Shrink Film
SHRINK WRAP
SHRINK FILM BASICS
BACK TO TERMINOLOGY
FILM CATEGORIES
The shrink film market is comprised of two basic categories; the polyvinyl chlorides (PVC) and the
polyolefin. Shrink polyethylene is not typically included in the competitive polyolefin category;
"poly" lacks the clarity, gloss and the tight second skin polyolefin provide. These attributes are
critical for retail appeal.
The polyolefin "family" consists of films made from polyethylene or polyethylene and
polypropylene copolymer resins. All Cryovac shrink films are polyolefin.
PVC shrink films derive their properties from additives, which are primarily plasticizers. As these
films age, the plasticizers. migrate and the film reverts to its brittle state, turning to a yellowish
color. Also, PVC films tend to be temperature-sensitive, developing a tendency to shatter and
split at cold temperatures (below freezing), and "shrink-back" and! or block when exposed to high
temperatures over a period of time. The color may also change to yellow when exposed to heat
(such as being stored in a non-air-conditioned warehouse over the summer).
FILM SEALING SYSTEMS For pictures and a comparison of other shrink wrap
methods click here
Until recently, most sealing systems used a hot wire in order to seal and cut-off the film at the
same time; now, a knife system has gained in popularity on many models, due to its durability.
The wire or knife seals the film against a pad, covered with Teflon tape to protect the pad. Time,
temperature and pressure are the three most critical elements affecting the seal quality. If the
sealing head is not held on the film long enough, the temperature is too low, or the pressure is
insufficient or uneven, the seal quality will be poor, and/or won’t cut. However, if the sealing
temperature is too low, or the pressure is insufficient or uneven, the seal quality will be poor,
and/or won’t cut. However, if the sealing temperature is too high, the film may break just behind
the seal. Following the impulse sealing cycle, a cooling cycle allows the film to "solidify" into a
solid seal. This dwell-time is critical in order for a seal to hold.
SHRINK FILM BASICS
PVC films require only heat in order to cut seal and cut. When run on a sealing system as
previously described, build-up of carbon char (black specs and flakes) will occur. The char will
need to be cleaned from the sealing head on a regular basis; otherwise, the carbon will interfere
with the sealing process, and will look unsightly on the sealed ends of the package.
Since only heat is needed to form a PVC seal, some machines use a hollowed out bottom platen
instead of the foam pad; direct contact with the seal wire is eliminated. Other systems employ a
much thinner nichrome wire (.020" diameter versus. a standard .036" to .040" for polyolefin)
against a hard bottom sealing pad. This system is insufficient to create strong polyolefin seals.
One other sealing system designed for PVC is called a Universal Sealing System. Despite the
name, the hot knife is typically too sharp to form a quality polyolefin seal. A rounded knife is better
suited.
FILM SHRINKING SYSTEMS
In order for proper shrinking to take place, polyolefin films need an air evacuation hole or multiple
perforations. A bag formed with PVC film does not need "artificially created" air escape holes.
Because of the makeup of PVC, the seal typically is full of small pinholes; this is where the air
escapes during the shrinking process. While this may seem advantageous (a step can be
eliminated), the small holes actually weaken the seal area. These holes are often located near or
in the package corners.
In order for proper shrinkage to occur, polyolefin film must be exposed to the correct temperature
for the correct amount of time (which is controlled by conveyor speed), and also be surrounded
by the correct air velocity, or wind turbulence. The air allows the film to stand away from the
product, and a "bubble" is formed around it. A good, even shrink should result when this occurs.
FILM TYPES & CHARACTERISTICS
TERMINOLOGY
BACK TO TERMINOLOGY
Balanced - Equal orientation in both LD and TD, i.e., 3 x 3 or 5 x 5.
Basic Film -A film made of one material.
Biaxially Oriented Film - Oriented along X and Y axes.
Blown Film -A film extruded by the blown (air inflation) system. Sometimes erroneously called "extruded" film.
Coextrusion -Two or more polymers extruded and combined in a die, each forming a distinct layer in the final film.
Copolymer - Polymers such as polyethylene/polypropylene are composed of repeating monomers and are actually
homopolymers. Copolymers result when two monomers are combined during polymerization.
Composite Film -A film made by joining two or more basic films. Composite films include laminates, co-extrusions, and coated
films.
EVOH - Ethylene vinyl alcohol (EVOH) resins are hydrolyzed copolymers of vinyl acetate and ethylene. EVOH has excellent gas,
aroma, and solvent-barrier properties.
Heat Shrinkable Films -Films which have gone through an orientation step in the manufacturing process, which shrink
significantly with application of heat, generating a substantial shrink force.
Laminate - A general term used to describe packaging structures composed of two or more materials, each designed to
contribute one or more desirable properties to the final construction. There are many techniques for producing laminate materials,
i.e., extrusion, adhesive laminating or extrusion coating. Syn. Composite.
Monoaxial - A film which is oriented to shrink in one direction (longitudinal or transverse) only.
Monolayer Film - A single layer film extruded from one or a blend of several raw materials (resins).
Multilayer Shrink Film - A film formed with multiple layers of similar or differing polymers. The purpose is to obtain specific
properties and characteristics.
Polyethylene - A simple thermoplastic polymer of ethylene. Each molecule consists of hundreds/thousands of carbon atoms. The
length of molecules and the amount of side branching determine the characteristics of the film, i.e., LDPE, LLDPE, HDPE, etc.
Polyethtlene is used for general wrapping, when appearance is not critical.
Polymer - A gas heated under pressure goes from a gas to a solid. This is called "polymerization". The resultant material is called
polymer.
Polyolefin - A term used to describe ethylene and/or propylene-based films that are generally a composite of several different
types of film. The shrink wrap industry uses this film because it can provide a very high strength to gauge ratio and the film is
generally very good for retail applications. Cryovac leads the industry in the highest performance shrink film available.
Polypropylene - A thermoplastic polymer of propylene. Polypropylene materials are generally oriented, heat-set (OPP) materials
which do not shrink.
Preferential Shrink - The characteristics of a shrink film which enable it to shrink more in on direction (longitudinal or transverse)
than the other. Longitudinal orientation is accomplished by a device which stretches the film in the machine direction. Transverse
orientation is induced by a process such as tentering which applies across the web stretching.
PVC (Polyvinyl Chloride) - Compounding modifications and a variety of production processes adapt PVC to a wide variety of end
uses. In manufacturing, the film can be blown, solution case, calendered, and slot die chill cast-in thicknesses from 0.0004-0.010
mil. It is readily oriented to produce a shrink film.
Saran (Polyvinylidene Chloride) - Saran films are made from copolymer that is predominately vinylidene chloride (PVDC). Due
to the very high chlorine content of the polymer, unplasticized saran film is highly crystalline and has high barrier to passage of
oxygen and other gases, water vapor, odors, aromas, and flavors.
Unbalanced - Unequal orientation in LD and TD; preferential or monoaxial orientation.
Cryovac D-955
D-955 Film has been specially formulated by Cryovac scientists to meet the demand for a
shrink film with exceptional toughness combined with excellent merchandisability. It can well be
described as a "work-horse" film: tough, durable, with the versatility to be used in a wide range of
applications.
Superior abuse and puncture resistance make D-955 ideal for packaging products that must
survive rough handling in distribution, such as multipackaging for warehouse clubs. Its high
shrink energy tightly unitizes multiple items, often eliminating the need for supporting trays or
banding.
Because of its wide range of shrink properties, D-955 Film performs equally well for unusualshape objects, window boxes, and heavy products with premium add-ons or "pack-ons." The
film's excellent memory prevents it from relaxing under fluctuating temperatures. This same
memory feature is especially important if a product is handled a great deal while on retail display;
the package stays taut and wrinkle-free.
Exceptional tensile strength enables D-955 Film to be used in thinner gauges than competitive
films while delivering the same degree of protection. It also produces very high-integrity seals
over a broad temperature range, and runs at excellent speeds on various types of packaging
equipment.
At the point of sale, D-955 outperforms other films in merchandising appeal with excellent
optics. Its exceptional clarity (both see-through and contact), high gloss and sheen impart a
premium look to consumer products, giving them a distinct advantage in eye appeal.
The versatile way to unlimited packaging
If versatility is what you
need, Cryovac® D-955
Shrink Film is what you are
looking for. Everything from
complementary products like
motor oil and transmission
fluid to sampling products
like mouthwash and chewing
gum, and multiple packages
of shutters, canned goods,
aerosol cans and so much
more.
®
D-955 offers both excellent strength and world
class optics. Its exceptional tensile strength
means you can save on packaging costs by
utilizing thinner gauges. This strength assures
abuse and puncture resistance and subsequent
product protection.
This makes D-955 ideal for multipacking and shrink-wrapping products with premium
add-ons. Its high shrink energy tightly unitizes multiple items while its clarity lends a
premium look to products that depend heavily on eye appeal at the retail level.
Film Highlights
Type of Material.
Appearance.
Extremely tough, multilayer, crosslinked polyolefin.
Superior clarity, gloss and sheen give
products maximum appeal at point of
sale.
Machineability.
Toughness.
Medium to high slip enables it to be run Superior abuse and puncture
on various types of equipment:
resistance; can be used in thinner
centerfold, reverse-fold and form-fill seal gauge.
machines.
Forms available.
Singlwound (SW) in widths to 63";
centerfolded (CF) in widths to 58".
Gauges.
Sealing techniques.
60, 75, 100 and 125.
Impulse, constant heat, electrostatic.
Comparative Properties Chart
CRYOVAC Series D-955 Films
Gauge
60
75
100
Minimum Use Temp.
-60 deg. F.
Maximum Storage
Temp.
90 deg. F.
125
(two years maximum)
Shrink Temp. , Air
250-350 deg. F.
Density @ 73 deg. F.
0.922
(g/cc)
Haze (%)
2.4
2.6
2.7
2.7
Gloss (%)
87.3
88.2
88.8
86
Ball Burst Impact
Strength (cm/kg)
17.7
21.7
28.5
30.3
8,548
6,726
4,941
3,350
1.38
1.09
0.82
0.74
Oxygen Transmission
Rate
(cc/m*m/24hrs., 73 deg. F., 1
atm)
Water Vapor
Transmission Rate
(gms/100 sq. in./24 hrs., 73
deg. F., 100% RH)
LD*
Tensile Strength (psi) 14,300
Elongation at Break
(%)
120
Modulus of Elasticity 50,100
(psi)
Tear Propagation (gms)
Unrestrained Shrink
(%)
6.1
TD**
LD*
TD**
LD*
TD**
LD*
TD**
17,300
15,400
16,800
15,200
17,900
14,700
16,400
105
130
110
140
110
155
135
55,800
52,500
57,200
52,900
58,600
47,400
52,800
4.6
8.7
7.1
13.2
9.5
17.5
14.5
@200 deg. F.
@220 deg. F.
@240 deg. F.
@260 deg. F.
13
21
47
78
19
30
54
78
16
24
51
78
18
30
56
79
13
20
48
77
22
35
59
76
9
20
62
76
20
32
66
77
Note: These are typical values for Cryovac films. They are intended for use as limiting
specifications.
*Longitudinal Direction **Transverse Direction
This information represents Cryovac's best judgement base on work done, but Cryovac & Pierce Packaging assumes no liability
whatsoever in connection with the use of information or findings contained herein.
D-955 complies with the requirements of the Federal Food, Drug and Cosmetics Act, as amended, for the packaging of all foods,
with the exception of high alcoholic substances, at temperatures of 100 degrees C. and below.
Cryovac D-940
D-940 Film is the result of break-through technology that creates the first true polyolefin soft
shrink film.
D-940 Film is a multilayer, electronically cross-linked film produced through a proprietary
coextrusion process and designed to provide a low shrink energy. This unique property enables
a variety of products to be effectively shrink-packaged without distortion or buckling to detract
from their sales appeal.
D-940 Film is ideal for paper products such as stationery, magazines, greeting cards and
computer manuals.
Excellent clarity and gloss of D-940 Film enhance merchandising of products whose true colors
are critical to the sale (wallpaper, giftwrap, textiles, etc.).
It is specifically suitable for window box packaging and for products that use lightweight
chipboard trays or containers.
D-940 Film provides excellent machinability on automatic equipment and produces highintegrity heat seals. Unlike PVC films, D-940 is noncorrosive and causes no carbon buildup on
sealing wires.
Superior cold-flex properties keep the film pliable even at sub-freezing temperatures.
Sometimes the softest things are the hardest things to package.
Products like linens, bedding, gift
wrap, stationary and snack foods.
Ironically, the very thing that makes
them so appealing also makes them
difficult to package. Cryovac® D-940
soft-shrink film allows you to package
soft goods without the buckling and
distortion that can turn shoppers off at
the point of sale.
D-940 film from Cryovac eliminates
unsightly dog ears, fish eyes and crow's
feet, and it gives products an additional
merchandising advantage with reduced
haze and greater sparkle. This
translates into great appeal on the retail
shelf.
This soft-shrink film helps
showcase items such as books,
magazines, computer manuals,
notebooks, photo albums, school
supplies and printed or converted
paper products. It's ideal for
products packaged in lightweight
chipboard trays or containers that
normally buckle when wrapped
with most shrink films. Since this
film conforms to odd shapes, it
creates a beautiful package for
hard-to-package
Film Highlights
Type of Material.
Multilayered, coextruded polyolefin.
Machineability.
Appearance.
Superior optics with low shrink energy.
Toughness.
Very "forgiving" film, because it runs on Excellent seal strength.
just about any kind of equipment, under Forms available.
just about any conditions.
Singlwound (SW) in widths to 63";
centerfolded (CF) in widths to 58".
Gauges.
Sealing techniques.
60 and 75.
Impulse, constant heat, electrostatic.
Comparative Properties Chart
CRYOVAC Series D-940 Films
Gauge
60
75
Minimum Use Temp.
0 deg. F.
0 deg. F.
Maximum Storage Temp.
90 deg. F.
90 deg. F.
(two years maximum)
Shrink Temp. , Air 200-325 deg. F.
Density @ 73 deg. F. (g/cc)
200-325 deg. F.
0.932
0.932
Clarity (%)
83
85
Gloss (%)
86
95
Ball Burst Impact Strength (cm/kg.)
8
11
13,800
12,000
2.8
2.4
Oxygen Transmission Rate
(cc/m*m/24hrs., 73 deg. F., 1 atm)
Water Vapor Transmission Rate
(gms/100 sq. in./24 hrs., 73 deg. F., 100% RH)
LD*
Tensile Strength (psi) 11,300
Elongation at Break (%)
98
Modulus of Elasticity (psi @ 73 deg. F.) 29,000
TD**
LD*
TD**
9,800
10,980
11,042
130
110
100
29,000
29,000
29,000
Tear Propagation (gms)
11
15
23
13
Unrestrained Shrink (%) @160 deg. F.
@180 deg. F.
@200 deg. F.
@220 deg. F.
@240 deg. F.
@260 deg. F.
@280 deg. F.
8
9
23
44
69
81
82
7
15
28
45
68
77
77
8
15
28
43
69
81
82
6
14
32
44
68
78
79
Note: These are typical values for Cryovac films. They are intended for use as limiting
specifications.
*Longitudinal Direction **Transverse Direction
This information represents Cryovac's best judgement base on work done, but Cryovac & Pierce Packaging assumes no liability
whatsoever in connection with the use of information or findings contained herein.
D-940 complies with the requirements of the Federal Food, Drug and Cosmetics Act, as amended, for the packaging of all foods,
with the exception of high alcoholic substances, at temperatures of 65 degrees C. and below.