Stretch-wrap films

It is generally claimed that metallocene polyethylenes (often abbreviated to m-PE) exhibit superior mechanical and optical properties as well as better organoleptic properties (resulting from the lower residue levels). As an example m-LLDPE is particularly favoured as a stretch film for wrapping because of the good prestretchability, high puncture resistance and tear strength, all of which are claimed to be better than with conventional LLDPE. 

Further, they can be used for medical purposes, such as press-through packages, disposable syringes, liquid medicine vials, and infusion bags. They are suitable for electric or electronic materials, such as wire coating. In addition, packaging films, such as wrapping films, stretch films, shrink films, and blister packs can be produced. 

Strength they are of interest as a stretch film for meat packaging and for ding-wrap purposes. Some EVA is used in coextrusion processes for the manufacture of laminated film. 

Outer or transit packaging can occasionally contribute to changes in the primary pack or the product. External wrapping materials may contain various migratory constituents, e.g. when a shrink or stretch film is in intimate contact with a primary pack or plastic components of a device. Odorous board, adhesives, printing inks on external packaging have also been known to cause flavour and/or odour changes. 

Flexible PVC film is often used for packaging food products, particularly fresh red meat. The oxygen permeability of PVC film is well suited to maintain the necessary oxygen requirements of the meat, to preserve its red color and appearance of freshness. PVC films also provide good toughness and resilience. PVC is also used to wrap fresh fruits and vegetables. Almost all poultry producers in the U.S. once used PVC stretch films for chilled, tray-packed poultry parts. However, multilayer barrier films have made considerable inroads in this market. PVC is also used for a variety of other food and nonfood packaging applications, as illustrated in Table 4.8. 

Shrink films, like stretch films, use the tendency of a film to try to return to a smaller dimension after deformation to provide a tight wrap around a packaged object. In shrink film the product is loosely packaged, and when it is exposed to heat, the film shrinks. The resistance of the product on the film provides the holding force. 

The gas permeability of 1, 2-PBD depends on the film thickness, as shown in Fig. 2. When the film thickness is increased to several few millimeters, the gas permeability of 1, 2-PBD is reduced and approaches that of LDPE. In this film the gas permeability of 1, 2-PBD is hl, which is assumed to be attributable to the good solubility of CO2, 2 and ethylene oxide gas in the 1, 2-PBD film surface, in view of the small gas diffusion coefficient of 1, 2-PBD measured by J.D. Ferry et aJ.(2), From these fundamental physical properties aM nontoxic in respect to food hydiene described previous paper, the 1, 2-PBD will be suitable for food packaging materials. Because of its good gas permeability in this film, 1, 2-PBD is used, as the most superior application example, for stretched film as a wrapping for fresh vegetables, fruits and others. 

Pallet wrap stretch film is the second largest North American market for LLDPE film. It consnmes over 0.545 billion kilograms of LLDPE annually. Pallet wrap stretch film is used to unitize loads to prevent shifting during shipping. It is also used as a protective film and as a tamper indicator. Film... 

Markets for cast film are (a) stretch film that is used in pallet wrapping and other types of shipping to secure the load, (b) high clarity films, and (c) more recently cast film is used in fabricating premium-grade trash bags. 

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