PBFY Glossary & Technical Information

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

Biaxial Orientation – Orientation of plastic films in both machine and cross machine directions by stretching. Properties of biaxially stretched films are generally well balanced in both directions.

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 vapor 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, 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.

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.

Cold Seal – A pressure sensitive adhesive coating on plastic films or laminates that will allow the packages to be sealed by application of pressure (with no heat or minimal heat).

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.

Doyn-Style Stand-up Pouch – A stand-up pouch that has seals on both sides and around the bottom gusset.

EAA – Ethylene Acrylic Acid copolymer. Because of its excellent adhesion to aluminum 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 coextruded plastic films to improve oxygen barrier properties. It is, however, a poor water vapor 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 coextruded plastic films, where it is shielded from moisture by protective layers of polyethylene. Its OTR also depends on its VOH (vinyl alcohol) content.

Foil – A thin gauge (0.2285-0.325 mils) aluminum foil laminated to plastic films to provide maximum oxygen, aroma and water vapor barrier properties. Although it is by far the best barrier material, it is increasingly being replaced by metallized films, (see MET-PET and MET-OPP) because of cost.

HDPE – 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.

Heatseal Layer – A heatsealable 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 Hot Tack).

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

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 vapor barrier properties.

MET-PET – Metallized 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.

MET-OPP – Metallized 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).

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.

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 vapor. 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 metallized for much improved barrier properties.

OPS Shrink Film – Oriented Polystyrene film. Very common alternative to PVC shrink films in Asia and Europe, but not readily available in the USA. Slightly higher priced than PVC films but more recyclable and has a greater shrink percentage.

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).

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.

PET-G – Shrink Film Polyethylene Terephtalate Glycol shrink film. The most expensive shrink film for full body shrink sleeves, but clear, glossy, strong, and most recyclable. The highest shrink percentage available is about 75%, so this film is often required when the container has a narrow waist or neck.

Plow-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. Hold more weight than Doy-style pouches, so are commonly used for products weighing more than one pound.

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

PVC Shrink Film – Polyvinyl chloride shrink film. Shrink percentages vary from about 40% for extruded PVC shrink tubing to over 60% for seamed material. The most cost-effective shrink film for full-body shrink sleeves.

PVDC – Polyvinylidene chloride. A very good oxygen and water vapor barrier, but not extrudable, therefore it mostly used as a coating to improve barrier properties of other plastic films, (such as OPP and PET) for packaging.

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.

Shrink Films – Oriented films that are not heat-set after orientation. These films can shrink back close to their unstretched dimension at temperatures higher than the temperature of their orientation. See PVC Shrink Film, PET-G Shrink Film, and OPS Shrink Film.

Side-Gusset Bag – A bag 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.

Surlyn – A special ionomer copolymer produced by Dupont. It has excellent heatsealability, maximum hot tack and it can be sealed through contaminants, and therefore it is used as a premium heatseal layer for packaging films, especially recommended for high speed packaging machines.

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

QUICK REFERENCE

OTR – Oxygen Transmission Rate

Table 1 shows OTR values for common polymer packaging films. Note that the table is divided into two sections. The first contains normalized (1 mil) values for common materials. The second section displays the OTRs for coated or metallized films where the total film thickness is unimportant, because the barrier is primarily coming from the additional layer.

WVTR – Water Vapor Transmission Rate

As shown in Table 2, gauge for gauge, OPP provides the best WVTR of all common polymer packaging films. (For homogeneous films like these, you can calculate the WVTR for a particular thickness by dividing the values in the table by the desired gauge in mils.)

Coatings, metallization, etc. can be applied to these films for an improved WVTR. Table 3 is a quick reference for various films as standalone components. If 2 or more films are laminated together, one must calculate the OTR and WVTR values accordingly.