The Effects of Ultra-High Molecular Weight Components on Crystallization under Shear Flow

Abstract

This paper reports investigations on crystallization processes of polyethylene under shear flow. We used depolarized light scattering (DPLS), small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS) techniques to reveal the effects of ultra-high molecular weight components in the polyethylene blends. The SANS/SAXS study on elongated blend showed that ultra-high molecular weight components exist in the micron-scaled structure aligned along the flow direction. The time-resolved DPLS and SAXS measurements showed that there existed a critical concentration of the ultra-high molecular weight polyethylene for the formation of the precursor of shish, suggesting that entanglements of ultra-high molecular weight chains play an important role. The role of chain relaxation in the shish-kebab formation was also discussed on the basis of the temperature dependence of the critical concentration.