Coextrusion also

Sequential coextrusion also offers the possibility of manufacturing a single part made with different regions of hardness, elasticity, strength, or heat deflection temperatures. This opens up a wide variety of applications. Sequential coextrusion can be used, for example, when the ends of a pipe must be flexible (for coimection purposes), but the middle section must be stiff and strong. Such a part, made out of thermoplastic elastomer (TPE), for example, can then be substituted for rubber parts. 

The review in coextrusion also applies with coinjection providing similar advantages. Two or more injection molding barrels are basically joined together by a common manifold and nozzle through which melts flow before entering the mold cavity by a controlled device such... 

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... 

Extrusion. Sheet, film, and profiled articles are made by extrusion (20). The resin is melted and forced through a die plate or head. Variations include multilayer and blown film applications. In multilayer coextrusions, different combinations of plastics are separately but concurrently extruded to form layered sheet or film. In the packaging industry, specialty resins such as high barrier ethylene—vinyl alcohol copolymers are combined with heat- and impact-resistant thermoplastics for food packages. The properties of each resin layer are additive, as opposed to the "averaging of property" in blends. Multilayers are also used for blow-molded containers, films, and sheet products (see also Film AND sheeting materials). 

More recently, the direct reaction of amines and amino esters with azetidin-2,3-diones 128 at 90°C, Scheme 43, leading to peptides 130, has also been reported. The reaction is believed to occur through formation of an aziridine intermediate 129 which then rearranges to the amino amide with coextrusion [119, 120]. 

Another approach to improving the properties of starch-filled polyolefin materials involves the use of ethylene-acrylate copolymers in blends with PE.45 Addition of copolymers of ethylene with methyl acrylate, ethyl acrylate or butyl acrylate were shown to improve the properties of PE films, allowing for higher starch contents. Coextrusion of starch-containing films with outer layers incorporating oxidative pro-degradants has also been utilized 46 The inner layer can contain up to 40% starch the... 

Cardboard baking dishes coated with crystalline PET or crystalline PBT can be used in convection ovens up to temperatures of 200-220 °C. Single portion dishes made from heat formed films find wide applications in microwave ovens. Biaxially stretched PET covers an important application area of bottles, wide mouth jars and cans. These containers are particularly well suited for carbonated beverages, edible oils and spirits. The gas barrier properties can be improved by coextrusion with a barrier layer such as polyamide. With improved barrier properties it can also be used for beer and wine. 

The aim of coextrusion is outlined and the tooling available for different types of profiles, including window profiles, sidings, fences and foam profiles, is described. Machinery for coextrusion is also described and details are provided on a specially designed coextrader (BEX 2-54CC/1) equipped with negative conical screws. 6 refs. 

Counter-rotating twin screw extruders are used almost exclusively for the production of uPVC pipes, profiles and sheet because they treat material more gently than single screws. Parallel screw and conical twin screw extruders are compared. Cincinnati Milacron Austria introduced its Argos parallel twin screw extruders last year. These machines are intended to complement the company s Titan conical screw range. Coextrusion of foamed core pipes is also described. 

The single-layer coextrusion process based on the use of low-volatility UV absorbers has been adopted for thin-walled sheet and profile manufacture, both in Europe and worldwide. Coextrusion coating using PC is important also from the point of view of recycling, because single-polymer systems increasingly are being required. 

Coextrusion of L-lactide (a cyclic dimer lactone of lactic acid) with hydroxy-terminated poly(caprolactone) in the presence of stannous octoate gave a block copolymer.74 Block copolymers can also be used as compatibilizers for the homopolymers, in addition to having interesting properties in their own right.75 Copolymers of ethylene and vinyl acetate can be treated with methanol and a little sodium methoxide to remove some of the acetate groups from the copolymer.76 The by-product methyl acetate comes out the vent of the extruder. n-Butyl alcohol can be used in the same way.77 The product copolymer is useful as a gas barrier coating on films for packaging food. 

Linear low density polyethylene (LLDPE) is the predominant stretch wrap material, but films based on LDPE combinations, EVA and plasticised PVC are also found. Stretch materials can be produced by various processes, i.e. from lay flat tubing, casting, etc. The latter process gives orientation in the machine direction which assists stretch in the wrap around direction. Cling properties required for grip may be achieved by incorporating a cling additive or coextrusion to the outer surface(s) of a more tacky material, e.g. EVA. 

Extrusion consists of extruding a film from a slit die where the hot film may be nipped in contact with a second material and then cooled to give a bond between the two (or three) materials. Extruded LDPE is widely used both as a film in its own right and as a ply which combines plies on either side of it. Circular die extrusion can also be employed without the nip stage in slit die laminating, i.e. it involves true coextrusion. 

Coextrusion, e.g. a process incorporating two or more plies of a plastic, will undoubtedly find more use in flexible pharmaceutical packs. Coextrudates can also be moulded into rigid containers, bottles, tubes, tubs, etc. subject to the quantities justifying the costs. 

Coextrusion is the process of forming an extru-date composed of more than one thermoplastic melt stream. The process came about because some service demands, particularly from the packaging industry, could not be satisfied by a single polymer although they could be met by a combination of polymers. Coextrusion was first practiced in the production of cast film and is now also used in blown film and sheet extrusion. The intention is normally to produce a laminar structure in which each layer contributes a key property to the overall product performance. Coextruded films may be very complex structures composed of many different functional layers, including tie layers whose purpose is to bond neighboring layers of limited compatibility. Five layers are not uncommon. However, side-by-side coextrusion is also possible. Fluoroplastics can be coextmded with other polymers such as ETFE and nylon. 

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