Material Terms


Generally used to describe a thin plastic material used in the manufacture of flexible packaging. Overwraps uses many different types of plastic film, but mostly Polyethylene (PE), Polyester (PET), Metallized Polyester (MET PET), Polypropylene (OPP), Metallized Polypropylene (MOPP), and Nylon (BON).


An unsupported thin metal membrane, typically aluminum in thicknesses of 0.000285 or 0.00035 inch thick for cookie packaging, or 0.0014 inch thick for coffee packaging. It is the best barrier film available for excellent shelf life providing moisture and vapor protection of the packaged product. It is most often used as a middle layer web of a three layer film lamination with PET as the printed layer, and PE as the sealant layer. It can also be used as an outside layer of a two layer lamination.


The material used at Overwraps to print hospital face masks, and gowns. It consists of a cellulose and polyester blend of fibers bound together with an acrylic polymer emulsion. The most common material we use is the Ahlstrom supplied 11399B for face masks.


Biaxially Oriented Nylon film, also known as BOPA film, is made of polyamide resin, which can be used for a wide range of applications especially where high barrier requirements to gas, fat and transmission of aroma are necessary. It has high resistance to impact puncture and pin holing.

PE, Cast and Blown

Short for Polyethylene which is a plastic composed of polymers of ethylene. We purchase primarily clear or white PE, but also yellow, blue and red for explosives emulsion packaging. There are four general classifications: Low Density, Linear Low Density, Medium Density, and High Density. Overwraps primarily uses Blown Polyethylene film which is manufactured in an extruded plastic tube that is continuously inflated by internal air pressure, cooled, collapsed flat rolls, and subsequently wound into rolls. The tube is usually extruded vertically upward, and air is blown through a passage in the center of the die as the molten tube emerges from the die. An air ring provides air flow around the outside of the bubble to increase initial cooling close to the die. Air is contained within the blown bubble by a pair of pinch rolls, which also serve to collapse and flatten the film. Film thickness is controlled by the die-lip opening, by varying bubble air pressure, and by the extrusion and take-off rate. Thin films with considerable biaxial orientation can be produced by this method. Cast film is made by extruding a thin curtain of thermoplastic melt onto a highly polished chilled drum. After the film solidifies, it is edge trimmed and wound into rolls for further processing.

PET, METPET, Saran, Heat Sealable

Polyester film is a high-performance film made from polyethylene terephthalate (PET) resin. It has high tensile strength, excellent dimensional stability, low moisture absorption, good retention of physical properties over a fairly wide temperature range (-70C° to 150°C), and good optical clarity. We typically use 48 gauge thickness PET. METPET is a metallized version of the PET on which a thin amount of aluminum has been vacuum-deposited, and is used primarily as a middle layer in a three layer film lamination with PET on the outside or printed side, and PE on the sealant side. It enhances the barrier properties and extends the shelf life of various packaged foods. SARAN is a coating made of poly (vinylidene chloride) (PVDC) and its copolymers. PVDC has very low permeability to gases and vapors, which makes it an excellent barrier material for packaging.

Saran is used most frequently as an applied coating to increase the barrier qualities of other base films.

HEATSEALABLE PET refers to PET that has a thin layer of heat sealable coating applied which enables it to seal to itself during the packaging form, fill and seal operation of foods.


Short for Polypropylene which is a plastic polymerized from propylene gas. Films are mostly oriented (OPP) or biaxially oriented (BOPP) which are stretched in both the machine direction as well as transverse direction. In this form they are used for high-clarity wrapping stock, and when printed, are the predominant film for snack food packaging. OPP film has excellent clarity, low elongation, good moisture-barrier properties, and good low-temperature performance. Gas barrier and heat-seal ability are provided by other added COEX material layers. CPP stands for Cast Polypropylene which is produced by extruding a thin curtain of thermoplastic melt onto a highly polished chilled drum. METPP is Metallized polypropylene and used primarily as a sealant web in a printed OPP lamination for snack food. It enhances the barrier properties and extends the shelf life of salted snacks.

Shrink Bundling Film

It is a super-strong polyethylene film used for packaging cases of water, soda, or other items needing to be bundled or bulk packed. It is stronger than standard shrink film and provides excellent puncture resistance. It can be used with packaging equipment and heat tunnels.

Shrink Film

A film used to shrink and conform to the contents of the package. Typically made of polyethylene, polypropylene, or poly(vinyl chloride), that is wrapped loosely about another container or product and then made to shrink and conform tightly about the container or product by the brief application of heat. Shrink films can be produced having biaxial or uniaxial shrinkage. Biaxial shrink film is most commonly used as package or product over-wrap while uniaxial shrink film is most commonly used for shrinkable label applications and for tamper evident neck-bands.

Stretch Film

A film made of low density or linear low density polyethylene used to bind the finished product to the shipping pallet.


The material (FILM) on which some action, such as printing, coating, adhesive bonding, and so on is being performed.


A Tyvek is a nonwoven product consisting of spun bond olefin fiber developed and manufactured by DuPont. It is used mainly as house wrap to provide moisture barrier, envelopes, and wristbands.


A cross laminated polyethylene film. It is made with two oriented polyethylene films laminated with their orientation directions crossed at roughly 90 degrees (45 degrees from the machine direction). It is used primarily in the explosives and construction industries.