Air Evacuation – A hole or series of holes placed in the film to allow the excess air in the bag to escape during shrinkage.

 

Antifog Film – A film containing a wetting agent which reduces the surface tension on the film to allow water to wet the surface rather than form water droplets; which causes a cloudy appearance.

 

Ballooning – The lifting action of the film away from the product caused by the pressurizing of the excess air in the bag during the shrink process.

 

Bead Seal – The resultant weld caused by the simultaneous sealing and cutting of two or more pieces of film.

 

Biaxial Orientation – A film that has been stretched under certain temperature conditions equally in both the machine and transverse directions.

 

Blocking – A condition where layers of film cannot be separated.

 

Blown Film – Film produced by extruding resin into a tube, which is expanded by air pressure.

 

Bubble – The inflated tube of film in the blown film extrusion process.

 

Burnthrough – A weakening of the film where the heat of the tunnel exceeded the heat resistance of film.  Typically, it will appear as a hole or a very cloudy area.

 

Centerfolded Film – Film folded in half in the machine direction and then wound into roll form.

 

Centerfolder – A device used to produce center folded film from flat film.

 

Clarity – The transparency of the film, which is a function of surface gloss and internal haze.

 

Coefficient of Friction – A comparative value indicating the ability of the film surface to move against itself or another surface.  The higher the coefficient of friction, the more difficult to slip or move.

 

Coextrusion – Two or more different materials simultaneously extruded into a composite film.

 

Copolymer – A resin polymerized from two or more monomers.

 

Core – A paper tube used as a base for forming a roll of film.

 

Crows Feet – The residual wrinkles that can be left in a poorly shrunk sample.  They are normally associated with the excess film in the corners of the pouch.

 

Dancer Roll – A mechanical device used to control the tension of the film between the film unwind and the film sealing area.

 

Density – Weight per unit volume.  Films with a low density offer more coverage per weight of film.

 

Dog Ears – The excessive film the corners of the pouch formed by placing a three-dimensional item in a flat pouch.  Excessive “dog ears” normally indicate poor shrinkage technique.

 

Electronic Hole Burner – a device that uses an electrical spark to burn a round hole in the film for air evacuation during shrinkage.

 

Electrostatic Seal – An electrostatic discharge is applied to the overlap of two edges of the film.  This keeps the edges aligned until film blocks together in the shrink tunnel.

 

Elmendorf Tear Resistance – A measure of the resistance to tear after the film has been cut.

 

Elongation – The percentage a film will deform or stretch prior to breaking.

 

Extrusion – A technique for producing film by melting a resin and forcing it through a die.

 

Fish Eyes – The circular or oval patterns that remain on a package that has been poorly shrunk.  They are normally associated with the absence of adequate heat or air velocity.

 

Fogging – A buildup of water droplets on the surface of a film.

 

Forming Head (Plow) – A mechanical device used to shape flat wound film into the desired bag shape needed for a particular package.

 

Gas Transmission Rate (GTR) – A measure of the rate a gas will permeate through a film.

 

Gauge – The average thickness of a film.

 

Gloss – A measure of the reflected light from the film surface.

 

Haze – A measure of the cloudiness of the film.

 

Hole Burner – A device that uses a hot wire formed in a circular shape to burn a round hole in the film for air evacuation during shrinkage.

 

Hole Punch – A device to punch a round hole in the film for air evacuation during shrinkage.

 

Impact Resistance – The resistance to impact of a film.

 

Impulse Seal – A seal produced by an intermittent electric pulse, which heats a round, wire or ribbon to cut and seal film.

 

Initial Tear Resistance – A measure of the force needed to begin a tear in a film.

 

Inverting Head – A mechanical device used to separate and invert centerfolded film as the film is transferred into the sealing area of the wrapper.

 

Irradiation – A process that uses high-energy electrons to cross-link a film.

 

Lap Seal – A seal produced by overlapping film and then sealing it together either thermally or electrostatically.

 

L-Sealer – The most common means of sealing film for heat-shrinkable applications.  An L-shape sealer produces two seals simultaneously on folded film.

 

Low Temperature Flexibility – The lowest temperature at which a film can withstand a flexing test without cracking.

 

Machine Direction (MD) – The direction the film was manufactured and also comes off the roll.

 

Modulus – A measure of film stiffness.

 

Moisture Vapor Transmission Rate (MVTR) – The rate moisture vapor will pass through the film.

 

Monomer – A simple compound, which can react at high temperature and pressure to form a polymer.

 

Orientation – The stretching technique used to obtain molecular alignment in a film during manufacturing, which increases tensile strength and stiffness and decreases tear strength.

 

Oxygen Transmission Rate – A measure of the permeability of a packaging film to oxygen.

 

Plasticizer – A substance blended into plastics such as PVC to improve flexibility and softness.

 

Polyethylene – A resin made from ethylene gas, which produces tough transparent film.

 

Polymer – A high molecular weight, long chain compound formed from one or more simple molecules.

 

Polypropylene – A resin made from propylene gas, which produces lightweight, highly transparent, stiff film.

 

Polyvinyl Chloride (PVC) – A resin produced from vinyl chloride.  Generally compounded with plasticizers and other additives to improve flexibility.

 

Sealing Wire – A nichrome wire, which is heated by its resistance to electrical current.  It is used for sealing and cutting shrink film.

 

Shrink Film – A plastic film, which has been produced under special orientation conditions that will allow the film to shrink when heat is applied.

 

Shrink Force – The force exerted on the product by the film during the shrink process.

 

Shrinkage / Percent Shrink – The decrease in dimension of a film when it is subjected to heat.

 

Single Wound Film – Flat film wound on a core.

 

Slip - How easily one surface moves across another.

 

Slip Agents – Lubricants added to films to improve slip and reduce friction.

 

Static – An electric charge generated by film moving across itself (unwinding from the roll) or any other surface.

 

Tear Strength – The ability of the film to resist tearing.  Highly oriented films generally have reduced tear resistance.

 

Tensile Strength – The force exerted on the film from external sources.

 

Tension – A force exerted on the film from external sources.

 

Transverse Direction – The direction at right angles to the film movement during its manufacture, usually the same as the width of the film.

 

Trim – The edges of film, which are cut from, a package formed on an L-sealer or side sealer when the seal is made.

 

Uniaxially Oriented Film (Preferential Shrink Film) – A film that will shrink in only one direction.

 

Yield – Coverage of a film per unit weight (usually sq in/lb) rolls.

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