화학공학소재연구정보센터
Journal of Applied Polymer Science, Vol.104, No.6, 3592-3600, 2007
Crystallization behaviors of linear and long chain branched polypropylene
The nonisothermal crystallization kinetics of linear and long chain branched polypropylene (LCB PP) were investigated by differential scanning calorimetry (DSC) at various cooling rates. Several methods such as Avrami, Ozawa, and Jeziorny were applied to describe the crystallization process of linear PP and LCB PPs with different LCB level under nonisothermal conditions. The values of t(1/2), Z(c), and F(T) show that LCB has the role of heterogeneous nucleating agent and accelerates the crystallization process of PP. Moreover, the Kissinger method was used to evaluate the activation energy of linear PP and LCB PPs. The result shows that the activation energy of LCB PPs are higher than that of linear PP, indicating that the presence of LCB baffles the transfer of macromolecular segments from PP melt to the crystal growth surface. Furthermore, the crystal morphology of linear PP and LCB PPs was observed through polarized optical microscopy (POM), and fine spherulites were observed for LCB PPs. (c) 2007 Wiley Periodicals, Inc.