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 α-crystallites,while N,N′-dicyclohexyl-2,6-naphthalenedicarboxamide TMB-5 was used to accelerate the crystallization kinetics and also induce formation of trigonal β-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 α-nucleating agents of talc broadened the temperature window for inducing Domain Ⅱ by elevating the transition temperature from Domain Ⅰ to Domain Ⅱ.Although β-nucleating agent(β-NA)of N,N′-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 β-NA TMB-5,the self-nucleation effect enhances the crystallization of α-crystallite,which show the competition with β-NA TMB-5.At last,the ternary PP/talc/TMB-5 blend was prepared with the same amounts of α-NA talc and β-NA TMB-5 and it exhibits a similar self-nucleation effect of crystallization,indicating the dominant role of β-NA TMB-5.