Numerical simulation of rheological effects in fiber spinning

Abstract

The fiber‐spinning process is an important industrial operation to manufacture synthetic fibers. The process occurs under free‐surface conditions, and the final properties of the fiber are characterized by the extensional properties of the polymer. Specifically, the non‐isothermal response of the polymer in uniaxial extension dominates the process. The fiber‐spinning process is analyzed by means of a unidirectional approach because the thickness of the fiber is very small with respect to its lateral dimension. The analysis accounts for the prehistory of the material inside the die, based on purely extensional strains. For viscoelastic polymer melts, the constitutive equation must be able to describe adequately the rheological behavior of the polymer in extensional flow. A good candidate for such modeling is the K‐BKZ integral constitutive equation, with a spectrum of relaxation times, which captures well the nonlinear viscoelastic response of polymer melts. The non‐isothermal response is taken into account with a temperature shift factor utilizing the Morland‐Lee hypothesis. The present work includes effects due to gravity, inertia, and air drag, where applicable. Simulation results are compared with experiments on polypropylene (PP), poly(ethylene terephthalate) (PET), and low‐density polyethylene (LDPE) melts at low and high speeds. Results are also compared with previous simulations. It is shown that in some cases the extrudate swell at the spinneret exit must be taken into account to accurately predict the drawing forces, which makes a fully two‐dimensional analysis a necessity for such operations. © 2000 John Wiley & Sons, Inc. Adv Polym Techn 19: 155–172, 2000

On-Line Measurement of Fiber Diameters along Spinning Line

“…A series of instruments developed by Professor Takeshi Kikutani form Tokyo Institute of Technology，are used to realize online measurement of diameter, temperature, velocity, orientation and based on which the use of PET during high speed spinning is studied [1] . Numerical simulation of spinning dynamics is researched in studying spinning dynamics formerly [2][3][4] , but there is a certain error between simulated result and the actual situation because of the difficulties which exist in the process of establishment of polymer model, determination of boundary condition and numerical calculation.Therefore, it is very important to study the equipment of the online diameter measurement for fiber spinning, which is very meaningful for realizing the high speed data acquisition, avoiding artificially error, protecting the quality of production efficiently and realizing the automatically collect information in the progress of the manufacture. The computer interface of the equipment is USB, which is of plug and play, high speed transmission, good scalability, easy using etc.…”