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Preparation and Characterization of Low-density Polyethylene-Polystyrene Graft Copolymer

Author: CuiLei
Tutor: LiWenZuo
School: Changchun University of Science and Technology
Course: Applied Chemistry
Keywords: Low density polyethylene polystyrene Silica nanoparticles melt blending suspension graft preirradiation
CLC: TQ317
Type: Master's thesis
Year: 2014
Downloads: 1
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Abstract


The LDPE-g-PS was synthesized by pre-irradiation technique and suspension graft copolymerization in this paper。 The effects of reaction temperature.reaction time,suspension composition,monomer ratio and the amount of initiator on degree of grafting were studied in this pepar. FTIR and NRM were used to analyze the structure of LDPE-g-PS. The results showed that PS has been successfully grafted onto LDPE. The thermal properties and crystallization behavior on the copolymer were analyzed by DSC, TGA and WAXD. The complex viscosity, storage modulus and loss modulus of copolymer were systematically studied by rotary rheometer. We also use the SEM to observe the morphology of the brittle fracture surface. Finally, the dielectric relaxation spectroscopy was used to analyze the dielectric properties of graft copolymer.Nano silica is widely used as filling material of polymer nanocomposites due to its mature preparation process, cheap price, special surface effect, small size effect and quantum size effect. But the nano particles dispersed in the matrix is prone to aggregation, due to the small particle size, large specific surface area, highly surface energy. This make the preparation of polymer nanocomposites difficult.Therefore, to improve the dispersion of nano particles in matrix is the first problem that must be solve for the preparation of polymer nanocomposites. Through in-situ grafting method. Nano silica was modified by grafting polystyrene with potassium persulfate as initiator. The surface modification of nano silica, surface coated with a layer of polystyrene, changed from hydrophilic to hydrophobic, so as to improve the compatibility with the matrix. Nano silica layer on the surface of polystyrene was demonstrated by FTIR in this paper. The thermal stability of modified nano particles were analyzed Using TGA, the test results further showed that polystyrene was grafted onto the surface of nano silica, and calculate the grafting rate and covering rate. Finally, the size and dispersion of nano silica particle modified by PS was observed by TEM.Polymer nano composite materials for its unique mechanical properties, optical electromagnetic properties and antibacterial properties, has been widely applied in various fields. In this paper, LDPE-g-PS/nano-SiO2composite material was prepared by melt blending process. The morphology, thermal properties of composite materials and crystallization properties were analyzed by SEM, DSC and TGA. By tensile test and impact test, the mechanical properties of composite materials were studied. Rheological properties of composite materials by using a rotational rheometer are discussed. The electrical properties of the composites were systematically analyzed by Holzer effect tester, dielectric relaxation spectroscopy and the breakdown field strength testing machine. The surface properties of composite materials was studied with contact angle measuring device.

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