采用Ｘ射线衍射法、ＤＳＣ法和ＩＲ法分析测定了超高和常规分子量聚乙烯晶体的晶胞参数、结晶度、晶粒尺寸、熔点、熔化热和短支链的甲基含量。研究这些特性参数随分子量的变化以及晶胞参数和微晶尺寸对熔点的影响。观测聚乙烯熔体冷却结晶后的结晶度与初生态聚乙烯结晶度的差别。 The crystal lattice parameters, crystallinity, grain size, melting point, heat of fusion and methyl content of short chain branches of ultra-high and conventional molecular weight polyethylene crystals were measured by X-ray diffraction, DSC and IR. The effects of these parameters on the melting point were investigated as a function of molecular weight and the cell parameters and crystallite size. The difference between the degree of crystallinity after cooling crystallization of polyethylene melt and the degree of virgin polyethylene crystallization was observed.