Avrami法研究微量司盘85对棕榈油结晶动力学的影响

采用差示扫描量热仪（differential scanning calorimetry，DSC）分析棕榈油及其与司盘85混合物的等温结晶及熔融行为，通过Hoffman-Weeks法计算出样品的平衡熔点。采用Avrami方程进一步研究样品的等温结晶动力学，从而得到与结晶动力学相关的参数。结果表明：DSC分析显示司盘85可明显降低棕榈油的结晶率和成核速率。通过Hoffman-Weeks法和Avrami方程求得的温度数据具有良好的线性关系，表明Avrami方程适用于棕榈油结晶过程的研究，但在结晶后期出现偏离。拟合得到的Avrami指数（n）在2.37～2.77之间，可知样品二维和三维晶体生长同时存在；结晶速率（k）和半结晶时间（t1/2）随着添加剂的添加均变小。

Crystallization Kinetics of Palm Oil with Trace Amounts of Span 85 Using Avrami Method

The isothermal crystallization and melting behavior of palm oil and its mixtures with sorbitan trioleate (Span 85)
were tested using differential scanning calorimetry. The equilibrium melting temperature was calculated by Hoffman-Weeks
method. The parameters associated with the crystallization kinetics were obtained by using the Avrami equation to simulate
the isothermal crystallization process of samples. DSC curves showed that the additive could reduce the crystallization rate
and nucleation rate. The temperature data obtained by Hoffman-Weeks method and the Avrami equation had a good linear
relationship, indicating that the Avrami model could be applied to simulate the crystallization process of palm oil although
there was a deviation in the late crystallization. The Avrami exponent n obtained by fitting the data is between 2.37 and 2.77,
which showed the simultaneous occurrence of two-and three-dimensional crystal growth. Moreover, the crystallization rate k
and the half-crystallization time t1/2 were smaller in the presence of Span 85.