Film casting process

Cast film extrusion. In a cast film extrusion process, a thin film is extruded through a slit onto a chilled, highly polished, turning roll where it is quenched from one side. The speed of the roller controls the draw ratio and final film thickness. The film is then sent to a second roller for cooling of the other side. Finally, the film passes through a system of rollers and is wound onto a roll. A typical film casting process is depicted in Figs. 3.53... 

Isothermal Film Casting of a Newtonian Melt5 The film casting process is shown schematically on the accompanying figure. 

CouzENs, E. G., Film Casting Process, 1965, Bexfords Ltd, Man-ningtree, Essex. 

Teijin has developed a new PC film with improved optical qualities to the extent that it was the only such film chosen for the cover layer of the next generation Blu-ray DVD. Currently made by the use of a film casting process but destined to transfer to a new extrusion process which will significantly reduce costs. 

PTFE crystallinity and the ionic aggregation needed to form a high quality membrane [39-42], Sulfonimide polymer 10 membranes that are annealed between 225°C and 250°C also exhibit some discoloration due to organic impurities in the film-casting process. Subsequent soaking in hot nitric acid restores a colorless appearance and fully converts the polymer to the protonated form. 

Recently, the thermal and mechanical properties of MWCNT/PMMA or SWCNT/PMMA nanocomposites have been thoroughly investigated [145, 146]. For instance, Lee et al. [146] reported the fabrication and characterization of MWCNT/PMMA by using both injection molding and film-casting processes. The tensile strength of the MWCNT/PMMA nanocomposite increased by more than 15% and tensile stiffness also increased by about 17.5%, compared to pure PMMA. It was confirmed that a combined fabrication process efficiently dispersed MWCNTs in the PMMA matrix and also maintained the well-dispersed state more effectively [146]. 

Further studies should be completed utilizing different film thicknesses and compositions. Copolymers of PCL and PLA and films cast from a mixture of chitosan and PCL or PLA from a common solvent should be studied. Thickness irregularities formed during the film casting process should be dealt with, as well as film thickness appropriate for dressing should be identified. A PLA film of 70/30 ratio should be tried as its more amorphous structure would increase the flexibility of the film in comparison to the somewhat brittle nature of the 98/2 currently used. Topographical characterization of the wound surface should also be included during the in vivo trials. 

The majority of plastics films made today are produced by the tubular process, although for certain applications the flat film casting process is used. The so-called water quench system in which film is extruded directly into water is now not in general use. 

In contrast to the fiber-spinning process, the film-casting process has received less attention in the literature. Dobroth and Erwin [109] examined the causes of thick edges or the edge bead effect (also called the hone effect) and attributed it to the change from planar extension in the center of the film to uniaxial extension at the edges. 

Figure 4.41 Schematic representation of the film-casting process.

Beaidne, M. and Mitsoidis, E. (1999) Numerical simulation of the film-casting process. Int. Polym. Proc., 14, 261-275. 

FIGURE 5.1 Schematic of a film casting process showing the polymer film being cast onto a rotating drum. 

FIGURE 9.17 (a) Geometry of the front view of the film-casting process. The polymer film between... 

Anturkar and Co (1988) studied the effects of viscoelasticity on the stability of the film-casting process in a similar fashion to that of Fisher and Denn (1976). The constitutive equation used in their theoretical analysis is the UCM (Eqs. 3.40 and 3.41) with the Carreau viscosity function (Eq. 2.8 with jjco = 0) ()/) = jo (l + which... 

Equation 9.126 is similar to Eq. 9.26 of the fiber-spinning case, and in general the film-casting process can be considered the two-dimensional counterpart of the fiber-spinning process (see also Problem 9A.4). 

FIGURE 9.18 Critical draw ratio, Dr, as a function of the viscoelastic parameter Ao(2A,)" and the power-law index n, for the film-casting process. (Reprinted by permission of the publisher from Anturkar and Co, 1988.)... 

Yeow, Y. L. 1974. On the Stability of Extending Films A Model for the Film Casting Process. /. Fluid Mech., 66(3), 613-622. 

Dry spinning usually uses a pump to feed a polymer solution to a spinneret. Dimensional stability now involves evaporation of solvent as in the film-casting process. Even when dried under some tension, the diffusion of solvent out of the partly dried fiber results in an uneven fiber formation. The skin that forms first on the fiber gradually collapses and wrinkles as more solvent diffuses out and decreases the diameter. The cross section of a dry-spun fiber characteristically has an irregularly lobed appearance (Figure 14.14). Solvent recovery is important to the economics of the process. Cellulose diacetate dissolved in acetone and polyacrylonitrile in dimethyl formamide are two current examples. 

The film casting process as described here is 3-D, non-isothermal and extension dominated hence modeling this process is a complicated exercise. Obtaining valid numerical solutions to the models is aided by the availability of suitable experimental data. The experimental film casting data helps in the evaluation of... 

The cmrent work is geared toward understanding the effect of material properties and process conditions on the film casting process and thermomechanical properties of the final film. We focus on two polypropylene samples with different molecular weights/viscosities. The experimental results are compared to model predietions. 

Silagy, D., Y. Demay, and J. F. Agassant. (1999). Numerical Simulation of the Film Casting Process, International Journal for Numerical Methods in Fluids, 30 1-18. 

Satoh, N., H. Tomiyama and T. Kajiwara (2001). Viscoelastic Simulation of Film Casting Process for a Polymer Melt, Polymer Engineering and Science, 41(9) 1564-1579. 

Lamberti, G. and V. Brucato. (2003). Real-Time Orientation and Crystallinity Measurements during the Isotactic Polypropylene Film-Casting Process, Journal of Polymer Science Part B Polymer Physics, 41 998-1008. 

G. Lamberti, G. Titomanlio, and V. Brucato, Measurement and modelling of the film casting process. 1. Width distribution along draw direction. Chemical Engineering Science, 56, 5749-5761, (2001). 

A continuous solution film casting process was studied for manufacturing novel polymer membranes for PEM fuel eells. A lab reverse roll casting machine was built and used to cast membranes with typical thickness of 25 micron to 50 micron. Investigation was made to establish the casting and drying conditions to produce voids-free, uniform membranes with desired thiekness. The proton conductivity, mechanical properties and morphology of the membranes were evaluated. 

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