Flexible Packaging Terms
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.
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.
Bagginess – 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 – 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.
Chemical Resistance – A materials chemical resistance level is its ability to retain utility and appearance after coming into contact with different chemical agents. A high chemical resistance implies there is no significant activity between the chemical and material when they come into contact.
Co-Extrusion – During co-extrusion processes, there is a simultaneous run of two or more thermoplastic resins into a sandwich-like film. This provides clearly distinguishable layers in the finished product.
Coefficient of Friction (COF)– A coefficient of friction is a measurement that represents the “slipperiness” that plastic films or laminates have.
Coating – A coating is any type of fluid material applied as a thick layer to a substrate material or object.
Corona Treatment – This treatment is able to alter the surface material of plastic to make them more receptive to printing inks.
Cross-Linking – This is a film conversion process where different polymer chains are bound together to create a web structure that increases the finished material’s strength and heat stability.
Curtain Coating – When applying wax or other types of coatings, a material is passed through a free-falling curtain of the fluid that makes the coating. This helps apply a quick and even distribution of the coating to the material.
Cute Edge – The is the uncovered edge of a laminated product. Such edges are often skived and folded back on themselves to seal the cut edge.
Delamination – Delamination is the separation of laminate layers caused by a lack of adhesion, or by mechanical disruption through peeling or shearing.
Directionality - The tendency for certain materials to have properties revealed by the flow direction through a machine.
Draw – This is the distance that a web travels between supporting rolls in flexible packaging laminates.
Extrusion Coating – The process of extruding a film or molten polymeric material onto the surface of another substrate. When cooling, it forms a continuous coating.
Extrusion Lamination – The laminating process where separate layers of packaging materials are bonded together by extruding a thin layer of molten synthetic resin, such as polyethylene, between the layers.
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.
Gauge – 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.
Gusset – A gusset is the fold in the side or bottom of a pouch that allows it to expand when contents are inserted.
HDPE – This stands for high density polyethylene. High-density poly has greater stiffness, temperature-resistance, and water vapor protection. But the material is considerably hazier.
Heat-Seal Coating – This is an adhesive coating that’s applied to a packaging material that is capable of being activated by heat and pressure to form a bond.
Heat-Seal Layer - A heat sealable layer embedded in plastic packaging films and laminates. Can be adhesive laminated or extrusion coated onto a non-sealable film or foil.
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.
Laminate – A product that is made by bonding together two or more material layers. Or, to unite layers of a material to produce a multilayer material.
Laminated Film - An adhered combination of two or more films or sheets made to improve overall characteristics. Also known as a multilayer film.
Lap Seal – A special seal made using two overlapping layers of film. Lap seals require less material than fin seals, so many packaging companies are converting to lap seals for sustainability purposes.
Laser Scoring – Using a high-energy light beam to partially cut a material in a straight line or special shape. This process is used to provide and easy-opening feature to various types of flexible packaging, known as a perforation.
LDPE – This refers to low-density polyethylene. It’s used mainly for lightweight packaging that needs a durable heat seal.
Lidding/Lidstock – A material that is used to form a lid, for example, anything that can be heat-sealed over open ends of a pharmaceutical blister card.
Light Resistance – The ability of a given material to withstand exposure to light, such as sunlight or ultraviolet rays, without changing in color or physical properties.
LLDPE – This term refers to linear low-density polyethylene. LLDPE is considered stronger than LDPE and has a better heat-seal strength. Although, this material has a higher degree of haziness.
Metallize – To metallize something is to apply a thin metal coating to a nonmetallic surface by chemical deposition or exposing the material to vaporized metal particles in a vacuum chamber.
Moisture Vapor Transmission Tate (MVTR) – The speed at which moisture transfers between a material. Usually measured at 100 percent relative humidity and expressed in grams per 100 square inches over 24 hours.
Off-Cut – 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.
Optics – Optics refers to any visual properties of a film, such as clarity, gloss, haze, or opacity.
Orientation – Orientation is the process of mechanically stretching plastic films to produce a straightening and alignment of the molecules in the stretch direction. If done only in one direction, it’s said to be uniaxially oriented. If done in two directions, it would be biaxially oriented.
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.
Polyethylene Film (PE) - Polyethylene is by far the most popular packaging film family, and is available in high density, low density, linear low density, and metallocene variations.
Polyolefin – 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.
Pouch – 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.
Primer Coat – Primer coats are applied to a given material for the purpose of improving a following process, such as ink acceptance or adhesive bonding.
Polyvinylidene Chloride (PVDC) – This material provides excellent oxygen and water vapor barrier properties, but is not extricable, therefore it is found usually as a coating to improve other plastic films’ properties.
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.
Retort – 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.
Slip – The ability of film to move easily over hard plastic, metal, or ceramic platforms or against another piece of film.
Splice – Joining two pieces of web material to form a continuous web.
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.
Surface Print – A process where ink is deposited right onto the outermost surface of a packaging material. This is commonly used for short runs of printing. Sometimes, an additional UV coating may be added to give a harder exterior finish that prevents ink from flaking or chipping.
Tear Resistance – The ability of a film to resist the propagation of a tear.
Tensile Strength – How much pull a film can withstand without tearing apart or stretching too far.
Thermoforming – A way to form plastics where a plastic sheet is heated to a point where it is soft and malleable.
Threading – The process of pushing and pulling web material through the various rolls and stations of any web-fed press, such as printing or laminating in preparation for production.
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.
Tie Layer – A material that bonds two incompatible layers in a coextrusion.
Transverse Direction (TD) – The specific direction that is perpendicular to the machine direction.
Tunneling – A laminating defect caused by incomplete bonding of the substrates.
Vapor Barrier – A layer of material through which water vapor will pass only slowly, or not at all.
Water Vapor Transmission Rate (WVTR) - A measure of the rate of water vapor transmission through a material. Usually measured at 100% relative humidity, expressed in grams per 100 square inches over 24 hours. Also see MVTR.
Web – A continuous length of paper film, foil, or other flexible material as it is unwound from a roll and passed through a machine.
Zipper Pouch - A type of flexible pouch with a molded-in-place sealing device, such as a string zipper or slide-seal zipper.