NCAR-TN-23 / AR

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Re-evaluation of Tapes for Reinforcing and RepairingPolyethylene Balloons

JOSEPH R. ZWACKROBERT C. BROWNMinnesota Mining and Manufacturing Company

November, 1966

NCAR -TechnicalN L

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'B 5 0583 01004591 III II i I l/B

The National Center for Atmospheric Research (NCAR) is dedicatedto the advancement of the atmospheric sciences for the benefit ofmankind. It is operated by the University Corporation for AtmosphericResearch (UCAR), a private, university-controlled, non-profit organiza-tion, and is sponsored and principally funded by the National ScienceFoundation.

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NCAR-TN-23

RE-EVALUATION OF TAPES FOR REINFORCING AND REPAIRINGPOLYETHYLENE BALLOONS

A research and development program conducted for the National Centerfor Atmospheric Research by the Minnesota Mining and ManufacturingCompany, 2501 Hudson Road, St. Paul, Minnesota

University Corporation for Atmospheric ResearchPrime Contract Number: NSF-C160Sub-Contract Number: NCAR-64

Prepared by: Joseph R. Zwack, Proj. Engr.Robert C. Brown, Proj. Leader

National Center for Atmospheric ResearchBoulder, Colorado

November, 1966

iii

PREFACE

This report describes a research and development program conducted

for the National Center for Atmospheric Research by the Minnesota Mining

and Manufacturing Company, St. Paul, Minnesota.

The objective of the program was to study current requirements

for tapes used in fabrication or repair of polyethylene balloons, and

to recommend possible new tapes based on tests correlated with suggested

performance requirements.

V

SUMMARY

Interviews with NCAR staff members and with balloon fabricators

established performance, application, and physical requirements for

tape to reinforce or repair polyethylene balloons. The preferred tape

is composed of a 2-mil balloon-grade film backing and a green-tinted

cross-linked silicone pressure-sensitive adhesive, and is supported in

roll form on a release liner.

This tape shows superior adhesion to balloon-grade polyethylene

under both static and dynamic conditions, in tests at 490 C, 250 C, and

-80 0 C. The tape is not subject to cold brittleness failure, and does

not degrade the balloon film. The light green color makes it easy to

locate taped areas.

vii

CONTENTS

PREFACE . . . . . . .·. . , . . . . . ;. i i

SUMMARY . . ... .. .. . . . . .. . . . v

LIST OF TABLES .. . ·.. , , ..· * · · · ix

LIST OF FIGURES . . . . . . . .* e o . . -. ix

LIST OF SYMBOLS . ... ... ... .. .· · · xiii

SectionI, INTRODUCTION .. . . . o . .. . .. . a a I

II. SURVEY REQUIREMENTS . . .. . . .... 3

III. SELECTION OF IMPROVED MATERIALS .... 7.

Materials Evaluation .e. o... 7

Testing * .O. * . o . e .· · 8

Tape Components e e ,.c o o. o e. 12

Tape-making Process . . a . .0 o o o o 15

Tape Properties .. . . . . o. o. 16

IV, CONCLUSIONS ,, . . . .... . .. . .. 21

FIGURES AND TABLES c c . .... . 23

REFERENCES .... . .a . . ... . . 39

BIBLIOGRAPHY ...... ··o ..... . . .. . 40

m

ix

TABLES

1. Hand-screening of tapes at -60 0 C on VisQueen X-124 polyethylene .. 23

20 Adhesive evaluation .. 0 o ... . .......... ... 24

3. Glass transition temperature for balloon tape adhesives ...... 25

4. Balloon tape constructions •.... • .... •...... .. . ..... 26

5. Tape adhesion properties . . . .............. .•. .. 27

6. Comparison of peel adhesion performance ..... .. . .. . 28

7. Comparison of shear adhesion performance .... . . . ........ 29

8. Comparison of TMI tack performance • . l .... 0 ..... ..a• • 30

9. Modified cold brittleness test at -80 0 C . ....... .... .. 31

10. Comparisons of resistance to blocking to VisQueen X-124

polyethylene . . . .... .. . . . ... . . . . . 32

11. Accelerated tape aging study (1000 F) ... . ......... 33

xi

FIGURES

1. Comparison of TMI tack performance . . ...... ...... o. 34

2° Comparative effects of temperature upon instant adhesion usingTMI tack tester . .. .... . . . . . . . .. 35

3. Break tensile values for VisQueen X-124 film with 1-in. by 1-in.tape area, aged at 25°C ... . . ............ 36

4, Break tensile values for VisQueen X-124 film with 1-in. by 1-in.area, aged at 49°C (120 ° F ) o . . . . .. . . . . . . 37

5. Break tensile values for VisQueen X-124 film with 1-in. by 1-in.area, aged at 66C. (1500) . . . . . . .......... . 38

I

xiii

SYMBOLS

CD cross direction

DOP dioctyl phthalate

DTA differential thermal analysis

EM error of the mean

gm gram

gr. grain

MD machine direction

oz/in. ounces per inch width

PE polyethylene

PIB polyisobutylene

SBR styrene butadiene rubber

Tg glass temperature

TMI Testing Machines, Inc.

m

I

I

I, INTRODUCTION

The research and development program described in this report

was undertaken because it seemed probable that technology developed

in the last decade by manufacturers of pressure-sensitive-tapes might

offer a basis for improved balloon tapes. The subcontract awarded the

3M Company called for an analytical review of the uses of tapes (other

than the Fortisan load tapes) in balloon fabrication and repair.

The review was conducted in two phases. The first phase consisted

of an analytical review of tape requirements, accomplished by inter-

views with staff members of NCAR, of Hauser Research and Engineering,

and of balloon fabricating firms. The second phase involved the character-

ization, testing, and construction of a new balloon tape to be submitted

to NCAR.

Good adhesion at sub-zero temperatures was a primary require-

ment for the new tape, and therefore a pressure-sensitive-tape screen-

ing procedure was established which consisted of two tests run at

-600C. In the first, a flutter test, tapes were placed on a panel

of balloon film and chilled in a cold chamber. The polyethylene panel

was then subjected to flutter and shock. Failures were easily noted,

since most of the tapes fell or were shaken off the film. The second

test, a peel test, provided a more meaningful screening evaluation,

since an actual peel force measurement could be obtained.

Some of the performance tests were related to the methods of

application and conditions of use of balloon tapes. These consisted

of blocking tests, peel and shear adhesions to polyethylene at various

2

temperatures, cold brittleness, and Testing Machines, Inc, (TMI) tack

tests. However, since it seemed possible to use a silicone-based

pressure-sensitive adhesive, it was also desirable to investigate the

compatibility of this new adhesive with balloon-grade polyethylene films.

A polyethylene-silicone compatibility study was conducted by placing

test tapes on balloon-grade polyethylene film and aging the panels at

various temperatures. Once a week strips were cut from the panels

and tested on an Instron tensile tester to determine whether the film

had been weakened by the adhesive. This film was also tested to deter-

mine any change in its cold brittleness property.

The performance of several experimental liners was evaluated

by roll aging tests. The force initially required to remove the liner

from the tape was measured, as was the subsequent tape adhesion to a

surface. These tests were reported at intervals during aging at a

slightly elevated temperature.

3

II. SURVEY OF REQUIREMENTS

The available literature was surveyed as a first step in the

subcontract program. This literature survey, along with personal

interviews with balloon fabricators, made it clear the proportion of

balloon failures had reached a critical point. The area of major

concern included balloon design, balloon materials (i.e., films), and

tapes. Extensive programs covering balloon design and materials studies

had been initiated in an effort to correct this situation; however,

except for a short period 10 to 12 years ago, very little has been done

toward development of a better pressure-sensitive tape for polyethylene

balloons. C 1

Large polyethylene balloons of three to thirteen million cubic

feet in volume suffered most of the failures, and 90% of the failures

occurred in the altitude region from 33,000 to 58,000 ft. (near the

tropopause). C2] In this region the balloon is subject to maximum

stress and minimum temperatures. The stresses are due to winds to

unfolding of the envelope material, or to changes in shape. Tropopause

temperatures as low as -87°C have been recorded above equatorial areas

of the earth. When tape failures occur they are considered to result

from adhesive failure under a shock or shear type stress at temperatures

of -40 to -80C,.

At ground level, heat rather than cold may be a problem when

balloons are launched in equatorial regions. There, ground temperatures

reach 550C, and temperatures above 380 C are common. When launches are

delayed, the combination of heat and air movement requires good tape

adhesion to balloon surfaces at the elevated temperature,

4

Another serious problem directly attributed to tapes is caused by

adhesive oozing or shrinkage of the tape backing. This exposed adhesive

causes the balloon layers to stick together if the balloon is not

adequately dusted with corn starch or polyethylene powder. This block-

ing can tear the film. The dusting operation might be eliminated if

adhesive blocking were eliminated.

Occasionally, gore reinforcing tapes are inadequatly heat-sealed,

and pressure-sensitive tape is used to improve the seal. In some

instances the pressure-sensitive tape has lifted from its original

gore and reattached itself over several adjacent gores. If this

adhesion is not discovered in a pre-flight inspection, the balloon could

fail. A colored tape is recommended to render repaired areas conspicuous.

However, with some colors, heat absorption due to solar heating might

weaken the taped seal. Light green was suggested during the interviews

as a suitable color.

Currently, 3M's tape #480 has a total thickness of 5.5 mils and

is used on balloon films ranging from 4 mils down to 0.25 mil. Most

balloon films are in the 0.75-to 1.5-mil range and it would be desirable

to have a tape more closely matched to the film in thickness. Also,

the tape backing should be made from balloon-grade film to provide

strength and elongation properties similar to the balloon itself. Tape

with a 1-to 2-mil polyethylene backing would be so stretchy that a

supporting liner would be needed. The liner would also make it easier

to position the tape before application. However, the tape should also

be removable if improperly positioned.

Many of these points were corroborated by the persons directly

connected with balloon fabrication and flight testing, who are listed

here:

Thomas W. Bilhorn NCAR

Al Morris NCARKarl Stefan NCAR

Roy L. Hauser Hauser Rs. & Engr. Co.

Jim Winker Raven Industries, Inc.

R. G. McCarty Raven Industries, Inc.

John A. Peasley Raven Industries, Inc.

Mike Pavey Raven Industries, Inc.

Vernon H. Stone Litton Industries

Roy Matheson Litton Industries

Walter B. Parsons Litton IndustriesDel Woode Geophysics Corpo of America

LeRoy Bushay Minnesota Aerospace

Don Williams Winzen Research Inc.

Gene Nelson Winzen Research Inc.

Optimum Tape Performance Requirements

The following list of tape performance application and physical

requirements was compiled from the interviews and does not represent

the views of any single organization or person.

1. The tape's adhesive must provide a high specific adhesion to

polyethylene film over a critical temperature range of -80

to + 550 C. The tape must also be repositionable if improperly

applied.

2. The tape must adhere to polyethylene film over this critical

temperature range when the film to which it is applied is:

(a) stressed under tension or pressure, resulting in a 6%

elongation of the "patched" film measured perpendicular

to the periphery of the adhered tape.

(b) crushed, folded and flexed by hand or when subjected to a

test designed to simulate flutter.

6

(c) subjected to shock.

3. Temperature for testing tape for cold brittleness should be equiv-

alent to that of balloon-grade film.

4. Blocking between adjacent layers of polyethylene film and the edges

of the tape should not occur when the test materials are subjected

to the 150 ° F , 1000 gm, five-day static load blocking test.

5. When the tape is applied to the polyethylene in a relaxed state

only negligible crawling, creeping, and channeling of the tape

should be evident, and should in no way impair the intended function

of the tape.

Application Requirements of Tape

1. The desired level of adhesion to polyethylene film shall be developed

by:

(a) light finger-pressure for patching tape.

(b) hand-operated roller for reinforcing tape.

2. Tape must possess suitable body to allow handling without carrier

support.

3. Normal tape application temperature will be 20±5°C, but consideration

should be given to application temperatures below 0°C.

Physical Specifications for Tape

1. Total tape caliper (exclusive of liner or carrier web if used) should

not exceed 4 mils.

2. The tape should have a slight tint of color--possibly green-- to aid

in positioning and in locating the tape after application,

3. Liners or carrier members may be included in the tape supply roll;

however, they must be easily removed before or after tape application.

7

III ,.l SELECTION OF IMPROVED MATERIALS

MATERIALS EVALUATION

BACKINGS

Balloon-grade polyethylene films produced by Winzen Research Inc.

and VisQueen Corp. were used as test surfaces and/or tape backings

whenever polyethylene is reported in this program, except when mention

is made of 3M Tape #480 and #480A. Industrial-grade polyethylene film

was used on these tapes. "Winzen StratoFilm" in calipers of 1.0, 1.5,

and 2.0 mils and VisQueen X-124 polyethylene film in a 1.5-mil caliper

were used.

Adhesives

All of the adhesives used were coated from a non-aqueous solvent

system° The solvents were primarily aliphatic or aromatic hydrocarbons.

Polyethylene film may swell when coated with a solvent-based adhesive.

Therefore an intermediate carrier web was required, and will be discussed

further in the section on tape processing.

Several adhesive systems were screened in the search for good

adhesion to balloon-grade polyethylene film at -800 C. The #480 tape

adhesive received considerable attention because of its present use on

a balloon repair and reinforcement tape. This adhesive consists of a

polyisobutylene elastomer tackified with a polyterpene-type resin system

common to the pressure-sensitive tape industry. Tape #480A, which has

been evaluated as a possible replacement for Tape #480 on balloons, uses

a polyacrylate adhesive on a 1.5-mil polyethylene film, and a treated

paper liner.

8

Tape Y-9241 has a nylon film backing and a polychlorprene elastomer-

based adhesive.

Several tapes with silicone adhesive were tested, including

Y-9133 with polyester backing, and Y-9188 and #549, both with Teflon

backings.

Cold temperature adhesion limitations were directly related to

the glass transition temperature, Tg, of the elastomers and resins used

in the adhesive. Glass transition temperatures of polymers commonly

used in adhesives are: [r3B

Polymer Tg( C)Polyisobutylene -70, -60Polyisoprene(natural rubber) -73Polybutadiene -90Polydimethylsiloxane -123Polychlorprene -50Polyacrylates +3 to -56

Adhesive lots were formulated with polybutadiene, silicone, and

polyacrylate materials for evaluation. In addition, blends of silicone

and polyacrylate, silicone and polybutadiene, and silicone and poly-

isobutylene adhesives were prepared.

TESTING

Test Conditions

Tests were run at temperatures of 49+10C, 25±10C, -60±1C, and

-80±1 0C. Humidity for most room-temperature tests was controlled at

50±2%.

The tests at -600C were conducted in a carbon dioxide environment

using dry ice. Tests at -80°C were held in a nitrogen atmosphere. The

chamber was cooled with liquid nitrogen fed on demand by a temperature

9

controller-recorder and solenoid valve arrangement. The tapes were

applied to test surfaces at room temperature.

Test Methods

Where possible, standard methods for tape testing were followed;

however, the limitations imposed by the cold temperature environment

and chamber size made some semi-quantitative tests necessary.

Several tests were devised for initially screening a number of

tapes. These tests were conducted at an easily attained temperature

of -60"Co The first, a flutter test, involved adhering 1-ino by 6-in.

tape strips on a 6-in. by 18-in. panel of VisQueen X-124 balloon film.

After conditioning for 10 min, the panel was fluttered, shocked, and

twisted by hand in the chamber0 Failures were easily noted, as many

of the normally pressure-sensitive adhesives lost their adhesive

properties, and the tapes were shocked off by the movement of the panelo

The peel removal force at cold temperatures was determined semi-

quantitatively by use of a Chatillon dynamometer pulled by hand in the

chamber. A correction was not made, for temperature effects on the

gauge due to the nature of the test. Peel rate was approximately 12 in/min.

Panels were prepared by bonding VisQueen X-124 film to steel panels with

Dow 280 pressure-sensitive adhesive. Sample strips 0.5-in. by 4-in. with

hooks for attaching the dynamometer were then adhered to the panel by

rolling with a 4-lb hand-operated, rubber-covered roller. Conditioning

time at the test temperature was 10 min. Adhesion to polished steel

was also determined,

An additional screening test served further to eliminate the poorer

candidate adhesives. Overlap shear samples were prepared by placing a

10

strip of tape onto a balloon film panel so that an area I-in. by 1-in.

was covered. This panel was placed in the cold chamber for 10 min and

then tested by hand-pulling at an angle of 0 ° . Tapes failing this shear

test were easily pulled off, while tapes with good anchorage to the

panel held well enough so that the strip of film broke.

A similar test provided additional data at temperatures of 49, 25,

and -80 0 C on both polyethylene and steel panels; however, a 500-gm

weight was used to give a measure of static load-holding powero

Other basic tape tests, such as roll unwind force and liner removal

force, were conducted at room temperature. The latter are pertinent

tests for roll aging, liner evaluation, and handling convenience. For

balloon tapes, handling convenience would include such factors as tape

stretching caused by high roll unwind or liner removal forces, backing

recovery after stretching, and tape curling. Roll aging data were

obtained from rolls stored at 100 and 1200 F,

Federal Test Method Standard No. 147a, Method 10, was used to

measure peel adhesion to balloon-grade polyethylene and to #4 finish

steel at room temperature. 1[43 Use of polyethylene film adhered to a steel

panel represents a modification of this standard procedure.

Tape blocking was evaluated according to paragraph III. B.of

Spec. No. M23010 from the Applied Science Division of Litton Systems,

Inc., C5] This stability test requires two I-in. by 4-in. strips of

tape, but was modified for this program by using a single 2-in. by 4-in.

strip taken from a 2-in. roll, the purpose being to simulate better

application conditions. A further adaptation compared blocking under

conditions of 1000-and 4000-gm loads. The 1.5-mil thick VisQueen X-124

balloon film used in this test was aged at 150+5°F for five days.

1I

Failure was noted if the overlying film adhered to the tape edges.

A brittleness test was conducted using ASTM D1790-62 as a guide. 671

The exact brittleness temperature was not determined, but the test

was used to evaluate taped specimens of balloon film at -800 C. Tape

strips 1-in, by 5.75-in. were placed on 2-in. by 5.75-in. strips of film

and attached to cards as prescribed. Five specimens for each material

were tested. Samples with tape in place and aged for five weeks were

included. However, only duplicate samples were tested.

A modified TMI Tack Tester tL7 provided the final data on tack

and adhesion. This instrument has a 1/16-in. diameter steel probe;

however, a probe of balloon-grade polyethylene was fabricated for use in

this program. Although contact speed, contact force, and dwell time

are variable on the TMI Tack Tester, the following conditions were used:

contact speed 2 cm/sec, dwell time 100 sec, and contact force 100 gm/sq cm.

The peel rate was the same as the contact rate. Tack values were obtained

in grams per probe area. In this case, the probe area was 3.07 x 10-3 sq

in. Cold temperature tack values were obtained by contacting the probe

at room temperature and then cooling the probe and tape in a chamber to

-80°C. Normal tack tests were also run at room temperature and at temp-

eratures down to -600 C.

A General Mills research report on balloon materials expressed

concern about the use of silicone adhesives on pressure-sensitive tapes,

suggesting the possibility of increased stress cracking based on test

results of polyethylene film held in contact with light silicone oils

for an extended period of time. C 1] Since a silicone-based pressure-

sensitive adhesive was of primary interest in this program, a study was

12

made of the effects of silicone tape on balloon film. VisQueen X-124

film of 105-mil thickness was used. Three silicone adhesive tapes and

Tape #480 were applied to panels of the film and aged at room temperature

at 120 and 1500F. A film panel without tape served as a control. Tensile

and elongation values were determined, initially and over a period of five

weeks. An Instron tester was used with crosshead speed and jaw speed

of 20 in/min and 2-in. jaw separation, as prescribed in ASTM D882-64T,

Method A. C8] The cold brittleness test ASTM D1790-62 was also run on

these films. C6]

Analysis

Test results were analyzed to select the most promising tapes

from the screening tests. To identify promising tapes in subsequent

testing, those tests amenable to multiple samples were conducted and

average values are reported. Errors of the mean, EM, were calculated

from the following equation:

EM =- S/N(N-1)j 2

where N is the number of readings and S is the sum of the squares of the

difference between a value and the mean.

TAPE COMPONENTS

Backings

Low-caliper, balloon-grade polyethylene film was of principal

interest for use as the tape backing material; however, low-caliper

polyester films were also considered. The relatively inelastic properties

of polyester film caused it to be dropped from this program even though

substantial coating and handling advantages could be obtained with the

polyester film. Hand samples of adhesive-coated tape were made using

13

1.0, 1.5, and 2.0-mil Winzen StratoFilm as backing. Although minimum

tape weight and caliper are desired, the handling properties of the 1.0

and 15 mil adhesive-coated examples suggested that major tape production

and use problems would be encountered due to excessive backing stretch

and limpness. Two-mil film was considered a practical minimum caliper

as well as being a substantial improvement over the 4.0-mil polyethylene

film used on Tape #480°

Adhesives

Dow 280 and Dow XC-3-0466 were obtained from Dow Corning, Midland,

Michigan, as representative silicone pressure-sensitive adhesives. Dow

280 is supplied as a 60% solids solution in xylene. It may be used as

supplied, or reduced with a suitable solvent such as toluene or xylene.

When coated without further compounding, an aggressive tacky pressure-

sensitive adhesive results; however, as received, it is slightly soft.

By adding a free radical catalyst, such as benzoyl peroxide, the polymer

can be partially cross-linked without serious loss of tack. The result-

ing adhesive is firmer and has improved shear strength. Levels of 0,

1.5, and 3% benzoyl peroxide were evaluated.

Dow XC-3-0466 adhesive is supplied at 40% solids in trichlorethylene.

It does not require curing, but only drying at 150°F. It was later

learned that this material is strictly experimental and may not be

supplied commercially.

Two polyacryJa te adhesives manufactured by 3M Company and covered

by U.S. patents were evaluated. An un-cross-linked polyacrylate was

used as supplied or was blended with both Dow 280 and Dow XC-3-0466.

It was also modified with dioctyl phthalate (DOP) plasticizer to improve

its low-temperature performanceo

14

A cross-linked polyacrylate was also evaluated. Blends with Dow 280

and XC-3-0466 were also prepared.

The polyisobutylene adhesive used on Tape #480 was also blended with

Dow 280 and Dow XC-3-0466, the objective being to improve its low-temper-

ature performance.

Two commercial diene rubbers were compounded for the balloon tape

program. One, Shell's Kraton D-101, was blended with 75 parts of a

polyterpene resin in n-heptane at a solids content of 25%. This adhesive

was also modified with DOP. Ameripol CB from Goodrich-Gulf was formulated

in three separate lots with 150 parts of polyterpene resin and 75 parts

Oronite #32 polybutene. All three formulations were dissolved in n-heptane

at 25% solidso

Liners

The following tables list materials evaluated as adhesive carrier

webs for direct coating with silicone adhesive, as well as those materials

evaluated as terminal liners which replaced the original adhesive carrier

web in the finished roll of tape. Use of a silicone adhesive greatly

-restricted the selection of a suitable adhesive carrier web and terminal

liner.

Carrier Webs

Type Designation or Caliper Supplier

Paper 2-60KG-1 Daubert Chemical Co.

Paper 2-60KG-R69-246 Daubert Chemical Coo

Cellophane Film 1.7 mil duPont

Polyester Film 2.0 mil 3M Company

Kapton Film 2.0 mil duPont

Teflon Film 2.0 mil Dixon Corp.

15Carrier Webs (cont)

Holland Cloth 4.5 mil Johanna Western

Teflon Coated 6.5 mil 3M CompanyGlass Cloth

Terminal Liners

Type Designation or Caliper Supplier

Paper RP 353 3M Company

Paper RP 358 3M Company

Paper RP 360 3M Company

Paper PSL-49703, Lot 50 3M Company

Paper 2-60KG-R69-246 Daubert Chemical

Polyester Film 2.0 mil 3M Company

Teflon Film 2.0 mil Dixon Corp.o -...

Polypropylene Film 3.0 mil 3M Company

Color Materials

Three coloring materials were evaluated in the Dow 280 adhesive

formulation. Chrome oxide in silastic fluid proved to be the preferred

material.

Material Supplier

Acetosol Green BLS Sandoz, Inc.

Keco Oil Fast Green GG Keystone Aniline &Chem. Co.

Prespersion, in Silastic Fluid Ware Chemical Co.70% Chrome Oxide

TAPE-MAKING PROCESS

Ideally, pressure-sensitive tapes are manufactured by directly

coating an adhesive solution onto the backing material. Initial exper-

iments proved that this method was not feasible for the low-caliper,

16

polyethylene-backed balloon tapes. Ordinarily, polyethylene is relatively

inert to the effects of solvent; however, in the low-caliper gauges,

solvent swelling caused wrinkling and severe curling of the film. This

was especially true with the use of toluene and trichloroethylene, but

not with n-heptane. The better cold-temperature-performing adhesives

were soluble only in the stronger solvents. Thus an adhesive carrier

web was required, and in the case of silicones, Teflon was the preferred

material,

The preferred tape-making process, therefore, involved coating

approximately 6 mils of wet adhesive onto the carrier web, passing the

web through a drying oven for drying and/or curing and laminating the

polyethylene film to the adhesive at the oven exit prior to jumbo windup.

The coated tape can then be slit with the original adhesive carrier

web in place, or the carrier web may be replaced by a less expensive and

more usable liner at the slitter.

During processing the least possible stress must be placed on the

backing material. If the backing film is stretched, the tape will tele-

scope in the rolls, or it will recover upon application, causing wrinkles

in the balloon.

TAPE PROPERTIES

Tests were run for flutter, peel adhesion, and shear adhesion at

-600C to screen out the poorer adhesive systems. Table I shows the

results of commercially available tapes adhered at 25"C to 1,5-mil

VisQueen X-124 polyethylene balloon film. This screening showed that

silicone adhesives were outstanding and that the other adhesive systems

would need considerable improvement to match their performance,

17

Table 2 shows peel adhesion values (in oz/in) from VisQueen X-124

polyethylene film at 25 and -60"C for several classes of adhesives,

including blends. Dow 280 silicone uncured and cured with benzoyl

peroxide, and certain blends, show better adhesion performance at

both 25 and -600C. Of the blends, an 85/15 blend of Dow 280 silicone

and acrylate and 50/50 mixtures of Dow XC-3-0466 with either acrylate

or cross-linked acrylate appear to perform well. A problem with the latter

two systems was incompatibility, corrected by addition of combining

solvents, especially ethanol. Blends of Dow XC-3-0466 and cross-linked

acrylate were modified with ethanol and evaluated. The test chamber

was slightly colder for this series of tests, the average temperature

being -64.5°C. In all cases the tapes failed due to adhesive transfer

from the tape backing to the balloon film at that temperature.

Adhesive transfer was the predominant type of failure during peel

adhesion tests of blends. Such failure probably results when one of the

component polymers reaches its glass transition region. Tg values are

given above for selected elastomers. To verify and compare those values

with values for elastomers used in balloon tape adhesive formulations,

Tg data were obtained by differential thermal analysis (DTA). Table 3

shows Tg values for several of the adhesives under evaluation. It appears

evident that for optimum adhesive performance at -800 C, a polymer with a

Tg value about 400 lower is required.

Table 4 lists characteristics of tapes prepared and eval uated during

this program. (Lot numbers which have been omitted were used for process

materials such as adhesives, liners and backings.) Adhesion properties

of these tapes are presented in Table 5.

Detailed performance data for three control tapes, two pilot

scale-up tapes, and the two current balloon tapes are given in Tables 6,

18

7 and 8 showing respectively peel adhesion, shear adhesion, and TMI

Tack. Values are given for adhesion to polyethylene and to steel. The

three control tapes are designated as SL 250382, Lots 24, 25 and 26.

Tapes designated SLP 50382, Lots 19 and 19A were prepared by a scaled-up

pilot process. All five tapes are made with Dow 280 silicone adhesive.

The first three were prepared as a controlled experiment, with nearly

similar coating weights. Lot 24 is uncured, while Lot 25 was cured with

1-5% benzoyl peroxide, and Lot 26 was cured with 3.0% benzoyl peroxide.

A 1.5% benzoyl peroxide cure was used for Lots 19 and 19A.

Figure 1 presents TMI Tack data from Table 8. Additional TMI

Tack performance is illustrated in Figure 2, which shows the comparative

effects of temperature upon instant adhesion. The temperature value on

the abscissa, where a curve approaches zero instant adhesion, represents

the minimum temperature for tape application. However, application is

considered possible in environments 5 to 10° colder, due to body heat from

the hands even when light gloves are worn.

The ASTM cold brittleness test was modified to determine whether

specimens of balloon film with tape applied would be weakened by materials

present in the adhesive. The test data shown in Table 9 were obtained at

-80"C. Samples aged five weeks at 25 and 490C were compared with non-aged

samples. The samples were prepared with 1-in. strips of tape applied in

both directions. That is, some had the tape applied parallel to the

machine direction for both the film and tape while others had the tape

applied parallel to the film cross direction. VisQueen X-124 film with-

out tape served as a control.

The tapes listed in Table 10 were tested for blocking stability

according to a Litton Industries specification. 5_1 A slight modification

19

was made by using tape taken directly from a 2-in. roll rather than by

cutting two 1-in, by 4-in. strips. Results are shown for samples subjected

to a 4000-gm load as well as the specified 1000-gm test.

Table 11 presents data on tapes subjected to accelerated aging at

1000F. The primary interest here was in the performance of the liner

under conditions similar to those found in balloon fabricating plants.

Federal Standard 147a, Methods 12 and 10 were followed in measuring liner

removal and tape adhesion, respectively. 43] The use of polyethylene film

in place of a steel surface represented the single deviation from the

Method 10 adhesion test.

As previously mentioned, concern was expressed about possible

deleterious effects that a silicone adhesive might have on polyethylene.

Therefore, a test was initiated to study the effect on polyethylene tensile

strengths of various tapes applied on the film and aged. Aging was

carried out at 25, 49, and 66°C (77, 120, and 150"F) respectively. Samples

aged at elevated temperatures were conditioned at 250C for 2 hr before

testing. Tensile values versus the number of weeks of aging are plotted

at 77, 120, and 1500 F in Figs-3, 4 and 5, respectively.

Shortly before the project ended, an effort was made to compare the

best silicone tapes with Tapes #480 and #480A, by means of a polyethylene

diaphragm test. A diaphragm of polyethylene was fitted over a container

which was then pressurized or evacuated. The polyethylene had a 1-in.

by 1-in. tape patch positioned over a 0.5-in.- long slit in the film. In

a preliminary evaluation using pressure and a room temperature environ-

ment, all of the tapes held while the film ruptured in an area away from

the patch. For these tests, approximately 2 to 3 lb of pressure in a

one-gallon-size container was required to rupture the filmo At -70°C

20

all of the tapes held at 2 to 3 lb pressure as long as conditions were

relatively static. When a 25-gm weight was dropped on the surface, Tape

#480A cracked. Tape #480 shocked off when the diaphragm retaining ring

popped loose. No failure was noted with SL 250382, Lot 19A under these

conditions.

Accelerated roll aging tests indicate that satisfactory adhesive

properties will be maintained on the Teflon linered tape (SLP-50382, Lot

19) for a period of one year when stored under normal factory or warehouse

conditionso However, the paper linered tape (SLP-50382 Lot 19A) must be

maintained at a temperature below 100 0 F, preferably below 80 °F, if

maximum adhesive properties are to be retained. Storage of the paper

linered tape in excess of three months is not recommendedo

21

IV. CONCLUSIONS

A survey of staff members of NCAR and of balloon fabricating

companies indicated that an improved repair and reinforcement tape

should meet the following physical, application and dimensional require-

mentso

The tape must adhere well to balloon-grade polyethylene film

through a temperature range of 4-55 to -800C while the film is stressed,

folded, and/or subjected to shocking forces. During storage of a

balloon, blocking of adjacent film layers should not occur due to

adhesive oozing or shrinkage of the tape backing,

The tape should be applicable with light finger pressure for

patching, or by rolling for reinforcing yet, if improperly positioned,

should be removable without damage to the balloon film. It should be

convenient to handle without excessive curling or stretching. It

should be applicable at temperatures below 0°C.

The tape thickness, exclusive of carrier liner, should not exceed

4 mils, to match more nearly the strength and flexibility of balloon

films. It should have a slight tint of color to make it readily visible

on the transparent balloon film. An easily removed support liner would aid

in positioning long strips of tape.

Tests carried out on a variety of possible adhesives indicate that

a silicone pressure-sensitive adhesive best meets the performance require-

ments. The preferred adhesive determined by these tests is Dow 280

using 1l5% benzoyl peroxide to provide partial cross-linking and 1/4%

color The color used for this adhesive was Prespersion, a 70% chrome

oxide in silastic fluid.

Current processing techniques make it possible to use as backing

2-mil balloon-grade polyethylene, and result in a tape less than 4-mils

thick. Winzen StratoFilm is a suitable tape-backing material,

A support liner is required and two materials are suitable. They

are Teflon film, and 3M paper release liner RP 358.

SUMMARY OF TAPE PROPERTIES ADHERED TO BALLOON GRADE POLYETHYLENE

SLP 50382Test Temp. Tape #480 Tape #480A Lot 19A

Adhesion 250C 22 3 10Method 10, oz/in. -80°0C 0 0 65**

TMI Tack, gm 25° C 205 165 58-80°C 3 8 230

Static Shear 490C 14.4 9.2 60.7Method 20, Min 25 0 C 415.0 109.7 2867.4

-80°C 60+ 60+ 60+

Glass Transition -64 -53 -124Temperature Tg, C

Minimum Instant -20 -32 -54Adhesion Temperature, O

Cold Brittleness -80 C Tape Tape OK *}Cracked Cracked

Tape Blocking 1500 F Fail OK OK

Tape Caliper, mil 5.5 2.3 3.3

*Hand Removal at -800C"Adhesion Method ASTM D903 at -80°C, SLP 50382 Lots 19 and 19A were

found to have average peel strength of 41.6 and 51.0 oz/in. TestReport 66-047, Hauser Research and Engineering Co., August 23, 1966.SL 250382, Lot 11 reported since Lot 19A was not made at time of this

test.

TABLE I

Hand-screening of Tapes at -600 C on VisQueen X-124 Polyethylene

Tape Backing Adhesive I" Overlap Shear 180 ° Peel Adhesion Flutter

#480 Polyethylene PIB Fair Low Fell off

New #480 Polyethylene PIB Fair Low Fell off

#480A Polyethylene Acrylate Good Low Fell off

#1525 Polyethylene Acrylate Fair Low Fell off

#245 Paper Crude-SBR Fair Low Fell off

Y 9241 Capran Neoprene Good Fair OK

Y9133 Mylar Silicone PE Film broke Good OK

#549 Teflon Silicone PE Film broke Good OK

Y 9188 Teflon Silicone PE Film broke Good OK__ L.,._ , , , , . , , , , i , ~ _ i , , , . , , . , l , , . , I , ,,~ , , L , , , , ,I,,.., ,

24

TABLE 2

Adhesive Evaluation

Adhesion to PolyethylenAdhesives on PE Film Blend oz/in. Comments

Ratio 25°C -60°C_____

SiliconesDow 280 25 50 Uncured, diluted to 40% solidsDow 280 12 11 1.5% benzoyl peroxide, 40% solidsDow XC-3-0466 22 -- Film broke at -60°C

AcrylatesAcrylate 6 0-40 Pop off & adhesive transfer at -60°CAcrylate, DOP modified 6 -- Adhesive transfer at -60°CCross-linked Acrylate 5 0 Pop off at -60°C

Rubber-Resin SystemsPIB/Polyterpene 25 0 Pop offKraton 101/Polyterpene 22 0 Pop offKraton 101/Polyterpene/DOP 22 -- Adhesive transfer at -60°CAmeripol CB 220 15 -- Adhesive transfer at -60°CAmeripol/Polyterpene 12 -- Adhesive transfer at -60°CAmeripol/Polyterpene blend 2 -- Adhesive transfer at -60°CAmeripol/Polybutene -- -- Adhesive transfer both tests

BlendsDow 280/Acrylate 75/25 7 -- Low 250 C adhesionDow 280/Acrylate 50/50 5 -- Low 250C adhesionDow 280/Acrylate 25/75 2 -- Low 250 C adhesionDow 280/Acrylate 95/5 24 Dow 280/Acrylate 90/10 26 50Dow 280/Acrylate 80/20 18 42Dow 280/Acrylate 50/50 12 -- Adhesive transfer, 5 mil coatDow 280/Acrylate 50/50 15 - Adhesive transfer, 7 mil coatDow 280/Acrylate 50/50 19 -- Adhesive transfer, 10 mil coatDow 280/Acrylate 85/15 16 57 Lots 9A-9F evaluation280/Cross-linked Acrylate 25/75 3 0 Adhesive transfer, pop off at -60°C280/Cross-linked Acrylate 50/50 0 0 Pop off at -60°C, phase separation280/Cross-linked Acrylate 75/25 10 0 Adhesive split, pop off at -60°CDow XC-3-0466/Kraton 101 50/50 13 0Dow XC-3-0466/Acrylate 50/50 15 32 Adhesive transfer at -600 CDow XC-3-0466/PIB 50/50 19 2 Grainy coatingXC-3/Cross-linked Acrylate 50/50 11 22 Gelled mixtureXC-3/Cross-linked Acrylate 50/50 -- 72 Toluene/ethanol addedXC-3/Cross-linked Acrylate 80/20 16 92 Adhesive transfer, ethanol addedXC-3/Cross-linked Acrylate 65/35 18 -- Adhesive transfer, ethanol addedXC-3/Cross-linked Acrylate 50/50 19 - Adhesive transfer, ethanol addedXC-3/Cross-linked Acrylate 35/65 15 -- Adhesive transfer, ethanol addedXC-3/Cross-linked Acrylate 20/80 12 -- Adhesive transfer, ethanol added

25

TABLE 3

Glass Transition Temperature for Balloon Tape Adhesives

Adhesive Tg, °C

Dow 280 silicone -124

Dow 280 + 1. 5% benzoyl peroxide -124

Dow XC-3-0466 silicone -118

Acrylate -53

Cross-linked Acrylate -35

Polyisobutylene -64

TABLE 4

Balloon Tape Constructions

Lot Adhesive Backing Backing LinerNo. I ___Thickness(mil) _____I.

3 Dow 280 Polyester 0.5 None4 Dow 280 Polyester 1.0 None5 Dow 280+1.5% Benzoyl Peroxide Polyester 1.0 None6A Dow 280+1.5% Benzoyl Peroxide VisQueen X-124 Polyethylene 1.5 RP 360 modified6B Dow 280+1.5% Benzoyl Peroxide VisQueen X-124 Polyethylene 1.5 PSL 49703, L 506C Dow 280+1.5% Benzoyl Peroxide VisQueen X-124 Polyethylene 1.5 RP 3609A 85/15 Dow 280/Acrylate VisQueen X-124 Polyethylene 1.5 Teflon9B 85/15 Dow 280/Acrylate VisQueen X-124 Polyethylene 1.5 Polyester (1 mil) 9C 85/15 Dow 280/Acrylate VisQueen X-124 Polyethylene 1.5 RP 353 c9D 85/15 Dow 280/Acrylate VisQueen X-124 Polyethylene 1.5 RP 3609E 85/15 Dow 280/Acrylate VisQueen X-124 Polyethylene 1.5 RP 360 modified9F 85/15 Dow 280/Acrylate VisQueen X-124 Polyethylene 1.5 PSL 49703, L 5011 Dow 280+1.5% Benzoyl Peroxide Winzen StratoFilm 2.0 Teflon12 Dow XC-3-0466 Winzen StratoFilm 2.0 Teflon15 Dow 280+3% Benzoyl Peroxide Winzen StratoFilm 2.0 Teflon15A Dow 280+3% Benzoyl Peroxide Winzen StratoFilm 2.0 Daubert 2-60KG-R69-24615B Dow 280+3% Benzoyl Peroxide Winzen StratoFilm 2.0 RP 35815C Dow 280+3% Benzoyl Peroxide Winzen StratoFilm 2.0 Matte Polypropylene15D Dow 280+3% Benzoyl Peroxide Winzen StratoFilm 2.0 Daubert 2-60KG-R69-24617 Dow 280+3% Benzoyl Peroxide Winzen StratoFilm 2.0 RP 35819 Dow 280+1.5% Benzoyl Peroxide Winzen StratoFilm 2.0 Teflon19A Dow 280+1.5% Benzoyl Peroxide Winzen StratoFilm 2.0 RP 35820 Dow 280 Winzen StratoFilm 2.0 Teflon24 Dow 280 Winzen StratoFilm 2.0 Teflon25 Dow 280+1.5% Benzoyl Peroxide Winzen StratoFilm 2.0 Teflon26 Dow 280+3% Benzoyl Peroxide Winzen StratoFilm 2.0 Teflon

TABLE 5

Tape Adhesion Properties

Lot Adhesion to Polyethylene Unwind or TMI Tack (25°C) Coating

No. (oz /in. Liner Removal( ) m Weight

__ 250C -60°C -80°C (oz /in.) - Polyethylene Steel (rain/24 sqin.)

3 22 30 -- 26 - 1 6,75

4 28 39 -- 34 1 - 6.75

5 26 5 -- 33 .. 6.5

6A 8 19 - 12 7 — 7.0

6B 7 5 -- 24 - -- 7.25

6C 7 8 -- 36 transfer -- -- 7.0

9A 22 56 -- 6 -1 11.2

9B 17 60 -- 46 transfer - -- 11.2

9C 14 54 -- 104 delaminated -- 11.2

9D 14 58 -- 60 transfer - -- 11. 29E 14 60 54 transfer - -- 11.2

9F 15 46 -- 60 transfer -- -- 11.211 17 88 -- 10 112 225 9.2

12 21 96 -- - 229 9.5

15 11 . 1 8 55 93 5.5

15A 9 —— 8 -- 5.75

15B 9 - 3 45 -- 6.25

15C 10 1 36 -1 -- 5.5

15D 9 | 6 27 -- 6.4

17 11 -- -- 1 - 177 7.8

19 13 - 71 8 110 165 8.5

19A 10 65 4 58 117 8.5

20 7 __ 10 75 98 4.0

24 16 -- 80+ 7 170 210 7.1

25 13 -- 69 10 158 225 8.7

26 12 -- 67 10 145 208 7.5L~~~~~~~~~~~~~~~~~~~~~~~~~0 .

TABLE 6

Comparison of Peel Adhesion Performance

Tape Adhesion to Balloon grade PE Adhesion to Steel..... I (oz in. )* (ozli n. )*

____250C -800C 250 C -80C_

#480 22 0 50 33

#480A 3 0 19 53

SL 250382, Lot 24 16 80+ 18 80+

SL 250382, Lot 25 13 69 17 80+

SL 250382, Lot 26 12 67 14 80+

SL 50382, Lot 19 13 71 16 80+

SLP 50382, Lot 19A 10 65 13 80+

*Values are maximum readings obtained. Cold temperature samples reinforced with filament tapeSL 242426, Lot 398.

TABLE 7

Comparison of Shear Adhesion Performance

Tape Shear to Balloon grade PE (min) Shear to Steel (min)490C 250C -800C 490C 250C -800C

#480 14.4 415.0 60+ 13.0 377 8 60+

#480A 9.2 109.7 60+ 377.8 232.0 60+

SL 250382, Lot 24 39.4 1928.2 60+ 55.0 1162.7 60+

SL 250382, Lot 25 106.9 3294.2 60+ 107.8 1757.7 60+

SL 250382, Lot 26 174.4 5275+ 60+ 292,9 5290+ 60+

SLP 50382, Lot 19 141.4 5710.4 60+ 131. 6 4515.9 60+

SLP.50382, Lotl9A 60.7 2867.4 ... 60+ 61.0 . 3633.2 60+

Modified Fed. Std. 147, Method 20; 500 gm. load, 112" x 1/2" shear area. Tapes for 490C & 250C testsreinforced with Tape #890. Tapes for -800C test reinforced with Tape SL 242426, Lot 398.

TABLE 8

Comparison of TMI Tack Performance

Tape . Polyethylene Probe(gramsEM) Steel Probe(grams EM)_____25C -800C- 250C -800C

#480 205 + 7.64 3 + I 337 +18.5 5 + 2.9

#480A 165 2.89 8 1.7 209 2.65 5 2.9

SL 250382, Lot 24 170 1 377 69..9 210 2.89 343 83.5

SL 250382, Lot 25 158 8.34 332 4.42 205 2.89 353 74.1

SL 250382, Lot 26 145 15.0 300 10.4 208 1.68 273 8.82

SLP 50382, Lot 19 110 3.26 263 42.1 165 4.18 320 64.8

SLP50382, Lotl9A 58 4.41 230 11.5 117 3.33 182 21.7

* Room temperature contact of pro!and dwell during cooling to -800C.Error of the Mean, EM = (sln(n-D)) , where s is the sum of the squares of the difference of a value from theMean.Probe diameters = 1/16 inch.

TABLE 9

Modified Cold Brittleness Test at -800C

Tape Identification Results Film/Tape Number ofNon - Aged Orientation Samples

SL 250382, Lot 9A No fail MD* 5SL 250382, Lot II No fail MD 5SL 250382, Lot 15 No fail MD 5SL 250382, Lot 12 No fail MD 5#480 Tape cracked CD* 5#480 Tape cracked MD I#480 No fail MD 4#480 A Tape cracked MD 5Control, VisQueen X-124 film only No fail MD 5Aged 5 weeks at 25 CSL 250382, Lot II No fail CD 2SL 250382, Lot 12 Nofail CD 2#480 Tape cracked CD #480 No fail CD Control, VisQueen X-124 film only Nofail MD 2Aged 5 weeks at 49 CSL 250382, Lot II Nofail CD 2SL 250382, Lot 12 No fail CD 2#480 No fail CD 2Control, VisQueen X-124 film only No fail i MD 2:MD = Machine Direction CD = Cross Direction

TABLE 10

Comparisons of Resistance to Blocking to VisQueen X-124 Polyethylene5 days at 150 150 + 50F, Load as indicated

Tape Identification 1000-gm Load 4000-gm Load

#480 Fail Fail#480A OK OKSL 250382, Lot II OK OKSL 250382, Lot 12 Fail FailSL 250382, Lot 15 OK OKSL 250382, Lot 24 OK OKSL 250382, Lot 25 OK OKSL 250382, Lot 26 OK OKSLP 50382, Lot 19 OK* OK*SLP 50382, Lot 19A . -OK* . OK**14 days at 150OF

TABLE II

Accelerated Tape Aging Study (100°F)

Tape Identification Liner Line Removal— Days Adhesion to PolyethyleneType oz/in. Aged oz/in.

I__________________itial Aged Initial AAged

SL 250382, Lot 15 Teflon 8 6 17 1 14

SL 250382, Lot 15D Daubert 6 10 21 9 132-60KG-R69-246

SL 250382, Lot 17 RP358 I 0-10 21 II 16

SL 250382, Lot 20 Teflon 10 10 17 7 I

SL 250382, Lot 24 Teflon 19 7 17 16 16

SL 250382, Lot 25 Teflon 10 10 17 13 16

SL 250382, Lot 26 Teflon 10 10 17 12 13

* Federal Standard 147, Method 12** Modified Federal Standard 147, Method 10

POLYETHYLENE PROBE STEEL PROBE

#480 1 _1IL

Lot 24

Lot 25i

Lot 26

Lot 19

Lot 19A

+25C -80C

0 100 200 300 400 300 200 100 0TMI TACK -1/16' PROBE (grams)

Fig. 1--Comparison of TMI tack performance

400 — '1 ... i .... I ... I——

Polyisobutylene

300 — — — — —.....— — — — — — — — — —Dow 280+1.5%

j'" Benzoyl Peroxide

Polyacrylate .____________200 ,C-3-0466Dow 280+3,

Benz Peroxide

100 . . . .

25 20 15 10 5 0 -5 -10 -15 -20 -25 -30 -35 -40 -45 -50 -55 -60

TEMPERATURE, oC.

Fig. 2--Comparative Effects of Temperature Upon Instant Adhesion Using TMI Tack Tester

10.0 ... .

-x-- SL 250382, Lot 11

^~~~~~~~9.0....-- SL 250382, Lot 12I ~ ~~~~-8.0---a Tape #480

8.0 --- No Tape-Control

7.0

z S.O k __ r I'd,__ _w g g45.0 -6

zLu

4.0

adm 3.0

2. -0

0 1 2 3 4 5 6 7 8WEEKS

Fig,3--Break Tensile Values for Visqueen X-124 film with l"x 1" tape area, aged at 25O C

10.0

-- X--- SL 250382, Lot 119.0 - ---- SL 250382, Lot 12-

._.__ Tape #4808.0 - -- No Tape-Control

7.0

LU

_ 6.0 ~ '_ - --r

2.0

h¢ 4.0LU

3.0

2.0

1.0

0 I .I I I I . .1

0 1 2 3 4 5 6 7 8

WEEKS

Fig.4--Break Tensile Values for Visqueen X-124 film with l"x 1" tape area, aged at 490 C (1200 F)

10.0 ' 1 .

-X---- SL 250382, Lot 11__0._a__ SL 250382, Lot 119.0 . -—-•—- SL 250382, Lot 12

-.-- _-- Tape #4808.0 L — No Tape-Control

7.0

6.0

5.0UJ c"-

z 4.0 "

I-

Ne 3.0

2.0

1.0

0 -0 1 2 3 4 5 6 78

WEEKS

Fig. 5--Break Tensile Values for Visqueen X-124 film with l t x It tape area, aged at 660 C (150 F)

39

REFERENCES

1o Anderson, A., E. E. Gear, and Go L. Morfitt,: Balloon BarrierMaterials, Final Report, General Mills, Inc. AF-CRC-TR-262,Contract No. AF 19 (604)-1393, 89-96, 1956.

2. Bilhorn, T. W.: "Balloon Performance Analysis--NCAR Scientific

Balloon Facility," Proceedings, AFCRL Scientific Balloon

Workshop, 1965 45, 63, May 1966.

3. Nielsen, L. E.: Mechanical Properties of Polymers, Reinhold

Publishing Corp., New York, 1962,

4. Fed. Test Method Std. No. 147A (GSA), Gummed and Pressure-Sensitive Tapes:Methods of Testing, as amended 26 June 1964.

5. Specification No. M23010 (Litton Systems Inc.), Specification for

Polyethylene Tape new release 24 March 64.

6. ASTM Standard D1790-62, Method of Test for Brittleness Temperature

of Plastic Film by Impact, Vol. 27, 563, 1965 Edition.

7o Hammond, F. Ho, Jr.: Polyken Probe Tack Tester, ASTM SpecialTechnical Publication 360, 123-133, 1964.

8o ASTM Standard D882-64T, Tests for Tensile Properties: of Thin

Plastic Sheeting (Tentative), Volo 27, 358, 1965 Edition,

40

BIBLIOGRAPHY

Kaelble, D. H.: "Peel Adhesion," Adhesive Age, 37-42, May 1960.

Kaelble, D. H.: "Theory and Analysis of Peel Adhesion: Rate-TemperatureDependence of Viscoelastic Interlayers," Journal of Colloid Science19, 413-424, June 1964.

McCarty, R. Gordon: "Balloon Technology," International Science andTechnology 50 54-63, February 1966.

NCAR Facilities Reports, National Center for Atmospheric Research,Boulder, Colo.FRB-1-64 Test of Balloon Materials, Nov. 1964.FRB-2-64 Standard Test Methods for Balloon Materials, Nov. 1964.FRB-3-64 Non-Standard Tests for Balloon Materials, Nov. 1964.FRB-4 Strength Characteristic of duPont "Surlyn April 1965.

NCAR Technical Notes, National Center for Atmospheric Research, Boulder, Colo.TN-5 Material Strength Properties of VisQueen X-124 Film, 1965.TN-9 Material Strength Properties of Startex SL 1883 Film, 1965.TN-14 Material Strength Properties of Winzen StartoFilm, April 1966.TN-15 Strength Characteristics of Grace Cryovac YH Polypropylene Film,

April 1966.

Scientific Ballooning, 12, National Center for Atmospheric Research,Boulder, Colo., 197.

I