Synergistic enhancement of crystallization and mechanical performance of polypropylene random copolymer by strong shear and β‐nucleating agent

Abstract

AbstractInvestigation of microstructure and properties is critical for the development and application of polymer materials. Polypropylene random copolymer (PPR) and β‐nucleated PPR are widely used in water pipe production. The effect of melt shear flow on the crystalline structure and mechanical properties of PPR containing β‐nucleating agent needs in‐depth understanding. In this paper, we demonstrated the preparation of PPR and PPR containing 0.1 wt% calcium pimelate (Ca‐Pim) samples by conventional injection molding (CIM) and oscillation shear injection molding (OSIM). The multilayer structures and morphologies of the samples were characterized by SEM, two‐dimensional X‐ray scattering and DSC. The mechanical properties and the microstructures of samples prepared by these two injection molding methods were compared. Compared with samples prepared by CIM, the stronger shear provided by OSIM induced the formation of a thicker layer of a shish‐kebab structure and a higher content of γ crystals, and dramatically suppressed the β‐nucleating effect of Ca‐Pim. The OSIM samples have more shish‐kebab structures and higher crystallinities than CIM samples and therefore the former exhibit better rigidity than the latter. The β crystals in the core layer and the thicker layer of shish‐kebab structure endow OSIM‐PPR/0.1 wt% Ca‐Pim with excellent impact toughness. © 2017 Society of Chemical Industry