Coextrusion technique

Coenzyme A (CoA), 20 249—250. See also Ace to acetyl- Co A in citric acid cycle, 6 633 Coenzyme Q10, 17 673 Coercivity, ofM-type ferrites, 11 70 Coextruded food packaging, 18 44, 45 Coextrusion techniques, for gelatin capsule preparation, 11 549 Cofactors, 10 253 11 4 folic acid, 25 801-802 for enzymes, 3 672-673 protein, 20 828-829 vitamin B12, 25 804 vitamins as, 25 781 Coffea arabica, 7 250 Cojfea Canephora, 7 250 Coffea liberica, 7 250 Coffee, 2 108 6 366 7 250-271 biotechnology, 7 265-267 decaffeinated, 7 263 economic aspects, 7 263-264 estimated maximum oxygen tolerance, 3 381t... 

Alginate-polylysine has been used to encapsulate hepatocytes (32-34), parathyroid cells (35) and growth hormone transfected fibroblasts (36). Poly (acryl-onitrile/vinyl chloride) (PAN/PVC) macrocapsules have been used with PC12 (37, 38), embryonic mesencephalon tissue (39), thymic epithelial cells (40), adrenal chromaffin cells (41) and islets (25) using preformed hollow fibers or more recently coextrusion techniques (41) similar to those we have developed microcapsules cannot be made since DMSO is used as the solvent. All these studies have concluded from the maintenance of viability of the islets or cells that immunoprotection provided by the capsule membrane was compatible with... 

Lamination is a fabrication process in which various materials such as paper, aluminum foil and polymer film are joined together. Contrary to the coextrusion technique, the materials are joined in the solid phase. The multilayer structure combines the properties of the components. Adhesion between the different substrates is accomplished by means of solvent-based or water-based glues. Lamination lines are operated at high line speeds. Typical applications include foodpackaging, pharmaceuticals and flexible packaging of industrial products. 

Du et al. [67] investigated effects of layered architecture and blend morphology on the SM behavior using thermoplastic PU and PCL. The PU/PCL ratios set were 75/25,50/50, and 25/75, respectively. The layered structure was achieved by a special multilayer coextrusion technique. The layer thickness varied with the composition ratio whereby keeping the number of layers and the overall thickness of the multilayer film as constants. of PCL served as 70 °C) during shape... 

The third coextrusion technique uses multi-manifold external-combining dies, which have completely separate manifolds for the different melt streams as well as distinct orifices through which the streams leave the die separately, joining just beyond the die exit. This technique is also referred to as multiple lip coextrusion. The layers are combined after exiting while still molten and just downstream of the die. For fiat film dies, pressure rolls are used to force the layers together. In blown... 

Microporous PP hoUow fibers are prepared as follows blending PP powder, filler and additives, followed by extrusion to prepare pellet, extrusion to prepare microtube, and stretching. The properties of hollow fibers can be controlled by the filler content (40-60 wt.%), particle size of fiUer (0.1-3 (xm), and the stretching ratio (4-6), respectively. Porosity and pore size of the resultant hollow fiber are in the range of 0.44-0.52 and 0.1-0.8 xm, respectively. In these hollow fibers, there are many slits (parallel to the fiber axis) in the surface whereas the inner section consists of fine interconnected PP fibrils. Also, microporous hollow fibers with double layers can be prepared by using coextrusion technique for preparation of the microtubes. These hollow fibers are used as a membrane filters (e.g. for water purification). 

Coextrusion. Coextrusion is a commonly used technique to combine two or more plastics passing through a single extrusion die. There are two major coextrusion techniques the feed block system and the multimanifold system. In the feed block system the different plastics are combined in the feed block module (see Fig. 18) and then enter into a regular extrusion die with a single inlet, manifold, and outlet. 

Recently Hadziioannou et al. (106) prepared amorphous polystyrene with extrusion ratios up to 10, using a solid-state coextrusion technique. Their poly-... 

Special polymer blends can be realized using the coextrusion technique. Using two or more extruders, the individual melt streams are put together in a multilayered arrangement, and polymer systems of two up to five clearly visible layers can be produced. Using the special multilayer coextrusion technique, polymer systems of two or three different polymers with a parallel arrangement of up to several thousands of very thin layers are possible see Section 9.3 in Part II. 

The coextrusion technique consists of two or more (depending on the number of polymers to be extruded) single-screw extruders that produce a melt with a specific thickness. The basic coextrusion technique comprises two single-screw... 

A special application of the coextrusion technique is the production of polymeric foamed materials with a high strength-to-weight ratio and good acoustic and thermal insulation. Control of the foam cell size is very critical in obtaining these key performance properties. The control of cell size in the thin layers by the microlayer coextrusion technology makes the creation of microcellular foam possible [8]. 

Blown film is usually produced at a film thickness of < 20 mils (0.020 inches, 0.5 mm), but primarily processed at 2 mils or less with thinner films of 0.5-1.0 mil, the most common thickness. Thin films are much more cost effective as long as the film has sufficient toughness for the particular application. The blown film process may produce a monolayer film or through coextrusion techniques, where multiple layers of different plastics are used to produce specialty films for more demanding applications where barrier properties are needed. 

Extrusion also allows the fabrication of core/clad preforms. Savage et al. successfully reported the coextrusion of a Ge-As-Se preform and its subsequent fiber drawing [152], The coextrusion technique produces preforms with optimum core/clad interface quality. Fibers with optical losses of 1.7 dB/m at 6.0 pm were fabricated. Recently Abouraddy et al. have extended the technology by coextruding composite macroscopic preforms made of two ChG materials and a thermoplastic polymer cladding [153], yielding mechanically robust fibers. 

Section 3. Properties of Oriented Ultrahigh Molecular Weight Polyethylene Prepared using the Powder and Coextrusion Techniques... 

S.4.4 Wall Base Extruded vinyl wall base is opaque and generally in black or dark colors, some product is produced through coextrusion techniques. Here, the top coat can be very colorful, while the base material contains a lot of recycled material. It is important that the level of recycled material be controlled because of its impact on extmdabihty (gauge variations and dimensional stability problems). Exceptionally high levels of lubricant are often used to improve processability. 

Coextrusion is an important process for manufacturing layered plastic composites, such as film, sheet, and tubing (Middleman, 1977 Schrenk and Alfrey, 1983 Schrenketal., 1963). A costly alternative would be the fabrication of individual layers of plastics followed by conventional lamination and coating. An additional advantage of the coextrusion technique is its ability to handle extremely thin films on the order of 10 xm. One of the most colorful applications of this technique is the iridescent film, which consists of hundreds of very thin layers of alternating low and high refractive indices. A typical example of this type of film consists of 116 layers of poly(methyl methacrylate) (PMMA) with refractive index 1.49 and 115 layers of polystyrene (PS) with refractive index 1.59 and total film thickness of about 20 o.m (Radford et al., 1973). 

Multilayer coextrusion is an effective tool for dispersing OMM in polymer melts. The lowest Af in Figures 2-5 was 24. For similar nanocomposite compositions, Af 15 was determined for samples prqrared using a batch mixer (12). A more direct comparison can be made using Figures 3 and 5. These samples have identical thermal and processing histories other than the additional multiplication dies needed to increase the layer number from 20 to 640. The additional shear stress in these dies increased Af from 33 to 48. Thus the multilayer coextrusion technique is viable for creating dispersed nanomaterials. 

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