Reverse temperature injection molding of Biopol™ and effect on its properties

Authors

  • Jinwen Zhang,

    1. Department of Plastics Engineering, University of Massachusetts Lowell, One University Avenue, Lowell, MA 01854 USA
    2. Metabolix Inc., 303 Third Street, Cambridge, MA 02142 USA
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  • Stephen McCarthy,

    Corresponding author
    1. Department of Plastics Engineering, University of Massachusetts Lowell, One University Avenue, Lowell, MA 01854 USA
    • Department of Plastics Engineering, University of Massachusetts Lowell, One University Avenue, Lowell, MA 01854 USA
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  • Robert Whitehouse

    1. Department of Plastics Engineering, University of Massachusetts Lowell, One University Avenue, Lowell, MA 01854 USA
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Abstract

A novel reverse temperature profile for the injection molding of Biopol™ was studied. It was found that both the mechanical properties and the part quality of Biopol™ were improved with this new reverse temperature process. When injection molded, most conventional thermoplastic polymers are processed at 30 to 70°C above the melting temperature; under these conditions, Biopol™ degraded rapidly and the resulting material showed poor mechanical properties. In contrast, when using a reverse temperature molding process, where Biopol™ was melted in the first zone and then was conveyed through the barrel with a decreasing temperature pathway and was injection-molded at a temperature below its melting point, the resulting material showed higher mechanical properties. The processing of Biopol™ was also greatly improved. The reverse temperature process uses the characteristically slow crystallization rate of Biopol™, which can be easily injected as hot melt even below its normal melting point. DSC analysis suggested that the reverse temperature process resulted in a more homogeneous crystalline phase than the conventional process. GPC analysis also indicated that thermal degradation of Biopol™ was largely reduced in the reverse temperature injection-molding process compared with conventional methods. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 483–491, 2004

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