INDUSTRIAL AND ENGINEERIN-G CHEMISTRY
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water temperature and that of the rubber extruding through the die, and the greater the power consumption. Figure 4 and the following table show the effect on the extrusion qualities of the variation in circulating water temperature: 7 -
Sample
NO. 1 2
3 4 6 a
M
@X
30.42 29.02 27.05 25.50 22.41
0 65
0.77
0.84 0 91
1 07
Original 40.8 37.7 32 2 28 0 20.9
Gz/A!-
Increase from original5 30.3 21.2 15.9 11.5 4.4
7
% increase from original 183 128 96 70 27
G z / M o n original rubber, 16.5.
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Jf have a direct relation when the same type of rubber or compound is compared, but not always when different types of rubber or different compounds are compared. For example, if we draw a curve of the G, values of five different types of rubber compounds and then below this show the J4 values, it becomes evident that tubeability and plastic flow are not directly related. Although the G,/M figure may mean little mathematically, it is a good index of the actual softness of the stock; if stocks are graded arbitrarily by "feel" on the mill, they fall into line with the G,/M figure more closely than with either G, or M . These data are given in Figure 5 and the following table: Qz
GX
zoo 34
I75
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Relation of Tubeability and Plastic Flow
All of the data 30 150 presented thus far I show a direct relation between tubeability a n d plastic flow, and conclusions m~ould be i d e n t i c a l if either G, or M w e r e u s e d and FIGURE 5. RELATION OF TUBEABILITY G,/M o m i t t e d . However, G, and AND PLASTIC FLOW 32
Tread compound Cushion Inner tube Loaded tubing Friction
* Corrected
*
29.7 35.2 38.2 41.5 46.9
,If 1.23 0.51 0.58 2.44 0.18
CX/M
24.2 08.0 05.8 17.0 260.5
t o 0.92 specific grairity.
I n this paper only one procedure for the successful operation of this tubed machine plastonieter has been described. A discussion of other procedures designed for factory control of stocks which permit of rapid testing of samples, for development of stocks of certain desired characteristics, for determination of tubing and plastic properties of pigments, for scorch tests of compounds would provide data enough for a number of papers. RECEIVED dpril 17, 1937. Presented before the Division of Rubber Chemistry at the 93rd Meeting of the American Chemical Society, Chapel Hill, N. C . , Bpril I2 t o 15, 1937.
Viscosity of Hydrocarbon Solutions METHANE-PROPANECRYSTAL OIL SYSTEM
liquids. Hersey and Shore (4) also d e t e r m i n e d t h e effect of p r e s s u r e upon s e a r c h u p o n the physical and thermodythe viscosity of lubricatnamic properties of hydroing oils a t several temperatures. B. H. SAGE, B. N. INMAN, AND W. N. LACEY carbon systems, a study of The authors (6, 8, 9, 10, the effect of pressure and California Institute of Technology, Pasadena, Calif. comnosition unon the vis11) reported measurements upon - t h e v i s c o s i t y of cosiiy of the liiuid phase of hydrocarbon liquids saturated with gases a t pressures as a part of the methane-propane-crystal oil system was made. high as 3000 pounds per square inch. This work deterThe work was primarily limited to a temperature of 100" F. and mined only the combined effect of changes in composition to liquid aompositions containing less than 5 per cent methane and pressure upon the viscosity of these liquids and offered and 20 per cent propane by weight. The viscosity of the no information concerning the individual effects of the variliquid phase of numerous mixtures in this composition range ables. was determined in both the two-phase and condensed-liquid regions a t pressures up to 3000 pounds per square inch abMaterials solute. The oil used in this investigation was a water-white Experimental investigation of the effect of pressure and paraffin-base oil refined from Pennsylvania crude stock. The composition upon the viscosity of hydrocarbon liquids has average molecular weight, as determined by the freezing not progressed sufficiently to perniit correlation of the vispoint lowering of benzene, was 342. Its specific gravity a t cosity as a function of state. Bridgeman ( 1 ) made measure100" F., relative t o water a t its maximum density, was 0.8244, ments of the effect of pressure upon the viscosity of several and the viscosity-gravity constant (5) was found to be 0.7979. hydrocarbons. His pressure range (17 X lo4 pounds per The results of an aniline extraction analysis upon similar square inch) was many times that recorded in the present material indicated that it was primarily composed of constitupaper, but no attempt was made to study systematically the ents of a narrow range of high molecular weights, which effect of composition upon the changes in viscosity of such
A
Snated PART program of a coordiof re-
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accounted for the oil's low volatility (lo+ inch of mercury as a result of the calibration was less than 0.5 per cent. For a discussion of the parameters involved in these calibrations, the a t 100" F.). Throughout the remainder of this paper this reader is referred to the work of Flowers (3) and Hersey (s), oil will be called "crystal oil," but it is quite different from and to a n earlier paper of this series (6). The effect of pressure the water-white oil used in other phase-equilibrium and visupon the calibration of the instrument was determined b y a cosity studies by the authors. The latter was refined from comparison of the measured increase in the viscosity of several western crude stock, The propane used in this investigation organicliquids with that found by Bridgewas obtained from the Philg& Company, man ( I ) . This comparison indicated that together with a special fractionation changes in calibration of as much as 0.5 analysis showing that the propane conThe effect of pressure per cent might be encountered a t the tained less than 0.05 mole per cent of upon the viscosity of the impurities. Investigation showed that higher pressures. Because of the limited liquid phase of eighteen over-all accuracy of the measurements the vapor-pressure of this material varied mixtures of methane, (2 per cent), it was not considered worth by less than 0.3 pound per square inch while to correct the measured viscosity between dew and bubble points at 100"F. propane, and crystal oil for this small change in calibration. The methane was prepared from natural was determined at 100"P. gas by methods previously described For this work on binary and ternary The work included meas(7). The methane was purified by charmixtures, the crystal oil was first added to urements a t bubble coal adsorption and partial solidification the apparatus, and then the desired amount of propane was distilled into it from a small point and throughout at liquid air temperature, and i t is the steel bomb. The quantities of crystal oil authors' belief that the material cont h e condensed liquid and propane, which were determined by tained less than 0.05 mole per cent ethane counterpoise weighing, were known with an region at pressures up to and heavier constituents, and probably uncertainty of less than 0.1 per cent. The 3000 pounds per square methane was measured into the apparatus n o t more than 0.2 mole per cent nitrogen by volumetric means, and it is believed inch. The results are .or other noncondensable constituents. that the quantity of methane added to the presented in t a b u l a r apparatus was determined within 0.3 per Experimental Methods cent. After the addition of the requisite form, and several diaamount of the components, the viscometer The instrument employed was a regrams illustrating the was allowed to come to thermal equilibvised form of the rolling ball viscometer, rium at the desired temperature. behavior of the system After the attainment of thermal and of previously described (6), which was are included. phase equilibrium, the liquid was circulated adapted from earlier forms used by through the roll tube forcing the ball to (3. In Flowers ( 2 ) and Hersev " . , L). ,, the top above the outlet tube. Circuprinciple the method consisted of measlation was then stopped, the ball was allowed to roll part way don-n the tube, and the u per conuring the time for a close-fitting steel ball under the influence tact was then lowered a definite small amount. C%ulation of gravity to move down a closed inclined liquid-filled tube was again started, and the ball was gently wedged against through a fixed distance. Figure 1 is a schematic diagram the upper contact. It was found that small inaccuracies (0.001 of the instrument as used for these measurements: inch) in setting the upper contact caused a negligible effect upon the roll distance of the ball. The valve a t the lower end of the The liquid under investigation filled the entire system, except roll tube was then closed and the upper contact lifted. The when measurements in the two-phase region were made; under break in the upper contact circuit actuated the chronograph these circumstances the upper part of saturation cell A was filled pen, thus automatically recording the beginning of the roll time. with gas. The liquid was circulated through chamber B, up The end of the period was recorded by the pen as the ball touched through the flow tube of the viscometer proper, and back to satuthe lower contact. The valve at the bottom of the roll tube was ration cell A by means of the small cam pump mounted in the then opened, circulation started, and the measurement repeated. lower part of the saturation cell. This circulation, in addition The pressure on the system was changed by the addition or to the action of a stirrer in saturation cell A , permitted the rapid withdrawal of mercury, and another set of measurements was attainment of equilibrium between the gas and the liquid portaken. tions of the system. The effective volume of the system could be varied approximately 25 per cent by the addition or withdrawal of The density of the liquid phase, which is required in order mercury from chamber B . This variation in volume permitted to determine the viscosity from the measured roll time, was the investigation of the change in viscosity of the liquid phase calculated from data upon the partial specific volume of the with changes in pressure for a system of constant composition. components. These latter data were obtained from exDeriThe roll time of the ball was ascertained by means of an electrically driven chronograph actuated through contacts C and D. The upper contact C was movable t o permit release of the ball. The chronograph was of such a design that the lapse of time between the breaking of the upper contact and the making of the lower one could be determined with a precision of 0.01 second. However, an uncertainty in the roll time as great as 0.2 per cent may have existed because of irregularities in the freauencv of the alternating current supdv - - used for driving *the chronograph. The temperature of the viscometer was maintained by means of an oil thermostat in which the maximum variation in temperature was 0.05' F. The pressure on the system was measured by means of a pressure balance connected to the mercury in cell B. The pressure within the apparatus was known within 0.3 pound per square inch at pressures below 300 pounds per square inch and within 1.5 pounds per square inch at higher pressures. \
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The instrument was calibrated by use of a series of hydrocarbon liquids of known viscosity. The viscosity of these calibrating liquids was determined at atmospheric pressure by means of a quartz Ostwald pipet. It is believed that the uncertainty introduced
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FIGURE 1. VISCOMETER ASSEMBLY
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FIGURE 3. RATIOOF VISCOSITY -4T A GIVENPRESSURE VISCOSITY AT VAPORPRESSURE FOR CRYSTAL OIL
PRESSURE
LB. PER
TO
SQ. IN.
FIGURE2. EFFECTOF PRESSURE AND TEMPERATURE ON VISCOSITY OF CRYSTAL OIL
VISCOSITYOF BUBBLE-POINT LIQUIDAND CONDENSEDLIQUID FOR TBE PROPANE-CRYSTAL OIL SYSTEM AT 100' F.
FIQURE5. 20 -
b
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with pressure is shown for five temperatures. Table I records the results of these measurements. The tabulated values were taken from smooth curves drawn through the experimentally determined viscosities. Figure 3 presents the ratio of the 02 viscosity a t a given pressure to the viscosity at the v a p r pressure for B series of temperatures. Although the per-~ ~
TABLEI. VISCOSITY OF CRYSTAL OIL
-
Abs. Pressure, Lb./Sq. I n . 100' F. Bubble point- 103.0
500 1000 1500 2000 2500 3000 3500
0
109.1 115.8 123.5 131.6 139.9 148.4 166.1
Abs. Viscosity, Millipoises 160' F. 190" F.
130° F. 62.5 66.1 69.8 73.8 77.7 81.8 85.9 90.2
40 9 43.2 45.7 48.2 50.6 53.2 55 6 58 0
28.2 29.9 31.5 33.1 34.7 36.4 38.0 39.6
220' F. 21.6 22.8 24.0 25.2 26.3 27.5 28.6 29.8
Maximum bubble-point pressure ma.& iess than 0.1 inoh of mercury.
AUGUST, 1937
INDUSTRIAL AND ENGINEERIXG CHEMISTRY
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1
M O L E PERCENT METHANE FIGURE 6. EFFECT O F COMPOSITION ON VISCOSITY FOR THE METHANE-CRYSTAL OIL SYSTEM AT 100" F.
30 MOLE
PERCENT
40
50
60
PROPANE
FIGURE 7. EFFECT OF COMPOSITION ON VISCOSITY FOR PROPANE-CRYSTAL OIL SYSTEM .4T 100" F.
THE
Figure 5 depicts the results of the experimental measurecentage increase in viscosity with pressure is not greatly ments upon mixtures of propane and crystal oil a t 100" F. affected by temperature change, there is a much smaller The general behavior is similar to that found for the mixtures change in viscosity with pressure a t the higher temperatures; of methane and crystal oil just discussed. All of the exalso the rate of change of viscosity with pressure a t a conperimental points taken in the two-phase region fell on the stant temperature increases with an increase in pressure. bubble-point curve within the experimental uncertainty of the Figure 4 presents the experimental results for the methanemeasurements, but most of them were omitted from the crystal oil system a t 100" F. The curve a t the left represents diagram. Comparison of Figures 4 and 5 shows that propane the variation in the viscosity of bubble-point liquid with does not affect the viscosity of the liquid phase as markedly bubble-point pressure. The points shown on this curve were as methane when compared on a weight basis. The results taken from measurements made with an appreciable quantity of the experimental measurements upon the propane-crystal of gas phase in equilibrium with the liquid. Actually there oil system are given in Table 11. should be a difference between the viscosity of the bubbleFor some purposes it is interesting to determine the effect point liquid and that in equilibrium with an appreciable of changes in composition upon the viscosity of a two-comamount of gas phase a t the same pressure and temperature. ponent liquid. Figure 6 presents the viscosity of the conHowever, with the materials involved, this difference was densed and bubble-point liquid as a function of composition less than the experimental uncertainty. Each of the curves o n t h e r i g h t i h a n d side of Figure 4 represents the change in viscosity with presT.4BLE 11. VISCOSITIES OF LIQUIDMIXTURESOF METH.4XE, PROPANE, AND CRYSTAL OIL AT 100" F. sure for liquid or constant Prosane and Crystal Oil Methane and Crystal Oil composition. T h e l i q u i d s 0.48 1.33 2.42 4.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 CH4, wt. % containing larger amounts of CsHs, wt. .% 0.00 0.00 0 00 0.00 1.79 4.12 4.72 6.52 9.19 10.78 17.54 77 96 99 132 56 62 Bubble-point pressure 276a 775 1390 2270 27 methane show a smaller isot h e r m a l increase in viscosAbs. Pressure, Lb./Sq. In. Absolute Viscosity, Millipoises i t y with pressure. All of the Bubble point 85.3 62.3 46.1 32.5 79.5 58 2 55.3 45 3 33 8 29.9 16 2 l i q u i d s , h o w e v e r , show a 500 87.7 . . 83.5 60.9 57.7 47.4 35.2 31.1 16.8 1000 93.2 63:s ' ' ,. 88.3 64.4 60.7 50.1 37.3 32.7 17.6 greater rate of c h a n g e of 1500 98.9 67.5 46:7 .. 93.5 68.1 63.9 52.8 39.4 34.4 18.3 viscosity with pressure a t the 2000 104.9 71.4 49.3 98.9 72.1 67.0 .56.6 41.4 36.0 19.1 2500 110.9 75.5 52.1 33:5104.5 76.0 70.3 58.3 43.4 37.6 19.8 higher pressures. The results 3000 117.1 79.6 55.1 36.1 109.9 80.1 73.6 61.1 45.5 39.3 20.6 of these rneasurements are reMethane, Propane, and Crystal Oilc o r d e d i n Table 11. These CH4, wt. ?& 0.81 1.58 2.76 0.45 1.23 2.56 0.40 1.08 0.41 0.85 2.13 3.93 4.10 4.07 4.02 6.49 6.45 9.65 17.39 17.17 16.85 1.70 1.74 C3H8, wt. % 1.78 values of bubble-point pressure 600 1165 275 425 Bubble-point pressure 415 795 1400 254 245 405 825 1400 were determined by the breaks Abs. Pressure, in the viscosity-pressure relaLb./Sq. In. -4bsolute Viscosity. Millipoises tions corresponding t o t h a t Bubble ooiiit 62.4 50.6 36.8 51.1 41.9 31.6 40 1 37 2 28.8 14.4 12.1 9 6 63.0 . . 52.4 . . 41 2 37.6 29.6 14.5 500 point. Because of the inci43.9 40.5 31.2 15.2 l2:4 1000 66.7 si:s 55.3 43:s dental character of the deter70.5 54.8 36,'9 58.4 46.3 32:6 46.8 43.5 32.7 15,s 12.9 9:7 1500 2000 74.5 58.1 38.9 61.6 48.9 34.3 49.7 46 5 34.3 16.4 13.4 10.2 m i n a t i o n s of bubble-point 2500 78.5 61.4 40.9 64.8 51.4 36.0 52.7 49.6 36.0 17.0 13.9 10.7 3000 82.6 64.5 42.9 68.1 54.0 37.7 55.9 52.7 37.7 17.6 14.4 1 1 . 1 pressure, these values are not considered reliable to better a Pounds per square inch absolute. than 5 per cent.
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100
80
60
40
20
I 1
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1000 PRESSURE
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1500
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2000
LB. PER SQ
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J
IN
FIGURE 8. VISCOSITY OF BUBBLE-POINT LIQUIDAND CoxDENSED LIQUIDFOR MIXTURES OF METHANE, PROPANE, AND CRYSTAL OIL AT 100’ F.
for the methane-crystal oil system. The rate of viscosity change with respect to composition under bubble-point conditions is smaller than the corresponding isobaric change in viscosity. This behavior results from the increase in pressure along the bubble-point curve, tending to increase the viscosity and thus offsetting a part of the decrease caused by the change in composition. A similar diagram for the propanecrystal oil system is presented in Figure 7. Comparison of Figures 6 and 7 shows that under bubble-point conditions the molal effect of methane and propane is similar but that the pressures existing in the two cases are different. A portion of the experimental work a t 100” E’. on mixtures of methane, propane, and crystal oil is presented in Figure 8. The general behavior of this system is similar to that found for the methane-crystal oil and the propane-crystal oil systems. The upper family of curves presents the effect of methane upon the viscosity of a mixture composed of a fixed ratio of propane and crystal oil. Throughout all of the measurements for this group of curves, the ratio of the weight of propane to that of crystal oil was 0.0183, while the weight per cent of methane was varied from zero to 2.76 per cent. The lower family of curves represents a similar set of measurements in which the propane-crystal oil ratio was 0.213. The bubblepoint curve a t the left represents the viscosity of bubble-point liquid as a function of bubble-point pressure for mixtures of propane and crystal oil. The results of the experimental work for this ternary system are reported in Table 11. The experimental work on this ternary system was not as complete
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2.0
WEIGHT
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FIGURE 9. EFFECTOF COMPOSITION ON THE VISCOSITY OF BUBBLE-POINT LIQUIDFOR THE METHANE-PROPANEAT 100” F. CRYSTAL OIL SYSTEM
as might be desired for certain purposes but was sufficient to permit an interpolation on a composition basis. Figure 9 presents the viscosity of the bubble-point liquid as a function of weight per cent methane for a series of propanecrystal oil ratios. The methane has a much smaller absolute effect upon solutions rich in propane than it does upon the crystal oil.
Acknowledgment This work was carried out as a part of Research Project 37 of the American Petroleum Institute, and the authors are indebted to that organization for financial assistance which has made this work possible. The assistance of D. C. Webster in the preparation of the figures is acknowledged.
Literature Cited (1) Bridgeman, Proc. Am. Acad. Arts Sci., 61,58 (1926). (2) Flowers, Proc. Am. SOC.Testing Materials, 14, 565 (1914). (3) Hersey, J. Wash. Acad. Sci., 6,525 (1916). (4) Hersey and Shore, Mech. Eng., 50, 221 (1928). (5) Hill and Coats, IKD.ENQ.CHEM.,20, 641 (1928). (6) Sage, IND. ENG.C ~ E MAnal. ., Ed., 5, 261 (1933). (7) Sage, Baekus, and Lacey, IND. EXG.CHEM.,27, 686 (1935). (8) Sage and Lacey, “Drilling and Production Practice 1935,” pp. 141-7, New York, Am. Petroleum Inst., 1936; Oil Weekly, 77, No. 10, 29 (1935); Oil Gas J . , 34,No. 1 (1935). (9) Sage, Mendenhall, and Lacey, Am. Petroleum Inst., Production Bull. 216, 45 (1935); Oil WeekZy, 80, No. 13, 30 (1936). (10) Sage, Sherborne, and Lacey, Am. Petroleum Inst., Production Bull. 216, 40 (1936); Oil Weekly, 80, No. 12, 36 (1936). (11) Sage, Sherborne, and Lacey, IND.ENQ.CHEM.,27, 964 (1935). RBCEIYED April 7, 1937.
