Air Evacuation - A hole or series
of holes placed in the film to allow the excess air in the bag
to escape during the shrink process.
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
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 comers of the pouch.
Dancer Bar- 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
in the corners of the pouch formed by placing a three-dimensional
item in a flat pouch. Excessive "dog ears" normally
indicate poor shrink technique.
Electronic Hole Burner - A device
that uses an electrical spark to burn a round hole in the film
for air evacuation during the shrink process.
Electrostatic Seal - An electrostatic
discharge is applied to the overlap of two edges of the film.
This keeps the edges aligned until film seals 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 the shrink process.
Hole Punch - A device to punch
a round hole in the film for air evacuation during the
Impact Resistance - The resistance
to impact of a film.
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 binding it together either thermally
L-Sealer - The most common means
of sealing film for heat-shrinkable applications.
An L shape sealer produces two seals simultaneously on folded
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,
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
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.