Physical Filling And Chemical Crosslinked Ultra High Molecular Weight Polyethylene Composites And Its Tribological Performance

Ultra high molecular weight polyethylene (UHMWPE) is a kind of engineering plastic with excellent properties. It has a wide range of applications in spite of some limitations such as weak heat resistant and abrasion resistant. In this thesis, UHMWPE was respectively modified with igorganic filler glass beads (GB) and boron nitride (BN), and also crosslinked by silane coupling agent KH-560. Friction and wear performances of the resulting GB/UHMWPE, BN/UHMWPE, and crosslined UHMWPE were invesitgated.1. UHMWPE and its composites filled with glass beads were prepared by heat compression molding. The mechanical properties, Rockwell hardness, crystal structure, morphologies, Vicat softening temperature, melting points and coefficient of linear expansion of the composites were examined, and their friction and wear resistant performances were tested by an MRH-3 high speed friction and wear tester and a water-sand slurry apparatus with water bath. It was found that the resulting blends exhibited better properties in the hardness, Vicat softening temperature, melting point and the glass transition temperature, which led to the lower coefficient of friction and the less wear of the composites. The Vicat softening temperature can be enhanced by 12.5% and the wear mass was reduced by 62%. It was also found that the content of glass beads between 5% and 20% was the optimal loading. However, the mechanical properties of UHMWPE composites present a reduction while increasing the filling.2. UHMWPE and its compsites filled with boron nitride were prepared by heat compression molding. The mechanical properties, Vicat softening temperature, melting points, coefficient of linear expansion, crystal structure and morphologies of the composites were examined, and their friction and wear resistant performances were tested by an MRH-3 high speed friction and wear tester and a water-sand slurry apparatus with water bath. It was found that the resulting blends exhibited better properties in the tensile strength and crystallinity, the lower friction coefficient and wear mass loss, and little impact on Vicat softening temperature, melting point and the glass transition temperature. The optimized UHMWPE composites filled with 1% of BN presented a similar friction coefficient and an 84% decrease in wear mass loss compared to the pure UHMWPE.3. UHMWPE and its compsites crosslinked by silane coupling agent KH-560 were prepared by heat compression molding. The feasibility of crosslinking by KH-560 was tested and analysised by Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). The effect of the content of KH-560 on gel fraction, mechanical properties, Vicat softening temperature of the resulting UHMWPE composites were examined, and their friction-and wear-resistant performances were tested by an MRH-3 high speed friction and wear tester and a water-sand slurry apparatus with water bath. It was found that the gel fraction of UHMWPE reached saturation in the case of the content of KH-560 between 0.5%～l%. The optimized UHMWPE composite, which was crosslinked by 0.5% of KH-560, presented a 72% decrease in wear mass loss compared to the pure UHMWPE, as well as the maximum tensile strength and highest Vicat softening temperature.Three different kinds of UHMWPE composites were prepared by means of physical filling and chemical crosslinking in this thesis, named as GB/UHMWPE, BN/UHMWPE and crosslinked UHMWPE, respectively. It was found that wear mass loss of the resulting composites decreased sharply compared with pure UHMWPE. An increase in Vicat softening temperature and hardness was found on GB/UHMWPE composites, an enhancement in the tensile strength and crystallinity on BN/UHMWPE composites, and an improvement in the gel fraction and tensile strength on crosslinked UHMWPE, which facilitate the use of UHMWPE in the oil wells with greater depth and higher temperature.