A common question raised by first-time manufacturers or manufacturers launching a new product is what type of flexible packaging film is appropriate for their product. While there is a large variety of films available today, we’ve listed the top 10 that we see used in horizontal form fill seal (flow wrapper) applications. The most popular film for flow wrapping by far is Polypropylene, used in some form in almost 90% of applications.
Polypropylene (PP – OPP) Film
Polypropylene is the most commonly used film for horizontal form fill and seal. It is used to over wrap snack foods, candy, baked goods, etc. The common make-up of this film consists of an outer layer, a polypropylene core and a sealant layer on the interior. The outer layer is commonly acrylic coated to prevent the film from melting on the crimping jaws and also to reduce friction on contacted surfaces.
Polypropylene film over wrap provides a containment seal and protection from dirt and dust. It also provides some degree of protection from moisture and oxygen, but over time this film does allow exchange of atmosphere from inside to outside.
Polypropylene film can come in literally hundreds of laminations depending on your specific needs. Unprinted polypropylene is a clear film that provides complete visibility of the product inside.
Polypropylene film can be supplied with several types of heat seal layers or with a cold seal adhesive layer. Sealant layers such as metallocene, surlyn or EVA melt at lower temperatures than most sealant layers and tend to increase line speeds.
Polypropylene films can be laminated with other materials such as low density polyethylene and used for Modified Atmosphere Packaging or gas flush applications. These gas flush applications require a barrier film and “hermetic” seals. Barrier films will not allow for exchange of atmosphere from the inside of the package to the outside or vice versa. In modified atmosphere packaging the oxygen inside the package is replace with nitrogen, carbon dioxide or a blend of both gases. This inhibits the growth of mold and extends the shelf life of the product inside the package.
Polypropylene film is also available in an opaque film. This film provides a nice white appearance and also provides for very attractive graphics when printed. This film is commonly used for chocolate bars and ice cream treat over wraps. This film can also be either heat sealable or cold seal. The white layer helps to slow product deterioration due to light sources.
A third type of polypropylene film is metalized. This film has a vacuum deposited aluminum layer applied when the film is produced. The metallization of film enhances the film’s ability to protect the product from outside oxygen and moisture. It also provides some degree of protection from light deterioration of the product.
Metalized opp is used for candy bars, breakfast bars and in some applications pharmaceutical applications where it replaces foil laminates.
Most polypropylene films run in a temperature range of 225F – 425F, depending on thickness of film, sealants, coatings and speed.
Polyester (PET) Film
Polyester films are commonly used as an outer layer in laminations with other materials. Polyester has good heat resistance which performs well in high speed applications. This film will not shrink due to high temperature setting like polypropylene will. The polyester layer in a laminate also adds some structure strength to the film.
Light gauged polyester has become the standard over wrap material for toaster pastries. Because of its heat resistance, polyester wrapped products can be heated in microwaves. There is also a variety of polyester that can be used in ovens. This material is used to wrap products such as French bread. It is also used for lidding material on most frozen trayed products. These products can go directly from freezer to oven!
48 gauge polyester along with a sealant layer of LDPE is widely used for moist towelettes and baby wipes.
Polyester films will typically accept temperature settings as high as 500F +.
Polyethylene (PE) Film
Polyethylene film comes in two common versions:
- Low Density Polyethylene (LDPE) commonly used in shrink applications such as pizzas, soap bars for South America and a variety of other shrink bundle applications. LDPE can also run on a fin seal type horizontal wrapper if the film is produced with a sealant layer on the inside. Typically EVA is used for a sealant layer. This film is primarily used for wrapping plastic cutlery, syringes for the pharmaceutical industry and literature over wrap. Sealing temperatures for LDPE with an inside sealant layer are usually in the 225F – 250F range. Linear Low Density Polyethylene (LLDPE) is used in laminations of materials to add tear resistant properties to the finished film structure. It can also be used as a sealant layer in laminated films.
- High Density Polyethylene (HDPE) requires a sealant layer in order to seal on a fin seal type horizontal wrapper. It is used as an outer layer along with LDPE and an EVA sealant layer for wrapping Waffles, crackers and plastic cutlery, to name a few applications. Sealing temperatures for HDPE blends are typically in the 250F -300F range.
Foil laminations are made up of an aluminum alloy sheet sandwiched between another film layer and an inside sealant layer. These laminations can be several layers thick depending on the desired film properties. Thickness of the foil layer can also vary widely.
Foil laminations are used for pharmaceutical products and light sensitive products. The outer layer of a foil lamination may be paper, polyester, nylon and polypropylene or others.
Foil laminates have the highest barrier properties of any material used for over wrap.
Seal temperature for foil laminations can range from 300F-500F depending on thickness, outers layer and sealant layer.
Foil laminations often require extended dwell wrappers to seal properly.
Paper/poly laminations are commonly used wrap gauze bandages. Several frozen food products such as pot pies and burritos are wrapped in paper/poly films. Some manufacturers have added a thin metalized layer to the film; this is called “suseptor” film. The suseptor layer works in the microwave to help brown or promote crispness of the product.
Paper/poly films typically do not run at high rates of speed due to the insulating factor that the paper creates.
Typical heat ranges are 350F – 500F and may require preheat in order to attain line speeds required.
Glassine is a grease resistant paper with an inner sealant layer. It is typically use for fried products such as fruit pies found in vending machines. This type of film is being phased out in favor of other materials that run faster and are not a prone to tearing.
This is a name that has been given to a film that was developed for its superior tear strength properties. It is used for wrapping most chlorine tablets for toilet tank and swimming pool use. This film provides an excellent moisture barrier, but its highest asset is its very high resistance to punctures and tears. These qualities make it child resistant which is a requirement for commercial chlorine products.
This film typically will not seal at speeds above 450 inches per minute. The film also has a very narrow sealing window. This means the temperature window between good seals and melting the film is very narrow!
There are several films that fall into the shrink film category and include films made from polyethylene. Low density polyethylene and linear low density polyethylene films are common along with some polypropylenes. Shrink films can also be made from an ethylene-propylene copolymer and multi-layer polyolefin.
These films are always run on a wrapper using a lap bottoms and a hot knife end seal.
Product wrapped using shrink films are: compact disks, candles, greeting cards, box over wrap and trays of frozen product.
Polyvinyl Chloride (PVC)
Also included in the shrink film category is Polyvinyl Chloride (PVC). PVC is used because of its high clarity and stiffness. It is used in place of polyolefin film where very high clarity is desired.
PVC films are run using a lap seal that is usually a static seal. The end seal is created by a special PVC knife that seals and separated the packages. These films are also used to wrap candles, greeting cards and compact disks.