Non-Isothermal Crystallization Behaviors of Isotactic Polypropylene with and without 1,3:2,4-Bis(3,4-Dimethylbenzylidene) Sorbitol as a Nucleating Agent

Abstract

1,3:2,4-bis(3,4-dimethylbenzylidene) sorbitol (DMDBS) is the third-generation sorbitol-based nucleating agent for isotactic polypropylene (iPP). In this study, the non-isothermal crystallization behaviors of iPP with and without DMDBS as a nucleating agent were investigated by means of a differential scanning calorimeter (DSC), and the Caze method was used to analyze the non-isothermal crystallization kinetics. The results show that the addition of DMDBS can increase the crystallization peak temperature (Tp) of iPP greatly under the same cooling rate. When concentration of DMDBS is 0.2 wt.% and the cooling rate is 10°C/min, Tp of iPP nucleated with DMDBS can be increased from 118.7°C of virgin iPP to 130.1°C. Under non-isothermal conditions, the addition of DMDBS changes the spherulite growth pattern of iPP. In addition, nucleation activity of DMDBS was calculated by using the method proposed by Dobreva and Gutzow, and the results showed that DMDBS had high nucleation activity.