期刊
JOURNAL OF NON-NEWTONIAN FLUID MECHANICS
卷 222, 期 -, 页码 45-55出版社
ELSEVIER
DOI: 10.1016/j.jnnfm.2014.08.018
关键词
Polyamide 6; High-speed spinning; Viscoelastic simulation; Transient elongational viscosity; Modified Rheotens test; Stress-induced crystallization
类别
This work addresses high-speed fibre spinning of PA6 in two ways: First, we provide isothermal viscoelastic simulations of the spinline up to the point of inflection (onset of neck formation) making use of a K-BKZ-type integral constitutive equation and Polyflow. We focus on a (as far as possible) reliable set of the material parameters and study the role of melt elasticity and non-Newtonian elongational viscosity on the shape of the filament. Second, we present non-isothermal Rheotens experiments at draw down speeds up to 4.4 m/s, to demonstrate the change of filament morphology from amorphous (due to rapid quench), to stress-induced semi-crystalline, using wide angle X-ray scattering (WAXS). As a result of the two approaches, we are able to identify tensile stress levels both for the onset of distinct elongational thinning as well as for the occurrence of stress-induced crystallization. Extrudate swell is complete at about 1 mm distance from the spinneret. The PA6 melt subsequently behaves Newtonian until onset of neck formation by distinct elongational thinning at about 1.5 MPa. Rheotens tests at 1 m filament length yield stress-induced crystallization at about 2.5 MPa, WAXS showing meridian reflexes from alpha-crystals. The ratio of the said tensile stress levels corresponds to the cross sectional change within the neck in PA6 high-speed spinning. (C) 2014 Elsevier B.V. All rights reserved.
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