Viscoelastic flow analysis of surface morphology on injection-molded polypropylene

Authors

  • Yutaka Kobayashi,

    Corresponding author
    1. Research and Development Division, Prime Polymer Company, Limited, Sodegaura-City, Chiba 299-0265, Japan
    2. Division of Material Sciences, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-Machi, Kanazawa-City, Ishikawa 920-1192, Japan
    Current affiliation:
    1. R&D Division, Advanced Composites, Inc., 1062 S Fourth Avenue, Sidney, OH 45365, USA
    • Research and Development Division, Prime Polymer Company, Limited, Sodegaura-City, Chiba 299-0265, Japan
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  • Yasuhiko Otsuki,

    1. Research and Development Division, Prime Polymer Company, Limited, Sodegaura-City, Chiba 299-0265, Japan
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  • Toshitaka Kanai

    1. Division of Material Sciences, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-Machi, Kanazawa-City, Ishikawa 920-1192, Japan
    2. Research and Development Laboratory, Idemitsu Kosan Company, Limited, Anasaki-Kaigan, Ichihara-City, Chiba 299-0193, Japan
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Abstract

The molecular orientation of a frozen layer in an injection-molded specimen of a polypropylene–rubber blend was investigated. A typical V-shaped pattern of birefringence was observed from the surface to the core in a crosscut section. From the comparison of the V-patterns near the gate to the flow end, it was assumed that a frozen layer formed from the surface to a depth of 0.06 mm in a plaque (3 mm thickness) during the injection molding filling process. Numerical viscoelastic analysis of the fountain flow was carried out using an original 2D unsteady flow simulation program and ignored crystallization. A large extensional deformation formed just when the molten polymer contacted the cavity wall and the deformation immediately froze. A layer with a small birefringence between the surface and the shear-oriented layer was divided into two parts. The depth profile of birefringence was compared to the principal stress difference calculated by numerical analysis. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers

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