基于差示扫描量热法的PBT非等温结晶行为研究

Non-isothermal crystallization behavior of PBT by DSC

研究了聚对苯二甲酸丁二酯(PBT)的非等温结晶动力学。结果表明:PBT的结晶过程存在温度依赖性,结晶时以生成较稳定的α晶为主,而在较慢的降温速率下同时伴随着β晶的生成。利用Jeziomy模型得到起始结晶阶段Avrami指数的平均值为4.21,说明起始结晶过程可能倾向于有均相热成核的三维球晶生长,且结晶速率常数随着降温速率的增大而下降;使用Ozawa模型不能很好地描述PBT的结晶行为,可能是由于不同的降温速率导致体系中晶核数量与密度存在差异;莫志深模型分析表明,在单位时间内达到更高的结晶度所需降温速率快,增大降温速率有利于聚合物结晶,莫志深法能很好地描述PBT的非等温结晶过程;Kissinger模型分析与实验结果一致,计算得到PBT的非等温结晶活化能为-193.4 kJ/mol。

Non-isothermal crystallization kinetics of polybutylene terephthalate(PBT)was analyzed.The results show that the crystallization process of PBT is temperature dependent,crystallineαis formed during the process and crystallineβis also formed at slower cooling rate.The average Avrami index can be obtained as 4.21 at the initial crystallization stage by Jeziomy model,which indicates that the initial crystallization corresponds to three dimension spherical growth with homogeneous thermal nucleation,and the crystallization rate constant decreases with the increase of cooling rate.The Ozawa model fails to describe the crystallization kinetics of PBT,which might be attribute to the difference in the number and density of crystalline nuclei in the system caused by different cooling rates.The analysis of Mo equation model indicates that a higher cooling rate contributes to a higher crystallinity under unit time,and accelerating cooling rate favors to crystallization of polymers.The Mo equation describes the non-isothermal crystallization of PBT well.The measurement results are in consistent with the predictions of Kissinger model.The activation energy of non-isothermal crystallization for PBT is calculated as-193.4 kJ/mol.