Modifying adhesion of linear low-density polyethylene to polypropylene by blending with a homogeneous ethylene copolymer

Authors

  • B. C. Poon,

    1. Department of Macromolecular Science and Engineering, and Center for Applied Polymer Research, Case Western Reserve University, Cleveland, Ohio 44106-7202
    Search for more papers by this author
  • S. P. Chum,

    1. Polyolefins and Elastomers R&D, The Dow Chemical Company, Freeport, Texas 77541
    Search for more papers by this author
  • A. Hiltner,

    Corresponding author
    1. Department of Macromolecular Science and Engineering, and Center for Applied Polymer Research, Case Western Reserve University, Cleveland, Ohio 44106-7202
    • Department of Macromolecular Science and Engineering, and Center for Applied Polymer Research, Case Western Reserve University, Cleveland, Ohio 44106-7202
    Search for more papers by this author
  • E. Baer

    1. Department of Macromolecular Science and Engineering, and Center for Applied Polymer Research, Case Western Reserve University, Cleveland, Ohio 44106-7202
    Search for more papers by this author

Abstract

Adhesion of a Ziegler–Natta catalyzed ethylene copolymer (ZNPE) to polypropylene (PP) was studied by measuring the delamination toughness G of coextruded microlayers by using the T-peel test. Low values of G compared to a homogeneous copolymer with approximately the same short chain branch (SCB) content were attributed to an amorphous interfacial layer of low molecular weight, highly branched ZNPE fractions. Blending ZNPE with a homogeneous metallocene catalyzed copolymer (mPE) increased G. In this regard, mPE with higher SCB content was more effective than mPE with slightly lower SCB content. The ZNPE interface was mimicked by microlayering ZNPE and ZNPE blends with polystyrene from which the ZNPE layers were easily separated without damage to the surface. Examination with atomic force microscopy revealed a soft coating about 8 nm thick on the surface of the ZNPE layer. Blending with mPE reduced or eliminated the amorphous interfacial layer. It was proposed that mPE increased miscibility of low molecular weight, highly branched fractions of ZNPE and prevented their segregation at the interface. After blending with mPE eliminated the interfacial layer, G increased to a value comparable to that of a homogeneous copolymer with about the same SCB content as ZNPE bulk chains. The increase in G was attributed to epitaxial crystallization of the ethylene copolymer in the absence of an amorphous interfacial layer. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 109–115, 2004

Ancillary