Overwrap Films

Oriented polypropylene film (OPP) may be classified as heat-set and non-heat-set, blown and tentered, coextmded and coated. Orientation improves the cold-temperature resistance and other physical properties. Heat-set biaxially oriented polypropylene film (BOPP) is the most widely used protective packagiag film ia the United States. It is used to wrap bakery products, as lamination pHes for potato and com chips, and for pastas and numerous other flexible pouch and wrapping appHcations. Nonheat-set OPP is used as a sparkling, transparent shrink-film overwrap for cartons of candy. 

Bubble packaging, envelope films Overwrap Strong and highly flexible... 

Metallised PP/PP laminate (outer PP film reverse-printed with nylon-based resin ink) bag PP film (fuUy printed on outer surface) heat-sealed single packs packed in PP film heat-sealed multipack (partially printed on outer surface) Cartonboard boxes in PP film overwrap (coated on both surfaces with VdC copolymer)... 

Note that although many films, laminates, etc. may have a 100% effective seal, the materials employed may be permeable to moisture, oxygen, carbon dioxide, etc. This property can be either a disadvantage or an advantage, e.g. plastic film overwrap can permit sufficient moisture permeability to cause a product to reach its critical (unacceptable) moisture level. Hence a laminate (without a foil ply) is not a hermetic pack. 

Film Applications Stretch film, shrink film, overwrap, trash bags, heavy-duty bags, and food packaging.l " ... 

Typical applications automotive/transportation, apphance, films, closures, tapes/stripes, opaque and matte finish oriented film, breafhable, microporous film, opaque thermoformed parts, and opaque or translucent injection molded parts, foam, food packaging film, overwrap film, bottles and rigid articles, food trays, tubing... 

Applications industrial film, packaging film, overwrap film, laminating for packaging. ... 

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. 

Hard baked goods such as cookies and crackers have a relatively low water and high fat content. Water can be absorbed, and the product loses its desirable texture and becomes subject to Hpid rancidity. Packagiag for cookies and crackers includes polyolefin-coextmsion film pouches within paperboard carton sheUs, and polystyrene trays overwrapped with polyethylene or oriented polypropylene film. Soft cookies are packaged in high water-vapor-barrier laminations containing aluminum foil. 

A small quantity of flexible packaging material, usually oriented polypropylene, shrink polypropylene, or polyethylene, is used to overwrap paperboard cartons. The film is wrapped around the carton and sealed by heating. Products such as boxed chocolates, candies, and cookies are overwrapped, sometimes by a printed film. 

Cast films provide a high clarity, heat sealable film and are primarily used as an overwrap for boxes and other packaging. These films have a lower density than cellophane and provide a longer product shelf life. Properties of polypropylene films are given in Table 12. 

Biaxially stretched film has proved of value as a packaging material. Specific uses include blister packaging, snap-on lids, overwrapping, envelope windows and de luxe paekaging. 

Overwrap films are used as wrappers of foods under storage or cooking. Conventional overwrap films are made of thin films of poly(vinyl chloride) or poly(vinylidene chloride), which are capable of withstanding heat at temperatures of about 140°C. 

Since the use of overwrap films has expanded, a demand has arisen for products that can withstand use at even higher temperatures, namely, those which have higher heat resistance. Polymers based on TPX melt at 220-240°C and are known to exhibit high heat resistance. 

Thus, overwrap films with high transparency and heat resistance... 

NAI-SMELL multi-layered barrier overwrapping film for food PLA Office Media... 

Evlon Ev HIS is a co-extruded one-side heat sealable PLA film for packaging applications either plain or printed and laminated, for horizontal and vertical packaging machines. Suggested applications include bags, overwrap and laminations. 

Thus if one tests blister packs in a carton (possibly overwrapped with a protective film) and from this predicts a shelf life, under actual conditions it could be expected that a much longer life could be achieved, i.e. the prediction has probably built in a significant safety factor , e.g. 6-8 weeks (no shelf life) has been extended to up to 60 months. 

Instant tack labels find special usage on seals, pleated overwraps, various header labels (cellulose films must be heat sealable variety). They are not used for bottle or can labelling. 

Polyethylene, as LDPE, LLDPE or a mixture or blend involving combinations of LDPE, MDPE, HDPE, EVA, etc., finds a wide usage in bags, sacks, sachets, overwraps, shrink wraps, stretch wraps, etc. Most deep freeze packs, for example, use LDPE or an LDPE mixture which is produced from a reel on a form fill seal type machine. However, as many of these packs are up to 100% printed, even ink of 2-5 Pm could be considered as a separate layer which modifies some of the physical and chemical properties. As all polyolefins need a surface (oxidative) treatment to ensure a good print key, this or any other surface treatment process may further modify the film properties. 

As a full overwrap—to provide a total wrap—where all of the item or items are enclosed by a film, i.e. an all-round wrap. 

Although regenerated cellulose plants still exist, worldwide usage has significantly reduced due to the better dimensional stability properties of various polypropylene-based films. However, regenerated cellulose still finds usage for certain special applications, e.g. overwraps. 

PVC is used in overwrap film, shrink film, shrink sleeving, thermoforming for all types of blister and bubble packs. Plasticised PVC IV bags are usually PP/Nylon overwrapped to reduce moisture loss. 

Shrink and stretch wrapping—shrinkable films (PVC, polypropylene, polythene), sleeve or complete overwraps. Stretchable wraps, e.g. LLDPE, modified PEs. 

Cheaper plies such as regenerated cellulose film provide the lowest cost form of unit pack coupled with restricted protection, but this can be improved by an overwrap. PVdC coated PP is the preferred substitute material today. 

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