Flexible Packaging Glossary

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These flexible packaging terms will help you navigate this newer industry like a professional. Take a look at our list of important terminology below to become more familiar with the lingo of the flexible packaging industry.


Adhesive lamination

A type of lamination where adhesive is used to bond films together.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.


Primarily used for pharmaceutical blister packaging, Aclar is the trade name for PCTFE (polychlorotrifluoroethylene polymer). This polymer is rigid, clear and easily thermoformable with good oxygen and moisture barrier properties.

Air Gap

 An air gap is considered to be the distance from the die lips of a polymer-melt extruder and the chill roll.

Anilox Roll

This is the engraved ink metering roll that’s used in flexographic presses to provide a controlled film of ink to the printing plate for transferring onto the material.



While processing flexible packaging materials, there can be slack areas in the film that should be flattened. This is usually caused by unequal thickness in the roll stock. This can also be caused when the material is stretched or permanently elongated.


Barrier packaging is able to stop or retard the passage of atmospheric gases, water vapor, and aroma ingredients. These materials are designed to prevent the diffusion of water, oils, water vapor, or certain gases into the bag or container. Barrier materials may serve to exclude or retain such elements without or within a package.

Biaxial Orientation

Biaxial orientation refers to the orientation of plastic films in machine and cross machine directions by stretching. Biaxially stretched films are more durable in all directions, making them resistant to tearing and ripping.


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.


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.


A polypropylene film that’s been stretched in both directions (“biaxial orientation”) for both improved and more uniform properties; also known as Oriented Polypropylene.


The area where ink extends into the slit area to provide a clean edge on a finished impression.

Blister Packaging

Blister packaging contains the product between a formed dome and a flexible surface or paperboard.

Blown films

Plastic films produced from synthetic resins (such as polyethylene) using a process where 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 reduced wall thickness, and then cooled with external air quenching.

Burst strength

A measurement of the ability of a pouch to resist rupturing when pressure is applied to it.

Burst testing

A test where pouches are exposed to internal pressure until the point of bursting to verify that seals are fused together on the molecular level.



The bottom part of a fitment designed for adhesion with the flexible packaging material of a spouted pouch.

Cast Nylon Film (CAN)

This film is primarily used for thermoformable flexible packaging products.

Coefficient of friction (CoF)

A measurement of how slippery a film is.


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.


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.


A cylinder around which packaging film is wound.


Die line

The layout or blueprint used for creating flexible packaging film or premade pouch graphics.

Doyen pouch (also known as a Doypack)

See “Doyen seal”.

Doyen seal

A type of U-shaped, bottom-gusset seal commonly found on stand-up pouches. A Doyen seal is typically used for liquids or lightweight products. Stand-up pouches with Doyen seals are typically referred to as Doyen pouches or Doypacks.


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.

Drop testing

A test typically performed on pre-made pouches that hold liquids. This test measures the height at which a filled pouch can be dropped and stay fully intact.


Extrusion lamination

A type of lamination where a curtain of molten polyethylene (PE) is used to bond films together.

Eye mark

A printed mark used to control repeat registration.



Raw material that can be made of a variety of different materials, but typically polyethylene. It can be printed, folded, cut, sealed, etc. to create custom flexible packaging options (bags, sheets, etc.)

Fill and seal machine

Also known as “fill/seal,” a machine that fills and seals pre-made pouches.

Fin seal

A type of seal where the inside layer is sealed to itself.


The area of a spout that bonds with flexible packaging film on a spouted pouch. This term is often used interchangeably with “spout.”

Form/fill/seal (FFS) machine

A machine that uses flexible packaging rollstock to form a pre-made pouch, then fills the pouch with product, and finally seals the 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.


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.


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.

Flexible Packaging

This represents are large part of the packaging industry involving various containers that are made of flexible or easily yielding materials. When filled and sealed, they can be readily changed in shape. Typically, flexible packaging is used to describe bags, pouches, or wraps made of materials ranging in thickness, such as plastic film, foil, or paper.

Form-Fill-Seal (FFS)

This kind of machine performs three important packaging operations, which is to form the bag or container being used, fill it with the product, and seal the package before it’s boxed or bundled. Flexible packaging is fed to the machine on a continuous roll and the final seal is created with heat. Machines can be configured so that the stock travels horizontally through the machine or vertically.

Four-Side-Seal Pouch

This is a flexible pouch with seals along all four edges. They can be made from a single stock or the front and back materials can be different. These pouches are commonly made on multilane pouch-forming machines where multiple pouches can be placed across the width of the web.


Gas Transmission Rate (GTR)

The quantity of a given gas passing through a unit area of the parallel surfaces of a film, sheet, or laminate in a given time under the test conditions. Test conditions may vary and must always be stated.


The thickness of a film or flexible packaging structure (typically expressed in mils). Gauge represents the thickness of a given material. American businesses measure thickness in Mils while European businesses use microns. A quick equivalency equation is: 1 mil = 25.4 microns.


A fold along the bottom, top, and/or sides of a premade pouch that allows the pouch to expand when filled with product.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.



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

The measurement of strength of a heat-seal AFTER it has cooled. Not to be confused with a Hot Tack, which is mentioned below.

Hermetic Seal

This is an airtight seal that is impervious to gases and fluids under normal conditions of handling and storage.

High Barrier

Describes a material or package that has very low gas permeability characteristics; that is, it offers a great deal of resistance to the passage of a gas through its volume.

Hot Tack – The strength of a heat seal measured before the seal finished cooling. This is important to know when working in high-speed packaging operations where the packaging may be moved before the seal can finish cooling.

Hooded slider

A slider positioned under a hermetically sealed film header, providing additional tamper evidence.

Horizontal form/fill/seal (HFFS)

A type of packaging line most commonly used for solid products, in which flexible packaging rollstock is formed, filled with product, and sealed.


Inno-Lok® bag

A bag with a built-in press-to-close zipper closure. Inno-Lok® pouches look like premade pouches, but they are actually created on vertical form/fill/seal (VFFS) machinery using Inno-Lok® pre-zippered film.



A type of bottom gusset with a seal shaped like a K. It’s commonly incorporated into stand-up pouches containing non-liquid products.


Lamination bond

The strength of the bond between two or more films measured in grams on a tensile tester.

Lap seal

A type of seal where the inside layer is sealed to the outside layer.

Laser perforating

A method of using lasers to create tiny perforations that facilitate oxygen and carbon dioxide exchange, extending the shelf life of certain items or allowing packaging to release moisture. Laser perforations can penetrate either partially or fully through the flexible packaging structure, depending on the desired breathability of the film.

Laser score or laser scoring

A method of using lasers to create a score line or pattern in flexible packaging material (while leaving the barrier layer intact), allowing the consumer to easily tear open the premade pouch along the line of laser scoring. This is typically accompanied by a tear notch.


Modified Atmosphere Packaging(MAP)

Modified atmosphere packaging (MAP) is a packaging system that involves changing the gaseous atmosphere surrounding a food product inside a pack, and employing packaging materials and formats with an appropriate level of gas barrier to maintain the changed atmosphere at an acceptable level for preservation of the food.

Matte and gloss pouch

A pouch printed with registered matte/gloss effects. This technique uses a registered matte varnish contrasting with high-gloss areas.


Number across

The number of lanes of impressions being printed at one time.

Nylon films

A material commonly used in flexible packaging structures to add strength and puncture resistance.



This is a trimmed section of material that is not used. In flexible packaging, a small amount of material can be left over after a full roll is cut to the desired length. This can sometimes be called a butt roll.

Oriented polypropylene (OPP) films

A multilayer material commonly used in flexible packaging with advanced seal properties and barrier properties. Non-cavitated films typically have a gauge of .5 to 1.2 mils. OPP can be metallized, matte, clear, or white.

Oxygen Transmission Tate (OTR)

The OTR of a given material varies considerably with the humidity level of where it’s stored, therefore it needs to be measured and recorded. Standard conditions of testing around 100 percent relative humidity. OTR is measured in cc/100 swuare inches over 24 hours. (cc = cubic centimeters)


Pillow Pouch

A pillow pouch is a specific type of bag or pouch that is formed with a tube of material sealed on both ends. Pillow pouches are commonly produced on a vertical form-fill-seal machines and are characterized by the seals created across the top and bottom of the bag. Sometimes, there is also a longitudinal seal that goes down the center of the bag faces.


A substrate that transfers ink onto the flexible packaging film.


This is a family name for polymers (plastics) derived by ethylene and propylene, such as polyethylene (PE) and polypropylene (PP).

Polypropylene Film (PP)

This unoriented film type is flexible and clear, but becomes stiff at lower temperatures. This property as well as stiffness, strength, and clarity is improved by orientation.

Polyester (PET) films

A stiff, heat-resistant material with good clarity commonly used in flexible packaging. It doesn’t stretch and is ideal for flexographic printing. PET can be metalized, matte, or clear.

Polyethylene (PE) films

Films commonly used in flexible packaging, with a variety of blends available that provide different properties. For example, high-density PE (HDPE) provides stiffness. Low-density PE (LDPE) provides puncture and tear resistance. Ethylene Vinyl Alcohol (EVOH) can be used to add barrier. Mettallocene can be added for clarity, stiffness and strength. PE films can be white or clear.

Print layer

The outer layer of a flexible packaging structure which ink is applied to.

Particle plow slider

A slider designed for powdered or granulated products that clears particles out of the track, allowing the package to reclose properly.


A pouch is considered a small bag that is constructed by sealing one or two flat sheets of material along the edges. There is no clear distinction between a pouch and sachet, other than the common understanding that a sachet is smaller.

Pouch converter

A manufacturer that creates formed premade pouches from flexible packaging material (as well as fitments/spouts if applicable).

Press-to-close zipper pouch

A pouch with a closure consisting of one or more projecting fins inserted into a mating channel. This closure creates a reliable seal when pressed together. Press-to-close zippers are one of the most common stand-up pouch closures.

Puncture resistance testing

A test analyzing how much pressure is required to puncture a flexible packaging structure.


Quad-seal pouch

A flat-bottom stand-up pouch made with two vertical panels and two gussets joined from two vertical seals, all formed from the same web.



How long an impression is in the machine direction.

Reverse print

Printing on the inside of the outer layer of a flexible packaging structure prior to lamination. This protects the printing from scuffing and prevents the need for an overprint varnish.

Release Coating

The release coating is used on the non-sealing side of a cold-sealable packaging film or laminate to allow the packer to unwind the film with ease. It prevents a material from sticking to itself while rolled on a core. This is very important for rolls that enter machines to prevent something from getting stuck.


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


Flexible packaging film in roll form.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.


Seal bond

The strength of a seal measured in grams on a tensile tester.

Sealant layer

Typically the innermost layer of a flexible packaging structure, with sealing properties.


The total combination of films that make up the finished flexible packaging film construction.


The sealed area at the bottom of a K-seal or Doyen gusset, used to make a stand-up pouch more stable.

Slider or slider zipper

A closure with a sliding mechanism positioned along a track with flanged interlocking profiles that create a reliable seal when pressed together by the sliding mechanism.

Slider pouch

A resealable pouch with a slider closure.

Stand-Up Pouch

A flexible pouch design where the bottom portion has been gusseted in such a way that that it provides a wide enough base to provide support so the pouch is able to be stood up for display or use.

Stick Pack

A narrow flexible packaging pouch commonly used to package single-serve powder beverage mixes such as fruit drinks, instant coffee or tea, and sugar or creamer products.


An injection-molded closure with an orifice from which the contents of a pouch are dispensed. Some spouts include valves or additional features that can expand the functionality of a pouch.

Spouted pouch

A pouch with an injected-molded fitment and closure from which the contents of a pouch are dispensed. Spouted pouches can be filled through the top opening of the pouch or through the spout.

Stand-up pouch (SUP)

A type of pouch with gussets or a closure providing a stable base which allows the pouch to stand upright.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.


Tear notch

A notch that serves as a starting point for the consumer to grasp and tear open a package.

Tensile testing

A test that analyzes the amount of force required to destruct a seal.

Three-Side-Seal Pouch

This is a type of pouch formed by folding a material into a U-shape and then sealing the three open sides. The pouch may be made with a gusseted bottom. Three-side-seal pouches are typically made on horizontal form-fill-seal machines.


Vertical form/fill/seal (VFFS)

A type of packaging line most commonly used for granular or loose products, in which overhead scales drop product into a package as it is formed and subsequently sealed.

Vacuum testing

A test performed to ensure that pouches are hermetically sealed. The test typically involves exposing pouches to external vacuum pressure.


Wicketed bag

A bag with two holes at the top that allow the bag to be mounted on wickets (thin metal rods). Wicketed bags can be loaded onto automatic filling machines to ease the loading and sealing process.


Zipper Pouch

A type of flexible pouch with a molded-in-place sealing device, such as a string zipper or slide-seal zipper.