS.