Texture and Strength Evolution inDeformed Polypropylene

Abstract

Semicrystalline polypropylene samples with high concentrations of crystallinity (≳62%) are deformed in uniaxial compression at different temperatures and different strain rates. The orientation changes of the crystalline part of the material are analyzed using X‐ray diffraction methods. Pole figure evaluation is used to obtain information about the crystal structure, the geometry of slip, and its correlation with the characteristic of strength evolution in polymers. The contribution of the crystalline part of the material to plastic flow is estimated and the textures are related to the characteristic effects in plastic and visco‐elastic response of the material during deformation and subsequent stress relaxation. The observed texture effects can be explained by the rotation of crystallographic c ‐axis (backbone axis) normal to the compression direction at high temperatures in a planar slip mode. The stress/strain and relaxation behavior of the material is interpreted as a combination of viscoelastic flow of amorphous volume and irreversible plastic flow of the crystalline part which contributes to an orientation dependence of deformation and stress relaxation.