Polyester fiber spinning analyzed with multimode Phan Thien-Tanner model

• The process of polyester fiber spinning is analyzed with a 2D algorithm based on PTT model.
• The algorithm makes use of a comprehensive relaxation spectrum with very short relaxation times.
• Swelling of the melt is predicted correctly, as is necking and crystallization.
• Crystallinity and tension vary strongly over cross section during high speed polyester spinning.

The fiber spinning of polyester is analyzed with an algorithm using the Phan Thien-Tanner model. The discrete relaxation spectrum, necessary for the multimode model, is determined with the storage and loss moduli. Experimental values of the moduli are extrapolated with the help of the Cox-Merz rule in such a way that they cover a frequency range of 106s-1. This allows determining the very short relaxation times necessary to handle the extreme deformation rates of 10,000 s−1 during high speed spinning. The algorithm correctly predicts the swelling of the polyester after exiting the spinneret, the elongation of the melt, and for high spinning speeds the crystallization as function of spinning stress. The spinning stress on its part is influenced by temperature and crystallinity. The computations therefore take into account the non-uniformity of the temperature profile in the melt strand. The same set of parameters in the algorithm is used without any change for intermediate and high spinning speeds. The algorithm is capable of simulating realistically the polyester spinning process. Good agreement was obtained with experimental data from industrial trial runs.