Synergistic toughening effects of elastomer toughener and nucleating agent on mechanical properties and crystallization behaviors of polypropylene

Abstract

A novel thermoplastic elastomer, kernel resin (KN), α‐nucleating agent (HPN), and β‐nucleating agent (DCHT), which acted as toughener and nucleating agents (NAs), were used to improve the mechanical properties and crystallization behaviors of isotactic polypropylene (PP). The impact strength of the PP/KN blends increased significantly with increase in KN concentration. Surprisingly, the impact strength of PP/KN/NA blends improved further upon addition of NA. The toughening effect of DCHT was stronger than that of HPN. The maximum impact strength of PP/KN/DCHT blend reached 69.2 kJ/m2 when the DCHT content was 0.05%, which was six times higher than that of neat PP. The SEM images of fractured surfaces of the blends showed a change from brittle fracture to ductile fracture. Moreover, the WAXD results showed that the incorporation of HPN promoted the formation of the α form of crystalline PP. Addition of DCHT induced the generation of α‐β crystal transition of PP. Furthermore, differential scanning calorimetry showed that the crystallizability and the overall crystallization rate of PP were enhanced by the addition of KN and NA. The half‐crystallization time of PP at 128°C decreased from 5.52 (neat PP) to 0.34 min (PP/KN/DCHT‐0.3).