Yam, Kit L. (ed.). The Wiley encyclopedia of packaging technology

Подождите немного. Документ загружается.

10. R. J. Winne, ‘‘What Really Happens to Your Package in Trucks

and Trailers’’ in Proceedings of Western Regional Forum of the

Packaging Institute, USA, 1977.

11. R. D. Newton, Fragility Assessment Theory and Test Proce-

dure, Monterey Research Laboratory, Inc., Monterey, CA,

1968.

12. D. E. Young and S. R. Pierce, Development of a Product

Protection System, Shock and Vibration Bulletin, No. 42,

Ofﬁce of the Secretary of Defense, Research and Engineering,

Washington, DC, 1972.

13. ASTM D3332-99, Standard Methods for Mechanical-Shock

Fragility of Products Using Shock Machines, American So-

ciety for Testing and Materials, 2004.

14. ASTM D3580-95, Standard Method of Vibration (Vertical

Sinusoidal Motion) Test of Products, American Society for

Testing and Materials, Philadelphia, PA, 2004.

15. J. P. Phillips, ‘‘Package Design Consideration for the Distri-

bution Environment,’’ Proceedings of the 1979 International

Packaging Week Assembly, Packaging Institute, October 1979.

16. J. F. Perry, A Brief Summary of Dynamic Test Methods for

Shipping Containers, Del Monte Corporation, Walnut Creek,

CA, March, 1982.

17. The 2008 ISTA Resosurce Book, International Safe Transit

Associon, 2008.

General References

C. M. Harris and A. G. Piersol, Harris’ Shock and Vibration

Handbook, 5th edition, McGraw-Hill, New York, 2002.

C. E. Crede, Vibration and Shock Isolation, John Wiley & Sons,

New York, 1951.

J. F. Perry, ‘‘Cost Reduction Through Dynamic Testing of Shipping

Containers,’’ Packaging Technology (June/July 1982).

W. Silver and E. Szymkowiak, ‘‘Recommended Shock and Vibra-

tion Test for Loose Cargo Transported by Trucks and Rail-

roads,’’ Proceedings of the Institute of Environmental Sciences,

1979.

ASTM D 5276-98, Drop Test for Shipping Containers, American

Society for Testing and Materials, Philadelphia, PA, 2004.

ASTM D 1596-97, Method of Testing for Dynamic Properties of

Package Cushioning Materials, American Society for Testing

and Materials, Philadelphia, PA, 2003.

ASTM D 999-07, Standard Methods for Vibration Testing of

Shipping Containers, American Society for Testing and Mate-

rials, Philadelphia, PA, 2007.

TESTING, SHIPPING CONTAINERS

ALFRED H. MCKINLAY

Consultant, Pattersonville,

New York

Shipping containers are tested in the laboratory to verify

their ability to survive hazards in the distribution envir-

onment. Tests may be conducted as a packaging develop-

ment tool for quantitative purposes, or as a qualitative

measure of performance. Objectives may be reduction of

damage, cost improvement, assurance of safe product

shipment, or other package-design reasons. Laboratory

preshipment tests, utilizing proven industry standards,

will provide a high level of assurance that a package

design will function properly and safely deliver its con-

tents, without cumbersome trial shipments. Such trials

require a large number of test packages and signiﬁcant

time delay before an indication of success or failure. They

provide no fundamental data, are expensive to conduct,

and may severely delay introduction of new products to

the marketplace. While some trial shipments are a good

idea as a ﬁnal check, prior laboratory testing is a much

quicker indicator of success or failure and can precisely

identify causes of inadequacy.

SOURCES OF TEST METHODS

The oldest and largest developer of packaging test meth-

ods, including those for shipping containers, is ASTM

International (American Society of Testing and Materi-

als). ASTM test methods, which are based on a balanced

consensus approval process, have worldwide acceptance.

Updated at least every 5 years, their standards for packa-

ging began development in 1914 and now include over 130

test methods, speciﬁcations, or practices, which are in-

cluded in the ASTM Annual Book of Standards, Volume

15.10 (1).

The International Safe Transit Association (ISTA) pub-

lishes several types of preshipment testing procedures.

These include: Series 1 Non-simulation Integrity Tests,

Series 2 Partial Simulation Tests, Series 3 General Simu-

lation Tests, Series 5 Focused Simulation Tests, and Series

7 Development Tests (2).

Internationally, the International Organization for

Standardization (ISO) develops and maintains test meth-

ods for shipping containers that are similar to, but not

exactly the same as, those of ASTM. ISO standards may be

obtained from the American National Standards Institute

(ANSI) in New York City.

ENVIRONMENTAL HAZARDS TO SHIPPING CONTAINERS

Shipping containers and interior protective packaging

serve the primary purpose of protecting products against

environmental hazards occurring in distribution. An early

deﬁnition of these hazards was set forth in a 1979 report

by the Forest Products Laboratory of the USDA (3), FPL

22, and still remains a source of many test methods and

levels of intensities. It identiﬁes the following hazards as

the major causes of damage in distribution: rough hand-

ling, shock and vibration in transit, compressive forces,

and temperature and humidity extremes. Experience of

many shippers supports the contention that these hazards

are still the major culprits, with rough handling clearly

the most severe and frequent cause of damage. Since the

late 1980s, instrumentaion progress has made it possible

to measure shock, vibration, temperature, and humidity

much more accurately and easily. Packaging researchers

1218 TESTING, SHIPPING CONTAINERS

have used these instruments to update and enlarge the

database from FPL22 (3) since that time.

TEST METHODS FOR REPRODUCING SHIPPING

HAZARDS

Each of the major distribution hazards of handling, shock

and vibration in transit, and compression can be repro-

duced by one of several test methods, depending on the

type of container, test equipment availability, or purpose

of test. The following discussion covers the most widely

used ASTM methods.

Drop test

Accidental or purposeful dropping or striking of contain-

ers during handling, loading, and unloading is the prime

source of damage to most packages under 200 lb. ASTM

test method D5276, Drop Test of Loaded Containers by

Free Fall, describes the equipment and methodology for

conducting a laboratory simulation of this hazard. All

types of shipping containers may be tested, including

boxes, cylindrical containers, bags, and sacks. Accuracy

of the drop-test equipment is speciﬁed, including a re-

quirement for impact surface mass of at least 50 times

that of the heaviest container to be tested. The method

may be used to check the ability of the container to survive

free fall, evaluate the protective capability of container

and inner packing, compare performance of different

package designs, or permit observation of progressive

failure of a container and damage to its contents.

An alternative to free-fall drop is ASTM test method

D5487, Simulated Drop of Loaded Containers by Shock

Machine. This method provides more accurate package

positioning for impacts, particularly on ﬂat impacts where

the shock transmitted to package contents is usually

greatest. While the shock machine method has been

shown to be quite accurate for most applications, rigid

package systems are not recommended for testing by this

method (where ‘‘rigid’’ means a natural frequency above

83 Hz for the system).

Incline Impact Test

For large shipping containers, an alternate method for

obtaining an impact is ASTM test method D880, Impact

Testing for Shipping Containers & Systems. A guided test

carriage, tilted at 101, is loaded with the test specimen on

the leading edge and pulled up the incline to a distance

sufﬁcient to produce the desired impact velocity. The

carriage is then released and travels down the incline

until the container strikes the impact surface, also tilted

at 101. When the incline test equipment, dubbed the

‘‘Conbur test,’’ is constructed with impact surface at least

50 times the mass of the heaviest test specimen, it is

considered equivalent to a free-fall drop test for intensity

of shock. ASTM D880 also includes the use of pendulum

equipment as an alternative to the incline.

A popular test sequence and level of intensity for the

incline impact test is the ISTA 1B procedure for containers

and skidded or palletized items weighing over 150 lb. It

speciﬁes an impact velocity of 5.75 ft/s with impacts on all

four sides, followed by a rotational bottom drop from 8 in.

high. The incline impact equipment may also be modiﬁed

such that it can reproduce shocks similar to railcar switch-

ing impacts. ASTM test method D5277, Performing Pro-

grammed Horizontal Impacts Using an Inclined Impact

Tester, describes the required carriage bulkhead, program-

ming material or device, and other modiﬁcations that are

necessary for simulating standard railcar draft-gear im-

pacts. The method is not appropriate for long-travel draft

gears or cushioned railcar underframes.

Horizontal Impact Test

A more accurate method of reproducing all types of railcar

impacts is described in ASTM test method D4003, Pro-

grammable Horizontal Impact Test for Shipping Contain-

ers and Systems. The test equipment speciﬁed is a

horizontal shock machine with precise control over impact

and rebound velocities. Dynamic compression of contain-

ers during railcar switching is great, due to backload of

other freight pressing against it; therefore, the test

method describes how such backload should be simulated

during testing. Proper instrumentation and calibration,

critical to the method’s accuracy, are speciﬁed in some

detail. ASTM D4003 may also be used for other types of

horizontal impact simulation, such as pallet marshaling.

Bridge Impact Test

Some handling systems place heavy stress on long

packages, particularly in small-parcel shipping. ASTM

test method D5265, Bridge Impact Testing, speciﬁes

equipment and methodology for applying impacts to the

center of long packages. Two options are included; A, for

using a free-fall drop tester; or B, for using a SMITE

tester. In both methods, the package is supported on its

ends and an impacting device drops onto its center at a

speciﬁed impact velocity.

Concentrated Impact Test

Thin-walled

shipping containers and

plastic wrapped

items often incur damage to contents due to impacts

from other packages or handling devices. The impacts

typically do not cause a puncture but do impose severe

deﬂection of the container wall, resulting in damage to the

contents. ASTM test method D6804, Test Method for

Concentrated Impacts to Transport Packages, speciﬁes

equipment and methods for applying concentrated im-

pacts to speciﬁc surfaces of the package.

Other Handling Tests

ASTM Standard D6179, Rough Handling of Unitized

Loads and Large Shipping Cases & Crates, contains a

number of test methods particularly suited to reproducing

handling hazards for either unitized loads or large con-

tainers or both. Included are the following:

Free-Fall Drop Test. This utilizes a quick-release hook

and sling for equipment to drop test on any con-

tainer surface.

TESTING, SHIPPING CONTAINERS 1219

Rotational Edge-Drop Test. One end of the specimen

is supported on a block while the opposite end is

raised to speciﬁed height and then dropped to the

ﬂoor.

Corner Drop Test. One bottom corner is supported on

a block while the diagonally opposite bottom corner

is raised to speciﬁed height and then dropped to the

ﬂoor.

Raised-Edge Drop Test. One end of the specimen is

raised to a speciﬁed height while the opposite end

rests on ﬂoor, and then the raised end is dropped to

ﬂoor.

Rolling Test. This determines the ability of a con-

tainer to withstand the effects of rolling.

Tip Test. This determines the ability of tall or top-

heavy containers to resist tipping over.

Tipover Test. This determines the protective ability of

loaded shipping containers when subjected to tip-

over impacts.

ASTM Standard D6055, Mechanical Handling of Uni-

tized Loads and Large Containers or Crates, provides

methods of testing handling capabilities using lift trucks,

grabhooks, or slings. A test course and methodology is

described for handling tests by four types of lift truck:

fork, spade, clamp, and push–pull.

VIBRATION TESTS

Although vibration-induced damage is not a frequent

problem for most packaged products, vibration does occur

with certainty on every shipment by any mode of trans-

port. It is therefore important to test all types of shipping

containers for vibration. Four methods of vibration testing

are available, depending on equipment and test objective.

ASTM test method D4728, Random Vibration Testing

of Shipping Containers, provides the closest simulation to

actual vibration received by containers in transit. Input

for the test may be generated from ﬁeld measurements

made with accurate recording instruments or from use of

the sample vibration spectra for commercial transport

that is included in the standard. Test durations frequently

run as long as 3 h or more, depending on the packaged

product, distance shipped, and objective of the test. Re-

sonance buildups during random vibration are less in-

tense than by sinusoidal vibration methods, and

unrealistic fatigue damage is therefore minimized.

ASTM Standard D999, Vibration Testing of Shipping

Containers, actually contains four distinct test methods

and utilizes two entirely different types of vibration

equipment. Method A is a repetitive shock test, not really

vibration in the pure sense, and is divided into A1 for

rotary motion and A2 for vertical motion. Both tests are

conducted with the package free to bounce on the table,

which is running at a frequency causing the package to

just lift off during the upstroke of each vibration cycle

(known as 1G+). The operating frequency and table dis-

placement are constant throughout the test, which is

usually performed on a mechanical-type vibrator. Typical

test duration is about 1 h with smaller, nonskidded

containers tested one-third of the duration on each axis.

The two methods do not create the same type of motion;

therefore, they also do not cause the same types of

damage.

Methods B and C of D 999 are resonance search and

dwell tests, typically performed on electrohydraulic equip-

ment that easily performs at 3–200 Hz as required for

most packaging tests. The table displacement varies in-

versely with the frequency so as to maintain a constant

level of force, usually 0.25 G to 1 G. The purpose of the test

is to locate natural frequencies of the packaged product

and then dwell for a speciﬁed time at each natural

frequency while the package resonates. Procedures are

described for sweeping the vibration frequency up and

down to locate the natural frequency points. Method B is

conducted on single containers while Method C is con-

ducted on stacks of containers or unitized loads. Typical

dwell times at resonance for both methods is 5–15 min for

each point, although some users dwell for up to 1 h.

Compression Tests

The effects of stacking one container on another in storage

or transportation can be studied by means of the compres-

sion test. Two ASTM test methods are available: D642,

Determining Compressive Resistance of Shipping Contain-

ers, and D4577, Compression Resistance of a Container

Under Constant Load. The former requires a testing

machine that applies a steadily increasing force to the

container until it fails. A recording device notes applied

load and container deﬂection during testing that generally

requires r2

min for completion.

ASTM test method D4577

may use a similar machine, but more typically utilizes a

simple stationary apparatus that positions the test speci-

men under a ﬁxed constant load for the desired time,

anywhere from 1 h to 1 year. Both methods may be used on

ﬁlled shipping containers or on empty ones, depending on

test objective.

Water-Vapor Transmission Test

To measure the resistance of shipping containers to water

vapor, ASTM D4279, Water Vapor Transmission of Ship-

ping containers, provides two test methods. The constant-

atmosphere method is conducted at 90% rh and 1001F. The

cycle method goes up and down, from 01F to 1001F., 90% rh

and back, for a number of speciﬁed cycles. Different

procedures are deﬁned for reclosable and nonreclosable

containers.

Water-Resistance Test

ASTM test method D951, Water Resistance of Shipping

Containers by Spray Method, determines how well a ﬁlled

container will resist water spray such as produced by

heavy rains or waves over the deck of a ship. The test is

frequently conducted in a series with other tests such as

drop or incline impact.

CONDITIONING FOR TESTING

A requirement in all ASTM shipping container test meth-

ods is for testing at a speciﬁed condition of temperature

1220 TESTING, SHIPPING CONTAINERS

and humidity. A variety of atmospheric conditions are

described in D4332, Conditioning Containers, Packages,

or Packaging Components for Testing. This standard

practice provides special conditions that may be used to

simulate particular ﬁeld conditions that a container may

encounter during distribution. The standard also de-

scribes procedures for preconditioning the containers to

ensure that they reach equilibrium in the atmosphere

before they are exposed to the ﬁnal test conditions.

Following preconditioning, containers are placed in the

conditioning chamber for a speciﬁed time, ordinarily at

least 72 h, to reach equilibrium at test conditions. Most

testing is conducted at the U.S. standard conditioning

atmosphere of 731F and 50% rh, but other test atmo-

spheres may also be used, as listed in Table 1.

PERFORMANCE TESTING

The test methods described to this point may be used in

several ways by package designers. The most frequent use

is as an engineering development tool to ascertain how

well design and materials are doing their job of protecting

the product. But the same methods may also be utilized to

indicate whether the package will perform as expected for

the total distribution cycle. Whereas engineering develop-

ment testing often overstresses the package to determine

its limits when subjected to a particular hazard, the

performance use of the same methods is a pass/fail, go/

no-go situation with the same container going unopened

through the full set of tests. Development testing is a

quantitative measure, while performance testing is

qualitative.

ASTM D4169, Standard Practice for Performance Test-

ing of Shipping Containers and Systems, has received

wide acceptance as a national standard for measuring

expected shipping-container performance. It is essentially

a matrix of test methods, distribution modes, and levels of

test intensities. Putting them together in a sequence that

simulates a particular distribution environment produces

a ‘‘distribution cycle’’ (DC) containing certain hazards

(tests). If the shipping container and contents survive

the DC, then it can be assumed that they will also survive

in actual handling and shipping by the same method of

distribution (DC). ASTM D4169 also requires that the

criteria of acceptance (deﬁnition of success or failure) be

predetermined and documented prior to testing.

Each hazard in distribution is identiﬁed in D4169 with

a test method to reproduce it. Table 2 lists the nine hazard

elements recognized in the performance standard, along

with the corresponding test methods.

Presently, there are 18 distribution cycles in D4169,

each containing a sequence of hazards expected by that

particular distribution method. Table 3 is a listing of the

cycles with hazards noted by their code letters from Table 2.

For those packaging engineers with a good knowledge

of their distribution environment(s), DC 2 has become the

performance test plan of choice. It permits them to develop

a test plan that ﬁts the often unique sequence of hazards

that their packages encounter in distribution.

Since 1997 ISTA has also developed several perfor-

mance or general simulation test procedures which are

somewhat different than ASTM’s. They are Procedure 3A

for Parcel Delivery System Shipments, 3E for Unitized

Loads of Same Product, 3F for Distribution Center to

Retail Outlet Shipments, and 3 H for Mechanically

Handled Bulk Transport Containers. There is also a

focused simulation Procedure 5B for Temperature Con-

trolled Transport Packages.

REGULATORY AGENCY USE OF CONTAINER TESTING

Shipping-container performance requirements, as a sub-

stitute for material or design speciﬁcations in regulatory

documents, has been slowly making progress. The U.S.

Department of Transportation (DOT) now requires that

many hazardous materials be packaged in conformance to

a brief set of performance-test speciﬁcations rather than

to cumbersome and complex material and design speciﬁ-

cations previously required (4). The National Motor

Freight Classiﬁcation in 1995 authorized an alternate

rule, Item 180, performance requirements for LTL ship-

ments, which can be utilized at the shipper’s discretion

Table 1. Special Atmospheres

Environment Temperature,

1F(1C)

Relative Humidity

(rh), %

Cryogenic 6776(5573)

Frozen-food storage 074 (–1872)

Refrigerated storage 4174(572) 8575

Temperate, high-humidity 6874 (2072) 9075

Tropical 10474 (4072) 9075

Desert 14074 (6072) 1572

Table 2. Hazard Elements and Corresponding Tests

Code Hazard Element Test Simulation of Hazard ASTM Designation

A Handling— manual and mechanical Drop, impact, stability D5276, D880, D4003, D6055, D6179

B Warehouse stacking Compression D642

C Vehicle stacking Compression D642

D Stacked or unitized vibration Random vibration D4728

E Vehicle vibration Random or sinusoidal vibration D4728, D999 Method B or C

F Loose-load vibration Vibration (aka repetitive shock) D999 Method A1 or A2

G Rail switching Longitudinal shock D4003, D5277

H Climate, atmospheric conditions Temperature, moisture humidity D4332

I Low Pressure Vacuum D6653

TESTING, SHIPPING CONTAINERS 1221

instead of other material- and design-based rules or

special package numbers (5).

BIBLIOGRAPHY

1. Annual Book of Standards, Volume 15.10, ASTM Interna-

tional, West Conshohocken, PA, 2007.

2. Pre-shipment Test Procedures, International Safe Transit

Association, East Lansing, MI, 2007.

3. F. E. Ostrem and W. D. Godshall, An Assessment of the

Common Carrier Shipping Environment, General Technical

Report FPL 22, U.S. Forest Products Laboratory, USDA,

Madison, WI, 1979.

4. Code of Federal Regulations Title 49, U.S. Department of

Transportation, Ofﬁce of Hazardous Materials Safety,

Washington, DC, 2006.

5. National Motor Freight Classiﬁcation, American Trucking

Association, Alexandria, VA, 2006.

THERMOFORM/FILL/SEAL

EDWIN HO

OSI Industries,

Lisle, Illinois

Thermoform/ﬁll/seal equipment is used for a variety of

food and nonfood packaging applications. Thermoform/ﬁll/

seal (TFFS) machines use two continuous webs or rolls of

ﬁlm (see Figure 1). Typically, the lower web is formed into

a cup, pouch, tray, and so on, which is then ﬁlled with

product. The upper web becomes the lid or cover. Although

over 90% of all TFFS machines are run with formed

bottom webs and unformed lidstock, it should be men-

tioned that this is not always the case. Sometimes both

webs are formed; sometimes the top web is formed, and

the bottom one is not, depending on product presenata-

tion, marketing need, competitive packaging advantages,

and so on.

PACKAGING APPLICATIONS

TFFS machines were originally designed as vacuum-

packaging machines to package ham, bacon, or sausage.

From cured meats, their use spread to other sectors of the

meat industry (frozen steaks, certain fresh meats, cook-in-

package delicatessen meats), and then to cheese products,

baked goods, fresh pasta, and a variety of perishable food

products requiring extended shelf life.

Nonfood applications of TFFS evolved from the original

vacuum-packaging machines for sausage and meat pro-

ducts. These are primarily sterile-medical applications.

Typical medical items packed on TFFS equipment are

syringes, needles, catheters, kidney-dialysis ﬁlters, scrub

sponges, surgical drapes and clothing, operating-room

kits, and many other items. Although medical TFFS

machines are structurally and conceptually the same as

TFFS machines used in the food industry, the materials

Table 3. Performance Test Sequence by Distribution Cycle

DC Hazard Element

Distribution Cycle (DC) Number Sequence

General schedule—undeﬁned distribution system 1 A, D, F, G, A

Specially deﬁned distribution system, user-speciﬁed 2 User-speciﬁed from Table 3

Hazard Elements

Single-package environment, r100 lb 3 A, C, F, E, A

Motor freight

Single package >100 lb 4 A, C, F, E, A

Truckload, not unitized 5 A, D, E, A

Truckload or LTL, unitized 6 A, D, A, B

Rail, carload

Bulk loaded 7A,D,G,A

Unitized 8 A,D,G,A,B

Rail and motor freight

Not unitized 9 A,C,E,G,F,A

Unitized 10 A, D, G, A, B

Trailer-on-ﬂatcar, container-on-ﬂatcar 11 A, G, D, F, A

Air and motor freight

>100 lb 12 A, D, I, E, A

r100 lb 13 A, C, F, I, E, A

Warehousing (partial cycle to be added to other cycles as needed) 14 A, B

Export/import shipment

By intermodal container or roll on/roll off equipment (partial

cycle to be added to other cycles as needed)

15 A, C, A

For palletized cargo ship (partial cycle added as needed) 16 A, C, A

For breakbulk cargo ship (partial cycle added as needed) 17 A, C, A

Non-commercial Government shipments 18 A, B, C, A, H, F, A

1222 THERMOFORM/FILL/SEAL

tend to be more difﬁcult to run and the quality standards

for cutting and thermoforming are more difﬁcult to meet.

Among the TFFS applications that are not food or medical

are the following: hardware items, cigarette lighters,

cosmetics, and similar applications where packages

made on continuous-web machinery are replacing pre-

formed plastic ‘‘blisters’’ (see Carded packaging).

Food Packaging

In food applications, the packages are almost always

hermetically sealed, and the ﬁlms have various degrees

of barrier properties. The primary application for vacuum

packaging is to improve shelf life of foods that are sensi-

tive to oxygen or susceptible to dehydration. Almost all

cured-meat products (ham, bacon, sausage, corn beef, beef

jerky, etc.) are vacuum-packaged, as are many cheeses. An

off-shoot of vacuum packaging is controlled atmosphere

packaging (see Modiﬁed atmosphere packaging). A mod-

iﬁed atmosphere package produced on TFFS equipment is

a step beyond vacuum packaging. First, the unsealed

package is indexed automatically into a vacuum chamber.

Then all the air is removed from the package. Once the air

is removed, the desired gas mixture is injected into the

package, usually until the pressure of gas inside the

package reaches about one atmosphere. Table 1 lists

some commonly used gas mixtures and their application.

Vacuum and modiﬁed atmosphere packages are gener-

ally used to protect refrigerated perishable foods that

would otherwise spoil in less than a week. In a modiﬁed

atmosphere, they may stay fresh for 4–6 weeks or longer.

Many frozen foods are also packed on TFFS machinery,

and a modiﬁed atmosphere can sometimes replace freez-

ing (see Figure 2). Some nonperishable foods with shelf

life of over one year can be packaged on TFFS equipment.

In Europe, for example, shelf-stable heat-processed vege-

tables are marketed in retorted thermoformed packages.

Thermoforming machines can be modiﬁed to mechanically

cold-form aluminum foil for retort processing of various

meat and nonmeat dishes. The taste, texture, and nutri-

tional quality of food in retort-sterilized aluminum foil

pouches is generally higher than that of conventionally

canned foods (see Retortable ﬂexible and semirigid

packages).

TFFS MACHINES

The essence of TFFS machines is their modularity. Within

any given machine designation, an almost inﬁnite number

of conﬁgurations is possible. There are six basic operations

that make up the production of a package on TFFS

equipment: ﬁlm advance, thermoforming, loading, sealing,

cutting, and labeling/printing (see Figure 3).

Film Advance

TFFS machines are built like miniature assembly lines

with separate stations for different operations. There are

several ﬁlm-advance mechanisms for moving the webs

through these stations. The drive mechanism such as 2

Figure 1. Thermoform/ﬁll/seal machine. Shown with lower web-

forming station in foreground. Note extensive product-loading

area.

Table 1. Gases Used in Packages Produced on TFFS Equipment

Gas Application

As a pressure-relief agent to prevent external atmosphere from crushing the product. N

is an inert gas. It does not react with

either the food substances or bacteria. Common applications include bulk-pack bacon and sausage, shredded and sliced

cheese, and beef jerky.

Depending on the application, 25–100% CO

may be used. CO

lowers the pH of the food product and can exert a powerful

slowing effect on the growth of bacteria and molds. Primary application is for baked goods, cookies, cakes, and breads, as

well as dough and pasta products. CO

tends to be absorbed into the actual body of the food product itself. On one hand, CO

is frequently mixed with N

to prevent the package from clinging too tightly to the product. On the other hand, some

products that are not sensitive to strong pressure or tight cling, but that are susceptible to spoilage by mold growth, are

packed in an atmosphere of 100% CO

. An example of this is chunk cheese. Many CO

gas packages have the appearance of

a vacuum package, with much of the CO

absorbed into the product itself. In an extreme instance, container collapse in

shredded cheese can occur due to extended CO

absorption by cheese causing negative internal pressure if 100% CO

used. A mixture of 80%/20% of CO

is recommended to prevent package collapse and is still able to prevent mold growth

in cheese.

The application using O

are primarily for red meat. The concept has been progressively used in the United States and

Europe for centrally packed retail cuts in the past decade. The O

is used as an oxygenating agent, at levels in the range of

40–80%, to form the bright-red, fresh-meat color called oxymyoglobin. When O

is used, it is usually mixed with CO

and

:CO

for its preservation effect, N

to provide a bulking agent. The O

tends to disappear inside the package. It can be

metabolized by the meat to CO

that is absorbed in the water phase of the meat as carbonic acid.

THERMOFORM/FILL/SEAL 1223

speed motor, frequency, servo driven, and so on (i.e., AC

Digital, DC Digital, Geneva, Elliptical Gear, Planetary

Gear, Emerson), differ as to accuracy of advance, accel-

eration curve, or suitability for print registration of

stretchable or nonstretchable materials.

Thermoforming

This is the ﬁrst step in the formation of a package.

Thermoforming (see Thermoforming) may involve heating

in the forming die or preheating in a separate station.

There are two main ways to thermoform: positive (male)

and negative (female). Female forming involves using

compressed air or vacuum to pull the heated, softened

ﬁlm into a mold. It is this mold or concave surface that is

the die that produces package shape and surface detail. A

mechanical plug (plug assist forming) may help to push

the ﬁlm down into the cavity and provide more uniform

material distribution.

Positive (male) forming is the reverse. Positive forming

usually permits the production of a package with greater

surface detail and more-uniform wall thickness. A male

die part operated by a piston provides package shape and

surface detail. Air outside the ﬁlm or vacuum on the

inside, or both air and vacuum, force the preheated ﬁlm

to drape itself onto the exterior of the plug. Positive

forming requires a separate station or two separate sta-

tions to preheat the ﬁlm. A typical package requires

thermoforming of only the lower web, but the machines

can also form both lower and upper webs. Usually each

product to be packaged requires its own separate forming

die. Major machine manufacturers have designed and

built thousands of different forming dies.

The lower web emerges from the forming station with the

pocket formed and ready to accept product. The loading

area must be long enough to accommodate the people

required for loading and inspecting, or automatic loading

equipment.

Sealing

Once the pockets on the web are loaded, the upper web is

indexed over them and the two webs are sealed (see

Sealing, heat). In food packaging, evacuation and, if

needed, gas injection (through nozzle or pin gas mechan-

ism) are performed at the sealing station. In order to

provide a more attractive package, sometimes all surfaces

of the top and bottom webs not in contact with the product

are sealed to each other. Sometimes, using a patented

process, steam is injected into the sealing die to shrink the

lower web (forming web) around the product to form an

attractive skin-tight package.

Cutting

Cutting systems range from the simple and inexpensive to

the complex and costly: paper-cutting-type knives (i.e.,

ﬂying knives and high-speed rotary knives); shear cutting

(machine direction) with cross-direction strip removal by

means of matched male and female dies; shear cutting

(machine direction) and cross-direction cutting by means

of steel rule dies; and complete package cutting with

matched male and female dies (Table 2). Among them,

matched male and female dies are the most suitable for

cutting application on semirigid and rigid material, but

they are also the most expensive compared to other

cutting methods.

Figure 2. Modiﬁed atmosphere package for perishable foods.

Fresh (unfrozen), precooked French fries (10 kg) packed in N

atmosphere. Positive (male) formed PVC/PE bottom, polyester/PE

cover. Print registration of ﬂexible upper web by means of

stretching with a brake.

Figure 3. A schematic of the simplest and most basic conﬁgura-

tion of a TFFS machine as would be used for ﬂexible, not

semirigid, upper and lower webs: 1, Lower or forming web; 2,

thermoforming die; 3, formed, unﬁlled pocket; 4, ﬁlled pocket; 5,

upper or lidding web; 6, vacuum/sealing die; 7, ﬂying knife for

across-the-machine direction package cutoff; 8, high-speed rotary

knives for package cutoff in the machine direction; and 9, ﬁnished

package (rectangular).

1224 THERMOFORM/FILL/SEAL

Labeling and Printing

Online printing may consist of simply printing, or emboss-

ing, a code date or lot number (see Code marking and

imprinting) or may consist of printing an entire index,

actually ‘‘bleeding’’ ﬁnished package edges. Labels may be

applied to either surface of either web by appropriate top

or bottom web labeler.

VACUUM AND SEALING-DIE OPERATION

At this station the package is evacuated and the two webs

are sealed together. In order to understand how this die

operates, it helps to think of the die as consisting of two

nesting, concentric boxes that close in sequence. The outer

box closes ﬁrst (see Figure 4). It mechanically seals off

that portion of the package represented by the lower web.

The upper web is narrower than the lower web and is not

sealed at this stage. Therefore, until the inner box closes,

atmosphere is free to enter or leave the package under the

lip of the upper web. The inner box is made up of the seal

mechanism. After the entire die chamber, including the

interior of the package, is evacuated, the inner box (the

seal mechanism) closes on both webs, ﬁrst sealing them

mechanically, so no air can enter or leave the package, and

then applying a permanent heat-seal (see Figure 5). The

key operation, package evacuation, takes place when air

ﬂows out of the package through the gap between the

narrow upper web and the outer wall of the die chamber.

This occurs during the interval after the outer box has

sealed off the lower web, but before the inner box has

closed off the package itself.

This is one of the most common methods of package

evacuation, also called the narrow web vacuum method. If

gas injection is required for modiﬁed atmosphere packa-

ging, the operation takes place in the sealing die using

nozzle or pin gas mechanism.

MATERIALS

The detailed design of a TFFS machine depends on the

packaging materials to be run. Therefore, any discussion

of how TFFS machines operate must refer to materials as

well. The two webs consist of a bottom web and a top web

on the type of equipment generally known as horizontal

thermoform/ﬁll/seal machines. In the usual case, the

bottom web is thermoformable and is formed by heat

into a cup or cavity, which forms a receptacle for the

articles to be packaged. However, all variations are

possible:

Top Web

Nonformable

Formable

Bottom Web

Formable

Nonformable

Formable

Nonformable

When food products are packaged, the webs are usually

made of multilayer materials selected for their barrier and

strength properties. Typically, a barrier material protects

against transmission of water and oxygen into or out of

the package. In the medical industry, however, products

are typically sterilized by ETO (ethylene oxide) gas. In this

case, high gas transmission is desired. As a result, the

TFFS machines use an upper web (also called lidding

material) (see Lidding) selected for high-gas transmission

Table 2. Cutting Methods for Rigid Materials

In-the-Machine Direction Across-the-Machine Direction

Squeezing knives Steel rule dies with rounded

corners

Shear cut knives with or

without strip removal

Strip removal for rounded

corners by means of

matched male and female

dies

Complete 3601 cut by means of

matched male/female dies

Figure 4. Evacuation. This shows the die after the ﬁrst or outer

box has closed. Vacuum is drawn inside the die chamber. Because

vacuum is drawn on the outside of the package from both above

and below, air pressure inside the package forces the two webs to

separate, providing a large opening for air to ﬂow out of the

package. During evacuation, the travel of air from the inside of

the package is through the gap between the narrow upper web

and the wide lower web. Package air exits along with air from

above the upper web. In this ﬁgure, the seal bar is in its upper, or

retracted, position so that air can leave the package.

THERMOFORM/FILL/SEAL 1225

properties as well as strength. Typical high-gas porosity

(lower gas barrier) materials include paper and Tyvek

(DuPont Company), a tough, spunbonded polyoleﬁn. Ta-

bles 3 and 4 list some commonly used materials in TFFS

applications.

Flexible materials such as nylon (see Figure 6) can

usually be formed by heating and pressure-forming into a

female die part. Cutting is usually by means of a ﬂying

knife in the cross-direction and high-speed rotary knives

in the machine direction. More severe draw ratios call for

a preheat station and plug assist. Nonrectangular shapes,

such as circles and ovals, can be cut with a ﬂying knife

traveling on a cam or with punch cutter.

Rigid and semirigid materials (Figure 7) usually re-

quire higher cost and more-elaborate forming and cutting

methods. Rigid ﬁlms usually call for one or more preheat

stations (single sandwich or double sandwich preheat) and

plug-assist forming in order to meet the package perfor-

mance and higher production speed requirement. If good

surface deﬁnition and uniform wall thickness is required,

positive (male-plug) forming is usually required.

In order to avoid sharp corners, rigid materials must be

cut by one of the methods shown in Table 2.

LATEST TTFS MACHINE DEVELOPMENT

Sanitary, easy-cleaning, easy-to-use design in TTFS ma-

chine development has been emphasized by the leading

suppliers in the past decades, especially for meat/food

packaging industry in which complete wash down at the

end of production prior to next production is required by

the USDA. Sanitary equipment design is needed to ensure

effective and easy cleaning to meet strict cleaning require-

ments. Aluminum frame machine has been completely

replaced by all stainless steel frame machine against

corrosion from caustic cleaning chemicals. In addition,

the latest TTFS machine has curved panel and tilted cover

to eliminate any possible harbors for bacteria growth that

may pose a food safety risk to consumers. An automatic

clean-in-place (CIP) feature is an option for the latest

machine manufactured by Multivac, a leading machine

supplier, if required. The interior of the machine can be

thoroughly cleaned under a predesigned programmable

automated cleaning protocol that includes four-stage

cleaning and sanitation sequence to rinse, clean with

Table 3. Common Food-Packaging Webs

Structure Comments

Nonforming Web

Polyester/polyethylene or polyester/ionomer Polyester is used for printability, strength, and general resistance

to moisture and abrasion. Normally it is reverse (capture)

printed (i.e., the polyester is printed on its inside surface for

protection of the printing). Printed polyester is normally stretch-

registered.

These structures may contain an intermediate layer of PVDC or

EVOH as oxygen barrier.

Forming Web

Flexible

Usually a nylon-base web is used for strength and formability,

combined with PE or ionomer as heat sealant and moisture

barrier, and, if needed, PVDC or EVOH as oxygen barrier.

Forming of ﬂexible web by compressed air, vacuum, or compressed

air and vacuum possibly has a heated plug for severe draw ratios.

Cutting by means of ﬂying knife in the cross-direction (XD), and

high-speed rotary knives in the machine direction (MD) for

rectangular packages. Circular, oval, or shape cutting by means

of ﬂying knife following a pattern or cam or by punch cutter.

Rigid

Semirigid PVC, acrylonitrile, amorphous PET, PETG, or HIPS,

combined with PE or ionomer for moisture barrier and, if needed,

PVDC or EVOH as oxygen barrier.

Forming of rigid web by either negative (female) forming with plug

assist or positive (male) forming for more uniform forming and

surface deﬁnition.

Cutting by steel-rule die, or matched male and female die and strip

removal in XD with shear, cut strip removal in MD. Complete cut

by means of matched male and female dies shaped to the ﬁnal

package size.

See Ionomers; Film, oriented polyester; Nylon; Nitrile polymers; Polyesters; thermoplastic; Polystyrene; Vinylidene chloride copolymers; Ethylene–vinyl

alcohol.

Figure 5. Heat sealing. After the package is evacuated, an air

bladder lowers the sealing bar and the package perimeter is

clamped shut and heat-sealed. In the next step, air is readmitted

into the die, the die opens, and the package is indexed out.

1226 THERMOFORM/FILL/SEAL

foaming detergent, rinse, and sanitize with alcohol-based

agent. Particularly the latest machine chain transport

redesign by Multivac, the ﬁrst one offered the CIP feature

in the ﬁeld, allows CIP features feasbile in their TTFS

machines. Side extraction tooling change feature in form-

ing and sealing stations is offered by leading TTFS

suppliers that minimizes downtime and negative ergo-

nomic impact from the tooling changeover process.

Some major TTFS equipment suppliers to the United

States market include Convenience Food Systems, Har-

pak, Multivac, Rapid-Pak and Ulma Packaging.

BIBLIOGRAPHY

E. Ho, ‘‘Thermoform/Fill/Seal’’ A. J. Brody and K. S. Marsh, eds.,

in The Wiley Encyclopedia of Packaging Technology, 2nd

edition, Wiley, New York, 1997, pp. 910–914.

Table 4. Common Medical-Packaging Webs

Structure Comments

Nonforming Web

Tyvek (spun-bonded polyoleﬁn) or paper used for wet strength and

resistance to puncture, also exhibits minimal ﬁber generation

when cut. Paper is used for superior printability and lower cost.

Tyvek can be stretched registered (by means of photocell and

brake). Paper cannot be stretch-registered, so it needs to be

registered by controlling the advance with either an AC or DC

servo drive.

Stretch or advance registration.

Both Tyvek and paper are usually heat-seal coated. Used for ETO

gas sterilization because of their porosity. Polyester or polyester/

aluminum foil for gamma sterilization or gas or moisture barrier.

These materials are used in conjunction with appropriate heat-

seal coatings and laminating adhesives.

Forming Web

Flexible forming webs: polyoleﬁn laminates or blends. Forming methods are similar to those used in ﬂexible food

packaging. Shear cutting is normally used in both directions for

superior cleanliness of cut with paper or Tyvek upper webs.

Rigid forming webs: PVC or acrylic multipolymer or high-impact

polystyrene (HIPS) or copolyester.

Forming is typically with temperature controlled plug or positive

forming depending on draw ratio and degree of surface deﬁnition

required.

Cutting, typically, matched male–female in across-the-machine

direction. Shear cut in-the-machine direction. Or 100% matched

male–female cutting. These cutting systems provide relatively

particulate-free packages with radial corners.

Figure 6. Sliced luncheon-meat package. Nylon-ionomer ﬂexible

forming web, OPET/ionomer top web. Circle cutting by means of

ﬂying knife. Print registration by means of stretching ﬁlm with a

brake.

Figure 7. Thermoformed medical-kit package. Typically, this

type of package would have a semirigid HIPS (high-impact

polystyrene) thermoformed bottom and a Tyvek or paper lid.

Forming would be positive (male-plug). Note both severe draw

ratio and enhanced surface detail. Print registration would be by

means of a dc drive since paper cannot be registered by stretch-

ing. Cutting could be a complete 3601 cut with matched male/

female dies, or shear cut (machine direction) with strip removal

by means of matched male/female dies (cross-direction). Package

is shown with lid removed.

THERMOFORM/FILL/SEAL 1227