双峰相对含量对聚乙烯薄膜树脂非等温结晶动力学的影响

Effect of Bimodal Relative Content on the Non-isothermal Crystallization Kinetics of Bimodal Polyethylene Film Resin

对双峰聚乙烯薄膜树脂的非等温结晶动力学行为进行了研究,利用Jeziorny法和莫志深法(Mo法)进行分析,讨论了双峰相对含量对结晶的影响。Jeziorny法表明,Jeziorny 方程可以描述非等温结晶的初期过程,随着结晶速率的增大,样品的半结晶时间 t 1/2 减小,结晶速率常数 Z c 增大。同时,Bimodal-HDPE-2样品结晶速率常数 Z c 大于Bimodal-HDPE-1,Avrami指数 n 为2左右,样品属于均相成核,三维生长的球晶。Mo法结果表明,结晶速率(ln Φ)和时间(ln t )的线性关系明显,随着降温速率的增加, F (T)增大;对比两种样品发现,Bimodal-HDPE-2的 F (T)值较大;a 值在2左右,变化不大。综合分析发现:样品的低分子量部分含量越高,结晶速率越快,越容易结晶。

The non-isothermal crystallization kinetics of bimodal polyethylene film resin was studied in this paper and the Jeziorny method and Mo method were used to analyze the non-isothermal crystallization kinetics process.The effect of bimodal relative contents on the crystallization of bimodal polyethylene was discussed.The Jeziorny method shows that the Jeziorny equation could describe the initial process of non-isothermal crystallization.With the increasing of the crystallization rate,the semi-crystallization time t 1/2 of the samples could decrease and the crystallization rate constant Z c could increase.At the same time,the crystallization rate constant of Bimodal-HDPE-2 is greater than Bimodal-HDPE-1.The value of n is about 2.The samples are spherulites with homogeneous nuclei and three dimensional growth.The results of Mo method shows that the linear relationship is obvious between ln Φ and ln t .With the increasing of cooling rate,the value of F(T) could increase.Comparing the two samples,it is found that the value of F(T) of Bimodal-HDPE-2 is larger than that of Bimodal-HDPE-1.The value of a is around 2 and it does not change too much.The comprehensive analysis shows that the higher the content of the low molecular weight part,the faster the crystallization rate and the easier the crystallization could be obtained.