聚丙烯断裂标称应变问题研究

Nominal tensile strain at break of i-PP resins

4组生产工艺完全相同的等规聚丙烯,其中有两组的注塑样条出现断裂标称应变偏低或者数据波动的问题,其性能难以满足产品的出厂要求。采用核磁共振波谱仪、高温凝胶渗透色谱仪、小角X射线散射仪、差示扫描量热仪和偏光显微镜表征了等规聚丙烯的微观结构。结果表明:4组试样的相对分子质量及其分布差异小,链立构规整度差别不大,分子链结构基本相同;断裂标称应变不合格的两组试样的结晶温度明显偏高,球晶细碎,且晶区厚度更大,说明其凝聚态结构存在明显差异。

Low values or fluctuation of nominal tensile strain at break occurred in two injection samplesfrom four isotactic polypropylene(i-PP)resins that were produced respectively via the same process,whichhas caused the failure of meeting the requirements of products.The microstructure of i-PP were investigated by13C-nuclear magnetic resonance(13C-NMR)spectrometer,gel permeation chromatograph(GPC),small angleX-ray scattering(SAXS)system,differential scanning calorimeter(DSC)and polarized light microscope(PLM).The results indicate that the molecular weight and molecular weight distribution of four samples are similar,the chain structure and tacticity are identical as well.However,the two samples that fail to meet the standardof nominal tensile strain at break represent the thick crystal layer,high crystallization temperature,smallspherulite,which mean great differences in morphology state of the samples.