Polybags Direct's glossary of terms

A

Anti-stat: Contains an anti-static additive that dissipates static electrical charges. Good for short-term storage.

Auto bander: Jumbo rolls of stretch film for automatic bundling equipment.

B

Bags on a roll: Continuous roll of seamless tubing perforated under bottom seal. Bags must be torn off to open.

Bar code: A way of labeling or coding a product that allows a clear description of the contents. Bar codes can only be read by scanners.

Bleed: Where the printing on a piece goes all the way to the edge of the plastic accomplished by printing beyond the margins of the piece and then trimming to the margin.

Blown films: Plastic films produced from synthetic resins (such as polythene) 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.

Bottom seal bags: Individually cut bags from seamless tubing, sealed on the bottom. Flat or side gusseted bags with a strong seal – usually have a tail.

Burn through: A temperature or condition where a film becomes cloudy or burns in the shrink tunnel.

Butylated hydroxytoluene BHT: A lipophilic (fat-soluble) organic compound that is primarily used as an antioxidant food additive (E number E321) as well as in cosmetics, pharmaceuticals, jet fuels, rubber, petroleum products and embalming fluid.

Biaxially oriented polypropylene plastic BOPP: Material used for re-sealable lip and tape.This material offers an even higher grade of clarity and is resistant to tears and wrinkles.

C

Caliper: The thickness of sheet material expressed in "points" or mils (thousands of an inch).

Cast film: The fabrication of a film by continuously pumping the polymer through a straight slot die, then chilling this hot plastic immediately through contacts with a chilled roll. Film width is determined by how fast the chill roll pulls the film away from the die.

Center fold film: A film that has been folded in half,lengthwise.

Center folder: A mechanical device used to create center folded film.

Clarity: Transparency of the film based upon surface gloss and haze.

Closing machine: a device that seals or closes filled packages by crimping, folding or tucking. Adhesives, gummed tape and ultrasonic welding are often used, in addition to heat sealing.

Co-extrusion: Two or more polymers extruded and combined in a die, each forming a distinct layer in the final film.

Co-polymer: Result of two monomers being combined through polymerization.

Core: A paper tube on which film is wound.

Corrugated: A durable, lightweight material used for making cases. Corrugated packaging has an arched layer, called fluting, between smooth sheets, called liner. The corrugated cardboard most commonly used to make cases has one layer of fluting between two smooth sheets.

Cellophane: Clear film derived from wood pulp has a memory and will crinkle like paper, it is a thin, flexible, transparent film formed from cellulose fibres. Cellophane is widely used in food packaging due to its high moisture barrier properties and sealability and is biodegradable.

D

Die: A device used in extrusion processes to shape the extrudate.

Dwell time: The time usually expressed in seconds at a given temperature that is required for the application of heat to seal a heat sealing membrane.

E

Elasticity: The ability of paper or plastic to rebound back to its original state after being stretched.

Extensibility: The ability of paper or plastic to be stretched without breaking.

Extruder: A machine that makes stretch film. It consists of a large steel barrel surrounded by heaters, which melt the plastic resin pellets. Inside of the barrel is a large screw to force the liquid plastic under pressure through a die to be made into plastic sheeting by either the cast or blown processes.

Extrusion: A product formed by pushing material through a die.

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 polythene) between the layers.

F

Flat bags: Two-dimensional bag (width x length) with bottom or side seals.

Flexibility: The property of a material, which will permit its being bent or twisted without breaking, the state of being non-rigid.

Four color process printing: Indicates the four-color plates or cylinders commonly used in color printing.

G

Gauge: A term used in referring to the thickness. The higher the gauge, the thicker the material. Here are some examples and equivalents:
1mil = 1/1000 of an inch = .001
1 mil = 25.4 microns
1 micron = one millionth of a meter
1 inch = 25.4 mm = 2.54 cm
100 gauge = 1 mil
80 gauge = 8/10 mil = .0008 inches

Gauge band: Thickness irregularity in films.

Gusset: The fold in the side or bottom of the pouch, allowing it to expand when contents are inserted.

Gusseted bags: Flat style bag with both sides or bottom tucked in to form gussets. Designated with three dimensions; Side Gusset (width x depth x length) or Bottom Gusset (width x length + gusset).

Grip seal: A bag which is resealable and reclosable by two plastic components interlock at the top of the bag. It is reusable and flexible.

H

High density polythene HDPE: Has much higher stiffness, higher temperature resistance and much better water vapour barrier properties than LDPE, but it is considerably hazier.

Header bags: Side-weld bag with continuous seal along top, 2"-3" below fold. Bag is loaded and sealed from the bottom and typically has a hang hole.

High density polythene LDPE: Thinner, yet stronger than low density polythene. Moisture and vapor barrier, non-porous.

Hole punch: A mechanical device used to produce an air evacuation hole.

I

Impulse sealer: 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.

J

K

Keyline: Also called a mechanical. This is the guide used in making plates or engraving cylinders and printing a piece - a diagram of copy and art for reproduction.

L

Lamination: Composite product consisting of two or more sheets or films joined together, with glue, adhesive, wax etc.

Low density polythene LDPE: A resin base for making film. Even though LDPE is a relatively strong transparent film with good tensile strength it does not match the performance of the newer LLDPE. Used mainly for heat seal-ability and bulk in packaging.

Linear low density polythene: Stronger than low density. Resistant to punctures and tears, non-porous and stretchable.

Linear low density polythene LDPE: Tougher than LDPE and has better heat seal strength, but has higher haze.

Lip: One side of the bag is longer than the other, allows bag to be opened more easily.

Low density polythene LDPE: Porous and somewhat stretchable. Good clarity.

M

Medium density polythene MDPE:Has higher stiffness, higher melting point and better water vapor barrier properties.

Memory: The ability of a film to maintain its characteristics after shrinking.

Metric conversions:
1 kilogram (kg) = 2.2046 pounds
1 meter = 39.37 inches = 1.0936 yards
1 pound = 0.4536 kilograms
1 mile = 1.6094 kilometers
1 short ton = 2000 pounds
1 yard = 0.9144 meter
1 kilometer = 0.6237 miles
1mil = 1/1000 of an inch = .001
1 mil = 25.4 microns
1 micron = one millionth of a meter
1 inch = 25.4 mm = 2.54 cm
100 gauge = 1 mil
80 gauge = 8/10 mil = .0008 inches

Mil: Thickness of material. The higher the mil, the stronger the material. (1/1000 inch = 1 mil)

Micron: Thickness of material: 1 micron = one millionth of a meter.

N

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.

O

Opacity: Hiding power of pigmented (mostly white) plastic films. It is beneficial for packing materials sensitive to light (visible or ultraviolet).

Opaque: Relatively impervious to light.

P

Pallet: A portable, horizontal, rigid platform used as a base for assembling, storing, stacking, handling and transporting goods as a unit load. A pallet typically contains a raised superstructure that allows it to be lifted and moved by a forklift without damaging any cases.

Perforations: The practice of creating a long series of holes so that plastic film can be torn more easily. Postage stamps are one common application of this.

Polythene: A simple thermoplastic polymer of ethylene. Highly puncture and tear resistant. Not affected by extreme temperatures. Does not possess barrier properties. Good clarity. Depending on its density, it may be low density (see LDPE). medium density (see MDPE). or high density (see HDPE).

Polymer: A material made through the process of polymerization.

Polymerization: A gas heated under pressure forms a solid.

Polypropylene: A thermoplastic polymer of propylene. Has much higher melting point, thus better temperature resistance than PE. Preserves freshness with vapor and moisture barriers. Non-porous and excellent clarity. Possesses ability to withstand high temperatures.

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

Q

R

Reclosable bags: Seal-top reclosable bags can be made with or without a tamper-evident adhesive seal. Also includes zipper and slider zipper bags.

Recovery: Stretch film trying to return back to its original form after it has been stretched. This action constantly pulls the load together since the stretch film tightly form-fits the load. Stretch wrapping continues to tighten the load as it settles during shipment, due to the recovery property, keeping the load safe and secure during shipment.

S

Seal strength: Measurement of force required to break or destroy a heat seal formed by any of the heat sealing sheets.

Sheeting: The cutting of a large master roll into sheets.

Shrink wrapping: a technique of packaging in which the strains in a plastic film are released by raising the temperature of the film, thus causing it to shrink over the package.

Side weld: Bags are sealed on the side. No bottom seal.

Singlewound film: A single layer of shrink film wrapped around a core.

Slitting: The cutting of a large master roll into smaller rolls used.

Static: An electrical charge built-up in plastic film.

T

Tear resistance: The ability of a film to resist the propagation of a tear.

Tensile strength: The force required to break through film and bags, or snap rope, cable ties, and wire by pulling on opposite ends. Determined by material thickness and width.

Tolerance: Allowable deviation from a nominal or specified dimension. Minimum/maximum range of measurement.

Top sheeting: A protective covering put on the top of a load to protect the top from dust, dirt, and other objects that might damage or dirty the load.

Transmission: Quantity of moisture and/or gas passing through the packaging film or foil over a specific period of time.

Trim: The amount of excess film severed during the sealing process.

U

V

Vent hole: Air evacuation holes in a film made by pin perforators.

W

X

Y

Z

Zip top pouch: A reclosable or resealable pouch produced with a plastic track in which two plastic components interlock to provide a mechanism that allows for reclosablility in a flexible package.

Star seal: This multilayered seal is full gusseted and then folded prior to sealing, allowing for the weight to be evenly distributed.

Gusset seals: A flat-style bag manufactured with both sides tucked in to form gussets.

Flat seal: Straight seal along bottom of a poly bahg (looks like a pillow case).

Seal: Term used to describe bottom of a can liner. The three types of seals are flat, gusseted and star.

Prime resin: Refers to the usage of high-quality, "fresh from the reactor," resin.

Hexene resin: Heritage uses Higher Alpha Olefin (High Grade Hexene) properties include high film strength and increased tear resistance.

Butene one resin: Butene has weaker film-strength properties than Hexene or Octene.

HAO (Higher Alpha Olefin Resin): A high-grade Hexene or Octene-based resin.

HMW-HDPE (High Molecular Weight - High Density Polyethylene): Bags made from HMW-HDPE resin provide excellent film strength and puncture resistance, but less tear resistance than LLDPE.

LLDPE (Linear Low Density Polyethylene): This is the primary type of resin used in modern poly bags. Bags made from LLDPE film provide excellent combination of film strength, puncture resistance and tear resistance.

LDPE (Low Density Polyethylene): This resin has good clarity but week film strength. Primarily for food and utility bags.

Resin: Short term for polyethylene (PE) resin. The three types of PE resins are LDPE, LLDPE and HMW-HDPE. Other plastic resins include vinyl, polypropylene, styrene and nylon.

Gauge: Term used to describe thickness. LDPE and LLDPE poly bags are measured by mil thickness and HMW-HDPE poly bags are measured by micron thickness.

Elmendorf tear test: Test used to measure the resistance to tearing.

Dart drop test: Test used to determine the resistance of a bag to local failure or puncturing of the film.

Film strength: Some resins have a higher film strength than others. Our products are made from highest quality resins.

Food and utility bags: Small clear bags designed to hold a variety of small objects - e.g. bread, poultry, vegetables

Can liner: Term used for garbage, trash or waste bags. Used in industrial, institutional and medical applications.