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Processing-improved properties and morphology of PP/COC blends

Authors

  • Tat'ana Vacková,

    Corresponding author
    1. Institute of Macromolecular Chemistry, The Academy of Sciences of the Czech Republic, Heyrovsky, 16206 Prague 6, Czech Republic
    • Institute of Macromolecular Chemistry, The Academy of Sciences of the Czech Republic, Heyrovsky, 16206 Prague 6, Czech Republic
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  • Miroslav Šlouf,

    1. Institute of Macromolecular Chemistry, The Academy of Sciences of the Czech Republic, Heyrovsky, 16206 Prague 6, Czech Republic
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  • Martina Nevoralová,

    1. Institute of Macromolecular Chemistry, The Academy of Sciences of the Czech Republic, Heyrovsky, 16206 Prague 6, Czech Republic
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  • Ludmila Kaprálková

    1. Institute of Macromolecular Chemistry, The Academy of Sciences of the Czech Republic, Heyrovsky, 16206 Prague 6, Czech Republic
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Abstract

The aim of this study was to improve mechanical properties of polypropylene/cycloolefin copolymer (PP/COC) blends by processing-induced formation of long COC fibers. According to the available literature, the fibrous morphology in PP/COC blends was observed just once by coincidence. For this reason, we focused our attention on finding processing conditions yielding PP/COC fibrous morphology in a well-defined, reproducible way. A number of PP/COC blends were prepared by both compression molding and injection molding (IM). Neat polymers were characterized by rheological measurements, whereas phase morphology of the resulting PP/COC blends was characterized by means of scanning electron microscopy (SEM). The longest COC fibers were achieved in the injection molded PP/COC blends with compositions 75/25 and 70/30 wt %. Elastic modulus and yield strength of all blends were measured as functions of the blend composition using an Instron tensile tester; statistically significant improvement of the yield strength due to fibrous morphology was proved. Moreover, two different models were applied in the analysis of mechanical properties: (i) the equivalent box model for isotropic blends and (ii) the Halpin-Tsai model for long fiber composites. In all PP/COC blends prepared by IM, the COC fibers were oriented in the processing direction, as documented by SEM micrographs, and acted as a reinforcing component, as evidenced by stress–strain measurements. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

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