Extruded film

Considerable amounts of polyethylene film are produced using coaxial extrusion processes in which two or more melt streams are combined in the die to produce extruded film of two or more layers of plastics materials. Layers in such a composite may be included, for example, to improve barrier properties, to enhance sealability or even simply to act as an adhesive between dissimilar layers. 

Because of the excellent gas barrier properties, EVOH is of interest as a packaging material. However, because of its high water absorption it is usually used as an internal layer in a co-extruded film, sheet, bottle or tube. For example, the system HDPE-EVOH-EVA may be used as a barrier film for packaging cereals, and the system polystyrene-EVOH-polystyrene for packaging coffee and cream, whilst the system polystyrene-EVOH-polyethylene has the additional advantage of heat scalability. 

Poly(ethylene terephthalate) film is produced by quenching extruded film to the amorphous state and then reheating and stretching the sheet approximately three-fold in each direction at 80-100°C. In a two-stage process machine direction stretching induces 10-14% crystallinity and this is raised to 20-25% by... 

The main reason for producing multi-layer co-extruded films is to get materials with better barrier properties - particularly in regard to gas permeation. The following Table shows the effects which can be achieved. Data on permeability of plastics are also given in Figs 1.13 and 1.14. 

Ziegler-Natta catalyst. A comparison of properties of resins and their extruded film samples are given in Table 5. 

During fabrication of products necking occurs such as extruding film where the width of extrudate leaving the die is necked-in as it moves downstream. 

Co-extruded films of polypropylene or other polyolefins and a flexible polyester are solutions for pouches for intravenous drug-delivery systems. 

ExxonMobil Chemical Company, On-line properties analysis of a molten polymer by Raman spectroscopy for control of a mixing device. Inventors D.G. Marrow, D.A. Yahn, and T.R. Veariel. 20 pp. (inch 10 fig.). Appl. 22 Jul 2005. Int. Cl. GOIJ 3/44 GOIN 21/65. US Patent Application Publication 2007/0019190 Al 105. V.S. Tumuluri, M.S. Kemper, I.R. Lewis, S. Prodduturi, S. Majumdar, B.A. Avery and M.A. Repka, Off-line and on-line measurements of drug-loaded hot-melt extruded films using Raman spectroscopy, Int. J. Pharm., 357, 77-84 (2008). 

Figure 13.2 Noncontact optic with the fiber-optic probe clamped over the extruded film formation. Reprinted from Tumuluri et al. (2008Copyright 2008, with permission from Elsevier Science.

V.S. Tumuluri, M.S. Kemper, I.R. Lewis, S. Prodduturi, S. Majumdar, B.A. Avery and M. Repka, Off-line and on-hne measnrements of dmg-loaded hot-melt extruded films using Raman spectroscopy, Int. J. Pharm., 357, 77-84 (2008). 

While other organic esters are commercially available, namely cellulose butyrate and cellulose propionate, by far the most widely used is cellulose acetate, which is available as plastics, in films, sheets, fibers, and lacquers. Cellulose acetate is used in the manufacture of display packaging and as extruded film for decorative signs, and to coat a variety of fibers. Injected molded products include toothbrush handles, combs, and brushes. It is also used in lacquers and protective coatings for metal, glass, and paper. Cellulose acetate films are used in reverse osmosis to purify blood, fruit juices, and brackish water. Some eyeglass frames are... 

Modacrylic staple fibers Polyamide resins Polyester thermoplastic Co-extruded film Polymelitimide Nylon-12 PVC PS... 

Non-contact measurements with the probe head sited remotely from the process are well established. Tumuluri et al. [10] have described a probe-based process measurement for monitoring the drug content in an extruded film. A commercially available probe head with a working distance of around 5 cm gave excellent results for quantitative monitoring of the process in real time. Appropriate working distance can be up to tens of centimetres depending on the application. However, for many pharmaceutical processes that involve... 

The end-fed-sheeting die, as presented in Fig. 6.9, is a simple geometry that can be used to extrude films and sheets. To illustrate the complexities of die design, we will modify the die, as shown in the figure, in order to extrude a sheet or film with a uniform thickness. In order to achieve this we must determine the length of the approach zone or die land as a function of the manifold direction, as depicted in the model shown in Fig. 6.10. 

Fig. 7.34 Photographs of extruded LDPE films with carbon black concentrate extruded at various conditions. The barrel temperature (°C) and screw speed (rpm) are as follows (a) 160°,40 (b) 160°, 60 (c) 160°, 80 (d) 180°,40 (e) 180°,60 (f) 180°, 80. [Reprinted by permission from N. Nadav and Z. Tadmor Quantitative Characterization of Extruded Film Texture, Chem. Eng. Sci., 28, 2115 (1973).]...

Fig. 7.37 Typical correlograms. (a) Along a line perpendicular to an equally spaced striped texture, (b) Over an area of a checkered board texture, (c) Along a line of an extruded film, as shown in Fig. 7.34, perpendicular to the extrusion direction.

Extruded films are sometimes bi-axially stretched, in particular PE and PP films, which gain in strength and transparency by biaxial orientation. The stretching takes place at elevated temperatures, but below the melting point. The edges of the film are gripped by a series of clips, which diverge in the transverse direction and simultaneously accelerate in the machine direction. 

Structurally modified PVF has been extruded.66 Thin films are manufactured by extrusion of a dispersion of PVF in a latent solvent.67 Such dispersion contains usually pigments, stabilizers, plasticizers, and flame retardants as well as deglossing agents if needed. The solvent is removed by evaporation. The extruded film can be biaxially oriented and the solvent is removed by evaporation only after the orientation is completed. 

---