Isothermal melt- and cold-crystallization kinetics and subsequent melting behavior in syndiotactic polypropylene: a differential scanning calorimetry study
Isothermal melt- and cold-crystallization kinetics and subsequent melting behavior in syndiotactic polypropylene: a differential scanning calorimetry study
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DOI：
10.1016/s0032-3861(00)00399-2
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发表时间：
2001
期刊：
影响因子：
4.6
通讯作者：
P. Supaphol;J. Spruiell
中科院分区：
文献类型：
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作者：
P. Supaphol;J. Spruiell
采用差示扫描量热法（DSC）研究了间规聚丙烯（s-PP）的等温熔融、冷结晶动力学及熔融行为。通过使用非线性多变量回归程序将实验数据直接拟合到Avrami和Malkin宏观动力学模型来确定总体结晶动力学。熔融结晶过程的结晶速率参数与结晶温度的关系曲线呈现明显的双钟形曲线，而冷结晶过程的结晶速率参数则呈现典型的钟形曲线。熔融和冷结晶过程得到的总体结晶速率参数的比较表明，从玻璃态的结晶进行在一个更大的速率比从熔融状态。在中低晶化温度下等温晶化的样品，其熔融呈现多重熔融现象。根据“线性”和“非线性”Hoffman-Weeks外推法测定平衡熔融温度提供了约分别为145和182°C。
The isothermal melt- and cold-crystallization kinetics and subsequent melting behavior of syndiotactic polypropylene (s-PP) were investigated using differential scanning calorimetry (DSC). The overall crystallization kinetics was determined by directly fitting the experimental data to the Avrami and Malkin macrokinetic models using a non-linear multi-variable regression program. When plotted as a function of crystallization temperature, the overall crystallization rate parameters for melt-crystallization process exhibited an unmistakable double bell-shaped curve, while those for cold-crystallization process showed the typical bell-shaped curve. Comparison of the overall crystallization rate parameters obtained for both melt- and cold-crystallization processes indicated that crystallization from the glassy state proceeded at a much greater rate than that from the melt state. Melting of samples isothermally crystallized at low and moderate crystallization temperatures exhibited multiple-melting phenomenon. Determination of the equilibrium melting temperature according to the “linear” and “non-linear” Hoffman–Weeks extrapolative methods provided values of ca. 145 and 182°C, respectively.