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

Fracture behavior and mechanical, thermal, and rheological properties of biodegradable films extruded by flat die and calender

“…This technology allows the industrial production of polymeric sheets and films with thicknesses ranging from 50 μm to 1 mm. 19 After establishing the processing method for the polymeric system, it was thermally characterized using differential scanning calorimetry (DSC). This technique facilitates the study of the crystallization behavior of PLA-PBAT films to evaluate the industrial processing problems directly.…”

“…Flat‐die extrusion, which consisted of extrusion through a linear die of the adjustable thickness of 1.4–3.0 mm, was used to produce the micrometer film. This technology allows the industrial production of polymeric sheets and films with thicknesses ranging from 50 μm to 1 mm 19 …”

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

“…It is important to mention that a different definition of relaxation time can be found in the reviewed literature. 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]…”

“…The observed opposite trend is due to the crystallization of the polymer in the drawing region. hardening, the ratio of planar to uniaxial extensional viscosity, the Deborah number, and the die exit stress state 38 [Eq. ( 6)].…”

“…( 5) is the absence of variables allowing us to evaluate the role of the Deborah number and the die exit stress state in NI. Barborik and Zatloukal 37,38 continued the research of the neck-in phenomenon in the period 2017-2018 with respect to the ratio of the second and first normal stress difference at the die exit, −N 2 /N 1 , uniaxial extensional strain hardening, ηE,U,max/3η 0 , melt elasticity (captured via the Deborah number, De), and the ratio of planar-to-uniaxial extensional viscosity, ηE,P/ηE,U . Using an isothermal 1.5-dimensional (1.5D) membrane model and viscoelastic modified Leonov constitutive equation, the following expression for maximum attainable neck-in was proposed:…”