Low density polyethylene-polypropylene blends Part 1 - Ductility and tensile properties

The composition-property relationships of LDPE-PP binary blends have been investigated. Young's modulus, yield strength and flexural strength of the blends varied monotonically with composition, whereas the elongation at failure and the true ultimate tensile strength for the blends with 30-50 wt-% PP exhibited synergetic effects. These blends showed strong cold draw hardening, and their elongations at failure and the true ultimate tensile strengths were much higher than those of the neat components. Meanwhile, impact strength showed an abrupt reduction with increasing PP content and the failure mode changed from ductile to brittle in the composition range of 30-50 wt-% PP. Failure mechanisms are discussed, addressing interfacial adhesion between LDPE and PP and the non-uniform shrinkage of the component domains upon cooling.