Primary polypropylene films

Some cast (unoriented) polypropylene film is produced. Its clarity and heat sealabiUty make it ideal for textile packaging and overwrap. The use of copolymers with ethylene improves low temperature impact, which is the primary problem with unoriented PP film. Orientation improves the clarity and stiffness of polypropylene film, and dramatically increases low temperature impact strength. BOPP film, however, is not readily heat-sealed and so is coextmded or coated with resins with lower melting points than the polypropylene shrinkage temperature. These layers may also provide improved barrier properties. 

Large volumes of polymer films are commercially vacuum metallized with aluminum every year and the metallization of roll substrates such as polyester, nylon and oriented polypropylene films for packaging applications are wide spread. In addition the metallization of paper is principally a decorative application where holographic or iridescent patterns are intensified by the reflective metal layer. The barrier properties of the aluminum layer are controlled by the base sheet onto which the aluminum is applied but also by the deposition process. In general the films are metallized to add a significant light barrier and to enhance the moisture and perhaps oxygen gas barrier properties of the film. Metal adhesion is also a primary concern. 

Table 6 shows the sales estimates for principal film and sheet products for the year 1990 (14). Low density polyethylene films dominate the market in volume, followed by polystyrene and the vinyls. High density polyethylene, poly(ethylene terephthalate), and polypropylene are close in market share and complete the primary products. A number of specialty resins are used to produce 25,000—100,000 t of film or sheet, and then there are a large number of high priced, high performance materials that serve niche markets. The original clear film product, ceUophane, has faUen to about 25,000 t in the United States, with only one domestic producer. Table 7 Hsts some of the principal film and sheet material manufacturers in the United States.

A primary use of vinyhdene chloride copolymer lacquers is the coating of films made from regenerated ceUulose or of board or paper coated with polyamide, polyester, polypropylene, poly(vinyl chloride), and polyethylene. The lacquer imparts resistance to fats, oils, oxygen, and water vapor (165). 

For battery separators, regenerated cellulose is placed on the surface of nonwoven so that the nonwoven is available to promote the wicking of the electrolyte. The nonwovens should not allow the penetration of viscose into itself. Suitable nonwovens are made from polypropylene, poly(vinyl alcohol), and hardwood hemps. Regenerated cellulose films are commonly used in alkaline manganese cells, both primary and secondary, in NiCd industrial batteries, as well as in silver—zinc batteries. 

Solid electrolytes for lithium-ion batteries are expected to offer several advantages over traditional, nonaqueous liquid electrolytes. A solid electrolyte would give a longer shelf life, along with an enhancement in specific energy density. A solid electrolyte may also eliminate the need for a distinct separator material, such as the polypropylene or polyethylene microporous separators commonly used in contemporary liquid electrolyte-based batteries. Solid electrolytes are also desirable over liquid electrolytes in certain specialty applications where bulk lithium-ion batteries as weU as thin-film lithium-ion batteries are needed for primary and backup power supplies for systems, devices, and individual integrated circuit chips. 

Lasers have been used primarily for welding polyethylene and polypropylene. Usually, laser welding is applied only to films or thin-walled components. The least powerful beams, around 50 W, with the widest weld spots are used for fear of degrading the polymer substrate. The primary goal in laser welding is to reach a melt temperature where the parts can be joined quickly before the plastic degrades. To avoid material degradation, ac-... 

The types of end products covered are primary plastic materials (mainly pellets, i.e. granules not to be confused with transportation pallets), loose-fill packaging material (packaging chips), films, bags, mulch films, printed wiring boards (for electronics), thickener for lacquer, two different panels for passenger cars, and transport pallets. These products are compared with equivalent products made from petrochemical polymers - in many cases polyethylene, polypropylene or polystyrene. 

Two fast growing markets for PSA s are in EDP labels (bar code labels nsed to track inventory or change pricing) and primary prodnct identification (food, personal care, and honsehold items). One of the major changes in the tape and label market is the introduction of new face stocks based on polystyrene, polypropylene, and polyediylene films. These new products will gain market share from the crrnent face stocks - coated, imcoated and saturated papers, polyester (PET), PVC, and orientated polypropylene (OPP). 

Most recently, high performance single and multilayer autocalvable films has been produced (6-7) with alloys of polyethylene copolymers and polypropylene coplymers. Due to their constraction simpUcity and low cost, widely available raw material, it offers the promise of becoming the material of choice for medical primary packaging. 

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