Stability of Newtonian‐PTT coextrusion fiber spinning

Abstract

Linear stability analysis has been applied to a coextrusion fiber spinning flow that consists of a Newtonian fluid as a core layer and a Phan‐Thien/Tanner (PTT) fluid as a skin layer. These two chosen fluids show entirely different rheological behaviors. The stability of this coextrusion system was affected by the choice of three characteristic parameters: the skin layer fraction (f), the extensional parameter (ϵ), and the shear thinning parameter (ξ) in the Phan‐Thien/Tanner model. The linear stability results indicate that the viscoelastic skin layer (PTT fluid) has a stabilizing effect that delays the onset of draw resonance. Under fixed compositions (f is fixed), the stability envelopes changed from upturned curves to flattened ones as extensional force dominated the system. The neutral stable curves closed to the horizontal line at a critical draw ratio of around 20, showing similar behavior to a Newtonian fluid where the system has a very high Deborah number or it is dominated by shear thinning effects.

Multilevel‐layer‐structured polyamide 6/poly(trimethylene terephthalate) nanofibrous membranes for low‐pressure air filtration

“…The PA6 nanofiber membranes fabricated at 28 wt % exhibited a relatively high tensile strength of 9.82 MPa, an elongation at the break value of 19.31%, and a tensile modulus of 122.25 MPa. 41,42 Different multilevel-layer-structured composite membranes, with PA6 and PTT nanofibers combined together, not only enhanced their flexibility but also made them more easily processed in applications. When the proportion of added PA6 increased, the tensile strength also increased.…”

“…28,29 Compared with membranes with only one polymer, multilevel-layered filters, which combine the excellent properties of different polymers, show better filtration performance. PTT as a polyester has better flexibility, fluffiness, and stain resistance 41,42 and could be processed easily for application as an air filter. 33 Consequently, obtaining a PA6 membrane with a high efficiency and low drop pressure was the main purpose in this study.…”

“…PA6 and poly(trimethylene terephthalate) (PTT) composite membranes have rarely been studied. PTT as a polyester has better flexibility, fluffiness, and stain resistance 41,42 and could be processed easily for application as an air filter.…”

Modelling of liquid crystalline compound fibres

“…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.…”

Flow instabilities in rheotens experiments: Analysis of the impacts of the process conditions through neural network modeling

“…Second, the procedure leads to exclude from the analysis the flow instabilities occurring at high draw down velocities. This phenomenon, which is known as draw resonance, is manifested by sustained periodic variations in spinline variables such as cross‐sectional area and tension [4–7]. Mathematically [8], the onset of the draw resonance corresponds to a supercritical Hopf bifurcation [9, 10], it is a hydrodynamic instability, not a viscoelastic one, albeit altered by viscoelasticity [11, 12] and thus, even Newtonian fluids can exhibit it.…”