Ethylene copolymers as sintering enhancers and impact modifiers for rotational molding of polyethylene

Abstract The objective of this work was to evaluate the effect of blending minor amounts of ethylene styrene Interpolymer or ethylene vinyl acetate (EVA) with polyethylene on cycle times and impact strength in rotational molding. The blends sintered significantly faster than polyethylene. The sintering rates were primarily influenced by the melting points of the minor blend components, and not by differences in melt viscosity and/or elasticity at low shear rate. Blending Interpolymer or EVA with polyethylene resulted in improved environmental stress crack resistance and decreased flexural modulus. In rotational molding, blending Interpolymer or EVA with polyethylene generally resulted in faster bubble removal, more uniform thickness and shorter cycle times. Ductile failure was generally observed at the peak mean failure energy (MFE). The blend containing Interpolymer yielded significantly increased MFE, possibly because the Interpolymer was compatible with polyethylene and was very well dispersed.