聚丙烯等温结晶实验参数的确定方法

The Setting Method of Experiment Parameters for Polypropylene Isothermal Crystallization

用差示扫描量热分析法,对纯聚丙烯PP在不同结晶温度Tc下进行等温结晶。应用Avrami方程进行数据处理的。结果表明结晶起始时间t0的不同取法,lg[-ln(1-Xc(t))]对lgt关系图的斜率变化很大,其线性关系的结晶度范围也不同;等温结晶温度Tc在128～134℃之间,斜率随温度升高而略有增大;成线性关系的结晶度范围基本不变;Tc在128℃以下,斜率随温度的降低减小很大,成线性关系的结晶度范围明显变窄。

The isothermal crystallization of polypropylene under the different crystallization temperatures was studied by using diferential scanning calorimetry. The parameters of isothermal crystallization kinetics were calculated with the Avrami equation. Results show that the setting of crystallization starting time (t0 ) has great effect on the slope of the relation of lg [ - ln (I - Xc (t) ) ] and lg t. The linear range of crystallization degree in which the lg [ -ln ( 1 - Xc (t))] and lgt showed a linear relation is also influenced by this factor. When the isothermal crystallize temperature (Tc) is increased from 128 Cto 134℃, the slope of the relation of lg [-ln(1-Xc(t))] and lgt increases slightly and the linear range of crystallization degree is affected insignificunty. However, when the Tv is below 128℃, the slop decreases greatly as the Tc decreases and the linear rang narrows down respectively.