TFE-PPVE共聚物组成均匀性的热分级方法表征

Composition heterogeneity of TFE-PPVE copolymers characterized by thermal fractionation methods

针对可熔融加工聚四氟乙烯组成均匀性难以分析的状况,应用连续自成核退火热分级(SSA)和逐步结晶(SC)方法表征四氟乙烯-全氟丙基乙烯基醚共聚物(TFE-PPVE共聚物,PFA)的组成均匀性及片晶厚度分布。结果表明,SSA对PFA的热分级效果明显优于SC。通过自成核熔融行为确定了PFA的SSA的初始热分级温度,进一步得到优化的热分解条件:升温/降温速率10℃·min^-1、分级步长△T为5℃、恒温时间5 min。SSA结果显示随着共聚物中全氟丙基乙烯基醚(PPVE)含量的增加,共聚物组成分布和片晶厚度分布变宽;对于组成相近的PFA,由于组成均匀性差异,也会导致片晶厚度分布、结晶度与熔融温度的差异。

Considering difficulties in analysis of composition heterogeneity of melt-processable polytetrafluoroethylene,successive self-nucleation annealing thermal classification(SSA) and step crystallization(SC) methods were applied to study the composition heterogeneity and lamellar thickness distributions of tetrafluoroethylene-perfluoropropyl vinyl ether(TFE-PPVE) copolymers(PFA).The results show that SSA has better fractionation result for PFA than SC.The initial thermal grading temperature Ts,0 of SSA was determined through the self-nucleation melting behavior of PFA,and grading parameters of SSA for PFA were optimized as follows:heating/cooling rate=10 ℃·min^-1,temperature step of fractionation △T=5℃and isothermal time=5 min.The thermal fractionations of different PFA samples show that the composition heterogeneity decreases and the lamellar thickness distribution becomes wider as the content of perfluoropropyl vinyl ether(PPVE) in PFA increases.Moreover,the lamellar thickness distribution,crystallinity and melting temperature also vary with the composition heterogeneities of PFA with near composition.