THE ESTIMATION OF BIREFRINGENCE IN POLYPROPYLENE MELT SPINNING PROCESS

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  • ポリプロピレン溶融紡糸中における複屈折の推定について

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The birefringence was measured along a liquid filament in the polypropylene (Chisso Co., Ltd. Grade No.1016) melt spinning process. According to the results, after the first gradual ascent of birefringence, it still increases abruptly and stops its development along the spin line. (Fig. 1) The first gradual and second abrupt ascents are attributable to the deformation of filament (attenuation) and the crystallization respectively.<br>It was found that the birefringence of the liquid filament can be related to the spinning stress as follows: where Δn0 is the birefringence in deformation domain and σ the stress (dyn/cm2) of filament.<br>The birefringence in the second abrupt increase region Δn is expressed as follows: where Δn′0 is the birefringence of the starting point of crystallization and is estimated by equation (1) from the spinning tension and the cross-section of take-up filament, and t (in sec) is the time for cooling down the filament from 110°C to 75°C. The second abrupt development of birefringence occurs mainly during this period (t).<br>When the spinning is performed without cooling air, equation (2) can be written in terms of the take-up speed and diameter of the filament instead of t.<br>In this way, the birefringence of a filament, immediately after take-up, is prescribed by the stress and the cooling speed of the filament.

Journal

  • Sen'i Gakkaishi

    Sen'i Gakkaishi 29 (5), T205-T210, 1973

    The Society of Fiber Science and Technology, Japan

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