INDUSTRIAL AND ENGINEERING CHEMISTRY
March 1948
LITERATURE CITED
Additional studies covering this point are planned, together with studies to determine whether results similar to those reported here are obtained when other sources of chlorine are utilized, such as chlorinated alkyd resins, vinyl resins, or chlorinated rubber. CONCLUSIONS
By the use of a thermoelectric tester, based on the principle of transformation of electrical energy into heat energy by short. circuiting, across the test specimen, the current delivered by a motor generator, it was possible to evaluate the role of pigment volume, antimony oxide, and chlorinated pariffins in fire-retardant paints. 1. Both antimony oxide and organically combined chlorine are of value as agents to impart fire retapdance. 2. Antimony oxide, used as the sole fire retardant, is effective only when the amount of organic matter in the dry film is smallthat is, only at pigment volumes of 50% or more. 3. The amount of organically combined chlorine necessary to achieve fire retardance depends on the amount of organic matter in the dry film and, t o a lesser extent, on the concurrent presence or absence of antimony oxide. ACKNOWLEDGMENT
The authors wish to express their sincere appreciation to W. W. Cranmer for his advice and criticism, both on the progress of the work and the finished paper, and to M. Alpert and M. Goldberg for their assistance in the preparation of paints and test specimens. The opinions expressed in this paper are those of the authors and do not necessarily represent the opinion of the Navy Department.
405
,
Am. Wood Preservers Assoc., ”Fireproofing,” Rept. of Committee 9 (1944). Brit. Standards Inst., No. 476 (1932). Bryan, J., and Doman, L. S., Wood, 21, 19 (Jan. 1940). C. D. I. C. Club, Oficial Digest Federation Paint & Varnish Production Clubs, 262, 512-17 (1946). Clayton, E. C., and Heffner, L. E. (to W. E. Hooper & Sons Co.), U. S. Patent 2,194,690, (April 25, 1933). Gardner, H. A., and Sward, G. G., “Physical and Chemicd Ex,amination of Paints, Varnishes, Lacquers, and Colors,” ‘10th ed., pp. 386-9, Bethesda, Md., H. A. Gardner Laboratories, Inc., 1946. Forest Products Lab., Madison, Wis., Bull. R-1280 (Sept. 1942). Landt, G. E., and Hausman, E. O., IND.ENG.CHEM.,27,288-91 (1935) MoElroy, J. K., Natl. Fire Protection Assoc. Quarterlg, 39, 4 , 307 (1946). MoNaughton, G. C., and Van Kleeck, A,, Forest Products Lab., Madison, Wis., Bull. R-1443 (Jan. 1944). Matiello, J. J., “Protective and Decorative Coatings,” Vol. 3, pp. 353-4, New York, John Wiley BE Sons, 1943. Navy Dept. Bur. Shipsspecification52P63(INT) (Oct. 10,1943). Navy Dept. Specification 52C26 (March 1.5, 1946). Ibid., 52P22a (June 15, 1946). Ibid., 52R13a (Aug. 15, 1945). N . Y. Club, Oficial Digest Federation Paint & Varnish Production Clubs, 250, 408-20 (1945). Ibid., 262, 575-615 (1946). Schlyter, R., Statens Provningsantalt, Stockholm, Medd., 62, 1-41 (1939). ‘Schulte, E., Oficial Digest Federation Paint & Varnish Production Clubs, 214, 123-34 (1942). Truax, T . R., and Harrison, C. A , Proc. Am. SOC.Testing Materials, 29, 973-89 (1929).
RECBIVED July 10, 1947. Presented before the Division of Paint, Varnish, and Plastics Chemistry at the 112th Meeting of the AMERICAN CHEMICAL SOCIETY, New York, N. Y.
Suitability of Gasolines as Fuel J
EFFECT OF CONTAMINATES EXTRACTED’ FROM SYNTHETIC VULCANIZATES ROBERT R. JAMES AND ROSS E. MORRIS Rubber Laboratory, Mare Island Naval Shipyard, Vallejo, Calif.
A test procedure is described which will enable determi-
GUM-FORMING CHARACTERISTICS OF EXTRACTIONS
nation of the gum-forming tendencies of contaminates of gasoline. I t has been demonstrated that extractable plasticizers can contaminate gasoline sufficiently to cause gum deposit in an internal combustion engine, and that contamination of leaded gasoline by phosphaterbqaring plasticizers will cause serious losses in octane rating.
The practice has been for purchasers t o specify a maximum amount of nonvolatile matter which may be extracted from a standard-size specimen cut from the article in question. The extraction fluid is generally gasoline or a synthetic test fuel. The amount of material extracted by the gasoline is determined by evaporating t o dryness on a water bath or electric hot plate, followed by further drying of the residue in an air oven a t moderate temperature (6). This procedure has two disadvantages: It is frequently impossible to evaporate the gasoline t o dryness on a water bath because many of the extracted plasticizers are high boiling liquids, and the vapor pressure of gasoline is reduced t o such an extent by the extracted material that the high boiling constituents in the gasoline are not removed by this treatment. Thus, the residue usually ‘consists of most of the extracted materials (part having been lost by evaporation) and the highest boiling fraction of the gasoline. The extracted material would presumably consist of plasticizers, sulfur, fatty acid, zinc salts of accelerators, antioxidants, and other miscellaneous compounding ingredients. Besides the uncertainty of this determination, the idea of accepting the total extraotables as being harmful to an engine is
P
. .
LASTICIZERS in considerable proportion are added t o nitrile rubbers for the purpose of improving the processing characteristics of the raw mixes and increasing the resilience and softness at normal and low temperatures of the vulcanizates. As most of these plasticizers, unfortunately, are extractable by gasolines, users of hose, gaskets, tanks, etc., which are lined or constructed with nitrile rubber vulcanizates and are in gasoline service, must beware the effects of the extracted plasticizers on the suitability of the gasoline as fuel. The purposes of the investigations described herein were twofold: to develop a method for evaluating extractables which would reflect truly the gum-forming tendencies of fuel contaminates, and t o determine the effect of extracted plasticizers on the performance characteristics of aviation-type fuels.
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appears in Figure 2. Dried air is blown into the coils, where it is warmed, and conducted to the adapters. The rate of air flow through each adapter is established at 1 liter per second. One hundred cubic centimeters of gasoline are evaporated in 50-cc. portions in each beaker. After the gasoline has evaporated, the beakers are heated for 15 minutes before removal. The stove with its Celectray control and Variac regulators is shown in Figure 3, and the stove itself is sketched in Figure 4. The stove is a thick-walled copper vessel which is well insulated with asbestos. The cover for the stove is pierced with four holes to allow the vapors to escape. The stove is heated by an electric hot plate, which is controlled by the Celectray operating in conjunction with a thermocou le located in the wall of the oven. An ordinary electric muffle krnace with temperature control can be used in lieu of this oven with its special heating and controlling arrangement. A master batch was prepared according to the recipe shown below, using Perbunan 26 as the typical oil-resistant nitrile rubber. Basic Reciue Perbunan 26 SRF black Zinc oxide Stearic acid Phenyl a-naphthylamine Benzothiazyl disulfide Sulfur
100.0 75.0 5.0 1.0 1.0 1.75 1.75
To portions of this master batch, plasticizers were added in the ratio of 30 parts of plasticizer to 100 parts of rubber. Slabs of these stocks were press-cured for 60 minutes a t 274 ' F. A list of the plasticizers used is shown in Table I. Two immersion media were used in the extractions-F-4 reference fuel and a blend consisting of 60y0by volume of F-4 reference fuel and 40% by volume of C.P. toluene. F-4 reference fuel is a secondary standard reference fuel used to dctermine octane ratings of gasoline. I t is essentially a commercial grade of isooctane. The characteristics of this fuel are shown in Table 11.
Figure 1. Six-Unit A.S.T.M. Evaporator
Two 1 X 2 X 0.080 inch specimens were immersed in 100 ml. of each of the test fluids for 48 hours. The immersion media open to doubt. I t seems that the plasticizers, which compose were maintained at 820 50 F. Each specimen was weighed the largest orODortion of the extractables. ~ o u l dbe carried as a on an analytical balance and its volume determined with a Jolly fog into the combustion chamber and burned or decomposed. The question is whether or not f0. D. these materials leave a carbon or gum residue on the valves and sides of the combustion chamber TO REFLUX ,% q, fCONDENSER which would reduce the efficiency of the engine. Under ordinary circumstances there would not be REMOVABLE A D A P T E R enough liquid plasticizer in the gasoline to cause dilution of the crankcase oil. The A.S.T.M. specifies a method (1) for determining the preformed gum content of gasoline by rapid evaporation of the gasoline a t 320' to 330 F. in a stream of heated air. The authors ( 5 ) have considered this method for evaporating the gasoline in the extraction test, but they now believe that the temperature of this evaporation is too low since carbonization does not occur. The evaporation method which the authors propose is as follows:
- . .
3''
rl
The gasoline containing the extracted material is first evaporated in accordance with the A.S.T.R.I. method. The beaker containing the residue is then stoved for 30 minutes a t 700' F. before cooling and weighing. Under these conditions the residue is almost always carbonized. The six-unit A.S T hI evaporation apparatus employed in this work appears in Figure 1. The apparatus consists essentially of a closed vessel provided with a reflux condenser, six wells into which beakers fit, coils for preheating the air, and conical adapters to deliver the air into the center of the beakers. The bath is filled with ethylene glycolandwarmed to 320330°F. with electricstrip heaters. A schematic diagram 01 one of the units
-b Figure 2.
4-
5"0.D.
Schematic Diagram of A.S.T.M. Evaporator
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INDUSTRIAL AND ENGINEERING CHEMISTRY
March 1948
Figure 3.
Stove with Celectray Control and Variac Regulators
balance before being immersed. At the expiration of the immersion period, the s ecimens were removed from the test fluids and their volumes regetermined with the Jolly balance. The initial and final volume values were used to calculate the degree of swelling. The contaminated test fluids were evaporated and stoved as described, with the exception that following the A.S.T.M. evaporation procedure, the beakers hontaining the residues were placed in a de'siccator and allowed to cool for 2 hours and the weight of residue was determined. The beakers containing the residues were then stoved for 30 minutes at 700" F., after which they were cooled for 2 hours in a desiccator and the residues were reweighed. RESULTSA N D .DISCUWION. The results of the extraction tests are presented graphically in the bar graphs, Figures 5 and 6. The results of the swelling tests are presented similarly in Figures 7 and 8. The numbers at the bases of the bars identify the plasticizers according to the corresponding numbers shown in Table I. As would be expected, the blend of F-4 reference fuel and toluene caused greater extraction as well as greater swelling than did
407
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F-4 reference fuel alone. It is apparent, however, that most of the residues were almost completely evaporated by the stoving treatment. The residues remaining after the stoving treatment consisted of hard carbonaceous deposits resembling a varnish. A few of the residues obtained by the solvent mixture extraction were still liquid after stoving. This was due to the fact that the solvent mixture extracted larger quantities of some plasticizers than could be volatilized by the 30-minute treatment a t 700 F. The weights of the residues after stoving were not proportional to the respective weights after the A.S.T.M. evaporation. In the case of the extractions made with F-4 reference fuel, only two tests showed a residue above 1% after stoving. In the case of the extractions made with the solvent mixture, there were eighteen tests above 1%, ten tests above 2a/,, three tests above 3%, but none above 4% after the stoving treatment. The high degree of contamination shown by the residues obtained with the solvent mixture is prohbly greater than would ever be encountered in service. It is believed that the residues obtained by extraction with F-4 reference fuel are more representative of
TABLEI. PLASTICIZERS USED IN EXTRACTION INVESTIGATION NO.
11 12 13 14 15 16 17 18 19 20
Trade Name Dibutyl phthalate Dimethyl phthalate Diphenyl phthalate Diethvlene alvcol Dhthalate Methox -Kronisol Dibutyl sebacate Dibenzyl sebacate Tricresyl phosphate Carbonex S KP-140 Diisobutyl adipate Santicizer E-15 Santicizer B-16 KP-120 Dibenzyl ether Rardol Bardol B Barrett oil No. 10 B.R.V.
21 S.R.O. 22 B.R.T. No. 7 23 Coal tar No 26 24 Cumar P-25 25 Cumar MH2i/n 26 Cumar AX
Composition Dibutyl hthalate Dimethy7 phthalate Diphenyl phthalate Diethylene glycol phthalate Methoxy glycol phthalate Butoxv zlvcol ohthalate Dibutylsebacate Dibenzyl sebacate Tricreayl pho8phate Coal tar modified with fatty acid
y ethyl phosphate
,
Dibenzyl ether Cbal-tar derivative Coal-tar distillate Coal-tar distillate Coal-tar distillate Refined coal tar Coal-tar distillate Coal tar Coumarone-indene resin Coumarone-indene resin Coumarone-indene resin
Trade Name No. 27 Dipolymer oil 28 Advagum 29 Pine tar 30 Hercolyn 6 1 Naftolen 510 32 Piccocizer 30 33 Cardolite 25 34 Cardolite 816 a5 _ _ Neophax A 36 Tetralin 37 Duraplex C-50-LV 38 Resin R-6-3 39 Triphenyl phosphate 40 Triethyl phosphate 41 Di-n-butyl-acid orthophosphate 42 Pentabutyl-acid tripolyphosphate 43 Mono-octyl-acid orthophosphate 44 Ethyl-isoamyl acid orthophosphate 45 Mono-isoamyl acid orthophosphate 46 Ethyloctyl acid orthophosphate
-.
Composition Mixed polymers of cumar and indene resins Polyterpene , Pine tar Hydrogenated methyl a,bietate Petroleum derivative Polymerized aromatic oil Vulvanized vegetable oil Vulcanized vegetable oil Vulcanized vegetable oil 1,2,3,4-Tetrahydronaphthalene Phthalic anhydride alkyd resin Soft nonthermoplastic resin Triphenyl hosphate Triethyl pgosphate Di-n-butyl-acid orthophosphate Pentabutyl-acid tripolyphosphate Mono-octyl-acid orthophosphate Ethyl-isoamyl acid orthophosphate Mono-isoamyl acid orthophosphate Ethyloctyl acid orthophosphate
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I N D U S T R I A L .AND E N G I N E E R I N G C H E M I S T R Y 0 AFTER DRYING BY A S T M
METHOD
I
AFTER
STOVING IO
10
n
n
I-
IO,
5
5
Figure 5.
Figure 4.
Effect on Extraction of 48 Hours' Immersion in F-4 Reference Fuel
Schematic Diagram of fitove
EF'FECT O F EXTRACTED PLASTICIZERS ON PERFORMANCE CHARACTERISTICS O F AVIATIOK-TYPE FUELS
A recognized index of performance of a motor fuel is its octane number. Thus, if contamination of a motor fuel reduces its octane number, it can be safely said that its performance characteristics have been adversely affected. Therefore, it was decided to determine the effects of the plasticizers used in the extraction studies on the octane rating of an aviation gasoline. In order to keep the tests on a practical basis-Le., simulate service conditions, the plasticizers were extracted from the stocks prepared previously. Fifty gallons of an unleaded Btraight-run aviation gasoline were procured from the Alameda Kava1 Air Station for use in extracting the plasticizers. The characteristics of this gasoline are shown in Table 111. Since most aviation fuels are fortified with tetraethyllead, it was decided to fortify this gasoline. In order to determine how much tetraethyllead to add, the tetraethyllead susceptibility of the gas was detel'mined by adding
serious contamination likely to occur when new equipment, such as gasoline hose, is put into service. The most significant fact disclosed by the extraction tests is that the plasticizers can leave gum deposits, since the residues remaining after stoving were variable in quantity. A constant amount of residue for each test would have indicated that the plasticizers were completely volatilized, leaving only the other extractable compounding ingredients as residues. In order to demonstrate that extracted plasticizers can cause gum deposits in an engine, a test run was made on a CFR motor methodoctane engine (5), using a gasoline that had been contaminated by extraction of the base stock after it had been compounded with one of the plasticizers shown in Table I. The degree of contamination of the gasoline was amroximately equivalent to that obtained with F-4 reference fuel. The engine was thoroughly cleaned just before the test. Aftel; the engine had run 0 AFTER for approximately 10 hours, it was dismantled and examined for gum deposits. I Figure 9 shows the condition of the valve I before and after the test. Figure 10 shows the condition of the fuel preheater after the test. Gum deposits can be seen clearly on both pieces of equipment. The foregoing is good evidence that extractable plasticizers can cause gum deposits in an internal combustion engine. a I .
I
DRYING BY A S T M METHOD
5
I
AFTER
STOVING
ll 5
1
W
TABLE 11. CHARACTERISTICS OF F-4 REFERENCE FUEL Total sulfur, 0.01%; induction period over 12 hours; specific gravity, 0.7024 at 60" 'F ' Reid vapor pressure, 2.2 pounds per square 'ihch Distillation
I.B.P. 5% 10% 15% 20% 25% 30% 35% 40% 45%
F.
Distillation
F. 214 215 215 215 216 216 217 217 226 226 253
O
5
5
0
0
Figure 6.
Effect on Extraction of 48 Hours' Immersion in 60% F-4 Reference Fue1-40% Toluene
March 1948
INDUSTRIAL AND ENGINEERING CHEMISTRY
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TABLE111. CHARACTERISTICS OF GASOLINE USEDAS A TESTMEDIUM
44
Octane No., 69.0; total sulfur, 0.02%; Induction period, over 11 hours; specifia gravity a t 60' F., 0.7005; Reid vapor pressure, 7.3 pounds per square inch Distillation Distillation
42 0
F.
F.
0 '.I
I.B.P.
A
5%
w -2
10%
5-4
165
%%
190 198 203 208
z
W
.
+6
140 154
15%
!-
;*e n
104
172 181
50%
216 221
65% 70% 75% 80% 85%
233
935.3.
284
%% 90%
225
239 244 253 2 59
271
316
44
+2
affected the octane rating of the gasoline only slightly. A loss of two or three octane numbers is not believed to be especially significant in view of the relatively high de-2 1 gree of contamination of the gasoline. HowFigure 7. Effect on Swelling of 48 Hours' Immersion in F-4 Reference Fuel ever, the large decrease in octane number caused by plasticizers 9, 11, and 39 through 46 is alarming. various quantities of tetraethyllead to the gasoline and measuring All rthese plasticizers caused a reduction in octane number its effect on the octane rating. The results of these tests are equal to or greater than the corresponding incfease in octane shown in Figure 11. The octane number increased rapidly with number caused by fortifying the gasoline with tetraethyllead. increasing tetraethyllead content up to a concentration of about This apparent coincidence indicates that the plasticizers affected 1.0 cc. per gallon; thereafter the increase was less pronounced. the octane rating by reacting with or blocking out the tetraethylOn the basis of the lead susceptibility data, the gasoline was fortified with 1.5 cc. of tetraethyllead per gallon of gasoline. lead. That the former was actually the case was proved by This ratio was selected because it was believed that possible analyzing a slight precipitate which was Observed to form while effects of the plasticizers on the octane rating of the gasoline these plasticizers were being extracted. Spectroscopic analysis would appear more clearly than if larger quantities of tetraethylof this precipitate showed that it was composed largely of lead lead were used. phosphate, All the plasticizers which caused large reductions The extraction of the plasticizers from the vulcanized stocks in octane number had one characteristic in common-namely, a was accomplished as follows: phosphate radical. This, in view of the precipitate of lead phosphate, explains their similarity of behavior. Rectangular specimens of the vulcanizates, 15/ie X 23/! X While the degree of contamination was high, varying from 0.080 inch, totaling a weight of 120 grams, were suspended in a covered glass vessel containing 2 1i:ers of the leaded gasoline for 48 hours a t 82 * 5 " F. During the immersion period, the gasoline was 60 agitated continuously- with a propeller-type stirrer which was inserted through the cover and revolved a t the rate of 150 r.p.m. A 2 liter blank of the leaded gasoline was placed 40 40 adjacent to the vessel while the extraction was in progress. At the end of the extraction period, the specimens were removed from the vessel, and the contaminated gasoline and the 20 20 blank were tested for their respective octane d ratings. . . I 0 0
.
*
W
*
The tests for determining octane number were performed for the most part on the CFR-1-c octane motor (2) shown in Figure 12. Approximately 10% of the tests were performed on a CFR motor method-octane engine (8) because of congestion of test facilities. However, all the tests are strictly comparable because tests on replicate samples on the two machines agreed within 0.1 octane number. RESULTSAND DISCUSSION.The results of the tests are presented in the form of a bar graph shown in Figure 13. The numbers at the bases of the bars identify the plasticizers investigated according to the enumeration in Table I. It will be observed that most of the plasticizers (and other extractables)
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0
b
z
Figure 8.
Effect on Swelling of 48 Hours' Immersion in 60% F-4 Reference Fuel-4Oq~ Toluene
Vol. 40, No. 3
INDUSTRIAL AND ENGINEERING CHEMISTRY
410
Figure 9.
Valve from CFR Octane Engine
