Polyethylene, depending on its density, it may be low density. Medium density. Or high density.
Low density, (0.92-0.934) polyethylene. Used mainly for heatsealability and bulk in packaging.
Linear low density polyethylene. Tougher than LDPE and has better heatseal strength, but has higher haze.
Medium density, polyethylene. Has higher stiffness, higher melting point and better water vapor barrier properties.
High density, polyethylene. Has much higher stiffness, higher temperature resistance and much better water vapor barrier properties than LDPE, but it is considerably hazier.
Polypropylene. Has much higher melting point, thus better temperature resistance than PE. Two types of PP films are used for packaging: cast, and oriented.
Oriented PP (polypropylene) film. A stiff, high clarity film, but not heatsealable. Usually combined with other films, (such as LDPE) for heatsealability.
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.
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).
Polyester, 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.
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.
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.
Polyamide resins, with very high melting points, excellent clarity and stiffness.
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.
Cast nylon film (see Nylon). Used mostly for thermoformable packaging applications.
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.
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.
Simultaneous extrusion of two or more different thermoplastic resins into a sandwich-like film with clearly distinguishable individual layers.
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.
Ethylene acrylic acid copolymer. Because of its excellent adhesion to aluminum foil, it is mostly used for extrusion lamination of foil to other surfaces.
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.
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.
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.
Polyvinyl chloride. A tough, stiff, very clear film. The oriented version is used mainly for shrink film applications.
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 corelayer 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.
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.
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.
Hiding power of pigmented (mostly white) plastic films. It is beneficial for packing materials sensitive to light (visible or ultraviolet).
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