January 15, 1929
INDUSTRIAL AhrD ENGINEERIiVG CHEMISTRY
Beckmann* suggested that the low results in this particular case were due not only to incomplete comkiustion but to the formation of pyromucates. which they found difficult tp burn completely. They found that, in spite of all precautions, the analyses for carbon, in the case of the esters of n-amyl. n-hexyl, n-heptyl, n-octyl of furoic acid, came out uniformly low, especially in the case of the higher esters, and also in the case of the esters of furoylacetic acid.Q With the use of this new device, however, the analysis of esters of similar nature, such as of a-tetrahydrofurfuryl alcohol synthesized by Zanetti,lo the author obtained very satisfactory results. The most difficult to burn in this series was found to be the isovalerianate of a-tetrahydrofurfuryl alcohol, for which the following analyses (not yet published by authors) were obtained : ~-
* Zanetti and Beckmann, J . A m 9 1
KEW DEVICE
Carbon Found Calcd.
70
Hydrogen Found Calcd.
70
%
%
17 CAPILLARY METHOD Carbon Hydrogen Found Calcd. Found Calcd.
%
70
%
%
Analysis of a Known Highly Volatile Liquid
As a final test two analyses were made of a highly volatile organic liquid compound, benzene, with the following results: Found
CARBON
HYDROGEN Calcd.
Calcd.
Found
70
70
70
70
91.97 92.06
92,30
7.73 7.88
7.69
These results indicate that volatile liquids like benzene can be weighed in this new device and introduced into the combustion tube without any material loss.
Chem. S O ~ .48, , 1067 (1926).
Ibid., SO, 1438 (1928).
OZanetti, Ibid., 60, 1821 (1928).
A New Physical Test for Vulcanized Rubber’ D. D. Wright HOODRUBBER COMPANY, WATERTOWN, MASS.
This test, by use of a sample of new design, subjects the jaws of the testing maTLCANIZED r u b b e r rubber to a combination of tensile and shearing chine (Figure l). The lower is frequently required stresses. Shear, however, is the predominating stress. jaw moves a t the rate of 10 to withstand, not only Certain aged inner tubes have been found which inches (25.4 cm.) per minute. the simple stresses such as deteriorated more when examined by this test than a I n the usual manner readthose of compression, tensile, comparison of their tensile-stress-strain curves with ings of load and elongation and shear, but also the comthose of fresh tubes would indicate. Tearing action are taken up t o and includbined effects such as torsion, seems to be approximated by this test. The effect of ing those at rupture. From tearing, bending, etc. It has overcure in some cases’ has been recorded at earlier these measurements and the been observed that, as some stages by this test than by the tensile criterion. The cross section of the tongue the vulcanized rubber s a m p l e s test is easy to perform and with usual precautions shear-stress-strain curve may age, their resistance to shearshould have an accuracy of approximately 10 per cent. ing and tearing stresses debe plotted and the relative creases inuch faster than their energy to start rupture estiresistance to tensile stresses, as determined under the stand- mated by determining the area under the curve. Figure 3 shows the comparison of the shear-stress-strain curves with ard procedure of rubber-testing. During a study of natural and artificial aging some inner- the usual tensile-stress-strain curves. The reasons that the tube samples, which tested very poorly after the oxygen bomb shear-stress-strain curves do not exactly coincide with the (50 hours a t 60” C. and 20.4 atm.), were filed for further tensile-stress-strain curves seem to be: (1) Different widths observation. As these tubes aged the tensile tests showed of samples were stretched; (2) different rates of stretching less deterioration than was expected. However, a close were employed; (3) near break certain stocks seem to yield examination of these tubes showed that they had developed some on shearing. In other words, the rupture is very slow a very poor resistance to tear and were weak when sudden while in other cases it is instantaneous. These curves are tensile stress was applied. For sake of brevity this lack of compared more fully in Table 111. resistance t o sudden stress will be called “shortness.” A shorter and slightly less accurate method of getting the After several attempts to measure this “shortness” property relative energy t o rupture the tongue is to take one-half the without resorting to some new testing machine, the tongue product, S X E/100, where S is the stress a t rupture (kg. per shear test was developed. It is so named because of the sq. cm.) and E is the per cent ultimate elongation. The shape of the test specimen and the effect that is produced. product, the “shear product,” is close enough for ordinary It seems to give about the proper rating to these “short” comparisons and closer to the real energy values than the tubes. tensile product is for the relation that it expresses, because lower concavity factors exist in the shear-stress-strain The Test curves.
V
A specimen like that in Figure 1 is prepared by means of a cutting die, as shown by the pattern in Figure 2. Two parallel marks exactly 1 inch (2.54 cm.) apart are placed on the test piece so that they will be near the middle of the parallel section of its tongue. The sample is then placed in 1 Presented before the Division of Rubber Chemistry at the 76th Meeting of the American Chemical Society, Swampscott, Mass , September 10 to 14, 1928.
Mechanism of Test
The manner of rupture and factors influencing the values obtained were studied to learn, first, what was taking place as the rubber was strained in this sort of specimen, and second, if the test piece was properly proportioned. The rupture always takes place a t the end of the tongue (C-D, Figure 1). A much smaller expenditure of energy is required to start
ANALYTICAL EDI TI0N
18
- 356mm-
i
'Ii
I
Expt.
A
24.5
Figure 1-Test
Specimen
Table I-Effect of Thickness SHEARTESTS Thickness
0.99 1.93 2.94 4.08 2.72 1.83
E
B
Vol. 1, No. 1
IPlies
I
Shearing stress
1 2 3 4 3 2
0,039 0.076 0.116 0.161 0.107 0.072
14 15 23 24 21 22
203 218 332 339 303 313
I
Ultimate eb;y
330 320 410 400 400 360
I
Shear product
Kp.-cm. I e s . cc. in.8
24 25 48 48 43 39
339 349 680 678 606 556
SHEARTESTS
1
I
Expt.
1
I
Thickness
Shearing stress
Ultimate elongation
Shear resilience
Kp.-cm. In.-lbs. 0.76 0.71 1.40 3.12
0.0300 0.028b 0.055
0.123
10.5 9.3 13.5 18.5
152 132 193 274
%
cc.
in.8
350 325 375 440
18 11 26 41
257 159 364 579
TENSILE TESTS
~
Figure 2-Pattern C u t t i n g Die
of
rupture than would be the case if the same section were broken with the standard dumbbell test specimen. Since rubber is so elastic, the mathematical analysis of the forces that follow the straining of the tongued specimen is difficult. Therefore, the specimen shown in Figure 1 was ruled off into squares before it was put under strain in order to present a picture of the lines of strain. As the tongue stretches out, the legs A and B twist upwards and the dips in the lines a t C and D become sharper. It is evident that a t these points the rubber suffers the greatest change in direction of strain and also that a marked shearing action is set up. If the cuts a t C and D are rounded with a punch, ruptures are not obtained a t such low energy values and the test behaves more like a tensile test. Studies of the effect of the width of the tongue and of the margin or legs outside the tongue are represented in Figures 4 and 5. These curves show that the specimen is so proportioned that it avoids the tensile effect as much as possible. The narrowing of T with X constant (Figure 4) does not produce the same type of curve as the widening of X with T constant (Figure 5 ) . If the distribution of fiber stresses in the tongue is taken into account, this difference for tongue widths under 0.5 inch seems to be satisfactorily explained.
Expt.
Thickness
Tensile
Ultimate elonga- Tensile resilience tion
Kp.-cm. *.I % 0.76 0.71 1.40 3.12
0.030a 0.0286 0.055 0.123
114 98
136 155
1575 1400 1900 2200
740 740 695 720
70ELONGATION
Curves of T o n g u e Shear a n d Standard Tensile Tests
cc. 272 226 306 418
in.8
3870 3220 4350 5950
a Outside, next to mold face. b Inside, next to a. Experiment A-Inner tubes of different thickness. Cured in same heat (open steam). Experiment B-Four-ply tube buffed down. Experiment C-Four plies of inner tube stock molded in one slab but separated with vellum t o give thickness shown. Cure, 75 minutes at 141' C.
Various articles2Jr4 have shown how much tensile results are influenced by the width of the specimen. I n the case of either ring or straight test pieces a decrease of width produces higher tensile values, especially on rich gum stocks. The Bureau of Standards3 shows that the more even distribution of fiber stresses in the narrow samples explains the results. The effect of thickness is difficult to determine, because 2 Report of A. C. S. Physical Testing Committee, IND.ENQ.CHEM., 17, 535 (1925). 8 Bur. Standards, Bull. 88. 4 Memmler and Schob, International Critical Tables, Vol. 11, p. 266; Mitt. Matrrialfirufungsamt Berlin-Dahlem, 29, 185 (1911).
AREAS OTB+O'TB': TENSILP RESILIENCI
Figure 3-Stress-Strain
I
I
TONGUE Wm l H dT ( X Figure 4-Effect
CONSTANT)
of Width of T o n g u e
INDUSTRIAL AND ENGINEERING CHEMISTRY
January 15, 1929
TONGUE SHEAR SAMPLE
Ultimate elongation
Stress
Kg. Lbs. cm.2 in.% Carbon-black tread stock Carbon-black tap sole Floating red tube, sp. gr. 0.98 Molded tube, sp. gr. 1.28 Ordinary red tube, sp. gr. 1.06 Truck tube (ZnO), sp. gr. 1.44 Cheap tube (whiting), sp. gr. 1.23 Black heel White suede leather Manila cardboard
103 75 36 48 24 42 15 34 202 190
1460 1067 505 682 335 590 215 480 2870 2690
STANDARD TENSILE
Shear product
Ultimate elongation
Stress
Kg.-cm. In.-lbs. Kg. Lbs. cc. in.8 cm.2 in.2
%
200 105 84 84 52 50 13.7 22 40
390 280 470 350 440 240 180 130 40 0.0
...
such factors as grain effect, heat lag, or heat developed while buffing the specimens may introduce serious variations. Table I shows some data obtained by three different experiments. These results leave much to be desired, but indicate that, even in the case of tensile testing of vulcanized rubber, strictly comparable results are not assured unless the specimens are of nearly the same thickness. Therefore, in per-
19
2847 1497 1186 1190 737 708 194 312 574
..
237 134 201 274 179 239 155 94 322 197
3370 1900 2850 3900 2650 3400 2200 1340 4583 2800
PARBASIS COMPARISON ~
Tensile product Kg.-cm.
% 630 335 785 650 785 578 596 417 50 0.0
cc.
1500 447 1570 1840 1410 1380 924 393 160
..
Shear Tensile product product
In.-lbs. in.’ 21,231 6,365 22,372
100 53 42 42 26 25 7 11 20
;:$?! 19,650 13,112 5,588 2290
....
0
100 30 105 123 94 92 62 26 11 0
era1 way with the tearing resistance of such stocks. In general, the effect of pigments on tear resistance is fairly well defined by the shear-product value, judging by hand-tear determinations. It has also been noted that certain accelerators give better results than others. Tahle 111-Comparison of a Worn a n d a New Tube CRITERION
EXPLANATION
UNIT
YORN NEW %BE T F G R~~~~ A A/B
% A. C. S. standard
Tensile
Resiiient B y Sheppard’s inteenergy gration formula Tongue shear stress (S) Tongue shear Ultimate elongation strain % (E) From area under Tongue shear I shear-strain curve resilience 1 / a shear stress X Tongue shear product strain ‘/a S X E 100 Or 100
I-
’g]
WfDTH of MRRGlN mm. 3I8 IN. O . I Z 5
a5 0.15
dX
0,37S
12.70 0.50
1588 0.625
Figure %Effect of Margin Outside of Tongue
forming the tongue shear test the thickness of all samples should not vary widely if comparable results are expected. Application of Test
The tongue shear test is applicable to practically every type of soft-rubber stock produced. It suggests many interesting studies, but its most striking applications are: (a) the demonstration of the shortn’ess property of aged inner tubes, ( B ) its use as a more sensitive index of the extent of artificial aging, and (c) its use with other criteria of cure or by itself to detect the beginning of overcure. Except for showing the comparison of different stocks on this test, only these three applications will be discussed. Various kinds of stocks are compared in Figure 6 and Table 11. For comparison, the carbonblack tread stock is taken as par, 100, and all other values are figured on this basis. Particular attention is called to the tread and tan sole stocks. which show very high shear resistance compared with the truck tube stock. This agrees in a gen-
150 17c 2130 2500 213 327 3024 4650 13 18.5 186 264
Kg.-cm In.-lbs.$n.a cc.
190 11 162
380 34 477
Kg.-cm cc. In.-lbs.in.a
12 176
35 502
85 85 67 70 50 34 35
The sensitivity of this test to the “shortness” in some aged inner tubes is shown in Table I11 and Figure 3. Here a worn tube is compared with a new tube compounded in nearly the same way. The worn tube had become absolutely unserviceable, yet the tensile criterion rated it 85 per cent as good as the new tube and the resilient-energy criterion, 67 per cent, while shear energy and shear product criteria rated it only 34 per cent as good. This worn tube, moreover, was very
C T CONSTANT) 253
-
Kg./cm.a I,bs./in.l Kg.-cm./cc. In.-lbs./in.a KgJcm.2 I,bs./in.2
/J0 /2 0
//O
30
70
60
60
SO
CTO
40
40
JO
k
PO
Figure 6-Comparison of Shear Product with Tensile Product on Various Stocks. Carbon-Black Tread = Par
ANALYTICAL EDITION
20
A
B
C D -INNER
Figure 7-Effect
E
F
G H I J TUBE SAMPLES-
-
K
L
M
N
of Bomb Aging on Tensile Strength a n d Shear Product
“short” while the new tube showed no Lishortness.” The worn tube also showed a very weak and grainy tear. The importance of developing high-speed tensile tests or their Table IV-Decrease El“.-
!
of Various Criteria on Aging
!
Loss I N BOMBA T 50 HOURS, Loss 6OoC., 20.4 ATM.
Tensile Shear product
%
+2119
Average
I
15 17 4 16 39 28 +2 33 2 11 9 50 16
Tensile Shear product
%
%
25 70 43 44 49 45 42
54 93 51 74 71 77 57 78 23
60
24 27
80
33
50
69 40 43 45
AIR A T 90° C., 48 HOURS
IN
66
1
29 64 61
% 63
96 68
89 76 76 60
75 11 65 73 78 70
VOl. 1, KO. 1
equivalents to show up this property of “shortness” in vulcanized rubber is evident. Figure 7 and Table IV show the effect of artificial aging on the tensile and shear product values of several makes of inner tubes. The oxygen bomb.test (50 hours a t 60” C. and 20.4 atm.) and a 48-hour air test a t 90” C. are shown. The tensile deteriorations were smaller than the shear product deteriorations in nearly every case, except in the 90” C. air test, which was so severe that tensile was reduced to about the same extent as shear product. The heat resistance of heavily pigmented tubes proves better than that of the rich gum tubes. The sensitivity of the tongue shear test to overcure is compared with tensile and tensile product in Figure 8. No doubt there may be cases where no greater sensitivity is s h o w n . T h e case given shows a tube stock cured with an ultra-accelerator. The s t o c k showed very little decrease of tensile on long overcures. O t h e r t e s t s showed e v e n t h e slightly overcured samples-to be poor in SHEAR PRODW s n i t e of t h e i r +.good . I I 6’ df , l e , ,?, tensiles. On s e r v i c e 5LA0 CURES e 141 ‘t tests tubes made from Figure 8-Shear Product us. Tensile or this stock developed Tensile Product on Overcures very poor resistance to sudden stress, weak shear resistance, and exceedingly poor tearing qualities. Further studies of its applications are being made.
1
I 1 I
Acknowledgment
64
69
Size 1, 29 X 4.40; size 2, 31 X 5.25; size 3, 33 X 6.00; size 4, 35 X 5.
The writer wishes to express his appreciation to W. E. Glancy, N. E. Tousley, and others who have assisted so much in the perfection of this test through their helpful suggestions.
Determination of Small Amounts of Carbon Monoxide in Ethylene’,’ Wright M . Welton with N. L. Drake UNIVERSITY O F
MARYLAND, COLLEGE PARK, 1WD.
HERMAN and others3 have reported one fatality and two cases of dangerous poisoning which were definitely shown to have been caused by the presence of carbon monoxide in ethylene administered as an anesthetic. The specifications of ethylene for anesthesia found in “Yew and Non-Official Remedies” for 1927 require that the gas show a negative test for carbon monoxide according to a method worked out a t the Bureau of Mines.4 This test will detect with certainty carbon monoxide in ethylene down to 0.02 per cent by volume, and probably down to 0.01 per cent by volume. have shown that 4 parts of carbon monoxHenderson et
S
Received July 11, 1928. From a thesis submiited by Wright M. Welton to the Graduate School of the University of Maryland in partial fulfilment of the requirements for the degree of master of wience. 8 Sherman et al., J. A m . Med. Associi , 86, 1768 (1926). 4 Ibid., 88, 322 (1927). 6 Henderson et&, J. I n d . H y g , 8, 72, 137 (1921). 1 2
ide per 10,000 of air is the maximuin concentration to which a normal person can be exposed for an hour without noticeable effects, and that 1 part of carbon monoxide per 10,000 of air (0.01 per cent) is the maximum concentration that can be tolerated without ill effects by a normal individual who is exposed continuously for seven hours a day. It seemed to us worth while, therefore, to develop a method that would determine with certainty concentrations of carbon monoxide in ethylene well below those which would give a positive test .with hemoglobin. The present paper reports the first results of the investigation. The possible interference of impurities which may be found in commercial ethylene with the determination will form the subject of a future communication. It seemed that the simplest method of attack was to absorb the ethylene in fuming sulfuric acid of 25-30 per cent SO, content, and then to pass the residual gas, diluted with air, over hot iodine pentoxide, absorbing the iodine evolved in
