制备了具有不同立构缺陷分布均匀性、不同相对分子质量的系列等规聚丙烯(iPP)样品,利用差示量热扫描仪、广角X射线衍射仪、扫描电子显微镜等深入研究了双组分β晶成核剂作用下,iPP的相对分子质量、立构缺陷分布均匀性对其多晶型行为、非等温结晶动力学行为,尤其是β晶含量、形态和热稳定性的影响.结果表明,立构缺陷分布的均匀性决定了iPP结晶温度的高低;而立构缺陷分布均匀性与相对分子质量都是结晶活化能的重要影响因素.在熔融方面,相对分子质量和立构缺陷均匀性都是影响β晶含量、β晶热稳定性的重要决定因素.相对分子质量越低、立构缺陷分布越不均匀,越不利于形成高含量β晶;然而,立构缺陷分布越不均匀,相对分子质量越高,越容易形成热稳定性高的β晶.上述研究结果表明,在双组分β晶成核剂作用下,iPP的相对分子质量和立构缺陷均匀性对iPP的β结晶具有不同的影响特征,因此在实际研究及加工过程中需综合考虑.
In this study,the crystallization behavior and polymorphic morphology of two series of β-iPP resins with nearly same average isotacticity (PP-A and PP-B) but different uniformities of stereo-defect distribution,different molecular masses were investigated by differential scanning calorimetry (DSC),wide angle X-ray diffraction (WAXD) and scanning electron microscope (SEM).Results reveal that the uniformity of stereo-defect distribution plays determining role in the crystallization temperature of iPP,while both stereo-defect distribution uniformity and molecular masses are crucial factors affecting the crystallization efficiency and thermal stability of β-crystallization.Lower molecular mass and less uniform stereo-defect distribution are less favorable for formation of high amount of β-phase;the higher molecular mass and less uniform stereo-defect distribution help to form β-phase with higher thermal stability.Above results reveal that in the case of iPP nucleated with dual component β-nucleating agent,molecular masses and stereo-defect distribution play different roles in determining the polymorphic behavior of iPP,which should be considered comprehensively during the process of practical manufacturing and research.
参考文献
- 下载量()
- 访问量()
- 您的评分：
-
10%
-
20%
-
30%
-
40%
-
50%