Packaging Glossary

This packaging glossary explains common terms, materials, and processes used across the packaging and sealing industry. It is designed to help buyers, engineers, and operators understand technical language commonly used when specifying packaging machinery, materials, and sealing methods. Whether you are selecting equipment, comparing packaging formats, or reviewing specifications, these definitions provide clear, practical explanations to support informed decision-making.

Adhesive Lamination

A laminating process in which individual layers of multi-layer packaging materials are laminated to each other with an adhesive.

AL

Aluminium Foil. A thin gauge (6–12 microns) aluminium foil laminated to plastic films to provide maximum oxygen, aroma and water vapour barrier properties. Although it is by far the best barrier material, it is increasingly being replaced by metallised films (see MET-PET, MET-OPP and VMPET) because of cost.

Band Sealer (Continuous or Rotary Sealer)

The band sealers are easy to use and once the temperature and conveyor speed have been set then the sealer can operate for long periods of time. The maximum speed is normally limited by the speed an operator can feed the sealer; you may be able to achieve more than 12 bags per minute (5000+ per day). Rotary continuous band sealers are designed for pre-made, single or multi-layer plastic bags including foils and craft paper laminate.

Biaxial Orientation

Orientation of plastic films in both machine and cross machine directions by stretching. Biaxially stretched films are generally well balanced in both directions and much stronger in terms of tear strength.

Blown Films

Plastic films produced from synthetic resins (such as polyethylene) by the blown process. In this process, the molten resin is extruded through a circular die into a tube. This tube is expanded (“blown”) by internal air pressure into a larger bubble with a much reduced wall thickness and cooled with external air quenching.

BON

Biaxially oriented nylon film, with excellent oxygen and aroma barrier properties (see Nylon), but it is a poor water vapour barrier. BON is much stiffer than cast nylon film, but cannot be thermoformed.

CAN

Cast nylon film (see Nylon). Used mostly for thermoformable packaging applications.

CAPP or CPP

Cast PP film (see PP). Unlike OPP, it is heatsealable, but at much higher temperatures than LDPE, thus it is used as a heatseal layer in retortable packaging. It is, however, not as stiff as OPP film. (PP = polypropylene)

Cast Film

Plastic film produced from synthetic resins (such as polyethylene) by the cast process. In this process, the molten resin is extruded through a slot die onto an internally cooled chill roll.

Coffee Valve

A pressure relief valve added to coffee pouches to allow natural unwanted gasses to be vented whilst maintaining the freshness of the coffee. Also called an aroma valve as it allows you to smell the product through the valve.

Coextrusion

Simultaneous extrusion of two or more different thermoplastic resins into a sandwich-like film with clearly distinguishable individual layers.

COF

Coefficient of friction, a measurement of “slipperiness” of plastic films and laminates. Measurements are usually done film surface to film surface. Measurements can be done to other surfaces as well, but not recommended, because COF values can be distorted by variations in surface finishes and contamination on test surface.

Doy Pack (Doyen)

A stand-up pouch that has seals on both sides and around the bottom gusset. In 1962, Louis Doyen invented and patented the first soft sack with an inflated bottom called Doypack®. Although this new packaging was not the immediate success hoped for, it is booming today since the patent has entered the public domain. Also spelt: Doypak, Doypac, Doy pak, Doy pac.

Direct Heat Sealer or Constant Heat Sealer

The jaws are heated to a preset temperature; these sealers are used for thicker material and foil based material.

EAA

Ethylene acrylic acid copolymer. Because of its excellent adhesion to aluminium foil, it is mostly used for extrusion lamination of foil to other surfaces.

Extrusion Lamination

A laminating process in which individual layers of multi-layer packaging materials are laminated to each other by extruding a thin layer of molten synthetic resin (such as polyethylene) between the layers.

EVA

Ethylene-Vinyl Acetate copolymer. Much softer and clearer than LDPE or LLDPE and has lower melt temperature. Its melt temperature goes down, while its softness increases with increasing vinyl acetate (VA) content. EVA resins with 2–18% VA content are used for cast and blown packaging films.

EVOH

Ethylene-Vinyl Alcohol copolymer, used in co extruded plastic films to improve oxygen barrier properties. It is, however, a poor water vapour barrier. Even its otherwise excellent OTR (oxygen transmission rate) is sensitive to high humidity, therefore, for packaging applications, it is usually the core layer of co extruded plastic films, where it is shielded from moisture by protective layers of polyethylene. Its OTR also depends on its VOH (vinyl alcohol) content.

Fill and Seal Machines

Packaging machines which combine the functions of filling and closing in one machine.

Flat-Bottom Stand-up Pouch

A stand-up pouch that is made from one piece of film. The front, gusset, and back are continuous, so there is no seal at the gusset. Holds more weight than Doy-style pouches, so are commonly used for heavy products.

Flexo (Flexography Printing)

Method of printing on a web press using rubber or plastic plates with raised images. Also called aniline printing because flexographic inks originally used aniline dyes. Abbreviated flexo.

Foil (AL)

A thin gauge (6–12 microns) aluminium foil laminated to plastic films to provide maximum oxygen, aroma and water vapour barrier properties. Although it is by far the best barrier material, it is increasingly being replaced by metallised films (see MET-PET, MET-OPP and VMPET) because of cost.

Form, Fill and Seal Machines

Packaging machines which form, fill and seal a package in the same machine.

Gravure Printing (Rotogravure)

With gravure printing an image is etched on the surface of a metal plate, the etched area is filled with ink, then the plate is rotated on a cylinder that transfers the image to the film or other material. Gravure is abbreviated from Rotogravure.

Gusset

The fold in the side or bottom of the pouch, allowing it to expand when contents are inserted.

Gas Flush

Gas flush consists of an inert gas such as nitrogen, carbon dioxide, or exotic gases such as argon or helium which is injected and frequently removed multiple times to eliminate oxygen from the package. This technique is called MAP (Modified Atmosphere Packaging). Most common applications for MAP include coffee, snack foods, pre-baked products, meat and poultry, as well as other more sophisticated applications.

HDPE

High density (0.95–0.965) polyethylene. Has much higher stiffness, higher temperature resistance and much better water vapour barrier properties than LDPE, but it is considerably hazier.

Heatseal Layer

A heatsealable innermost layer in plastic packaging films and laminates. Can be either adhesive laminated or extrusion coated onto a non-sealable film (or foil).

Heatseal Strength

Strength of heatseal measured after the seal is cooled (not to be confused with “hot tack”, see next item).

Hot Tack

Strength of heat seal measured before the seal is cooled, which is very important for high-speed packaging operations.

Impulse Sealer

Also known as a heat sealer or a plastic bag sealer. These units use an electrical current passed through a Ni-Chrome wire heating element to seal bags and tubing. Can be used on many plastic materials to create strong permanent welds. The heat is applied for a pre-set period set on a timer dial and when not in use no heat is applied.

LDPE

Low density (0.92–0.934) polyethylene. Used mainly for heatsealability and bulk in packaging.

LLDPE

Linear low density polyethylene. Tougher than LDPE and has better heatseal strength, but has higher haze.

MDPE

Medium density (0.934–0.95) polyethylene. Has higher stiffness, higher melting point and better water vapour barrier properties.

MET-PET

Metallised PET film. It has all the good properties of PET film, plus much improved oxygen and water vapour barrier properties. However, it is not transparent. See also VMPET.

MET-OPP

Metallised OPP film. It has all the good properties of OPP film, plus much improved oxygen and water vapour barrier properties (but not as good as MET-PET).

Monoaxial Orientation

Orientation of plastic films by stretching in one direction (machine or cross machine direction) only. These films are generally much stronger and stiffer, but have very poor tear strength in the direction of orientation.

MVTR

Moisture vapour transmission rate, usually measured at 100% relative humidity, expressed in grams/100 square inches/24 hours (or grams/square meter/24 Hrs.). See WVTR.

Mylar™

Mylar is a registered trademark of the Dupont-Teijin Corporation. It is the industrial brand name for that corporation’s polyester (PET) film. Polyester film is a staple of multi-layer packaging for a wide variety of applications.

Nitrogen (N2)

An inert gas used to exclude air, particularly oxygen. It is also used as a filler gas to make up the difference in a gas mixture, to prevent the collapse of packs containing high-moisture and fatty foods, caused by the tendency of these foods to absorb carbon dioxide from the atmosphere. For modified atmosphere packaging of dried snack products 100% nitrogen is used to prevent oxidative rancidity improving shelf life. Many vacuum sealers include a gas flush option where the oxygen is removed and refilled with nitrogen.

NY (Nylon)

Polyamide resins, with very high melting points, excellent clarity and stiffness. Two types are used for films: nylon-6 and nylon-66. The latter has much higher melt temperature, thus better temperature resistance, but the former is easier to process, and it is cheaper. Both have good oxygen and aroma barrier properties, but they are poor barriers to water vapour. Also, nylon films can be cast (see CAN), or oriented (see BON).

Opacity

Hiding power of pigmented (mostly white) plastic films. It is beneficial for packing materials sensitive to light (visible or ultraviolet).

OPP

Oriented PP (polypropylene) film. A stiff, high clarity film, but not heatsealable. Usually combined with other films (such as LDPE) for heatsealability. Can be coated with PVDC (polyvinylidene chloride), or metallised for much improved barrier properties.

OTR

Oxygen transmission rate. OTR of plastic materials varies considerably with humidity, therefore it needs to be specified. Standard conditions of testing are 0, 60 or 100% relative humidity. Units are cc./100 square inches/24 hours (or cc/square meter/24 Hrs.). (cc = cubic centimetres)

PP

Polypropylene. Has much higher melting point, thus better temperature resistance than PE. Two types of PP films are used for packaging: cast (see CAPP) and oriented (see OPP).

PE

Polyethylene; depending on its density, it may be low density (see LDPE), medium density (see MDPE), or high density (see HDPE).

PET

Polyester (Polyethylene Terephtalate). Tough, temperature resistant polymer. Biaxially oriented PET film is used in laminates for packaging, where it provides strength, stiffness and temperature resistance. It is usually combined with other films for heat sealability and improved barrier properties.

Pillow Pouch (Three Side Weld)

A pouch made from two pieces of film, sealed on three sides leaving one side open. This has no gusset.

PMS Number

The Pantone Matching System is the universally accepted colour definition system. Colours can be blended or individually specified to match a specified Pantone reference colour exactly.

PVC

Polyvinyl chloride. A tough, stiff, very clear film. The oriented version is used mainly for shrink film applications.

PVDC

Polyvinylidene chloride. A very good oxygen and water vapour barrier, but not extricable, therefore it is found primarily as a coating to improve barrier properties of other plastic films (such as OPP and PET) for packaging. PVDC coated and “saran” coated are the same.

Release Coating

A coating applied to the non-sealing side of cold-sealable packaging films and laminates supplied in a roll form that will allow the packer to unwind these films or laminates on packaging machines.

Retort

The thermal processing or cooking packaged food or other products in a pressurized vessel for purposes of sterilizing the contents to maintain freshness for extended storage times. Retort pouches are manufactured with materials suitable for the higher temperatures of the retort process, generally around 121°C.

Reverse Printing

The majority of all products are reverse printed. In this case, the outermost layer is printed on the backside and laminated to the rest of the multi-layer structure. While not mandatory in all industries, it is the preferred method for the food industry as it guarantees there will be no ink contact with the food product.

Rotogravure Printing (Gravure)

With gravure printing an image is etched on the surface of a metal plate, the etched area is filled with ink, then the plate is rotated on a cylinder that transfers the image to the film or other material. Gravure is abbreviated from Rotogravure.

Side-Gusset Pouch

A pouch with gussets on both sides, with a fin-seal running from top to bottom and sealed horizontally at the bottom and the top. Commonly used in the coffee industry.

Spout Pouch

A recloseable or resealable pouch produced with a weld spout and a cap which allows for recloseablility in a flexible package, particulary appropriate for liquids. Many forms and sizes of caps and spouts are available.

Surface Print

The process where by the ink is deposited directly onto the outermost surface of the packaging film or material. The process is most commonly used in short run printing. A UV (ultraviolet) coating may be added to provide a hard exterior finish that prevents the ink from flaking or chipping.

Stand-up Pouch

A pouch that has seals on both sides and around the bottom gusset having the ability to stand up. See Doy Pack.

Three Side Weld Pouch

(Pillow) A pouch made from two pieces of film, sealed on three sides leaving one side open. This has no gusset.

Trap Print

Another term for Reverse Printing (see Reverse Printing). Trap printing derives its name from the fact that the ink is trapped between the outer layer of material and the substrate.

Vacuum Sealer

Vacuum bag heat sealing machines serve a host of purposes and allow you to safely package food, pharmaceutical goods and other materials into tightly-sealed bags with the air removed from the inside. There are many different vacuum bag sealing machines on the market to suit a wide range of requirements and budgets; they are often referred to as vacpackers or vacsealers.

Vacuum Sealer Types

These vacuum sealer machines fall into two main categories: internal or chamber vacuum sealers (the bag is placed inside the chamber where the air is removed using a vacuum pump, ideal for smaller, wet, dry or liquid products) and external (nozzle or probe type) machines (ideal for larger plastic bags; more suitable for dry products but not for liquids).

VMPET

VacuumMetallised PET film. It has all the good properties of PET film, plus much improved oxygen and water vapour barrier properties.

Weld Spout

See Spout Pouch.

WVTR

Water vapour transmission rate, usually measured at 100% relative humidity, expressed in grams/100 square inches/24 hours (or grams/square meter/24 Hrs.). See MVTR.

Zip Top Pouch

A recloseable or resealable pouch produced with a plastic track in which two plastic components interlock to provide a mechanism that allows for recloseablility in a flexible package.