|
Glossary of Flexible Packaging
Terms | |
|
|
Adhesive Lamination: A laminating process in which
individual layers of multi-layer packaging materials are laminated
to each other with an adhesive. Biaxial Orientation: Orientation
of plastic films in both machine and cross machine directions by stretching.
Properties of biaxially stretched films are generally well balanced
in both directions. Blown Films: Plastic films produced
from synthetic resins (such as polyethylene) 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. BON: Biaxially oriented nylon
film, with excellent oxygen and aroma barrier properties, (see Nylon),
but it is a poor water vapor barrier. BON is much stiffer than cast
nylon film, but cannot be thermoformed. CAN: Cast nylon
film (see Nylon). Used mostly for thermoformable packaging applications. CAPP
or CPP: Cast PP film, (see PP). Unlike OPP, it is heatsealable,
at much higher temperatures than LDPE, thus it is used as a heatseal
layer in retortable packaging. It is, however, not as stiff
as OPP film. Cast Film: Plastic film produced from synthetic
resins (such as polyethylene) by the cast process. In this process,
the molten resin is extruded through a slot die onto an internally
cooled chill roll. Cold Seal: A pressure sensitive adhesive
coating on plastic films or laminates that will allow the packages
to be sealed by application of pressure (with no heat or minimal heat). Coextrusion: Simultaneous extrusion of two or more different thermoplastic resins
into a sandwich-like film with clearly distinguishable individual
layers. COF: Coefficient of friction, a measurement of
“slipperiness” of plastic films and laminates. Measurements are usually
done film surface to film surface. Measurements can be done to other
surfaces as well, but not recommended, because COF values can
be distorted by variations in surface finishes and contamination on
test surface. Doyn-Style Stand-up Pouch: A stand-up pouch
that has seals on both sides and around the bottom gusset. EAA: Ethylene acrylic acid copolymer. Because of its excellent adhesion
to aluminum foil, it is mostly used for extrusion lamination of foil
to other surfaces. 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 polyethylene) between the layers. EVA: Ethylene-Vinyl Acetate copolymer. Much softer and clearer than LDPE
or LLDPE and has lower melt temperature. Its melt temperature goes
down, while its softness increases with increasing vinyl acetate (VA)
content. EVA resins with 2-18% VA content are used for cast and blown
packaging films. EVOH: Ethylene-Vinyl Alcohol copolymer,
used in coextruded plastic films to improve oxygen barrier properties.
It is, however, a poor water vapor barrier. Even its otherwise excellent OTR, (oxygen transmission rate) is sensitive to high humidity, therefore,
for packaging applications, it is usually the core layer of coextruded
plastic films, where it is shielded from moisture by protective layers
of polyethylene. Its OTR also depends on its VOH (vinyl alcohol) content. Foil: A thin gauge (0.2285-0.325 mils) aluminum foil laminated to plastic
films to provide maximum oxygen, aroma and water vapor barrier properties.
Although it is by far the best barrier material, it is increasingly
being replaced by metallized films, (see MET-PET and MET-OPP) because
of cost. HDPE: High density, (0.95-0.965) polyethylene.
Has much higher stiffness, higher temperature resistance and much
better water vapor barrier properties than LDPE, but it is considerably hazier. Heatseal Layer: A heatsealable layer in plastic
packaging films and laminates. Can be either adhesive laminated or extrusion coated onto a non-sealable film (or foil). Heatseal
Strength: Strength of heatseal measured after the seal is cooled,
(not to be confused with “hot tack”, see next item). Hot Tack: Strength of heat seal measured before the seal is cooled, which is
very important for high-speed packaging operations. LDPE: Low density, (0.92-0.934) polyethylene. Used mainly for heatsealability
and bulk in packaging. LLDPE: Linear low density polyethylene.
Tougher than LDPE and has better heatseal strength, but has higher
haze. MDPE: Medium density, (0.934-0.95) polyethylene.
Has higher stiffness, higher melting point and better water vapor
barrier properties. MET-PET: Metallized PET film. It has
all the good properties of PET film, plus much improved oxygen and
water vapor barrier properties. However, it is not transparent. MET-OPP: Metallized OPP film. It has all the good properties of OPP film, plus
much improved oxygen and water vapor barrier properties, (but not
as good as MET-PET). Monoaxial Orientation: Orientation
of plastic films by stretching in one direction, (machine or cross
machine direction) only. These films are generally much stronger and
stiffer, but have very poor tear strength in the direction of orientation. 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. Also, nylon films can be cast (see CAN),
or oriented, (see BON). Opacity: Hiding power of pigmented
(mostly white) plastic films. It is beneficial for packing materials
sensitive to light (visible or ultraviolet). OPP: Oriented
PP (polypropylene) film. A stiff, high clarity film, but not heatsealable.
Usually combined with other films, (such as LDPE) for heatsealability.
Can be coated with PVDC (polyvinylidene chloride), or metallized for
much improved barrier properties. OPS Shrink Film: Oriented
Polystyrene film. Very common alternative to PVC shrink films
in Asia and Europe, but not readily available in the OTR: Oxygen transmission rate. OTR of
plastic materials varies considerably with humidity, therefore it
needs to be specified. Standard conditions of testing are 0, 60 or
100% relative humidity. Units are cc./100 square inches/24 hours,
(or cc/square meter/24 Hrs.) PP: Polypropylene. Has much
higher melting point, thus better temperature resistance than PE.
Two types of PP films are used for packaging: cast, (see CAPP) and
oriented (see OPP). PE: Polyethylene, depending on its
density, it may be low density (see LDPE). medium density (see MDPE).
or high density, (see HDPE). PET: Polyester, (Polyethylene
Terephtalate). Tough, temperature resistant polymer. Biaxially
oriented PET film is used in laminates for packaging, where it provides
strength, stiffness and temperature resistance. It is usually combined
with other films for heat sealability and improved barrier properties. PET-G
Shrink Films: Polyethylene Terephtalate Glycol shrink film. The most expensive shrink film for full body shrink sleeves, but clear,
glossy, strong, and most recyclable. The highest shrink percentage
available is about 75%, so this film is often required when the container
has a narrow waist or neck. PLA Shrink fIlm: A film made from corn instead of oil. Not only is it produced from renewable resources but it is biodegradable in composting conditions. Currently being introduced, it is destined to be the shrink film of the future.
Plow-Bottom Stand-up Pouch: a stand-up pouch that
is made from one piece of film. The front, gusset, and back
are continuous, so there is no seal at the gusset. Hold more
weight than Doy-style pouches, so are commonly used for products weighing
more than one pound. PVC: Polyvinyl chloride. A
tough, stiff, very clear film. The oriented version is used
mainly for shrink film applications. PVC Shrink Films: Polyvinyl chloride shrink film. Shrink percentages vary from
about 40% for extruded PVC shrink tubing to over 60% for seamed material. The most cost-effective shrink film for full-body shrink sleeves. PVDC: Polyvinylidene chloride. A very good oxygen and water vapor barrier,
but not extrudable, therefore it mostly used as a coating to improve
barrier properties of other plastic films, (such as OPP and PET) for
packaging. Release Coating: A coating applied to the non-sealing
side of cold-sealable packaging films and laminates supplied in a
roll form that will allow the packer to unwind these films or laminates
on packaging machines. Shrink Films: Oriented films that
are not heat-set after orientation. These films can shrink back close
to their unstretched dimension at temperatures higher than the temperature
of their orientation. See PVC Shrink Film, PET-G Shrink Film,
and OPS Shrink Film. Side-Gusset Bag: A bag with gussets
on both sides, with a fin-seal running from top to bottom and sealed
horizontally at the bottom and the top. Commonly used in the
coffee industry. Surlyn: A special ionomer copolymer produced
by Dupont. It has excellent heatsealability, maximum hot tack and
it can be sealed through contaminants, and therefore it is used as
a premium heatseal layer for packaging films, especially recommended
for high speed packaging machines. WVTR: Water vapor transmission
rate, usually measured at 100% relative humidity, expressed in grams/100
square inches/24 hours, (or grams/square meter/24 Hrs.) |