研究高聚物结晶动力学的等速升温 DSC 方法

A DSC METHOD FOR CALCULATING CRYSTALLIZATION KINETICS OF POLYMERS UNDER THE CONSTANT HEATING RATE CONDITIONS

本文把等温 Avrami 方程推广应用于等速升温的非等温结晶过程。从推广的方程可得到Avrami 方程能得到的结晶动力学参数,如 Avrami 指数 n、复合结晶速度常数 K 和结晶半衰期t_(1/2)。等速升温方法可克服用 DSC 进行等温扫描时在实验上的不足,具有实验简单、获取的结晶信息量较大的特点。用 DSC 对 PET 树脂进行了等速升温结晶和等温结晶实验,并分析了实验结果。结果表明,由升温 DSC 方法得到的 n 和 t_(1/2)比等温方法稍大,K 则稍小。等温结晶结果与非等温结晶结果稍有不同的原因之一可能是这两种结晶过程的结晶机理有差别。等温结晶结果与非等温结晶结果的一致性是令人满意的。

Avrami equation for the isothermal crystallization was extended to the non-isothermal process of the constant heating rates so that the parameters characteringcrystallization kinetics,such as Avrami exponent n,the crystallization rate constantK and the half life of crystallization t_(1/2),which are usually obtained from Avramiequation,could be calculated from the extended equation for non-isothermal crystal-lization.The heating method can avoid the limitations that exist experimentallywhen a DSC method is used to study the isothermal process of polymer.Using theheating method,the experiment is easier and more informations of crystallizationcan be obtained than the isothermal one.After analyzing the results of the heatingcrystallization and isothermal crystallization of PET resin with DSC method,it isfound that the values of n and t_(1/2)obtained from the heating crystallization at agiven temperature are slightly larger than that from the isothermal one respectively,and the value of K is smaller than that from the isothermal crystallization.For thediffe rent results above,one of the reasons may be that the crystallization mechanismsof the two processes are not the same.Generally,the consistancy between the resultsof two crystallization processes is satisfactory,