Plastics have different properties. Here is an explanation of some of the different sources from which film for wrapping is made, a description of their properties and some of the applications in which they are commonly used.
Petroleum based films are the most common and usually the most inexpensive films used for wrapping today. Most of these films require stabilizers in order to prevent them degrading prematurely. Discussion about how to use stabilizers to permit degrading is ongoing at this point.
Low Density Polyethylene LDPE/LLDPE
These two polyethylene resins often are talked about as if they are one because they have similar properties—both have good clarity, are good moisture barriers and fair gas barriers, can be heat sealed and are strong and highly flexible. They both are also used in similar applications, including but not limited to stretch wrap and shrink wrap.
High Density Polyethylene HDPE
Because it is part of the polyethylene family, HDPE film is found in many of the same applications as LDPE and LLDPE. In recent years, it has made inroads into the film market mostly because of its ability to allow manufacturers to use less material (i.e., source reduction) to make a package that can deliver an equal amount of product. HDPE also tends to be stiffer than other polyethylene films, which is an important characteristic for packages that need to maintain their shape. In addition, HDPE is strong and puncture resistant, has good moisture barrier properties and is resistant to grease and oils.
PP film comes from a resin that has a high melting point, which makes it desirable in packages that require sterilization at high temperatures. PP film commonly is used to package such things as cigarettes, candy, snack foods, bakery products, cheese and sanitary goods. Because PP has only average gas barrier properties, it often is used in combination with such things as a PVC coating or acrylic, which provide additional barrier properties.
BOPP film (Biaxially Oriented Polypropylene) film in has become one of the most popular, high growth films in the world market. BOPP film is available in a wide range of film variations targeting the packaging, pressure sensitive tape, label, stationery, metallizing and decorative markets.
At Package, our wrapping machines use BOPP for its clarity, crispness and strength.
PVC film can be found in stretch wrap for industrial and pallet wrap (although in very small amounts), shrink wrap (again in very small amounts), some bags and liners, adhesive tape, labels, blood bags and I.V. bags. It also is used exclusively to package fresh red meats. That is because it is semi-permeable, which means that just enough oxygen can pass through in much smaller quantities that impart special properties to a package.
These films come from a variety and growing list of sources. A non-exhaustive list follows. It is important to keep in mind that the source does not dictate the molecular structure. A bio-based film is not necessarily biodegradable, although it may come from a renewable source. Similarly a petroleum based film can be biodegradable but does not come from a currently renewable source. Here we discuss corn and wood based plastics. New bio-plastics from sugar and other materials are coming to market..
Polylactic Acid Film (PLA)
This films is currently made from corn. It is an effective substitute for polyethylene but has performance problems at higher temperatures (over 100º F). It is very suitable for refrigerated liquids such as milk or juice for for films that will be kept cool such as frozen pizza.
These films are customarily made from wood. Think of them as clear paper. Cellophane is the original cellulose based film. They make an excellent substitute for polypropylene film. If properly treated, moisture should not be an issue and the biodegradability is preserved.