Melt-extensional properties and orientation behaviors of polypropylene-layered silicate nanocomposites

Polypropylene-layered silicate nanocomposites consisting of three components-pure polypropylene, maleated polypropylene, and organically modified silicate-were prepared by the melt-intercalation method to investigate melt-extensional properties such as melt strength, neck-in test, and orientation behavior. The nanocomposites showed an enhanced tensile modulus, enhanced storage modulus, much enhanced melt tension, and reduced neck-in during the melt processing as compared with neat polymer. The uniaxial drawing induced the silicate surface to align parallel to the sheet surface. The c and a* axes of the polypropylene crystals were bimodally oriented to the flow direction, and the b axes were oriented to the thickness direction. The bimodal orientation of the polypropylene crystal was enhanced with the concentration of silicates. (C) 2004 Wiley Periodicals, Inc.