Often when people talk about plastic films—which technically are defined as plastic sold in thicknesses of up to 10 mils—they treat them as one type of material, grouping all flexible plastic packaging into a single category. Actually, plastic films compose a broad category of materials that can be relatively simple or complex depending on the demands of a particular product or package. Like plastic bottles and containers, film can be made with different resins, each of which has a unique combination of properties that makes it ideal for certain applications. For example, low-density polyethylene (LDPE) film acts as a gas barrier, which is necessary for packaging such things as chicken, which would quickly spoil if exposed to oxygen. Polyvinyl chloride (PVC) film, on the other hand, is gas permeable and necessary for packaging such things as red meat, which require a small amount of oxygen inside the package in order to remain fresh. Plastic film also can be clear or colored, printed or plain, single- or multilayered, and combined with other materials such as aluminum and paper. Thus, the only thing that all plastic film really has in common is that it is flexible in nature, as used in grocery bags, as opposed to rigid, as used in soft drink bottles and butter tubs.
Food Packaging Film
Food packaging film is used in such things as in-store bags for produce (such as apples and potatoes); all nonfrozen baked goods (such as rolls and breads); bakery bread and bun bags; tray covers for institutional deliveries of bakery products; bags-in-a-box (film used to contain fluid in a supportive box, such as boxed wine); boil-in-bags (film used to contain food prepared by keeping it in the package and placing it
in boiling water); candy and confection bags and wrappers; carton liners (for such products as cake mixes); and meat, poultry and seafood wraps (such as hot dog and bacon film).
Nonfood packaging film refers to such things as industrial liners (film used to line supported structures such as gaylord boxes, frozen pork box liners and liners for shipments of nuts and bolts), shipping sacks (film used to protect and/or contain contents such as bark and mulch bags), bubble packing, envelopes, multiwall sack liners, overwrap, and rack and counter bags. LDPE is the polyethylene resin used most frequently in nonfood packaging applications.
The other types of packaging in which film is found are stretch and shrink wrap. Stretch wrap is a strong, highly flexible film that can be stretched to take the shape of a product or products. It is used in a variety of applications ranging from overwrapping fresh meats to securing shipping cartons to pallets. Stretch wrap usually is made of co-extruded LLDPE and LDPE, although it can be made from individual plastic resins, such as LLDPE, LDPE and PVC. Shrink wrap, on the other hand, is a plastic film that is applied loosely around products, sealed by heating the seams and shrunk through a heating process to take the shape of the products. In shipping, it can be used to bind multiple packages of less than pallet size together (such as five 20-ounce cans of beans or three juice boxes) or used over an entire pallet of packages. In these applications, shrink wrap typically is made of LDPE, although it can be made from other resins as well, such as LLDPE and PP. In addition to shipping applications, shrink wrap also can be used for bundling purposes, such as bundling magazines and papers, and it can be used to protect and display such products as albums and compact disks. There are several ways to tell stretch wrap and shrink wrap apart: stretch wrap usually feels somewhat tacky to the touch and is very flexible, whereas shrink wrap may be more brittle (or crinkly) to the touch and does not stretch when pulled. In addition, stretch wrap usually is wrapped around products, whereas shrink wrap will enclose the product (that is, have a top and bottom cover), which makes it an often used choice for shipping products in extreme weather conditions or for products that need extra protection.