Fracture behavior of mica-reinforced polypropylene: Effects of coupling agent, flake orientation, and degradation

The effects of such factors as flake size, orientation, and surface treatment on the fracture mechanism of mica-reinforced polypropylene were investigated. Concepts of post-yield fracture mechanics were used to characterize the crack initiation and propagation resistances of the composite. It was found that better flake alignment slightly increases the yield strength but does not affect the crack growth resistance of the material. Flake size degradation during processing leads to an increased crack initiation resistance but reduces the tearing capacity and the maximum crack growth resistance of the composite, due to a reduction of the extent of matrix deformation. In the same manner, the use of a coupling agent diminishes the effect of matrix drawing and the total energy dissipated during the fracture process, even though the crack initiation resistance can be increased.