Strain rate sensitivity of homopolymer polypropylenes and micrometric wollastonite-filled polypropylene composites

The strain rate sensitivity of neat polypropylene (PP) and wollastonite-mineral filled polypropylene (PP-W) and concurrent microstructural evolution is investigated. Both the materials are strain rate sensitive and the change in strain rate sensitivity index parameter with strain reflects the change in micromechanisms of deformation and modes of fracture. Deformation processes in neat polypropylene involved craze-tearing and brittle mode of fracture, while wollastonite-filled polypropylene composite was predominantly characterized by wedge, ridge-tearing, fibrillation and brittle fracture. The dependence of yield stress of neat polypropylene (PP) and wollastonite-filled polypropylene (PP-W) with strain rate follows Eyring’s equation and yield similar activation volume implying similarity in the onset of plastic deformation.