| Fiber spinning and extrusion flow in general, of viscoelastic liquids through dies, are the primary stages of many polymer processes. The former is dominated by a uniaxial extensional flow, whereas the latter includes a simple shear flow inside the die and a mixed flow of shear and extension near the exit of the die commonly called extrudate-swell flow.;The two processes are studied in this work by means of nonlinear integral constitutive equations, Galerkin finite element method, and Newton iteration. The analysis of fiber spinning accounts for elongational and shear prehistories, spectrum of relaxation times, extension-thinning or thickening, and for specified tension or spinnability conditions at the take-up end. An apparent elongational viscosity is calculated along the spinline and compared with the true one. A pseudo-time is used in order to account for temperature effects in non-isothermal processing. The extrudate-swell is analyzed by means of the Curtiss-Bird molecular constitutive equation and a streamlined finite element method.;Solutions for fiber-spinning are obtained up to high elasticity, high draw ratio and large drawing force. The results agree with the analytic asymptotic solution for Newtonian liquid and with experimental data on isothermal spinning of polystyrene melt at 170;The computer-aided analysis of viscoelastic flow, developed in this thesis, can be easily utilized to study any confined or free surface flows which arise in extrusion and coating operations, and can be extended to other basic polymer processing operations. The advantages of the developed analysis are: (a) The use of more realistic, integral, constitutive equations that can represent real viscoelastic materials with multiple relaxation times, shear-thinning, and extension-thinning or thickening. (b) Convenient streamlined finite elements that eliminate particle tracking, and Newton iteration that converges fast and quadratically. (c) Achievements of solutions at high elasticity that in addition compare well to reported experimental data. |
