等规聚丙烯自成核的等温结晶动力学

近年来 ,有关等规聚丙烯 (i PP)的自成核研究已引起了人们的关注 [1 ] ,但有关其结晶动力学的报道并不多见 .Carfagna等 [2 ]用膨胀计法研究了 i PP在未完全熔融重结晶情况下的等温结晶动力学 ,得到的 Avrami指数远远小于 3 .张新远等[3 ] 研究了 i PP未完全熔融情况下的非等温结晶动力学 .到目前为止 ,i PP自成核的熔体降温等温结晶动力学尚未见报道 .本文在 i PP自成核研究的基础上 [4] ,用 DSC方法研究了 i PP自成核在较高温度下的等温结晶动力学 ,讨论了结晶机理 .结果表明 ,在本实验的自成核条件下 ,i PP依然是三维球晶生长 ,…

Isothermal Crystallization Kinetics of iPP During Self-nucleation Process

In this paper, the isothermal crystallization kinetics of polypropylene(iPP) during self-nucleation was studied by means of differential scanning calorimetry(DSC). The iPP was melted at 438 K and then isothermally crystallized in the range of temperature between 421 and 425 K. The mechanism of nucleation and growth of iPP was discussed. The Avrami equation was applied to analyzing the process of isothermal crystallization of iPP from the melt. The average value of Avrami exponent is n=3.01, suggesting that the primary crystallization maybe corresponds to three-dimensional spherulitic growth.The Kg value obtained from Lauritzen-Hoffman equation is 1.128×105 K2, which suggests that crystallization species should be regime Ⅱ. The decrease of crystallization active energy and chain folding work indicates that the self-nucleation can greatly promote the overall crystallization of iPP.