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本工作系研究以高效催化聚合获得的超高分子量聚乙烯的结构和性能。用扫描电子显微镜观察了高效催化剂及初生聚乙烯的形态。透射电子显微镜观察了初生聚乙烯粉未,发现毛遂边缘的超分子原纤维状织态结构。用偏光显微镜观察了不同分子量聚乙烯粉末的熔融和冷却结晶过程,生成的球晶随分子量增大而增大。用X-射线衍射、差热分析、倒换气相色谱测定了初生聚乙烯的结晶度随分子量而增大;用X-射线衍射、差热分析及密度梯度法测定经退火或热压制的聚乙烯样品的结晶度均随分子量增大而下降。X-射线衍射测定其晶粒尺寸亦随分子量增大而减小。差热分析和倒换气相色谱测定超高分子量聚乙烯粉末的结晶熔点温度(T_m)要比普通分子量聚乙烯高8—12℃。不同分子量聚乙烯的热形变曲线表明,超高分子量聚乙烯在熔融温度后出现明显的橡胶态。此外,还用差热与热重分析研究了超高分子量聚乙烯的热老化行为。测定了超高分子量聚乙烯的优异抗冲强度和沙浆磨耗量。并用扫描电镜对比观察了常规分子量和超高分子量聚乙烯试样的冲击断面的织态结构。
This work is to study the structure and properties of ultra-high molecular weight polyethylene obtained by efficient catalytic polymerization. The morphology of the high-efficiency catalyst and virgin polyethylene was observed with a scanning electron microscope. Transmission electron microscopy was used to observe the virgin polyethylene powder and to find the supramolecular fibrillar structure at the edge of the hairline. The melting and cooling crystallization processes of polyethylene powders with different molecular weights were observed with a polarizing microscope. The spherulites formed increased with increasing molecular weight. The crystallinity of primary polyethylene was measured by X-ray diffraction, differential thermal analysis and reversed-phase gas chromatography. The crystallinity of primary polyethylene increased with the molecular weight. The samples annealed or hot-pressed by X-ray diffraction, differential thermal analysis and density gradient The crystallinity decreases with the increase of molecular weight. X-ray diffraction measured its grain size also decreases with increasing molecular weight. Differential thermal analysis and reversed-phase gas chromatography determination of ultra-high molecular weight polyethylene powder crystallization temperature (T_m) higher than the average molecular weight of polyethylene 8-12 ℃. The thermal deformation curves of polyethylene with different molecular weights show that the UHMWPE shows obvious rubbery state after the melting temperature. In addition, the thermal aging behavior of ultrahigh molecular weight polyethylene was also studied by differential thermal and thermogravimetric analysis. The excellent impact strength and mortar wear of UHMWPE were measured. Scanning electron microscopy was used to observe the weaved structure of impact cross section of conventional molecular weight and ultrahigh molecular weight polyethylene samples.