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TRANSCRIPT
-FRB..4 ...
NCAR Facilities Report
Strength Characteristics of
DuPont "Surlyn A" Film/
National Center. for Atmospheric Research
Boulder, Colorado
i=,, : ' _ APRIL 1965 .... ^ 5 '"NCAR Library
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STRENGTH CHARACTERISTICS OF DUPONT "SURLYN A" FILM
NCAR Facilities Report FRB-4
A test program conducted for the National Center forAtmospheric Research, by the Hauser Research and Engineering
Company, 2965 Peak Avenue, Boulder, Colorado
(Hauser Report No. 5034-65-05)
April 1965
I
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PREFACE
This report is one of a series prepared for the Materials Research
Project of the NCAR Scientific Balloon Facility. The Materials Research
Project is one of several related efforts undertaken by the National
Center for Atmospheric Research (NCAR) to increase the reliability,
and to extend the capabilities, of scientific ballooning.
NCAR was founded in 1960, to conduct basic research in the atmos-
pheric sciences, and to foster such research on the part of the
universities and research groups in the U.S.' and abroad. NCAR is
operated by the University Corporation for Atmospheric Research (UCAR),
and sponsored by the National Science Foundation.
The present report covers certain investigations performed by
Hauser Research and Engineering Company, Boulder, Colorado, under sub-
contract with UCAR. Other reports published in this balloon materials
research series include: FRB-1-64, Tests of Balloon Materials; FRB-2-64,
Standard Test Methods for Balloon Materials; and FRB-3-64, Non-Standard
Tests for Balloon Materials.
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SUMMARY
A new plastic film of the ionomer class, developed by DuPont,
and tradenamed Surlyn A, appeared to have possibilities as a balloon
material. Samples of the film were subjected to standard tests for
mechanical strength. The test data indicate that Surlyn A is comparable
in many of its material properties to a good polyethylene. However,
the samples tested carried high static charges which would make the
material unsuitable for use in balloons. If current development pro-
grams succeed in eliminating the static charge, Surlyn A may become
a good prospect for balloon use.
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CONTENTS
PREFACE. ............................. ii
SUMMARY ............. iii
LIST OF TABLES .......................... v
Section
I. INTRODUCTION ... ................. 1
II. MANUFACTURER'S SPECIFICATIONS .............. 2
III. DESCRIPTION OF SAMPLES ................. 4
IV. TESTS AND RESULTS -- MECHANICAL PROPERTIES OF SURLYN A . 6
V. CONCLUSIONS. ...................... 8
FIGURE AND TABLES. ........................ 9
REFERENCES ............................ 15
v
LIST OF TABLES
1. Summary of Tests.................. . 10
2. Test Data, 1-Mil Surlyn A . ................ 11
3. Test Data, 2-Mil Surlyn A .................. 12
4. Comparisons of Films Tested at 25C ....... .. 13
5. Comparisons of Films Tested at -80°C. ............ 14
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I. INTRODUCTION
In September 1964 E. I. DuPont de Nemours & Company announced
the development of a new class of plastic films called "ionomers. "
Only one form of ionomer film, tradenamed "Surlyn A," is commercially
available at present.
The trade literature on Surlyn A indicated it might have value
as a balloon material. Under subcontract to the National Center for
Atmospheric Research, an investigation was begun in December 1964 to
determine the strength characteristics of this film.
One- and two-mil thicknesses of the film were subjected to
the standard tests used in earlier film test programs for NCAR. These
consisted of 160 tests to determine Surlyn A properties of ultimate
tensile strength, tensile yield strength, elongation at yield, ulti-
mate elongation, tensile modulus of elasticity, tear initiation
strength, and tear propagation strength.
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II. MANUFACTURER'S SPECIFICATIONS
DuPont classifies their ionomers as thermoplastics -- materials
which soften when heated, harden when cooled, and can be reshaped many
times by alternate heating and cooling.
DuPont asserts(l) that Surlyn is stronger and tougher than unmodified
polyethylene, and that it has the stiffness of a medium-density poly-
ethylene with the high elongation and low-temperature flexibility of
many polyolefins. Because its structure consists of oxidized polymer
chains and inorganic cation groups, the attractive forces between oxidized
chains and cations give a partial cross-linking effect, as in thermoset
plastics. However, in thermosets such cross-linking is irreversible.
The ionic linking of the ionomers, on the other hand, is thermally
reversible. Thus, the ionomers can be worked like thermoplastics, but
offer some attributes of thermoset plastics.
The manufacturer claims that the incorporation of inorganic metallic
ions, such as sodium and potassium, increases the material's modulus of
elasticity and yield point, as well as its chemical resistance to oil
and solvents.
DuPont ascribes the following properties (at room temperature) to
Surlyn A: (
Specific gravity 0.93 -- 0.94
Tensile strength 3500 -- 5500 psi
Yield strength 2000 -- 2500 psi
Elongation 300 -- 400%
Modulus 28,000 -- 40,000 psi
Tear strengthElmendorf 20 -- 80 g/mil
3
The resin in bulk quantities costs 50¢/lb. Film of 1- or 2-mil
thickness costs $0.85 to 1.00/lb.
DuPont is continuing development on the ionomer family. They
expect that other polymers, such as polypropylene, with various cation
groups (sodium, potassium, magnesium, and zinc) will give ionomers
with a wide range of properties.
When additional ionomer films are developed, they will be con-
sidered as possible balloon materials.
4
III. DESCRIPTION OF SAMPLES
The 1-mil sample of Surlyn A was shipped on two rolls designated
as:
Surlyn 'A'ER 16011 mil
The rolls, each 24 in. wide and 50 ft long, were received in excellent
condition in December 1964. (We do not presently know if this film is
available in lay-flat tubing or other production widths.)
The 2-mil sample was shipped later and bore a similar notation.
It was also received in good condition. This roll was 24 in. wide; its
length was not measured.
Each of the three rolls of film had slight ripples parallel to
the machine direction. These ripples may have collected as a result of
uneven rolling following fabrication. The rippling seemed to have no
effect, except in the transverse-direction tensile modulus tests.
This effect, consisting of a small inflection, was virtually negligible.
(An example of the effect can be discerned in Fig. 1, near the origin
of the curve for the -80 C test of the Surlyn film.)
Close inspection of the film revealed that it contained many gel
granules. During examination of a few tensile specimens by polarized
light, these particles were observed to serve as centers of stress con-
centration.
In handling the film to prepare test specimens, a high static charge
was noted on its surface, similar to that which can be observed on Saran
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Wrap. We did not make a quantitative measure of this force. It was
present to such a degree, however, that it may cause balloon manu-
facturing problems. It may also present considerable restraint in
unfolding any large balloon made of Surlyn. We cannot at present ascer-
tain whether buildup of high static charges might also cause perforations
in this material. Surlyn is very resistant to corona degradation
but perforation cannot be ruled out. DuPont engineers are working on
the static problem and may develop more satisfactory materials in the
near future.
The film was weighed, and can be compared in this respect with
films tested previously:
Material Nominal Thickness Weight (lb/1000(mil) sq ft)
Surlyn A 1 5.2
Surlyn A 2 10.3
Consolidated GF19X 1 4.8
Consolidated GF19X 2 9.9
Visqueen 1.5 7.4
Film thickness was measured around 2 ft-square samples from 1- and 2-mil
rolls, and was found to be quite uniform. The dial gage used was accurate
to 0.0001 in., interpolating to .00001 in. Ten readings were taken on
each sample. The 1-mil sample had as average thickness of 1.005 mil
with a variation -+J 8%. The 2-mil sample had an average thickness of 2.068
mil, with extremes of 2.19 and 2.01 mil.
Personal communication from J.P. Broussard, Industry Representative,Polyolefins Division, DuPont, 18 December 1964.
6
IV. TESTS AND RESULTS -- MECHANICAL PROPERTIES
OF SURLYN A
The tests were standard procedures, described in Refs. 3 and 4.
They are summarized in Table 1.
The tests were conducted under two temperature environments:
25 - 10C (73.4 - 1.80 F) and -79 - 2 C (-110.2 + 3.60F). The cold-
environment chamber used for the latter tests is described on p. 5 of
Ref. 3.
Humidity in the testing area varied from 20% to 50%. Samples were
preconditioned in the 50% humidity chamber. DuPont's technical descrip-
tion of Surlyn indicates that moisture absorption should not be a problem
with this type of film.
The results of the tests are presented on Tables 2 and 3 (pp. 10
and 11). Tables 4 and 5 summarize these data and compare them with test
results on other films.
The methods used for deriving these test results and deviation
coefficients are described on p. 24 of Ref. 5.
For all tests, our data show lower strengths than those reported
by DuPont. This is because our tests are run at slower rates
(0.125 in./in./min) than are most commercial tests.
In ultimate strength, Surlyn A film is slightly lower than Visqueen
at 25 C, and comparable at -80 C. The rather large value (.220) of the
deviation coefficient for I-mil Surlyn A at 25°C in the transverse direction
is due to an average of two high and three low values for this series.
We could assign no cause for this variation.
7
The test values at 25°C for tensile yield strength and tensile modulus
are superior to those of any other film listed in Table 3. At -80 C these
properties are comparable to, or slightly lower than, those of other
films. Surlyn A thus appears to have better creep resistance than standard
polyethylene balloon films.
In Fig. 1, typical tensile modulus test curves are plotted for 1-mil
Surlyn A, and for two other films, using data from Tables 4 and 5 and
from Ref. 3.
In tear initiation and propagation strengths, Surlyn is comparable
0to, or (at -80 C) slightly inferior to, Visqueen.
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V. CONCLUSIONS
On the basis of the samples tested, Surlyn A is comparable in many
of its material properties to a good polyethylene. At room temperature
it is superior to most of the other films tested in tensile yield strength
and modulus. At low temperature it appears slightly inferior in modulus
and tear properties.
The film should be evaluated for sealing qualities and brittleness
at low temperature. No tests were made of these properties during the
program reported here.
Surlyn film may become a good prospect for balloon use if it can
be treated to eliminate its static charge.
We believe our data to be representative of the samples received.
These same data may not be representative of commercial production.
10,
8 10 -800C
II/ ,8 0 0 C _ Surlyn A, I milc , ^^ / __.___ Visqueen, 1.5 mil
_ /—__._. _ Consolidated GF 19X, 1.5mil
- / ,,~ ..... Visqueen (adjusted to I mil)
4
--» / i ,,
(n I,
0 4—1 S ——————-- - - -' - - -1
(/)
25°C
^______________0 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.__ 16
0 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16
Strain
Fig. I--Typical Modulus Curves (machine direction)
Table 1
SUMMARY OF TESTS
(5 samples each in machine and transverse directions, on Dillon Model M Tester)
Test Method Sample Size Crosshead Rateor Type Strain Rate
(in./min)
Tensile ASTM D882 61T 1" x 6" 0 .5a
Strength method B (4" gage length)
UltimateUltimatie l(determined from tensile strength test)Elongation
b ITensile ASTM D882 61T 1" x 12' (10" 1 oModulus gage length)
Yieldieldgh l(determined from tensile modulus test graphs)Strength
Tear ASTM D1004 61 die-cut specimens 2Initiation Graves tear test
Tear ASTM D1004 die-cut specimens 2Propagation Hauser-modified -- 1/16" slit
0.1 2 5 in./in./min strain rate
Autographic stress-strain curves made of load vs elongation.Pendulum-head travel corrected.
Table Z
TEST DATA, 1-MIL SURLYN A
Direction Ultimate Ultimate Tensile Tensile Elongation Tear TearTensile Elongation Modulus Yield at Yield Initiation PropagationStrength (%) (psi) Strength (%) Strength Strength
(psi) (psi) (lb/in.) (lb/in.)
-25 C
Machine 2700 196 39,600 1640 8 460 3203200 262 40,000 1670 8 490 3803180 285 41,000 1500 8 470 3502800 213 36,800 1480 8 450 3702800 247 36,800 1610 8 410 350
average 2936 241 38,800 1580 8 456 354
Transverse 2400 .292 30,900 1480 8 360 2901600 177 32,000 1480 8 560 2001500 168 31,400 1480 8 540 1901700 198 33,700 1500 8 550 200 2300 320 33,400 1550 8 340 190
average 1900 231 32,300 1500 8 470 214
-80 C
Machine 8900 13 440,000 5310 3 850 4507700 14 333,000 4400 3 640 4709650 24 340,000 4300 3 740 4309950 27 249,000 4960 3 750 4809000 21 308,000 4960 3 800 410
average 9040 20 334,000 4760 3 756 448
Transverse 7200 18 203,000 4460 3 870 5208800 25 229,000 4460 3 800 3608600 15 234,000 4400 3 630 3708050 18 229,000 4370 3 700 3408600 17 187,000 4320 3 680 430
average 8340 19 216,400 4400 3 736 404
Table 3
TEST DATA, 2-MIL SURLYN A
Direction Ultimate Ultimate ' Tensile Tensile Elongation Tear TearTensile Elongation Modulus Yield at Yield Initiation PropagationStrength (%) (psi) Strength (%) Strength Strength
(psi) (psi) (lb/in.) (lb/in.)
-+25°C
Machine 3170 180 40,200 1850 8 502 3653250 205 40,700 1750 8 501 3553450 182 41,400 1700 8 495 3453750 217 40,600 1750 8 502 3703280 259 41,800 1850 8 506 400
average 3380 209 40,900 1780 8 501 367
Transverse 2750 352 36,800 1600 8 501 320 2100 237 39,600 1700 8 600 2802900 345 41,600 1650 8 502 2953150 370 43,000 1650 8 400 3702750 324 42,300 100 08 603 295
average 2730 326 40,700 1640 8 521 312
-800C
Machine 12,400 67.5 238,000 5000 3 805 39510,200 28.8 236,000 4450 3 870 38510,850 38.8 208,000 4300 3 800 35010,050 43.3 209,000 4500 3 980 50512,000 70.0 227,000 4600 3 840 410
average 11,100 49.8 224,000 4570 3 859 409
Transverse 9050 47.0 197,000 4400 3 1105 5108900 33.5 200,000 4600 3 995 3809000 31.3 254,000 5050 3 1105 4009000 27.5 200,000 4600 3 845 500
9450 33.0 222,000 4600 3 1000 400
average 9080 34.5 215,000 4650 3 1010 438
Table 4
COMPARISONS OF FILMS TESTED AT 250C
(elongation at yield, 8% for all samples; no deviation)
Film Weight Direc- Ultimate Tensile Ultimate Tensile Tear Tear(lb/1000 tion Tensile Yield Elongation Modulus Initiation Propagation
sq ft) Strength Strength ____average d.c? average d.c. average d.c. average d.c. average d.c. average d.c.(psi) (psi) () (psi) (lb/in.) (lb/in.)
Surlyn M 2936 .080 1580 .054 241 .149 38,800 .034 456 .063 354 .062A 5.2
1-mil T 1900 .220 1500 .020 231 .302 32,300 .039 470 .074 214 .201
Surlyn M 3380 .068 1780 .038 209 .155 40,900 .159 501 .007 367 .060A 10.3
2 -mil T 2730 .142 1640 .026 326 .160 40,700 .061 521 .162 312 .114
Winzen Strato- M 2054 .087 720 .078 193 .249 13,200 .166 374 .056 245 .114film 320 3,30.75-mil T 1734 .109 848 .090 285 .233 16,300 .117 360 .086 240 .05
Winzen Strato- M 1720 .159 690 .141 192 .302 13,600 .205 390 .046 290 .064film 320 6.31.5-mil T 1890 .078 820 .079 290 .146 16,900 .150 400 .083 290 .042
Winzen Strato- M 1540 .133 940 .068 260 .323 20,300 .152 380 .100 280 .082film 320 7.9
2-mil T 2600 .084 970 .103 380 .121 23,200 .067 448 .087 330 .127
Consolidated M 2140 .016 1020 .094 200 .300 15,200 .040 590 .048 510 .049GF19X 4.8I-mil T 1330 .100 1000 .059 236 .320 17,200 .070 510 .087 360 .110
Consolidated M 2080 .150 1000 .052 387 .160 17,300 .087 543 .069 450 .01GF19X 9.92-mil T 2020 .073 996 .005 438 .058 17,800 .087 493 .032 400 .051
Visqueen M 3970 .170 850 .040 456 .170 14,400 .035 581 .036 416 .018A 7.4
1.5-mil T 3510 .180 800 .027 442 .110 13,500 .130 440 .037 388 .036
deviation coefficient
Source: Data from Hauser Research & Engineering testing programs
Table 5
COMPARISONS OF FILMS TESTED AT -80 C
(elongation at yield, 3% for all samples; no deviation)
Film Weight Direc- Ultimate Tensile Ultimate Tensile Tear Tear(lb/1000 tion Tensile Yield Elongation Modulus Initiation Propagation
sq ft) Strength Stren th _____________________________average d.c.* average d.c. average d.c. average d.c. average d.c. average d.c.(psi) (psi) (%) (psi) (lb/in.) (lb/in.)
Surlyn M 9040 .096 4790 .028 20 .308 334,000 .200 756 .102 448 .064A 5.2
1-mil T 8340 .092 4400 .013 19 .196 216,000 .094 736 .161 404 .165
Surlyn M 11,100 .096 4570 .057 49.8 .366 224,000 .064 859 .085 409 .143A 10.3
2-mil T 9080 .024 4650 .051 34.5 .214 215,000 .112 1010 .106 438 .137
Winzen Strato- M 6984 .041 4250 .041 78 .105 245,000 .115 1134 .016 962 .155film 320 3.30.75-mil T 7254 .033 4900 .028 22 .264 304,000 .049 1012 .131 676 .197
Winzen Strato- M 7440 .161 5990 .156 30 .433 308,000 .138 1050 .068 630 .185film 320 6.31.5-mil T 7090 .051 5802 .078 23 .413 279,000 .105 1070 .054 658 .186
Winzen Strato- M 7070 .161 5830 .178 23 .478 210,000 .109 1160 .149 700 .050film 320 7.92-mil T 9040 .079 6610 .046 48 .854 224,000 .061 1090 .139 734 .189
Consolidated M 10,300 .200 5420 .155 206 .120 339,000 .130 1400 .064 1080 .100GF19X 4.81-mil T 7500 .024 5470 .127 22.2 .530 468,000 .095 970 .035 750 .130
Consolidated M 8560 .072 5420 .025 187 .420 276,000 .038 1210 .100 950 .088GF19X 9.92-mil T 8160 .066 5700 .108 104 .370 299,000 .200 1120 .120 760 .029
Visqueen M 8490 .026 5690 .125 45.5 .500 373,000 .110 1190 .140 740 .170A 7.4
1.5-mil T 7540 .084 6500 .081 7.3 .420 403,000 .076 1040 .091 710 .098
deviation coefficient
Source: Data from Hauser Research & Engineering testing programs
15
REFERENCES
1. "New Tough Transparent Plastics," Materials in Design Engineering 60,
No. 3, 106-107, September 1964.
2. Surlyn A Ionomer Resin, Brochure A-38352, Plastics Dept., Polyolefins
Div. E. I. DuPont de Nemours & Co., Wilmington, Del., undated.
3. Tests of Balloon Materials, NCAR Facilities Report FRB-1-64, National
Center for Atmospheric Research, Boulder, Colo., November 1964.
4. Standard Test Methods for Balloon Materials, NCAR Facilities Report
FRB-2-64, National Center for Atmospheric Research, Boulder, Colo.,
November 1964.
5. Non-standard Tests for Balloon Materials, NCAR Facilities Report
FRB-3-64, National Center for Atmospheric Research, Boulder, Colo.,November 1964.
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