快速扫描量热法研究聚对苯二甲酸-1,4-环己烷二甲醇酯的结晶和熔融行为

采用快速扫描量热法(FSC)结合传统的差示扫描量热仪(DSC)考察了聚对苯二甲酸-1,4-环己烷二甲醇酯(PCT)聚酯在接近玻璃化转变(T_g)和熔融温度(T_m)范围(100~270 ℃)的结晶和熔融行为。 较大过冷度时PCT聚酯结晶较快,FSC有效地抑制降温过程结晶的发生,而较低过冷度下传统DSC可以避免样品降解对实验结果的影响,二者的结合能很好地对PCT聚酯结晶动力学进行测量,实验结果表明在175 ℃时结晶速率最快。 并且利用Flash DSC对等温结晶温度下形成的片晶熔点进行加热速率的相关测量,在熔融动力学建模的基础上进行校准,以确定零加热速率下片晶的熔点。 Hoffman-Weeks方程中T_m与结晶温度(T_c)的线性关系与T_c=T_m的交点给出了PCT晶体的平衡熔融温度$T_m^o$为315 ℃。

Crystallization and Melting Behaviors of Poly(1,4-cyclohexylene Dimethylene Terephthalate) Studied by Fast-Scan Calorimetry

The crystallization and melting behavior of poly(1,4-cyclohexylene dimethylene terephthalate) (PCT) was studied by fast scanning calorimetry (FSC) combined with traditional differential scanning calorimetry (DSC) in the range of near glass transition temperature and melting temperature (100~270 ℃). The crystallization rate of PCT is faster when the supercooling degree is larger. FSC can effectively inhibit the crystallization of PCT during the cooling process while the traditional DSC can avoid the influence of sample degradation on the experimental results under the lower supercooling degrees. The combination of FSC and DSC can well measure the crystallization kinetics of PCT. The experimental results show that the crystallization rate is the fastest at 175 ℃. FSC is also used to measure the melting point dependence of heating rate after isothermal crystallization, and calibrated on the basis of the modeling of melting kinetics for the determination of the melting point at zero heating rate T_m. The Hoffman-Weeks plot of T_m against T_c with the intersection of T_c=T_m suggested the equilibrium melting point $T_m^o$?315 ℃ of chain-extended infinite-size crystals of PCT.