Glossary

The flexible packaging terms you will find on a technical data sheet, a quotation or a purchase order.

BOPA

Biaxially oriented polyamide (nylon). Middle layer that provides puncture and flex resistance; essential in retort, vacuum and sharp-edged products.

BOPP

Biaxially oriented polypropylene. Clear, matte or metallized film; outer layer for snacks and lamination of woven PP bags.

COA (certificate of analysis)

Manufacturer's document per lot listing layers, gauge, basis weight and tests performed. Checked against the approved technical data sheet on receipt.

Coextrusion

Film made by extruding several resins at the same time as bonded layers (3, 5 or 7). Combines sealing, strength and barrier in one film.

COF

Coefficient of friction: how easily the film slides over itself or over metal. Determines how it runs on the packaging machine.

Core

Cardboard tube the film is wound on. Inside diameter of 76 mm (3 in) or 152 mm (6 in).

Corona treatment

Electrical discharge that raises the surface energy of the film so it accepts ink and adhesive.

CPP / RCPP

Cast polypropylene, a sealant layer with more heat resistance than PE. RCPP is the grade that withstands retort sterilization.

Degassing valve

One-way valve that lets CO₂ escape from freshly roasted coffee without letting oxygen in.

Denier

Unit of linear weight of woven PP tape (grams per 9,000 m). Higher denier means a thicker tape and a stronger bag.

Die cut

Cut made with a cutting die that defines the pouch outline, rounded corners, eurohole or handle.

Dieline

Technical drawing of the package with dimensions, seal areas, die cuts, gussets and eye mark. Artwork is placed on it without modification.

Doypack

Trade name by which the stand-up pouch is widely known: a bottom gusset keeps it standing on the shelf.

Eurohole

Hole at the top of the pouch for hanging on a display hook; round or mushroom-shaped.

EVOH

Ethylene vinyl alcohol. Very high oxygen-barrier resin coextruded between PE layers because it loses barrier with humidity.

Eye mark (photocell mark)

Dark, high-contrast printed registration mark that the packaging machine's sensor reads to cut and seal each package in place.

Gauge (microns)

Thickness of a film or a structure, in microns (µm). Higher gauge means more stiffness, strength and barrier, and higher cost.

Grammage (basis weight)

Weight of material per unit area, in g/m². Used for woven PP, paper and to calculate the weight of a structure.

Gusset

Fold of material at the bottom or sides of a bag that gives it volume and lets it stand or stack.

Heat seal

Closing a bag or woven sack by fusing the sealant layer with heat, without stitching; on woven bags it is known as a T-bag.

HFFS

Horizontal Form Fill Seal: horizontal packaging machine that forms, fills and seals from rollstock; flow wrap is the most common case.

IML

In-Mold Labeling: label fused into the mold as the rigid container is formed; it does not peel or scratch.

Lamination

Bonding two or more films with adhesive to form a structure with the properties of each layer.

Liner

Inner PE bag or layer inside a woven sack, loose or laminated, that adds hermeticity and moisture and dust barrier.

Matte-to-register

Matte varnish applied only to defined areas of the design, leaving others glossy, to highlight brand or product.

Mesh (weave count)

Density of the woven PP fabric, in tapes per inch in each direction (for example 10 × 10). Together with denier, it defines strength.

Metallized film

Very thin aluminum layer vacuum-deposited on PET or BOPP (VMPET, VMBOPP). Improves oxygen, moisture and light barrier.

MOPE

Machine-direction oriented polyethylene. Printable outer layer that enables all-PE structures, candidates for recycling.

OTR

Oxygen transmission rate, in cc/m²·24 h (typically at 23 °C and 0 % RH). The lower, the higher the oxygen barrier.

PE

Polyethylene. Inner sealant layer of almost every lamination; clear or white; flexible, seals at moderate temperature.

PET

Biaxially oriented polyester. The most common printed outer layer; stiff, stable and heat-resistant, not heat-sealable on its own.

Repeat length

Length of each print on the roll, equal to the pouch length; measured from eye mark to eye mark.

Retort

Sterilization of the filled and sealed package in an autoclave, at 121–135 °C (250–275 °F) under pressure. Requires structures with BOPA and RCPP.

Reverse printing

Printing on the inner face of the clear outer film, so the ink is protected between layers after lamination.

Rotogravure

Printing with engraved cylinders, one color per cylinder. High definition and consistency on long runs; the standard in flexible packaging.

Seal

Area where two sealant layers are joined with heat and pressure. Its width and strength (N/15 mm) are specified per product.

Sewn seam (hemmed)

Reinforced stitching at the mouth or bottom of a woven PP bag; may include EZ-tape for tool-free opening.

Splice

Joint between two sections of film inside a roll. Limited per roll and flagged so the operator can remove it.

Spout

Plastic fitment with a cap that is sealed into the pouch to dispense liquids and semi-liquids.

Tear notch

Small cut in the side seal that starts the tear and lets the pouch be opened without scissors.

Tin tie

Flexible metal strip attached at the top of the bag that folds over to close it; common in coffee and bread bags.

VFFS

Vertical Form Fill Seal: vertical packaging machine that forms the tube, fills and seals from rollstock; common for powders and granular products.

VMPET / VMBOPP

Vacuum-metallized PET or BOPP. Barrier layer with a metallic appearance.

WVTR

Water vapor transmission rate, in g/m²·24 h (typically at 38 °C and 90 % RH). The lower, the higher the moisture barrier.

Zipper

Resealable closure built into the pouch, press-to-close or with a slider; its position from the top edge is specified.