Flexible Packaging Materials
|BOPP||biaxially oriented polypropylene|
|BON||biaxially oriented nylon|
|EAA||ethylene acrylic acid|
|HIPS||high impact polystyrene|
|LLDPE||linear low-density polyethylene|
|PETG||poly(ethylene terephthalate) glycol|
Trade name for a polychlorotrifluoroethylene (PCTFE) polymer. The polymer has outstanding moisture and excellent oxygen barrier properties, as well as being clear, rigid, and relatively easy to thermoform. Its main packaging application is for pharmaceutical blister packages.
A monomer with the structure ( CH = CHCN). Its copolymers have good gas barrier and chemical resistance properties. Also known as trade name Barex.
The distance from the die lips of a polymer-melt extruder and the chill roll.
Engraved ink metering roll used in flexo presses to provide a controlled film of ink to the printing plates which print onto the substrate.
A thin gauge (.285-1.0 mil) aluminum foil laminated to plastic films to provide oxygen, aroma and water vapor barrier properties.
(a) In processing flexible packaging materials, slack areas in the web that should be flat. Usually caused by bands of unequal thickness (gauge bands) in the rollstock. (b) A roll in which the tension is not even across the width of the roll. A slack floppy area in the web is caused by the material being stretched and permanently elongated in the tighter areas. Rolls of film or laminate where one side of the material coming off the roll is loose or baggy while the opposite edge is tight is said to have a baggy edge.
A trade name for acrylonitrile plastic.
In packaging, this term is most commonly used to describe the ability of a material to stop or retard the passage of atmospheric gases, water vapor, and volatile flavor and aroma ingredients. A barrier material is one that is designed to prevent, to a specified degree, the penetrations of water, oils, water vapor, or certain gases, as desired. Barrier materials may serve to exclude or retain such elements without or within a package.
The original form in which a film exists before coating or laminating.
Orientation of plastic films in both machine and cross machine (transverse) directions by stretching. Biaxial stretched films are generally well balanced in both directions and much stronger in terms of tear strength.
Image or color that extends beyond the trim edge of the finished printed piece.
A package type where the item is secured between a pre-formed dome or “bubble” and a paperboard/flexible surface.
A measure of the ability of a sheet to resist rupture when pressure is applied to one of its sides by a specified instrument under specified conditions.
(a) To join with overlap or space between. (b) Butt register is where two or more colors meet with no significant overlap or space between.
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.
Ability of a material to retain utility and appearance following contact with chemical agents. Chemical resistance implies that there is no significant chemical activity between the contacting materials.
chemical compatibility testing
Any procedure that exposes a material to chemicals or mixtures of chemicals to determine whether such exposure has a negative effect on the material being eva luated.
Simultaneous extrusion of two or more different thermoplastic resins into a sandwich-like film with clearly distinguishable individual layers.
COF (coefficient of friction)
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.
Cast nylon film. Used mostly for thermoformable packaging applications.
Any fluid material applied as a thick layer to a substrate material or object.
The process of translating specific color information from the computer screen image, through prepress, plate-making, printing presses and finally to a substrate in such a manner that color accuracy is maintained at acceptable levels throughout.
The lightness or darkness of a color. A color may be classified as equivalent to some member of a series of shades ranging from black to white. The other two fundamental characterizers of color are hue and saturation.
The ability of a container or material to resist chemical degradation or physical change caused by the product, or where a container or material does not chemically degrade or physically change the contained product.
The ability of a material to be bent or shaped around a form without being damaged or marred in any way.
A treatment to alter the surface of plastics and other materials to make them more receptive to printing inks.
A film conversion technique in which polymer chains are bound into a web or network to increase the web’s heat stability and strength.
A monomer that is mixed with one or more other monomers for a polymerization reaction, to make a copolymer.
The tendency of a paper sheet to curl as humidity conditions change due to the hygroexpansive nature of paper. A paper sheet that is identical in construction on each side will expand and contract as humidity changes with little tendency to curl. However if the sheet is printed, varnished, or laminated to a plastic film or a foil, then the two sides will have different expansion and contraction rates and the paper will curl as the humidity changes from the conditions when the printing, varnishing or laminating were done. The greater the humidity difference, the greater the curl.
A method of applying wax or other coating to a material where the material is passed through a free-falling curtain or film of the fluid coating.
The uncovered edge of a laminated product. For example a high-barrier paper/foil laminate made into a hermetically-sealed carton using lap seals would have an exposed cut edge of paperboard through which oxygen could still permeate into the product. Such edges are often skived and folded back on themselves to seal the cut edge.
ln web-fed processing, the cut or print length corresponding to the circumference of the plate cylinder.
A term used mostly in flexographic printing to describe a single print station with plate, impression cylinders, and inking rolls.
A change or break-down in a material’s chemical structure.
Separation or splitting of laminate layers caused by lack of or inadequate adhesion, or by mechanical disruption such as peeling or shearing forces.
The tendency for certain materials to have properties imparted by the flow direction through a machine.
A physical and/or optical measurement and theoretical calculation of the apparent increase in dot area from one medium to another. Normally expressed as the difference between a midtone (nominal 50%) dot area on a film negative and the printed dot area; for example, a 50% film dot area which prints as a 78% dot has 28% dot gain. Dot gain (and loss) are normal and must be controlled throughout the press and printing process.
ln flexible packaging laminates, the distance that a web travels between supporting rolls.
A swatch of color or coating made by spreading a small amount of ink or varnish across a sheet of material. Made for visual comparison to a standard color swatch or chip.
ethylene acrylic acid (EAA)
EAA is a copolymer of ethylene and acrylic acid. lts ionic nature allows for excellent adhesive bonding to metal foil and other polar surfaces. EAA’s adhesive and toughness qualities are taken advantage of in high performance multi-layer laminates.
ethylene-ethyl acrylate (EEA)
The copolymerization of ethylene with ethyl acrylate produces an ethylene acid copolymer. The polymers are produced with varying percentages of acrylate content, most typically between 15 and 30%. EEA is compatible with all olefin polymers and often is blended with these to modify properties. EEA is used in hot-melt formulations. lt also can be used alone or as a component of heat-sealable coatings where it offers improved toughness at low temperatures, excellent adhesion to nonpolar substrates, and a broad service temperature range. EEA is used as a tie layer between mating laminate films.
ethylene-methyl acrylate (EMAC)
The copolymerization of ethylene with methyl acrylate produces an ethylene copolymer, one of the most thermally stable of the olefin copolymers. The polymers are produced with varying percentages of methyl acrylate content, most typically between 1 8 and 24o/o of the structure. Alone or in blends, it has found applications in film, extrusion coating, sheet, laminating, and co-extrusion.
ethylene-vinyl acetate (EVA)
A polar copolymer of ethylene and vinyl acetate, retaining some of the properties of polyethylene but with increased flexibility, elongation, and impact resistance. EVA is frequently specified as the extrusion coating on polypropylene, aluminum foil and poly(ethylene terephthalate), to provide good heat-seals at high converting rates, or as the adhesion layer in some laminates.
ethylene-vinyl alcohol (EVOH)
Can be regarded as a copolymer of polyethylene in which varying amounts of the -OH functional group have been incorporated. A typical packaging EVOH is about 20 to 35% ethylene. EVOH is one of the best polymeric oxygen barriers available to packagers. However, its susceptibiliÇ to water requires that for most applications it be laminated or co-extruded into a protective sandwich with materials that will keep the EVOH layer away from water.
The process of forming a thermoplastic film, container, or profile by forcing the polymer melt through a shaped orifice.
A process where a film of molten polymeric material is extruded onto the surface of a substrate material and cooled to form a continuous coating.
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.
eye mark register
A printed rectangular mark most often found along the edge of webstock that can be identified by an electric eye. The mark identifies a point on the web where an individual package is to be cut.
Generally used to describe a thin plastic material usually not more than 75 micrometres (0.003 inch) thick.
Any final operation done to packaging before shipping.
A device attached to the container finish to provide a performance function’ For example, a pour-out fitment is plastic component for a glass, plastic or metal package, designed to improve the dispensing action of liquid products.
A package or container made of flexible or easily yielding materials that, when filled and closed, can be readily changed in shape. A term normally applied to bags, pouches, or wraps made of materials ranging in thickness from 13 to 75 micrometres (0.0b0á to 0.003 inch) such as paper, plastic film, foil, or combinations of these.
A method of printing using flexible rubber or photopolymer printing plates in which the image to be printed stands out in relief. Fluid ink metered by an engraved roll is applied to the raised portions of the printing plate and then transferred to the substrate.
A packaging machine that forms, fills, closes and seals a package in one continuous or intermittent-motion operation. Flexible packaging stock fed from a roll is folded to the desired package shape and stabilized by heat sealing. The product is placed into the formed package, and the remaining opening is sealed. Machines can be configured so that the stock travels horizontally through the machine (horizontal form-fill-seal) or vertically through the machine (vertical form-fill seal).
Printing with cyan, yellow, magenta, and black ink (CMYK) using halftone screens to create a full color reproduction.
A pouch with seals along all four edges. Four-side-seal pouches can be made from a single stock or the front and back can be different stocks. The pouches are most commonly made on multilane pouch-forming machines where 16 or more pouches can be placed across the width of the web. gas chromatography An instrumental method of accurately determining the composition of volatile solvents and oils, and their residual presence in materials such as laminates or plastics.
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.
A thickness irregularity found in rolls of film. A thicker area in the machine direction at some location across the width of a flat film will produce a raised ring in a finished roll. Gauge bands can cause winding problems and when unwound, the material tends not to be perfectly flat.
Thickness. In North America, film thickness, measured in mils, is usually given in gauges. A 100 gauge shrink film is one mil, or 1/1000 of an inch, thick. In Europe, the film thickness metric is the micron. A quick equivalency equation is: 1 mil = 25.4 microns.
good manufacturing practice (GMP)
Good manufacturing practice implies that the entire manufacturing procedure has been designed in such a way as to produce a quality product that presents a minimum risk to the consumer. GMP will vary from industry to industry depending on the nature of the product being packaged. Many GMPs have been formalized and are required by law for critical industries such as food and pharmaceutical packaging. Typically these GMPs describe the kind of equipment to be used, its validation, manufacturing procedures, inspection types and frequencies, record keeping, container types and approvals, and registration of company and product.
Gravure is abbreviated from the term rotogravure. During gravure printing an image is etched on the surface of a metal cylinder and chrome plated for hardness. The ink fills the cells and is transferred onto the printing substrate.
The fold in the side or bottom of the pouch, allowing it to expand when contents are inserted
High density, (0.95-0.965) polyethylene. Has much higher stiffness, higher temperature resistance and much better water vapor barrier properties than LDPE, but it is considerably hazier.
An adhesive coating applied to a packaging material that is capable of being activated by heat and pressure to form a bond.
A heat sealable innermost layer in plastic packaging films and laminates. Can be either adhesive laminated or extrusion coated onto a non-sealable film (or foil).
Strength of heat-seal measured after the seal is cooled, (not to be confused with “hot tack”, see next item).
Airtight or impervious to gases or fluids under normal conditions of handling and storage.
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.
Strength of heat seal measured before the seal is cooled, which is very important for high-speed packaging operations.
Also known as a heat sealer. These units use an electrical current passed through a Ni-Chrome wire heating element to seal bags & tubing. Can be used on many plastic materials to create strong permanent welds.
(a) noun A product made by bonding together two or more layers of material. (b) verb To unite layers of material to produce a multilayer material.
An adhered combination of two or more films or sheets made to improve overall characteristics. Also multilayer film.
A seal made with two layers of film overlapping one another. Because lap seals require less material than fin seals, packagers are converting to lap seals in the name of sustainability, lean operations and economics.
Use of high-energy narrow light beam to partially cut through a material in a straight line or shaped patterns. This process is used to provide an easy-opening feature to various types of flexible packaging materials.
Low density, (0.92-0.934) polyethylene. Used mainly for heat-seal ability and bulk in packaging.
Material or stock used to form a lid. For example, material that can be heat-sealed over the open ends of pharmaceutical tablet blister cards.
The ability of material to withstand exposure to light (usually sunlight or the ultraviolet part of the light spectrum) without change of color or loss of physical and/or chemical properties.
Linear low density polyethylene. Tougher than LDPE and has better heat-seal strength, but has higher haze.
The ability of a film to run on packaging equipment.
machine direction (MD)
The direction that film moves through the packaging equipment.
Permissible variations from rated or marked capacities or dimensions established by standards or specifications for those.
Medium density, (0.934-0.95) polyethylene. Has higher stiffness, higher melting point and better water vapor barrier properties.
Appying a thin coating of metal to a nommetallic surface by chemical deposition or by exposing the surface to vaporized metal in a vacuum chamber.
Metalized OPP film. It has all the good properties of OPP film, plus much improved oxygen and water vapor barrier properties, (but not as good as MET-PET).
Metalized PET film. It has all the good properties of PET film, plus much improved oxygen and water vapor barrier properties. However, it is not transparent. see also VMPET.
moisture vapor transmission rate (MVTR)
A depreciated term, usually measured at 100% relative humidity, expressed in grams/100 square inches/24 hours, (or grams/square meter/24 Hrs.) See WVTR.
Mylar is a registered trademark of the DuPont-Teijin Corporation. 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.
A synthetic chlorinated butadiene rubber used to make flexographic rollers resistant to alcohols, Cellosolve, water, aliphatic hydrocarbons, and esters.
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 vapor.
Trim that is not utilized. In flexible packaging, a narrow roll of material left over when an material order does not call for the full roll width. Sometimes called a butt roll.
Oriented PP (polypropylene) film. A stiff, high clarity film, but not heat sealable. Usually combined with other films, (such as LDPE) for heatsealability. Can be coated with PVDC (polyvinylidene chloride), or metalized for much improved barrier properties.
The visual properties of a film, such as clarity, gloss, haze, opacity, etc.
The process of mechanically stretching plastic film or parts in order to produce a straightening and alignment of the molecules in the stretch direction. If done in one direction, the material is said to be uniaxial or monoaxially oriented. if done in two directions, the film is biaxially oriented.
Oxygen transmission rate. 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 centimeters)
One trip of a material through a production machine or manufacturing step.
A bag or pouch in the form of a tube that is sealed at both ends. Pillow type pouches are most commonly produced on vertical-form-fill-seal (VFFS) machines and are characterized by seals across the top and bottom, and a longitudinal seal going down the center of one of the faces.
Non-print area where the two ends of flexo plate butt together after being wrapped around the plate cylinder on the printing press.
The Pantone Matching System is the universally accepted color definition system. Colors can be blended or individually specified to match a specified Pantone reference color exactly.
polyethylene film (PE)
Made in high density, low density, linear low density and metallocene variations. By far the largest volume packaging film family.
poly(ethylene terephthalate) film (PET)
Polyester, (Polyethylene Terephtalate). Tough, temperature resistant polymer. Biaxial 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.
Family name for the polymers (plastics) derived by ethylene and propylene, such as polyethylene (PE) and polypropylene (PP)
polypropylene film (PP)
Unoriented film is soft and clear but brittle at low temperatures. This property as well as stiffness, strength and clarity is improved by orientation.
A small bag usually constructed by sealing one or two flat sheets along the edges. There is no clear distinction between a pouch and a sachet other than the common understanding that a sachet is smaller.
A coating applied over a substrate for the purpose of improving an ink or adhesive bond.
Color printing created by separating the copy into the primary colors to produce individual halftones of each color, that are recombined at the press to produce the complete range of colors of the original. Process printed photographic reproduction would normally be done with cyan, magenta, yellow and black (CMYK) inks.
Polyvinylidene chloride. A very good oxygen and water vapor 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.
Exact alignment of one part or operation with another part or operaion.
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.
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.
Printing wrong-reading on the underside of transparent film. 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. The majority of all products are reverse printed.
Said of any flexible packaging material that is in a roll form.
The ability of film to move easily over hard plastic, metal, or ceramic platforms or against another piece of film.
The conversion of a given width of a film or sheet material into narrower widths. Web stock is unrolled past a series of knives set to the correct widths, and the slit web is rewound back into roll form. ^ top
Joining two pieces of web material to form a continuous web.
Solid colors not created by using screens. Usually a Pantone Matching System (PMS) color.
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.
A narrow flexible packaging pouch commonly used to package single-serve powder beverage mixes such as fruit drinks, instant coffee and tea and sugar and creamer products.
Double-faced adhesive-coated material used for mounting elastomeric printing plates to the plate cylinder.
The process whereby 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.
The ability of a film to resist the propagation of a tear.
The amount of pull a film can withstand without tearing apart or stretching.
A method of forming plastics where a plastic sheet is heated to a point where it is soft and formable.
The placing of a web material through the various rolls and stations of any web-fed press such as a printer or laminator in preparation for production.
A pouch that is formed by folding the web 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.
A material that bonds two incompatible layers in a coextrusion.
transverse direction (TD)
The direction perpendicular to the machine direction.
In printing, inks may be overlapped slightly by increasing the image size to ensure that no substrate shows through within the register variations of the printing press.
A laminating defect caused by incomplete bonding of the substrates.
unit-dose package (UDP)
A pharmaceutical package that holds individual items of use. A complete unit-dose package may hold a number of discrete items, but each unit of use must be released individually from the package, generally in a non-resealable manner.
A layer of material through which water vapor will pass only slowly, or not at all.
An emptiness or absence of a substance. For example, an area of coated film that is not coated.
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/100 square inches/24 hours, (or grams/square meter/24 Hrs.) See MVTR.
A continuous length of paper film, foil, or other flexible material as it is unwound from a roll and passed through a machine.
A flexible plastic pouch with a molded-in-place sealing device wherein a projecting rib or fin is inserted into a mating channel to effect a closure. A zipper seal can be repeatedly opened and closed.
Sources include Glenroy packaging experts and the following publication, with permission:
Soroka, Walter, CPP. 2008. Illustrated Glossary of Packaging Terminology 2nd Edition. Naperville IL: Institute of Packaging Professionals.
Visit www.iopp.org for additional resources from the Institute of Packaging Professionals.