Effect of nucleating agent incorporation on mechanical, morphological, and rheological properties of in-situ copolymer polypropylene and PPH/POE blends

Toughening of homopolymer polypropylene (PPH) in the post reactor step by incorporating external elastomers has become an attractive area of research. In this investigative work, PPH was post-reactor blended with different types of Polyolefin elastomers (POE) that were selected based on the co-monomer type and density. The performance behavior of PPH/POE blends with and without a nucleating agent was compared to in situ (in the reactor) modified PPH with Ethylene Propylene Rubber (EPR). The addition of POE in PPH, increased toughness at room temperature and the stiffness of the blends decreased. The addition of a nucleating agent was noted to improve the toughness and stiffness compared to their non-nucleated counterparts, while the tensile strength remained unchanged. At -20 °C, the impact strength results showed no significant improvement in PPH/POE blends with and without addition of the nucleating agent. The morphology analysis have shown clearly phase separation of the blends components thus demonstrating the immiscibility of the blend systems. The addition of the nucleating agent was seen to decrease the domain size of POE phase thus leading to the improvement in the toughness properties of the blends. ICP materials have shown better mechanical properties and more uniform rubber dispersion than the blends system. The rheological results of PPH/POE blends based on POE1 (butene co-monomer) and POE4 (octene co-monomer) indicate that increase POE content leads to an increase in the blends viscosity across the shear range. However, the trend was different in blends containing copolymers POE2 and POE3.