Uniplanar oriented isotactic polypropylene: 3. Properties and morphology

Abstract

Isotactic polypropylene was uniaxially compressed by a forging (uniplanar) process. The physical properties and morphology of the compressed samples were investigated by means of mechanical tests, trirefringence measurement and microscopy. Four major effects of planar deformation on the physical properties and morphology were observed. (1) The glass transition temperature of the compressed sample (evaluated from dynamic mechanical analysis) increased with draw. (2) The smectic phase induced by the compression draw increased sample transparency. (3) Both tensile modulus and strength parallel to the uniplanar direction increased with draw. The smectic phase generated, however, reduced the tensile modulus with no significant effect on tensile strength. (4) The compressed samples possessed a layered structure which was developed by the flattening of the original spherulites.