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Keywords:

  • polycarbonate;
  • injection molding;
  • pattern formation;
  • fluorescence

Abstract

The pattern change in a laminar flow of molten polycarbonate in a disk mold was experimentally investigated by altering the flow velocity. By use of a light-scattering method, a radial pattern characterized by a periodic array of needlelike regions and the matrix was found to form as the flow velocity was increased. The density distribution of the polycarbonate molecules was an essential factor for pattern formation. As a result of the formation of this pattern, it was found that the boundaries between the needlelike regions and the matrix emitted weak fluorescence in the wavelength range of 600–700 nm under laser irradiation. An analysis indicated that transitions between excited π electron states in the phenylene groups were the sources of this fluorescence and that a key factor behind its occurrence was a decrease in the molecule density at the boundaries. These results reveal that the radial-pattern formation changes the fluorescence property of polycarbonate in the visible and near-infrared regions. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 468–473, 2004