Enthalpy Relaxation during Non-Isothermal Crystallization from the Melt of Polymer: For <i>I</i>PP as Example

Abstract

The enthalpy relaxation rate (rh) is defined by enthalpy change in unit time to describe non-isothermal crystallization behavior of iPP from its melt. Dates of rhare transformed from those of heat flow rate which are collected by means of DSC directly. The curve by plotting with rhto time indicates that the process of non-isothermal crystallization can be separated into two stages by the time point of inflection at rhcurve. The two stages are called stage Ⅰand stage Ⅱ. The curve of rhis differentiated and the curve of Ahproduced. There are two time inflection point in curve of Ah. Combined different trends of rhand Ahduring the whole process, the non-isothermal crystallization are further separated into four sub-stages, which are called stage Ⅰ1, stage Ⅰ2, stage Ⅱ1and stage Ⅱ2. The critical values of time and relative crystallization degree which divide the process of non-isothermal crystallization of iPP are present. It provides one new method to uncover the details of non-isothermal crystallization process.