High-Strength Welds in Metallocene Polypropylene/Polyethylene Laminates

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Science  23 Jun 2000:
Vol. 288, Issue 5474, pp. 2187-2190
DOI: 10.1126/science.288.5474.2187

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Spectacular advances in organometallic chemistry over the past two decades have resulted in single-site catalysts that are revolutionizing production of polyethylene (PE) and isotactic polypropylene (iPP). This report describes an unanticipated benefit of metallocene-catalyzed semicrystalline polyolefins, namely welded joint strengths in PE/iPP laminates that can exceed the cohesive strength of the constituents. We propose that interfacial polymer entanglements, established in the molten state and subsequently anchored in chain-folded lamellae upon crystallization, are responsible for this intrinsic property. The poor adhesion exhibited by traditional Ziegler-Natta–catalyzed polyolefins is shown to derive from the accumulation of amorphous polymer, a by-product of the polymerization reactions, at the interface. These results should facilitate fabrication and improve the properties of composites based on materials that dominate the plastics industry.

  • * Present address: Medtronic, Materials and Biosciences Center, Brooklyn Center, MN 55430, USA.

  • To whom correspondence should be addressed. E-mail: bates{at}

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