Abstract

Plastic film and sheet products represent a significant use for polymeric resins of all types. Film and sheet products serve a wide range of consumer, commercial, and industrial markets, including packaging, communication materials (magnetic tape, reprographic and photographic products, and stationery), thermal and electrical insulation, optical products (glazing, filters, and light control), agricultural mulching, and construction, as well as for component manufacture in appliances, transportation equipment, and electrical equipment. The principal film and sheet resins are the polyolefins (polyethylene and polypropylene), polystyrene, the vinyl resins, polyesters, and the cellulosics. Specialty markets, in smaller volume, exist for film and sheet products made from higher cost or high performance polymers.

Film properties may vary from strong, stiff materials to soft, pliable, even rubbery films. Sheet may be hard and rigid or soft foams. Properties such as tensile, impact, and tear strength can be obtained over a wide range, dependent on the polymer used, the presence of additives or modifiers, and the process used in their manufacture. Similarly, variations in slip, handleability, sealability, optical properties, electrical properties, and color or transparency can be altered to meet end use requirements.

Films and sheet are commonly manufactured by such melt-extrusion processes as flat die extrusion, blown tube extrusion, and calendering, or by solution casting. Other processes include reactive casting of sheet or the regeneration of cellulose. Auxiliary processes used in film or sheet manufacture include coextrusion of multilayers, coating, laminating, and orientation (monoaxial or biaxial).