The influence of loading rate and concurrent microstructural evolution in micrometric talc- and wollastonite-reinforced high isotactic polypropylene composites

The paper describes the response of neat high isotactic polypropylene (iPP) and talc (iPP-T) and wollastonite (iPP-W)-reinforced polypropylenes to tensile loading rate and the evolution of microstructure during plastic deformation. Unreinforced and reinforced polypropylene materials exhibit significant sensitivity to tensile loading rate (strain rate) and the change in strain rate sensitivity index parameter with strain signifies a change in the micromechanism of plastic deformation and mode of fracture. Plastic deformation in neat high isotactic polypropylene is characterized by craze-tearing and brittle mode of fracture, while both talc- and wollastonite-reinforced polypropylenes are characterized by wedge, ridge-tearing, fibrillation, and brittle fracture. The brittle fracture is associated with debonding of mineral particles from the polypropylene matrix. However, yield stress of all the three materials exhibit similar dependence to loading rate and similar activation volume that suggests similarity in the onset of plastic deformation process. (C) 2004 Elsevier B.V. All rights reserved.