화학공학소재연구정보센터
Journal of Applied Polymer Science, Vol.71, No.6, 897-901, 1999
Nonisothermal crystallization of s-PP fractions
Syndiotactic polypropylene (s-PP) was prepared by metallocene catalyst and was fractionated with the temperature rising elution fractionation (TREF) technique. The nonisothermal behavior of the obtained fractions was investigated. Fractions was first cooled at different rates and then heated at a constant rate. The parameters such as the peak crystallization temperature (T-c), the onset crystallization temperature (T-on), the difference between T-on and T-c (Delta T-1 = T-on - T-c), the crystallization enthalpy (Delta H), the peak melting temperatures (T-m1, T-m2), and the difference between the T-m1 and T-m2 (Delta T-2 = T-m2 - T-m1) were obtained. The dependence of these parameters on cooling rate, syndiotacticity, and molecular weight was discussed. It is found that T-c, T-on, Delta H, T-m1, and T-m2 systematically increase with increasing syndiotacticity and are depressed on increasing the cooling rate. Cooling rate, syndiotacticity, and molecular weight show different influences on BT,. In the melting process of s-PP, double peaks were observed.