Kinetics of crystallization of polyamide 6 from the glassy state
Kinetics of crystallization of polyamide 6 from the glassy state
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聚酰胺6从玻璃态结晶的动力学
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发表时间：
2007
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通讯作者：
W. Kozłowski
中科院分区：
文献类型：
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作者：
W. Kozłowski
通过在210°K下将熔体在液体甲苯中骤冷获得玻璃态聚酰胺6。在这种聚酰胺的DSC热分析图上，观察到在310°K处的玻璃化转变的小吸热峰和在325°K处的冷结晶放热峰（两个温度都通过外推到零加热速率来计算）。
用DSC技术研究了321-339°K范围内的冷结晶动力学，采用三种不同的测量方法：1）标准等温，2）米勒等温，3）Ozawa非等温。用简单的Avrami方程分析了从1和2中获得的数据，用修正的方程分析了从3中获得的数据。结果表明，指数n不是常数，在328°K以下平均值为2.2，然后随着结晶温度的升高而变化。不幸的是，n的变化机制是未知的，这妨碍了从非等温动态数据计算结晶速率。
因此，假设结晶遵循一级动力学：计算不同温度下的K和t0.5;绘制Arrhenius函数;并从中估计活化能为69.7 kcal/mole。
Glassy polyamide 6 was obtained by quenching the melt in liquid toluene at 210°K. On the DSC thermogram of such a polyamide a small endothermic peak of glass transition at 310°K, and an exothermic peak at 325°K of cold crystallization are observed (both temperatures were calculated by extrapolation to zero heating rate).
The kinetics of cold crystallization was investigated in the range 321-339°K by DSC technique using three different methods of measurement: 1) standard isothermal, 2) isothermal by Miller, and 3) nonisothermal by Ozawa. The data obtained from 1 and 2 were analyzed by the simple Avrami equation, and from 3 by a modified equation. It was confirmed that the exponent n is not constant; in the range up to 328°K it has an average value of 2.2, and then varies with the rise in crystallization temperature. Unfortunately, the mechanism of the variation of n is not known and this prevents the calculation of the crystallization rate from the nonisothermal dynamic data.
Thus, an assumption was made that crystallization follows first-order kinetics: K and t0.5 for different temperatures were calculated; the Arrhenius function was plotted; and from it the activation energy of 69.7 kcal/mole was estimated.