Flexible Packaging Glossary
Adhesive Lamination
The process by which two or more layers of barrier films are joined together using a bonding agent or adhesive. The adhesive is applied to the less absorbant of the two substrates.
Barrier Films
Specially engineered plastic films used in flexible packaging. Common films used are polyester (PET), Polypropylene (BOPP, CPP), Polyethylene (LLDPE), Nylon; occasionally, metallized films employing a thin layer of aluminum on one side are used for enhanced barrier properties.
Biaxially-Oriented
Characteristic of a plastic film where it is stretched in both primary orthogonal directions, namely the machine (in-line) and transverse (perpendicular) directions. This stretching improves and uniforms mechanical properties (such as tear strength) throughout the film.
Biaxially-Oriented Polypropylene (BOPP or OPP)
A polypropylene film that’s been stretched in both directions (“biaxial orientation”) for both improved and more uniform properties; also known as Oriented Polypropylene.
Blown Film Extrusion
The most common method to produce a variety of plastic films. In the process, molten plastic resins are extruded through a tube into the shape of a very thin bubble and subsequently guided through rollers while being cooled by the surrounding air.
Cast Polypropylene (CPP or CAPP)
A glossy polypropylene film with excellent heat resistance and heat sealable properties. Commonly used as the main heat seal layer in retort packaging.
Cast Film Extrusion
The plastic film manufacturing method by which molten plastic resins are extruded direclty through chilled rollers, locking their configuration and and properties in place.
Cold Seal
A method of sealing flexible packaging by pressure only, without the application of heat. Cold Sealing requires a special adhesive coating on the sealing layers. This method is commonly employed for packaging items such as chocolate or ice cream, when using heat would melt or otherwise negatively affect the product.
Coextrusion
The extrusion of two or more layers of films at the same time to create a single film. The process starts with two different molten resins and results in an indistinguishable laminate with properties distinct from those of its components.
Extrusion Lamination
A lamination process that doesn’t use an adhesive bonding agent. Instead, a layer of extruded molten plastic known as a “tie layer,” usually polyethylene, acts as the bonding agent between the two layers. Extrusion Lamination is less common than adhesive lamination in food and beverage applications.
EVOH
Ethylene-Vinyl Alcohol copolymer, a coating used for its excellent oxygen barrier properties. It is poor at preventing water vapor transmission, however, and therefore the oxygen barrier properties can be compromised at high humidity levels. For this reason alone, EVOH is usually sandwiched in between co-extruded films.
Flat-Bottom Pouch or Side-Gusseted Bag
A type of flexible package that resembles a box as it sits completely flat. Flat Bottom Pouches typically have side gussets to provide balance and structural support. They are commonly used to package coffee beans.
Flat Pouch or 3-Side-Seal Pouch
Also known as a 3-side-seal pouch, which has no gussets. A cost-effective pouch containing no gussets. Flat Pouches use a very minimal amount of film and are thus economical. They are generally used to package single serve products and products that aren’t susceptible to damage due to flexing or bending such as beef jerky.
Flexographic Printing
A versatile printing method dating back to the late 1800s that uses rubber printing plates engraved with a positive mirrored image. Very common in North America, although the resulting print has a lower color density when compared with that produced by rotogravure. Technological advances have dramatically improved flexographic print quality, but rotogravure still remains the gold standard for printing on flexible packaging.
Foil
An aluminum foil layer used in the laminate structure when the most stringent barrior properties are required. Many applications avoid foil by using metallized films when barrier characteristics are only slightly greater than what plastic films alone can offer. Foil is different from metallized film in that it is a separate layer in the overall laminate structure composed of aluminum. Metallized film, on the other hand, is plastic film that’s simply been coated with a very thin layer of aluminum.
Form, Fill, & Seal or FFS
A single process by which printed rollstock is simultaneously converted into a pouch or bag, filled with the contents, and sealed shut so that it is ready for the store shelf. Common for products such as chips bags.
Gusset
A structural element consisting of “extra” material that provides reinforcement on a corner or seam of a body. In the case of a flexible pouch, a gusset is the extra material that folds inwards creating a wider edge, such as at the bottom of a stand up pouch.
Heat Seal
A method of sealing flexible packaging by application of both heat and pressure. Heat Sealing requires that the appropriate layers of film have a low enough melting point so that the plastic softens and a seal can be initiated. The packaging is then cooled to allow the layers to set.
Heat Seal Strength
Strength of a heat seal after it’s been cooled; this is the final seal strength of the ultimate package.
Hot Tack
Strength of a heat seal before it has been cooled; this information is necessary in high-speed packaging applications where there is concern of a seal opening during the process.
K-Bottom Gusset
The most common bottom gusset style in a stand up pouch; the seals are angled up at the corners such that it looks like the letter “K.”
Laminate or Laminate Structure
The sandwich of barrier films laminated together by either an adhesive or extrusion process, to be formed into either a flexible pouch or other package.
Linear Low-Density Polyethylene or LLDPE
A tough, puncture- and tear- resistant copolymer with excellent heat seal properties. Commonly the inner layer of flexible packaging.
Metallized Polyester or MetPET
A polyester film coated with a thin layer of aluminum through a metallization process. Metallization uses physical vapor deposition (PVD), a process where the aluminum is heated and evaporated in a vacuum which subsequently condenses on the polymer. The coating thickness is on the order of 2 gauge (0.5 microns), significantly thinner than a layer of foil.
Metallized Oriented Polypropylene or MetOPP
A BOPP film coated with a thin layer of aluminum through a metalization process. Metallization uses physical vapor deposition (PVD), a process where the aluminum is heated and evaporated in a vacuum which subsequently condenses on the polymer. The coating thickness is on the order of 2 gauge (0.5 microns), significantly thinner than a layer of foil.
Nylon
A polymer with high temperature resistance, excellent oxygen barrier properties, stiff mechanical properties, and great clarity. Nylon has poor water vapor transmission rates, thus susceptible to moisture ingress.
Opacity
The property relating to light or UV barrier. Clear plastic films are coated with white or colored pigments to achieve high opacities.
Oxygen Transmission Rate or OTR
The property relating to oxygen or air permeation, commonly measured in cc/100 in2/24 hours and cc/m2/24 hours. OTR is highly sensitive to ambient humidity levels, so it’s usually reported for a variety of moisture conditions (generally 0%, 60%, and 100% relative humidity).
Polypropylene or PP
A thermoplastic polymer with excellent temperature resistance and high melting point. Used in flexible packaging in the form of BOPP or CPP.
Polyethylene or PE
The most widly used plastic in the world, PE is a polymer of ethyelne and is used in all kinds of packaging applications. In flexible packaging, it’s mostly used in the form of LLDPE film.
Polyester or PET
A very versatile plastic with great toughness and temperature resistance. Used for textiles, packaging, and other applications, in flexible packaging PET is usually an oriented film that’s laminated with other materials to form laminate structures for pouches, bags, etc.
Plow-Bottom Gusset
A bottom gusset style on a stand up pouch where there is no bottom seal. This style of pouch relies on the weight of its contents to stably stand up, and is thus well suited for heavier products and granular contents such as salts, sugars, seeds, etc.
Polyvinylidene chloride or PVDC
A polymer with with excellent oxygen and moisture barrier properties. Since PVDC cannot be extruded, however, it’s applied as a coating on flexible packaging to improve barrier properties of films such as PET and BOPP.
Roll Stock
Generally refers to printed and laminated flexible packaging film that’s wound up in roll form. All flexible packaging products—whether pouches, bags, granola bar wrappers, etc.—are in roll stock form at some point. Customers with in-house form, fill, & seal (FFS) processes will procure their flexible packaging in rollstock form.
Rotogravure Printing
The printing process where engraved copper plated steel cylinders rotate in a pool of ink and translate the image onto a substrate. The engraved image is a negative mirror impression, and the print quality is regarded as the most superior in the flexible packaging industry today.
Round-Bottom Gusset or Doyen Style
A gusset on a stand up pouch featuring a curved seal profile on the front and back sides of the bottom edges. Commonly used for packaging light products, liquid products, and ideal for pouches that should be shorter in height relative to width.
Stand Up Pouch
One of the most popular forms of flexible packaging, becoming increasingly prominent and used to package a variety of products in several industries. They feature bottom gussets allow them to stand up on their own when filled with product.
Water Vapor Transmission Rate or WVTR
The property relating to moisture permeation, commonly measured in cc/100 in2/24 hours and cc/m2/24 hours. Usually reported at 100% humidity.
Round-Bottom Gusset or Doyen Style
A gusset on a stand up pouch featuring a curved seal profile on the front and back sides of the bottom edges. Commonly used for packaging light products, liquid products, and ideal for pouches that should be shorter in height relative to width.