Mechanical Properties and Morphology of Polypropylene/Nano-Montmorillonite Composites Prepared by Dynamic Packing Injection Molding

Abstract

In this article, dynamic packing injection molding (DPIM) technology was used to prepare injection samples of pure polypropylene and its composites (PP/OMMT). The DPIM technology led to remarkable mechanical enhancement from 43.23 MPa and 26.16 J/g of conventional injection-molded PP(CIM-PP) to 60.46 MPa and 29.03 J/g of DPIM-PP for tensile strength and impact strength, respectively. More importantly, the samples containing OMMT (termed PP/OMMT) exhibited excellent dispersion under the same flow condition. This special structure gave rise to further reinforcement from 40.91 MPa and 39.23 J/g of CIM-PP/OMMT to 54.87 MPa and 168.19 J/g of DPIM-PP/OMMT for tensile strength and impact strength, respectively. The morphology of DPIM samples was characterized through differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD) and scanning electron microscopy (SEM). It was found that a much better dispersion of nano-OMMT was achieved by DPIM. Moreover, γ-crystal was generated in shear layer of DPIM samples. The crystallinity of PP matrix in DPIM sample increases by 7% compared to CIM sample. The excellent mechanical properties of DPIM PP/OMMT nanocomposites sample could attribute to the homogeneous distribution of OMMT particles, the intercalation or exfoliation of montmorillonite lamellas as well as the morphology change of PP matrix under the influence of dynamic shear stress.