聚丙烯结晶形态与力学性能及其疲劳稳定性

基于Haake转矩流变仪,分别将α和β成核剂熔混到等规聚丙烯中以改变其结晶形态.用偏光显微镜法、X射线衍射法和力学性能测试方法研究了疲劳作用前后α晶和β晶相互转变及其结构性能.实验结果表明:α成核剂在降低球晶尺寸和增加结晶度同时,在晶胞内产生了内应力,在疲劳初期,结晶应力消除、拉伸强度增加,继续疲劳时,结晶度和拉伸强度都下降,疲劳后,β含量相对增加.当β成核剂用量较少时,β晶含量增加,拉伸强度降低；在β晶结晶度适中时,疲劳并不改变晶胞结构与结晶度,表现较好的耐疲劳性；结晶度较高时,疲劳降低了结晶度,但拉伸强度有所增加.

Crystalline Morphology,Mechanical Properties and Fatigue Stability of Isotactic Polypropylene in the Presence of Alpha-and Beta-nucleating Agents

The modification of crystallinity morphology of isotactic polypropylene(IPP) by using alpha-and beta-nucleating agents was conducted with Haake rheometer at high temperature.The crystalline morphology and mechanical properties of the modified IPP prior to and after dynamic fatigue experiment were investigated with polarized light microscopy,x-rays diffraction and tensile test.Crystalline stress was released and tensile strength was increased slightly during initial fatigue period for alpha-nulceated IPP while no crystalline stress was found,the degree of crystallization was decreased,and tensile strength was increased after short fatigue period for beta-nulceated IPP.The transition under dynamic load was still found for alpha-nulceated IPP but to much less extent for the case of beta-nulceated IPP.