Self-nucleation Effect of Crystallization with Various Nucleating Agents

In this work, the self-nucleation effect on crystallization was studied for polypropylene with various nucleating agents. The talc was employed to accelerate crystallization of monoclinic & alpha;-crystallites, while N, N & PRIME;-dicyclohexyl-2,6-naphthalenedicarboxamide TMB-5 was used to accelerate the crystallization kinetics and also induce formation of trigonal & beta;-crystallites. To induce self-nucleation effect, the occurrence criterion was assessed by the transition temperatures from various domains and the available temperature width. More importantly, the resulting influences of self-nucleation effect were quantified by the change of crystallization kinetics and the potential polymorphism variation. It was found that the & alpha;-nucleating agents of talc broadened the temperature window for inducing Domain II by elevating the transition temperature from Domain I to Domain II. Although & beta;-nucleating agent (& beta;-NA) of N, N & PRIME;-dicyclohexyl-2,6-naphthalenedicarboxamide TMB-5 elevated cooling crystallization temperature obviously, the temperature window for Domain II was narrowed. It should be emphasized that in presence of & beta;-NA TMB-5, the self-nucleation effect enhances the crystallization of & alpha;-crystallite, which show the competition with & beta;-NA TMB-5. At last, the ternary PP/talc/TMB-5 blend was prepared with the same amounts of & alpha;-NA talc and & beta;-NA TMB-5 and it exhibits a similar self-nucleation effect of crystallization, indicating the dominant role of & beta;-NA TMB-5.