Sheet film extrusion, polypropylene

Polypropylene film is found in a variety of applications. Films are thin plastic sheets with thicknesses less than 250 pm. Applications for these films include candy mappers, plastic label material, electrical capacitors (which requires very pure polymer), and fiber glass insulation backing. There are two general categories of polypropylene films unoriented and oriented. Films are manufactured through either a cast or a blown film extrusion process. Oriented films exhibit improved strength relative to unoriented films. This means that they can be... 

Products A wide range of polypropylene products (homopolymer, random copolymer and impact copolymer) can be produced to serve many applications, including injection molding, blow molding, thermoforming, film, extrusion, sheet and fiber. Impact copolymer produced using this process exhibits a superior balance of stiffness and impact resistance over a broad temperature range. 

Plasblak . [Ctd>ot Plastics Ltd.] Carbon or furnace black masterbatt widi polyethylene, EVA, polypropylene, polystyrene, or SAN carriers black mast atch for molding and extrusion of articles for pkg., electronic equip, cases, radios, TVS, domestic appliances, pipe and sheet, film, cable sheathing. 

Biaxial orientation effects are important in the manufacture of films and sheet. Biaxially stretched polypropylene, poly(ethyleneterephthalate) (e.g., Melinex) and poly(vinylidene chloride) (Saran) produced by flat-film extrusion and tentering are strong films of high clarity. In biaxial orientation, molecules are randomly oriented in two dimensions just as fibers would be in a random mat the orientation-induced crystallization produces structures which do not interfere with the light waves. With polyethylene, biaxial orientation often can be achieved in blown-film extrusion. 

The production of foamed films and sheets from polypropylene and polystyrene is discussed, with particular reference to packaging applications. Advantages of foamed materials for this application are examined, and the chemical and physical foaming processes are described. Extrusion technology for film and sheet by chemical and physical foaming processes is discussed, and recent developments in the coextrusion of multilayer packaging trays for the food industry are considered. 

Chicago, II., 29th Aug-2nd Sept.l993,p.403-6. 6A MULTILAYER EXTRUSION DIE GEOMETRY FOR THERMOFORMED POLYPROPYLENE FOAM SHEETS AND BIAXIALLY ORIENTED FOAM FILMS Raukola J Savolainen A Tampere,University of Technology (TAPPI)... 

Fortilene . [Solvay Polymers] Polypropylene homopolymets and copolymers resins for extrusion, sheet, strapi ng, profiles, inj. molding, ctq>s, closures, thin-wall containers, diqmsable tableware, films, fibers, filaments. 

Most films are produced by extrusion. Thermoplastic materials are heated and pushed through a die to form a flat tube. Warm air is blown into the extruded tube to produce a balloon which is then cut open and laid flat. Calendering can also be employed to produce film. Hot thermoplastic is passed through a series of temperature-controlled metal rolls with progressively smaller gaps to produce a continuous sheet (Figures 3.27 and 3.28). The technique is used to make shower curtains, food wrap films, carrier bags and protective films. The most widely used films are polyethylene, nylons, polypropylene, cellulose acetate, PVC and polyesters. 

An extrusion system used extensively for thin films of polyethylene and polypropylene is the blown film process. In this process the polymer is extruded as a relatively thick tubular extrusion and is then blown up by internal air pressure to form a thin-walled tube. The tube is then sUt to form a sheet of film up to 10 ft in width or is left as a flattened tube known commercially as lay-fiat tubing. To improve gauge uniformity in this process, the circular extrusion die, the air cooling ring, or both are frequently rotated. Although low-density polyethylene and polypropylene are the materials most used for this process, polyvinyl chloride, polyamides (nylon), and some polystyrenes have all been used. (See also blown film lay-flat tubing.)... 

Polypropylene is the only high-volume thermoplastic that is processable by all major fabrication methods molding, extrusion, film, and fiber. Many new polypropylenes with improved engineering properties have been developed. The most promising are glass-reinforced polypropylene, foamed polypropylene, heat-resistant-polypropylene, and oriented sheeting. 

Drickman, R. and McHugh, K.E. (1993) Balancing extrusion and thermoforming capability for polypropylene.. Plast. Film Sheeting, 9, 22-34. 

Film, injection molding, sheet extrusion, and polypropylene polymerization... 

If the sheet has been subjected to biaxial orientation during extrusion (see Section 14.2), heating above the deformation temperature will cause the sheet to shrink. A tight package can be made by wrapping an article in a biaxially oriented sheet followed by a brief heat treatment. Such shrink packaging with polypropylene film is widely used for everything from lettuce and meats to books and video tapes. 

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