Mechanics of steady flow in coextrusion fiber spinning

Abstract

The steady flow of isothermal bicomponent coextrusion fiber spinning has been investigated. A model has been chosen in which a Newtonian fluid and a Phan‐Thien/Tanner (PTT) fluid were considered to be the core and the skin layer, respectively. This model was adopted to study the effect on spinline velocity of an interaction between two fluids with quite different extensional rheology. The effects of the hoop stress, gravity, inertia, and surface and interfacial tensions were disregarded. Only viscous and viscoelastic forces were considered. A uniaxial extension was also assumed as the radius variation in the axial direction is small. The Newtonian fluid has been considered prone to fluctuate during melt processing while the viscoelastic skin layer has a stabilizing effect. The velocity profile was affected by the choice of two characteristic parameters: extensional and shear‐thinning parameters, as well as the viscoelastic skin flow rate ratio. Both shear‐thinning and extensional parameters play important roles in melt flow. The results show that as the draw ratio increases, the system is dominated by the extensional parameters, whereas slow drawing is dominated by shearing, in spite of the thin viscoelastic skin.

Evaluation of surface modification impact on PP/MWCNT nanocomposites by rheological and mechanical characterization, assisted with morphological image processing

“…The samples mechanical characterization was performed via tensile testing on molded composites [42]. Stress-strain plots of pure PP and nanocomposites are shown in Fig.…”

Modelling of liquid crystalline compound fibres

“…(9) and (10), together with the solution of the following (nondimensional) equations for the degree of orientation, s, defined as the ensemble average of the alignment of the molecular direction to the axial direction, and the degree of crystallinity, q, of the core and sheath…”

“…Previous studies of bicomponent fibres have mainly considered isothermal flows [7][8][9][10][11][12][13]. The most remarkable non-isothermal study of bicomponent fibres known to the author is that of Kikutani et al [14] who modelled the highspeed melt spinning of bicomponent fibres consisting of poly(ethylene terephthalate) (PET) in the core and polypropelene (PP) in the sheath by means of simple, one-dimensional equations of mass, linear momentum and energy conservation, and included both Newtonian and upper-convected Maxwell rheologies and drag on the fibre.…”

Preparation of composite hollow fiber membranes: co-extrusion of hydrophilic coatings onto porous hydrophobic support structures

“…Co-extrusion avoids many of the manufacturing steps required by conventional lamination and coating processes, such as making and handling of individual films, application of coating primers, and solvent drying. Because of these economic and technical advantages, the application of co-extrusion is growing rapidly [5][6][7][8][9][10].…”