聚己内酯等温结晶的Avrami动力学研究

Avrami Kinetics Study of the Isothermal Crystallization of Poly(ε-caprolactone)

利用示差扫描量热仪(DSC)分析了3种不同分子量的聚己内酯(PCL)在30～45℃的等温结晶,并通过Avrami方程对其进行了等温结晶动力学研究。在此温度范围内,PCL的结晶度与等温结晶时间的关系曲线都呈现S型,说明其均采用异相成核的方式。根据Avrami关系式解出的双对数图都存在很好的直线关系部分,推导出Avrami指数(n)的值大都约为整数,在相同的Tc下,PCL生长方式类似,与分子量基本无关。lnK(结晶速率常数)随Tc的升高逐渐减小,说明晶体生长速率逐渐下降。在相同的Tc下,随着分子量的增加,结晶速率逐渐下降。半结晶时间(t1/2)随Tc的升高而降低,说明在此温度范围内晶体的生长速率随着Tc的升高而减慢。通过原子力显微镜(AFM)研究了PCL在30～45℃等温结晶的晶体表面,推导出的n值与Avrami方程拟合出的n值基本一致,说明Avrami动力学分析的结果是比较可靠的。

The isothermal crystallization of three samples of poly（ε-caprolactone） with different molecular weight between 30-45℃ is studied using differential scanning calorimetry analysis. The isothermal crystallization kinetics is approached according to Avrami equation. Isothermal crystallization all preferred a heterogeneous nucleation pathway regardless of its molecular weight. The Avrami index n is approximately integral. Under the same isothermal crystallization temperature, the crystallization rate decreases gradually as the molecular weight increases. The half- crystallization time（h/2 ） and the natural logarithm of crystallization rate constant（InK） declines as the crystallization temperature lowers, indicating in this temperature range, the crystal growth rate rises as crystallization temperature drops. Meanwhile, the PCL crystal surface isothermally crystallized at 30-45℃ is studied using the atomic force microscopy（AFM）. The dimensional number of space deduced from the phase images of AFM is basically consistent to the Avrami index n.