2280
i N D U S T R I A L AND E N G I N E E R I N G CHEMISTRY -0
TABLEVII. PRECIPITATI~S OF GEOS 3 1 1 SAMPLES
F I L I I FROX
TEST
,Added 9 ml. of pure diovane to each sample: added 30 nil. of petroieniii other t o each sample; each sample contained 50 qranis of oil. d a t a i n d l c a t e a solubility of less t h a n 6 p.p.m. 07 Geon filrnj Sample Immersion Test Relatire No. T y p e Oil Period Transmissinn 89 Peaniit Vane 84 83 I Teeh 84 84 1 Week 81 85 I Month 84 86 1 Xonth 8-1 87 2 RIonths 83 88 2 Months 81 96 Lard None 84 90 i Veek 8i 91 I Week 80 93 92 I Month 93 1 1Ionth 92 94 2 Month90 9; 2 Months 90
all the peanut oil tests, on removal from the oven, xvere found tu be 70, which corresponded to the value of the original peanut oil. The data on the lard oil immersion tests, on removal from the oven, mere rather surprising in that the relative transmission increased t,hrough a maximum value, as shovm by Figure 4. The peanut oil immersion tests, after subjection to the petroleum ether precipitation method, Tvere found to have a relative t,ransinission of 84, which corresponded to the value obtained by this method for the original peanut oil. The lard oil immersion tests, treated to precipitate Geon 315, were found to increase through a masimum in the same manner as the ~rontrolsample of oil r~mol-rtl from the oven. Since the readings on all of the ~wmpleswere negative---tliat is, the relative transmissions ivere all as high as for the control J B ~ I ples-and since the method was shown by the calibration curves to be sensitive to as little as 6 p,p.m. of film in the oil, it was concluderl that there 11-as no solubility of the film a t more than 6
5
__--
1
Vol. 41, No. 10
7-7-
I T E S T OILS 2 TES- CILS T R E b T E D TO PPECIPITA-E G E O N 31 I
70 1 0
3
2
4
S
I,
1
I
1
6
7
e
---
-7--
1
MKERSION TIME. W E E K S
Figure 4.
Variation in Light Transmission for Lard Oil
p.1j.m. in the oils after the designated t,est periods of u p to 2 ninii t lis. CONCLUSIOriS
Based on the results of the total chlorine analyses of thr leached solutions, the solubility of thoroughly dried Geon filme in aqueous solutions was found to be less than 1 p.p,m. This corresponds to less than 1.48 mg. per square foot of film surface Variations in the pII of the test so.utions from 3.5 to 9.6 had no effect on this result. The solubility in edible-grade lard or peanut oil n-as no greater than 6 p.p.m. .iCKNOWLEDGMEST
The assistance of 11.K. Loftfield, formerly of Batt,elle IIemorial Institute, who contributed to the development of a technique for handling the cast films, is acknorledged. LlTERATURE CITED
(1, Crhring, H., Kolloid-Z., 90,257 (1940). ( 2 ) Haldy, K. L., Wright, J . H., and Todd, F. C . , J . A m . C e m m Soc., 30,153 (1917).
RECEIVED August 26, 1948.
Oxygen Absorption of Vulcanizates A MEANS OF EVALUATING AGING RESISTANCE LOUIS R. POLLACK, ROBERT E. A\ICELWaAIN,AND PAUL T. WAGNER Industrial Laboratory, Mare Island !Yaval Shipyard, Vallejo, Cal;,f. Rates of oxygen absorption have been measured for tw-o natural and six synthetic rubber stocks. In addition, the course of aging in the oxygen bomb and air oven was followed by means of the changes in tensile strength and ultimate elongation for the same eight stocks. Correlation between oxygen absorption rates and deterioration of physical properties is close enough to justify substitution of a rapid oxygen absorption measurement for longer standard prwedures in evaluating aging characteristic* of rubber stocks.
I
T IS recognized (4,10) that the principal cause of deterioration
of rubtwr I& an oxidative one. The present study confirms previous itifilriri+rioti t o rhe effect that rates of oxygen uptake by a rubber s t o r k t i i i v be vorrelated, a t least roughly, with the e\-
tent of deterlor t o o t i raused by accelerated aging and by natural aging. Beraux! (11 natural deleterious effects other than by o ~ y -
gen (such as by stretching, ozone, ultraviolet light, heat, and pressure), no rapid aging method can be expected to do more than a p p r o ~ i m s t ethe reaction of a rubber stock to its service environment. Despite the nonquantitative nature of rapid evaluations of ~ P I ’ V I C life, ~ such tests are of value to compounders, purchasers, and research workers because of the basis rvhich they provide for comparison of similar stocks. In view of the lack of correlation between standard aging procedures ( 1 7 , 18), the question may ell arise as to which method to use. I n the absence of a compelling reason to choose one procedure over another, bomb aging has been used most co~nnionlybecause of i t s advantage of rapidity. The purpose of this paper is to show that routine volumetric measurement of rates of ovygen absorption of vulcanizates can give comparisons which, for control purposes, are a t least as adequate as those provided by standard procedures and are a considerable saving of time and apparatus.
INDUSTRIAL A N D ENGINEERING CHEMISTRY
October 1949
228 1
PKOCEDUKt
Eight vulcanizates, including t n x natural and six synthetic stocks, were prepared according t o the formulations in Table I. Tensile test specimens were die cut from sheets approsiniatrly 6 X 6 X 0.08 inches. Specimens n-ere aged in a circulating air oven at 70" C. for periods of 3, 7 , 14, 21, and 28 days a n d in a Bierer-Davis pressure bomb at 70" C. under 300-pound per square inch ,)sygen pressure for periods of 1, 3, 7 , and 14 days. Sufficient specimens for all aging periods were suspended in the aging chamber, one stock a t a time. At the expiration of each time interval six specimens were removed and the physical propb:rties measured. As only a small number of 3amples were used, precautions were taken t o minimize loss of statistical validity by u5e of a Latin square-type randomization technique. KO two specimens from a group of sextuplicates were Cut from the same sheet or from the same relative position on different sheets. Further precautions were taken i n positioning specimens during aging, in order to eliminate, through randomization. pos3ible ilffwts of small temperature and air rate yradients. The sheet material remaining after the test specimens had been cut out was utilized for oxygen .tbsorption measurements. It was coinposited and ground in a \Tilev mill. T h e resultant, Darticle &e wa3 such t h a i no dimension was great'er than 0.5 mm., which was small enough t o eliminate diffusion rate effects (3, 1 5 ) . Considerable sample was introduced into the mill in order t o accumuLate the required amount of ground sample a s rapidly as possible. In this way, the milling time was kept down to very short periods-f the order of l to 3 minutes. Absorption was allowed to prnwed in oxygen at 1 atmosphere at a temperature of 120" c. ABSORPTION APPARATUS
Figure 1.
Oxygen A hsorption ipparatus
TABLE I. STOCK TORVLLITIOSS ...Stock 1 Hevea w i t h o u t Antioxidant, - Cured 30 N i n . a t 290" F. Smoked s h e e t 100.0 Zinc oxide 5.0 PellPtPY
2 0
Stearic acid Cottonserd oil Heliozone D.O.T.G. fdi-o-tolylaiiarii-
1.0 2,s 3 i)
~
Oxygen absorption measurements were made in the apparatus pictured in Figure 1. This design is a modification of t h a t used hy van Amerongen ( 2 ) . T h e complete apparatus, as shon-n in Figure 1, consists of a measuring apparatus plus accessory equipment,. These accessories are: an oxygen cylinder, I ; a Cenco-Hyvac'pump, G; a differential manometer, J ; and a constant temperature oil bath, H . The bath v a s made by removing the viscometer tube from a TagSaybolt thermostatic viscometer and plugging the resulting hole in the bottom of t h e oil bath. T h e hole at, the top was used t,o permit insertion of the absorption chamber, F , into the oil. T h e measuring apparatus consists of three branches. Th(z oir, E , is connected: through a straight stopcock, C , t o the mercury leveling bulb, D; through a calibrated eapilLary tube, L. t o the absorption chamber, F ; and through anothrr capillary tube, K , t,o either t h e atmoqphere or the outer system. which consists of the manometer, J , and either oxygm, I , or vacuum, G. T h e method of using the apparatus is as follows: Start with one 3-way stopcock, *-l,open to the atmosphere, the other 3-n-ay stopcock, B , in the closed position, and the straight stopcock, C, open. .idjust leveling bulb D until the mercury level is on a previously marked line on the mercury reservoir, E. Close C. Place a finely ground sample, of such size as to represent 1 gram of elastomer and contained in a small tube, in the oxidation chamber, F . Open d to the outer system. Open B to the operating vacuum pump, G. JT-hvn a full vacuum has bCen drawn, as indicated by the manometer, J , lift the entire measuring apparatus and place F in the 120" C. constant temperature bath, H . Wait 10 minutes to allon- the sample to come t o thcrmal equilibrium. Reverse the position of B , admitting oxygen from cylindt3r Z at about 2- or 3-pound per square inch gage plcssurc. Start timing immediately upon admitting the oxygen. Rapidly revc'rse B , alt,ernatcl,v evacuating and filling the sJ-steni with oxygen, twice more. K h v n filling with oxygen for the last, time. admit onlv enough to leave a vacuum of approximately 15 em. of mercurf, BS i n d i c a t d by J . Close B , open C, raise D until in-rcury rises i n t g hoth capillaricxs, A- and L , anii open A to the atinoiphere.
1.0 :i , ci
Ilevea with .intioxidant.
_ _ _ Cured 30 LIin. at 290" F.
Smoked j h e e t
dine) Sulfnr
4mRite Resin D
u s ~ . ~manometrically l by closing stopcock C after t h e initial adjustment. Although t,his was not done in the reported
. i b a u r t d oxygen for the various stocks is plotted against time in Figure 2. The curves show individual characteristics. Stocks 1
and 2 show no deviation from linearity. There is no evidence of the autocatalytic nature of rubber oxidation. It may be t h a t the lower portion of the S curve had been passed before initial readings were made, but the small amounts of oxygen absorbed in these experiments make it more likely that, even at the h a 1 reading, the linear portion of the curve had not been reached. If
z - 3000
0: in
2 -I
I I
z
2000
W
0: I-
cn W
=!
v, 2
w
L
1000
1 01
\ I
'
'
A
* ' 5I
' ' '
'
'
IO
'
'
I
DAYS AGED
Figure 3.
' 1
\
'
15
Change i n Tensile Strength during Aging i n Oxygen Bomb
Temperature,
i o 0 C.;
pressure, 300 lb./sq. inch
4000 I
the latter vien. is correct, the apparent linearity is due to the fact that such a minute portion of the total absorption curve is reported. Stock 8 also shows a linear rate curve. Stocks 3, 4, and 7 show an initial depression of the mercury column. This is due to evaporation of volatile compounding ingredients. As soon as the partial pressure equals the vapor pressure of the offending ingredient a t 120" C., the curve assumes linearitv. The reduction in oxygen partial pressure is not serious, heing of the order of 1% in the worst case encountered. N o e\planntion is offered for the slight curvature shown by stock 6 near the origin. T h e curvature shoxrn by stock 5 , hoxever, ma) indicate a genuine induction period. The scope and purpose of this x o r k were not such as t o give nnx- information regarding autocatal>si? in the oxidation mechanism of GR-S.
-i 0 ('
2 A I
L5
1
G.
Ela-tonier 4 . r,.; 4 , (38 4.i3
2
2.34 ?.35 L . 31
i
1.16 1.90
I
0.394
1.20
0.883 0.394
I67
w
0.215
7
8
0,323 0.305
0.302 0.132 0.107 0.132 0.145 0.142 0.161
t
"\ DAYS AGED
\lr,an
ll:-an Deriation
%
Deviation
Figure 1. Change ifi Tenwile Strength during \gin2 in Air Oven, 70" C.
5;
0.040
0.9
tiou x c u r s during the aging procedure. Because of its simi1:rrity stock 2, stock 1 may be presumed to have an initid tensile increase also, although t,his is not evident froin the data. I n addition, theoretical considerations demand n slowing down of rate a t the end of the curve. T h e dotted portions of curve 1 probably represent a truer picture of the tensile change than does the solid curve which was drawn from the data. Stocks 3, 4,5, and 8 have a n initial period of rapid tensile loss followed by asloiver, steady rate. This effect is far less evident in stock 8 than in the other three. Stock 6 shows, initially, neither a rise nor rapid decline of tensile strength. Instead, there is a short period during which the deterioration rate is less than its ultimate value. Oven aging, as shown in Figure 4, gives curves whose characterist'ics differ somewhat from the bomb aging curves. Stocks 1, 2, 3, and 7 have an initial tensile increase. This represents a reversal in the behavior of stock 3, as compared with bomb aging. Stock 1 shows a flattening of the curve, which compares favorably with the postulated dotted portions of curve 1 in Figure 3. The initial increase for stocks 2 and 7 and rapid decrease for stock 5 show retention of the characteristics evidenced during bomb aging. Stocks 4, 6, and 8 give a small, but positive, increase in tensile strength duriug oven aging. T h e curves show no sensible departure from linearity. Ultimate elongation curves, plotted in Figure 5 for bomb aging and Figure 6 for oven aging, generally follow the characteristics of the corresponding tensile strength curve. The exceptions are stock 3, which reverses the initial curvature during bomb aging, and stock 8, which shows t h a t effect bot,h in the bomb and oven. S o positive rates of increase in elongation were noted for any of the stocks during either bomb or oven aging. Tables I11 and IV summarize the data for changes in tensile strength and ultimate elongation, respectively. The first and third columns of both tables list the rates of decrease of the appropriate physical property, as calculated from the slopes of the linear portions of the various curves. In the usual determination of resistance to accelerated aging, no effort is made to establish steady rates of deterioration-i.e., after the initial effects have disappeared. Instead, the total change during a fixed period is determined. This net change, of course, may include an initial increase followed by a subsequent decrease. I n order to evaluate t h e stocks according to some standard procedure, t h e net decreases in tensile strength and ultimate elongetion are presented in t h e second and fourth columns of Tables 111
i
IO
L 33
0.016
0.:
I 19
0.017
1.4
0 390
0.005
1.3
0,218
0.008
3.7
0.310
0,009
2.9
0.124
0,011
8.9
0.146
0.003
2.1
0.230 0.210 A
2000
n
1
Oxyeen .4hsorbed. Jtd. 111. Ouyprn per Hr. per
3000
I
I-
8tocb
2283
INDUSTRIAL AND ENGINEERING CHEMISTRY
October 1949
5x
Table I1 gives the oxygen absorption values, as calculated from the slopes of the linear portions of the curves in Figure 2. Satisfactory precision was obtained for all stocks except stock 7. This exception appears to be caused by one bad run. In order to establish the best value for the oxygen absorption rate of stock 7, a replacement run would be indicated. This, however, would sacrifice the routineness of the determinations and \T as not done. Only thrpe runs were made for each stock, and all values are reported. Stock 5X has the same formulation as stock 5, but n a s prepared and run one year previously. The good agreement of absorption values, and excellent agreement of the deviations, confirms that the oxygen absorption rate is actually a function of the stock formulation and does not depend, to any serious extent, on the minor deviations between different batches of the same ntock. PHYSICAL RESULTS
Tensile deterioration of the eight stocks in the oxygen bomb is shown graphically in Figure 3. Stocks 2 and 7 show the initial tensile increase n-hich is commonly observed when after-vulcaniza-
INDUSTRIAL AND ENGINEERING CHEMISTRY
2284
TABLE 111. EFFECT OF A G I S G
ON
TESSILESTRENGTH
-Decrease in Tensile Streneth. (." 7,Oxygen Bomb Air Oven Per .4fter Pcr After da, 28 d a j s dayn 96 hours 40 93b 6.0 1 I7 5.1 15 2. I .i 3.9 29 1 0 I! 1.1 16 -0.1 1.8 17 0.5 20 -- ? 7 --o 1 2.3 0 0.2 0.7 0.6 5 -0.3 -I,] I
Stock 1 2 3
.,
4
5 6 7 8 0
7
From linear portions of the curves in Figurea 3 and 4.
b After 72 hours.
TABLE IT'. EFFECT OF
Stock 1
2 3
2 !
b
A G I N G O S G L T I X k T E I:LOKGATIClS
-Decrease in Ultimate Elongation, %-Oxygen Bomb Air Oven Per After Per Aft r r 28 days 96 hours daya dayo 3.8 66 53 82 b 10 1.6 5 0.4 5.1 10 1.5 2: 0.3 0.7 7 1.6 3G 3.0 17 3.1 11 0.6 16 0.9 -2 0.6 13 0.7 -2 0.9 30
From linear portions of t h e curves in Figures 5 and 6. b After 72 hours.
a
and IV, respectively. T h e aging periods used are 96 hours in the oxygen bomb and 28 days in the air oven. C H E M I C A L C H A N G E S DURING AGIhG
Acetone extractables arc reported to incrcase when natural rubber ages. The alcoholic potassium hydroxide extract, according to van Rossem and Dekker, (19), is very sensitive to oxidation of the rubber, and increases long before the acetone extract. It seemed desirable to investigate the change in amount of extractables as aging progrrssed in the cight stocks. After tensile and elongation nwasurc~inentswere made, each group of sextuplicate tensile specimens was cut up and triplicate 1-gram composite samples Rere removed for extraction. The samples were first extracted for a period of 8 hours with a mixture of 32 parts of acetone and 68 parts of chloroform by volume (8). After drying, alcoholic potassium hydroxide extracts Tyere determined (9). Both the acetone-chloroform and alcoholic potassium hydroxide extracts vere determined for each aging period in the bomb and oven. The expected progressive increases in extractables rwr(' not found. Although those stocks containing volatilc compounding ingredients decreased in acetone-chloroform extract, as expcctoil, i t was hoped t h a t the curves could be analyzed to give thc increasing and decreasing components. This could not be done as t,he values obtained n-cre extremely erratic. Even those S t ~ J C h which should have shon-n continuous increases in extractahlcs gave very inconsistent results. Inconsistencies were so great, in fact, t h a t no curves could be dralvn. Even replicate sanipl(3s gave results which could hardlv be called checks. I t was concluded, therefore, t h a t the determination of change in amount of extractables offered no great promise for even a qualitative evalnation of the extent to which vulcaiiizates had undvrgone aging.
Vol. 41, No. 10
a decidedly greater effect on tensile strength. It is interesting t o note, ill comparing stocks 1 and 2 (Tables I11 and I T ) , t h a t the addition of a n antioxidant increases the ratio of tensile t o elongation deterioration. During oven aging, all synthetic stocks show a more pronounced decrease in ultimate elongation than in tensile strength. Stock 2, as during bomb aging, shows a greater effect on terijile strength and an increase of tensile to elongation decay ratio over stock 1. It is important to consider,. a t this point, which propert>- provides the best estimate of the degree to which deterioration has occurred in a rubber stock. Also, the question again arises as t o what conditions of aging will give the best measure of decrease of the property decided upon. Virtually all combinations of property and aging conditions have been used as criteria. Although decrease in tensile strength during several days of aging in the oxygen bomb is most commonly used for stock evaluation, it is the opinion of the authors that, a better measure is provided by the rate of decrease after initial effects have disappeared. The use of the histograms in Figure 7 for ranking the stocks according to aging resistance makes clear the problems involved. Table V ranks the stocks in groups of nearly equal aging characteristics, as evaluated from Figure 7. T h e most serious inconsistency is to be found in the decrease in ultimate elongation during oven aging. hIany stocks almost completely reversed their positions in rank. Correlation of rate of oxygen absorption is better Tr-ith tensile than Rith elongation decay, and, am i g h t lie e \ pected, better with bomb than FT ith oven aging results. T h e c o r r e l a t i o n of absorption rate with tensile decay rate in the bomb is excellent, and IS, in fact, closer than the correlation of the latter n ith the %-hour test.
COBIPARISON O F 0 x 1 - G E l ABSORPTION WITH AGING U.iT.i
T h e histograms in Figure 7 shorr- the relative effects of various aging procedures on stocks 2 to 8. T h e rapid rates of oxygen allsorption and physical deterioration during accelerated agirig of stock 1 are so pronounced as to make it o1,viously and uriqualifiedly the poorest aging stock of the group. Compariso!l.. t ; l c x fore, are necessarj- only for the remaining seve~lstorlis, C'( quentlj-, the data for each stock were comii:iri~l!\.it11 t l i c C#CY 011 0 5 10 I5 stock 1 under similar conditions. Ilelatix-e cft'ivt. 011 t l i ( * t. )(,IC, Tii!. tion d u r i n g .Iging in Oxygen Bomb one exception, stock 4 , and tlic natural r u h l w , stock 2. I ' o t : ~s h ~ , ~ - Temperature, 703 C.; pressure, 300 lb./sq. i noh
DISCUSSION
T h e correlution of oxygen absorption rate lvith accelerated aging, as measured liy declinc in physical p r o p e r t i e s , is attwted to 1)y several investigators (1, 5, 6 , 2 0 ) . Such ~ o r k had been confined principally t o natLlr:11 r u 11 1, e r a 11t l GR-S.T\vo recent oxidation studies ( 2 , 1 4 ) included aoveral
October 1949
2285
I N D U S T R I A L AND E N G I N E E X I N G CHEhlISTRY
c:~!n:)ar:itive puralld, O f ~ t ' ~ l 011 , Sui]st:lilti:llly similar stoc.ki, the scmncl type of :iiitiox>.geiiic activity rrill sclclom iic?(l comitkration. ;1 steady rate of detcriolntion ~ o u l d!)e cxpecte(1 t o provide a better incasure (it' aging resisttiiicc than can be obtained from short-term aging. Initial ciTects ( J I ~ physical properties arc frcquently so great as t o yicld false conclusions. It is understantiable, of course, t h a t the time and work required to establish the decay rate make this method impr:ictical for routine testing. A 3 rate of osygen absorption correlates .so closely w i t h mtc of loss of tensile strength during osygen bomb aging, equivalent information can be obtained in vcry short periods of time snd without the necessity o f r u n n i n g whole wries of determinations, as xvould be required to c-t3blisIi n, tcmilc loii ratc. Although t h e small amount of osygen al)sort)cd during a determination niay classify the result as a n initial rate, the criticism of use of initial physical effects does not apply. Esamination of the many longperiod oxygeii a b s o r p t i o n curves reported in the literature reveals no rapid changes or reverse? of rate, such as are found n-ith tensile curves. Furthermore, the absorption of even r e l a t i v e l y s m a l l amounts of oxygen is sufficient to change the vulcaniaate t o a st'ate corres p o n d i n g to the constant rate portion of the tensile curve. It is concluded, therefore, that, in most cases mcasurcments of oxygen absorption rates can provide comparative aging information of high reliability and absolute information of at least good validity. yu11
I
f(J1'
ilO-.f'>
Stock
"L1 60
4
Absorp. Rate
20
0
Tend le Str.,
3
1
I
0
Tensile
Str., Bomb,
96 hrs. 0
synthetic elastomers in the investigation, but, in general, synthetic stocks have been ignored. Theories of t h e oxidation of natural rubher (?, f2) are based on the combination with oxygen t o form peroxides or hydroperoxides, follon-ed by a rearrangement of t h e molecule. Deterioration is esplained by a further change in the rubber molecule-i.e., chain scission. There is no reason why such a mechanism could not operate in any polymer containing sufficient ethylenic linkages. This criterion is met by all elastomers used in this study, except stock 8. .Ilthough Thiokol is not unsaturated, it was included because of interest in its behavior toward oxygen. LeBras and Viger (1I, 1 3 ) have demonstrated t h a t two antioxygenic effects niay occur. T h e usual antioxidant acts by diminishing t h e extent t o which t h e rubber combines with oxygen, as measured by the oxidizability. Hoxever, several compounds, notably mercaptobenzimidazole, provide considerahle protection against deterioration without greatly reducing the oxidizability. Such compounds, supposedly, direct the molecular rearrangement t o forms which do not terminate in scission of the chain.
Tensile Str., Oven, Rate
40 20
0
1.1
-20
Tensile Str., Oven, 28 days
Gr Elong.,
0
Ult.
CONCLUSIONS
Elong.,
T h e information in this paper appears t o justify the use of oxygen absorption rate a s a criterion of aging resistance. It is almost certainly true t h a t where t h e rate is found to be low, resistance to aging \rill be high. T h e evidence of LeBras and Viger, however, must he considered in t h e opposite case. With high axidizabilities and in the absence of positive information regarding compounding ingredients, it would be well t o proceed cautiously in drawing conclusions. Here, a standard bomb oxidation would be indicated as a confirmatory test. Since most aging tests are
0
96 hrs Ult. Oven,
60
TABLE V. RAXKIXG O F STOCK> .ICCORDING T O AGIXG
40
RESISTASCE
l g i n g Method Oxygen absorption rate Tensile strength Bomb, r a t e Bomb, 06 hours Oven, rate Oven, 2 8 days L-ltimate elongation Bomb, rate Bomb, 06 hours Oven, r a t e Oven, 28 days
Ranhlnr: of Stocks 7
8
5
.
6
8 7 8 a
7 . 6 1
8 4 4
G
8 8 4 4
4 7 2 2
4
.
3
.
2
4
5
0
0 7
. .
2 5
1 .
3 5 3
. . .
2 3 2
.
3
j
.
2
20 iCKNOWLEDG\IEYT
7 3 .
i 6 7
2
4
6
.
. 8 .
5
3 . 3
6
6 3 8
.
.
3
5 5 . . 5
Figure 7 . Oxygen Absorption Rate and Keduction of Physical Properties Expressed
as p e r c e n t a g e stock 1
of
T h e a u t h o r s wish t o thank the Bureau of Ships, L-, S. S a v y Department, for sponsoring this work and for p e r m i t t i n g publication of t h e rcsultq. .ill vienq vx-
2286
INDUSTRIAL AND ENGINEERING CHEMISTRY
presbed, however, are those of the authors and are not to lie construed as representing the official views of the S a v y Dcpnrtment. Thanks are due t o L. J. Cole and E. L. Shook for their help in obtaining chemical results; t o H. Moser, L. 9. Turcios, A. IT. Scott, and E. J. Boche for providing the physical test data and to E. R. DeLew, who built the oxygen absorption apparatus. The authors are particularly indebted t o the 3Iare Island Rubber Lahoratory for advice on stock formulations and for preparing the vulcanizates. LITERATURE CITED (1) .llLert, H. E., Smith, G. E. P., J r . , and Gottschaik, G. K., ISD. E m . CHEM.,40, 4S2 (1948). (2) Amerongen, G. J. van, Rubber Chem. and Technol., 19, 170 (1946). ( 3 ) Carpenter, A . S., ISD. ENG.CREM.,39, 1 8 i (1947); Rubber Chem. and TechnoZ., 20, 728 (1947). (4) Dufraisae, C . , “Chemistry and Technology of Rubber,” Davis, C. C . , and Blake, J. T., ed., New York, Reinhold Publishing Carp., 1937. ( 5 ) Dufraisse, C., and LeBras, J., Rubber Chem. and Technol., 12, 668 .. f1930). ~ . ~ (6) Ibid., 13, 604 (1940). (7) Farmer, E. H., and Sundralingam, A . , J . Chem. Soc., 1943, 125; Rubber Chem. and Technol., 16, 790 (1943). (8) Federal Specification ZZ-R-GOla, paragraph 111-7b (June 25, 1940) *
Vol. 41, No. 10
(9) Ihid., paragraph 111-7h. ( i o ) Kern[>,A . It., Ingmanson, J. II., and Mueller, G. S.,IXD. ENG. CHEN..31, 1472 (1939); Rubber Chem. and Technol., 13, 376 f 1940,. ( 1 1 ) LeBras. J . ,Rea. 06,. caoutchouc, 21, 3 (1944); Rubber Chem. and Techno/., 20, 949 (1947). (12) LeBras, J.,Ren. yBn. caoutchouc, 21, 243 (1944) ; Rubber Chem. and Techno/., 20, 972 (1947). (13) LeBras, J.. and S’iger, F., Reu. gBn. caoutchouc, 21, 39 (1944); Riihber Chem. and Technol., 20, 962 (1947). (14) SIesiobian, 11. B.. and Tobolaky, A. V., J . Polymer Sci., 2, 463 ( 1 9 4 7 1 : Rubber Chem. a7~dTechnol., 21, 398 (1948). (15) Slilligan, A . G . , and Shaw, J. E., Proc. Rubber Tech. Con/., Lond o l i , 1938, 5 3 7 : Rubber Chem. and Technol., 12, 261 (1939). ( 1 6 ) SIorgan. L. B.. and Naunton, W. J. S., Proc. Rubber Tech. Conf.. L o n d o n , 1938, 599; Rubber Chem. and Techno/., 12, 236 (1939). (17) S e a l , ;i. l f . , and Ottenhoff, P., I N D . E S G . CHEM.. 36, 352 (1944). (18) Newon. K. G., and Scott, J. K., J . Rubber Research, 16, 37 (1947): Rubber Chem. and Technol., 20, 760 (1947). (19) R o s e i n , A . van. and Dekker, P., Kautschuk, 5, 13 (1929); Rubber d o e ( S . Y . ) , 25, 85, 143 (1929); Rubber Chem. end Technol.. 2 , 341 (1929). (200) Shelton, J. K., and Winn, 11.. IND.EKQ.CHEM.,38, 71 (1946); Rubber Chem. and Technol.. 19, 696 (1946). (21) JTiIliams, I . , and Neal, ii. M., ISD.ENG.C H E M .22, , 8 i 4 (1930). R E C E I I - EOctober D 18, 1918. Presented before the Hixh Polymer Forum a t t h e 111th .\leetino of the AMERICASCHEYICIL SOCIETY, St. Louis, .\Io.
Antirachitic Sulfonation of Fats and Oils LESTER YODER AND B. H. THOMAS Zowa Agricultural Experiment Station, Ames, Zowa
Antirachitic sulfonation was applied to a variety of sterol-containing commercial products under various conditions of composition, reaction, temperature, and time, to produce residues which were biologically antirachitic. The reaction was most effective with fats containing cholesterol. The vitamin D in a concentrate of fish liver oil unsaponifiable was inactivated b> antirachitic sulfonation. When reference cod li\er oil and Chemosterol-D produced from degras unsaponifiable were fed at comparable levels (U.S.P.) to chicks receiving the 1.0.l . C . rachitogenic ration, the latter was more effectit e in preventing rickets. A similar relationship prebsilecl M hen the loutig chicks were fed a practical ration siniilarl> fortified with Chemosterol-D and cod liver oil. The effectire differences occurred in a narrower range of feedinz l e ~ c l * .
IIElIOSTEROL-D refers t o the antirachitic residue produced by heating certain steroids in anliydrous acetic acid folsolution for a f e r hours with a strong sulfonatiiig rc~:~gmt. lowed by vacuum distillation of the acetic acid: t h c renetioii is referred to as antirachitic sulfonation. The first and subscqueiit tests of Ctiemosterol-D demonstrated t h a t i t call be utilized more effectivel>-by chicks, unit for unit (U.S.P.), than certain recognized forms of vitamin D ( 2 , 4 ) . Furthermore, antirachitic sulfonation (5)of crude cholesterol was found t o produce a residue with relativcly good vitamin D potency. These results indicated that Chemosterol-D of sufficient potency might be produced directly from certain naturally occurring steroids n-ithout much, if any, previous purification. Furthermore, i t was possible t h a t these less refined preparations of Chemosterol-D produced from the more crude sterol-containing mixtures might not require fur-
ther refinement for commercial use. Transformation of certain sterol-containing crude materials by antirachitic sulfonation and biological tests of t,he resultant less refined residues constitut,e the basis of this report. ASTIRACHITIC SULFONATION OF UlVSAI’OSIFIABLES
Since antirachitic sulfonation mas applied successfully to crude cholesterol (3),sulfonation of the unsaponifiable fractioris of some sterol-contaiiiiug fats and oils was attempted. The results are reported i i i Table I. The unsaponifiable fractions mere heated with the q u u t i t i e s of reagents indicated for 3 hours a t t,he specified The acetic acid was dist,illed under partial vacuum. The distillation residues remaining Twre teated biologically a t the levels specified. The biological tests with rats were conducted iii nccordance with the line test of U.S.P. XI with exception. as to numbers and grouping indicated in the tables. At the feeding levels indicated, no antirachitic activity was evidrnt in the reaction products derived from the unsaponifiable frnctioii of tall, fish liver, or corn oils. However, antirachitic potency was pruduced from the unsaponifiable of avocado oil and degras (crude Tool fat). Thc effect of antirachitic sulfonation on the vitamin D activity of aeoncentrateof fish liveroilwasstudied. This concentrate had a vitamin 1) activity of approximately 3,000,000 naturally occurring units (U.S.P.) p e r gram. The concentrate gave a positive Lieberniaun-Burchard color rc,action. Upon the addition of sulfuric acid to the acetic acid anhydride solution of this concentrate a t room temperature, a resin was precipitated. Sulfonation appeared to have destroyed the naturally occurring vitamin D since biological tests of a composite sample of the sulfonated resin and solution (experiment, 246) revealed it to have little, if any, antirachitic ILP-
