Performance Evaluation Of Nucleating Agents In Polypropylene Homopolymer

Types of nucleating agents and their dosage level play an important role on the crystallinity of the polymer which controls the final properties like optical clarity, stiffness and reduced cycle time during molding. In this study, the efficiency of two different types of commercially available nucleating agents, phosphate ester and dicarboxylic acid based, have been studied. Both the nucleating agents were compounded with molding grade polypropylene homopolymer having melt flow index (MFI) of 12 g/10min at 2.16 Kg and 230 degrees C, in a co-rotating twin screw extruder at two different dosage level, i.e. 300 ppm and 600 ppm. The effectiveness of the nucleating agents was evaluated from several parameters like stiffness, crystallization behavior in terms of crystallization onset, % crystallinity and isotropic shrinkage. A crystallization kinetic study was also carried out at four different cooling rates. Addition of nucleating agent at 300 ppm dosage level showed an increase in flexural modulus of neat polypropylene by around 14%. Dicarboxylic acid based nucleating agent showed better isotropic shrinkage behavior as compared to phosphate ester based nucleating agent at both 300 ppm as well as 600 ppm dosage level. The efficiency of this type of nucleating agent was further supported by comparatively lower activation energy as evaluated from crystallization kinetics study.