Experimental and Theoretical Analyses of Film Casting Process

Abstract

A film casting process of polymer melts was discussed in this report and, in particular, the experimental measurement for rheological properties in film casting was carried out using with polypropylene and low density polyethylene. As a result, no remarkable difference in the viscoelastic properties was observed between two polymers except for the elongational ones. Low density polyethylene showed a remarkable increase in the elongational viscosity at high strain. Serious differences in the elongational properties were observed in the behavior of the necking phenomenon in the experimental film casting process. The necking width at the film edge of polypropylene was increased under the condition of higher draw ratio.However, in the case of low density polyethylene it was nearly constant and independent of the draw ratio. From these experiments, we concluded that the necking phenomenon in film casting depends on the elongational properties.Furthermore, to clarify the behavior in film casting, the flow simulation was carried out using three rheological models (the Newtonian, the Bird-Carreau and the Giesekus models) and their applicability was evaluated respectively.The simulation results on the necking phenomenon and film thickness distribution calculated with the Giesekus model was quantitatively agreed

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

“…A specific attention was given at certain aspects of the process. The effect of thermal conditions including crystallization [24][25][26][27][28][29][30][31] as well as influence of macromolecular architecture on the extent of neck-in [32][33][34][35][36] was put under research abundantly. 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).…”

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

“…Aniunoh 107 PP Experimentally aimed study on how material properties and process conditions affect EFC. Kometani et al 111 PP severely limit the desired film quality and quantity. Their formation is influenced by processing conditions, heat transfer, and rheology of the processed polymer.…”

“…13). This constitutive equation was used in the following studies: 1D (4 works), 22,26,80,82 1.5D (10 works), 18,27,53,86-90,97,100 2D (10 works), 12,28,39,101,102,104,105,[111][112][113] and 3D (1 work). 114…”

“…The model was used in the following studies: 2D (2 works) 110,111 and 3D (1 work). 115 Carreau-Yasuda model:…”

“…The model has been found to provide reasonable predictions for the film neck-in, the centerline velocity profile and the temperature drop in the air-gap, and it also predicts an increase in film neck-in and the temperature drop in the air-gap as the air-gap length is increased. 107 This constitutive equation has been used in the following studies: 1D (1 work), 79 1.5D (0), 2D (3 works), 107,111,113 and 3D (0).…”