Effect of viscoelastic relaxation modes on stability of extrusion film casting process modeled using multi-mode Phan-Thien-Tanner constitutive equation

Effect of die exit stress state, Deborah number, uniaxial and planar extensional rheology on the neck-in phenomenon in polymeric flat film production

“…More recently, a sequence of articles based on the one-dimensional membrane model [20] have been published dealing with both experimental and theoretical investigation of the effects of long chain branching and molecular weight distribution on the neck-in [37][38][39] (XPP and RPs), and discussing the role of individual viscoelastic relaxation modes of a polymer melt [40] (UCM and PTT). In the latest works of this series [41] and [42], the evaluation of a draw resonance onset with model based on PTT constitutive equation and neck-in degree simulation using two-dimensional model with UCM constitutive equation [33] was addressed, respectively.…”

“…First, all stress components are set to zero considering entire stress relaxation due to the die swell phenomenon ( [16,17,50] and [51]). Second, at least one stress component is given by a Newtonian solution for downstream side independently on the utilized type of constitutive equation [18], [20,21], [39], [41], [52] and [53]. Third, two extra stress components are adjusted manually without more reasoning [37,38,40].…”

Steady-state modeling of extrusion cast film process, neck-in phenomenon, and related experimental research: A review

“…In the studies based on single-mode constitutive equations, the utilized Maxwell relaxation time 27 and the shortest 35 or characteristic relaxation time (determined by the reciprocal frequency at the intersection of the storage modulus G ′ and the loss modulus G ′′ curves 36 or by fitting the strain rate dependent steady uniaxial extensional viscosity data 37,38 ) are typically used to calculate De. In the case of multi-mode constitutive equations, the relaxation time for each mode [39][40][41][42][43][44] or an average relaxation time, λ, is calculated to determine De by using the following expression: [45][46][47]…”

“…Individual research groups focused on experimental works 30,48,52,55,[65][66][67][68][69][70][71][72][73][74] dealing with flow visualization, effects of temperature, crystallization, molecular weight distribution, or long chain branching on kinetics of the film casting process (see Table I). Theoretical research has not disappeared, and attention has been drawn to the development and use of numerical models (primarily considering steady-state conditions) of different dimensionalities such as 1D, 22,25,26,45,[75][76][77][78][79][80][81][82][83][84][85] 1.5D, 18,27,29,35,37,38,[41][42][43][44]47,53,[86][87][88][89][90]…”

Non-Newtonian effects on draw resonance in film casting

“…The results are correlated with the dependence of the steady shear and uniaxial elongational viscosities on the deformation rates and shear thinning is found to lead to destabilization, while strain hardening can lead to a stabilization depending on the range of relaxation time and strain rates occurring within the process. While all of the above mentioned studies employ single mode models, there exist up to now also some works on draw resonance for a multi-relaxation-mode PTT model [19,20,21]. In two of these studies, the relaxation spectra are obtained from measurements of actual polymeric fluids [19,21].…”