Mechanical and high speed fracture properties of polypropylene and hydrogenated poly(cyclopentadiene) blends

Abstract

Mechanical tensile tests and fracture mechanics analysis at high speed were carried out on specimens of isotactic polypropylene (P P) -hydrogenated poly (cyclopentadiene) (HPCP) blends obtained under different crystallization conditions. In addition a morphological investigation of the fractured surfaces by means of scanning electron microscopy was also performed. Improved low strain properties (modulus and yield stress) were found by the addition of HPCP to PP for both quenched and highly crystallized materials. This effect is enhanced when the quenched samples undergo a further heat treatment such as annealing. The fracture toughness parameters (Gc andKc decrease with increasing amounts of HPCP in the blend. The annealing improves the toughness of quenched samples enhancingGc andKc while it has no effect on samples crystallized at high temperature. All the above mechanical and fracture results were explained at the molecular level in terms of the interconnection existing in the material which depends on the crystallization conditions, annealing and blend composition.