Structure of blown film from blends of polyethylene and high melt strength polypropylene

The structure of blown film processed from linear low density polyethylene blended with up to 30 wt[percnt] of a high melt strength polypropylene (hmsPP) was examined using primarily atomic force microscopy and wide angle X-ray scattering. The study focused on two polyethylene resins with the same density: a conventional Ziegler–Natta catalyzed linear low density polyethylene (znPE) and a blend of a Ziegler–Natta catalyzed and a metallocene catalyzed linear low density polyethylene (zn/mPE). Parallel characterization was performed on blown film of the hmsPP and blown film of each of the polyethylene resins. In films of the blends, the hmsPP was well-dispersed in the polyethylene matrix as elongated domains. In the domains, the hmsPP crystallized as planar row-nucleated structures with the long axis of the lamellae perpendicular to the extrusion direction. Row-nucleated hmsPP lamellae provided a template for epitaxial crystallization of polyethylene lamellae. The 42° angle of the lattice match imparted a characteristic herringbone texture to the polyethylene. Blending with hmsPP increased the tensile modulus and strength of polyethylene film without significantly affecting the ultimate elongation.