FEBRUARY, 1938
INDUSTRIAL AND ENGINEERING CHEMISTRY
An important consideration emphasized by this study is the effect on the dilution ratio values of small quantities of impurities, particularly alcohols. As long ago as 1914 Schwarz (26) pointed out that the values for the solvent strength of solvents for nitrocellulose can be significant only if their purities are exactly indicated. Keyes (18) in 1925 stated that the improved solvent strength exhibited by solvents of commercial purity was due to the alcohol impurities, and many other early investigators have pointed out the effect of impurities on the solvent ability of solvents for nitrocellulose. I n spite of this adequate background, however, the published values of dilution ratios have seldom indicated the purity of the solvents used in making the determinations; this factor has served to discredit somewhat the reliability of the dilution ratio determination. I n the present study great pains were taken to obtain solvents of the highest practicable purity, and this effort constituted the major part of the experimental work involved in obtaining the data reported here. Table I1 summarizes the analytical data of each of the solvents, diluents, and couplers employed. I n order to obtain comparable figures in all cases, the same blend of nitrocellulose was used throughout. This was Hercules R. S. half-second nitrocellulose lot 6041, 12.10 per cent nitrogen content. Unfortunately, slight differences in the nitrocellulose used for the dilution ratio determination give slightly different results, and therefore some of the values reported here do not check absolutely the values given in a previous paper by the author on this subject (11) in which the nitrocellulose used was Hercules R. S. half-second nitrocellulose, lot 4203.
€95
Summary 1. The solvent strength of the pure members of the homologous series of acetic esters, ketones, and ether-alcohols has been evaluated by the toluene dilution ratio method. The values for the esters and the ether-alcohols are shown to pass through maxima as the homologous series is ascended, but in the case of the ketones there is a continual diminution in solvent strength as the size of the molecules increases. The same empirical equation is shown to define the curves connecting the dilution ratio values of the solvents of each class, using appropriate constants for each curve. 2. The change in toluene dilution ratio with the proportion of solvent is shown for thirty-four binary mixtures of solvent and coupler; it is apparent that normal alcohols of low molecular weight are, in general, most effective in improving the toluene tolerance of the mixtures. The curves connecting the toluene dilution ratio with the composition of most of the binary mixtures studied can also be defined by the same mathematical expression that relates the pure members of homologous series, when the appropriate constants are found for each curve. 3. Isopropyl acetate-ethanol is a much stronger solvent mixture than isopropyl acetate-isopropanol and is even slightly more desirable than ethyl acetate-ethanol, since equivalent toluene tolerance occurs with the isopropyl ester when a smaller proportion of ethanol is present. RECEITEDApril 17, 1937. Presented before the Division of Paint and Varnish Chemistry at the 93rd Meeting of the $meriaan Chemical Society. Chapel Hill, N. C., April 12 to 15, 1937.
Comparative Viscosities of Nitrocellulose Solutions in Pure Solvents and Solvent-Coupler Mixtures
T
H E study of the solvent strength of pure solvents and solvent-coupIer mixtures, outlined in the previous section, has been continued and data are presented in this section relating to the viscosities of solutions of nitrocellulose in them. These solvents and couplers were highly purified compounds (Table I1 of the first section gives their principal physical constants). The solutions on which the viscosity measurements reported in this section were made consist solely of nitrocellulose and solvent or solvent plus coupler. No hydrocarbon diluent was used in this phase of the work, and in this respect the systems studied in the second section differ from those studied in the first. The viscosity of a nitrocellulose solution in a pure solvent is not a significant index of solvent strength to the lacquer formulator because thinner costs depend on the extent t o which the solvent may be diluted with cheaper hydrocarbons. Consequently, solutions of nitrocellulose in pure solvents are seldom used commercially. The viscosities of solutions of nitrocellulose in solvent mixtures containing no hydrocarbons are, furthermore, grossly misleading as a measure of solvent strength, especially in the case of the two-type solvents such as the Cellosolves. For example, the viscosity of an 8 per cent solids solution of half-second nitrocellulose in pure Cellosolve was found to be 77.4 centipoises, a much higher value than the viscosity of a corresponding solution in n-butyl acetate (90 per cent ester), which is given as 39.6 centipoises. When, however, thinners containing 65 per cent toluene were used instead of the undiluted solvents, the viscosity of the 8 per cent solution containing Cellosolve was 37 centipoises whereas
the solution containing butyl acetate had a viscosity of 45 centipoisea. The relations involving a diluent will become more apparent in the third section which follows. In spite of the inadequacy of such viscosity relations to serve as a measure of solvent strength, much more work has been reported in the literature (1,1,1~-15,18,19,~1-Z3,27) on the viscosity relations of nitrocellulose solutions in undiluted solvents than on other methods of evaluating solvent strength. It waa therefore considered advisable t o carry out Viscosity studies on the same carefully purified solvents and couplers that were employed in the dilution ratio work previously reported, in order to compare the results by both methods. Solutions of exactly 8.00 * 0.05 per cent were made up in each of the solvents or solvent-coupler mixtures listed in Table 111,using dry R. S. half-second nitrocellulose (Hercules lot 9002, 12.08 per cent nitrogen content), and these solutions were aged for 3 weeks a t a constant temperature of 20" * 0.05"C. At the end of the aging period, the viscosities were carefully measured in a Hoeppler Precision viscometer thermostated to 20" * 0.05" C. The viscosities of the pure solvents were likewise determined in the Hoeppler instrument at this same temperature. The experimental results obtained for the various nitrocellulose solutions are given in Table 111. The figures under the column "Mean Molar Volume" are taken from Table I, where this term is defined and its use explained. The viscosities of the pure liquids are recorded with other analytical data in Table 11. To provide a visual picture of the relations studied, the data
VOL. 30, NO. 2
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VISCOSITIES O F NITROCELLULOSE SOLWhONS IN PURE SOLVENTS AND SOLVENT-COUPLER MIXTURES Viscosity Viscosity Viscosity of Soln Mean Mean of Soln Mean Per Cent Mean of Soln., Molar Centi-" Molar Centi-'' Molar Solvent Molar CentiVol. poises Vol. poises Vol. by Weight VoI. poises Meth 1 ethyr ketone Methanol Methanol Ethanol Isopropanol 0.0793 16.4 0.0714 13.8 100 0.0897 10.1 0.0897 10.1 0.0897 10.1 .. 0.0651 13.0 90 0.0798 9.3 0.0851 9.8 0.0881 10.0 0.0600 12.8 80 0.0720 9.5 0.0809 10.2 0.0866 10.8 .. 0.0558 12.6 70 0.0656 9.9 0.0771 11.1 0.0852 11.9 0.0523 12.5 60 0.0602 10.4 0.0736 12.4 0,0838 13.6 50 0.0556 11.2 0.0705 13.8 0.0824 16.0 Methyl n-propyl Ethanol Isopropanol Methanol ketone 0.0978 20.0 0.0978 20.0 100 0.1002 14.0 0.0908 17.0 0.0948 17.6 0.0852 16.2 0.0921 17.7 Methyl 0.0801 16.4 0.0896 18.6 n-butyl 0.0757 17.3 0.0872 20.1 ketone 0.0719 19.1 0.0851 23.0 n-Butanol Isobutanol sac-Butanol 100 0.1222 19.0 0.1222 19.0 0.1184 0.1222 19.7 19.0 90 0.1182 18.4 0.1185 18.0 0.1150 26.4 80 0.1144 20.8 0.1150 21.0 0.1149 21.0 70 0.1108 24.1 0.1117 25.2 0.1115 22.8 60 0.1076 27.3 0.1087 29.4 0.1084 25.0 Ethanol Isopropanol Methanol Methyl n-amyl 0.1170 24.5 0.1170 24.5 ketone 0.1054 20.3 0.1105 20.8 0.0960 18.9 0.1048 20.5 n-Amyl alcohol Methyl amyl alcohol 0.0884 18.8 0.0998 21.7 100 0.1400 27.0 0.1400 27.0 0.0820 19.4 .... .. 0.0954 23.8 90 0.1360 25.3 0.1385 25.2 0.0766 20.4 .. 0.0914 26.8 80 0.1321 26.6 0.1370 26.4 0.0719 21.9 .. 70 0.1284 28.6 0.1356 29.8 0.0678 23.7 .. 60 0.1251 31.1 0.1342 39.6 .. Methyl n-hexyl Isobu tanol eec-Butanol a-Butanol ketone 0.1317 35.0 0.1317 35.0 0.1317 35.0 100 0.1568 38.7 0.1260 31.7 0.1259 29.8 0.1258 30.9 0.1208 32.3 0.1204 29.9 0.1204 30.7 Methyl 0.1160 34.5 0.1156 30.9 0.1156 32.3 n-nonyl 0.1116 38.2 0.1112 32.1 0.1112 34.3 ketone
TABLE 111. Per Cent Solvent by Welght ' Methyl acetate
100 90 80 70 60 50 Ethyl acetate 100 90 80 70 60 50 n-Propyl acetate 100 Isopropyl acetate 100 90 80 70 60 50 40 30 n-Butyl acetate 100 90 80 70 60 n-Butyl acetate 100 90 80 70 60 n-Amyl acetate 100 90 80 70 60 Acetone 100 90 80 70 60 50
Viscosity of S o h , Centipoises
.... .... ....
.. .. ..
.. .... .... .... ....
....
..
.,..
..
.... ....
.. ..
.
....
..
I
..
..
.... .... .... .
I
.
.
....
sec-Amyl alcohol 0.1317 35.0 0.1289 31.4 0.1261 31.1 0.1234 32.5 0.1210 34.7
....
....
.. ..
....
....
.,
..
....
%-Amyl alcohol 0.1482 46.3 0.1425 40.3 0.1373 40.5 0.1325 42.9 0.1282 47.7
sec-Amyl alcohol 0.1482 46.3 0.1427 40.0 0.1376 39.3 0.1329 40.2 0.1289 42.0
Methanol 0.0733 6.83 0.0678 7.11 0.0631 7.60 0.0590 8.01 0.0554 8.90 0.0522 9.63
Ethanol
..
....
..
..
Isopropanol 0.0733 6.83 0.0736 7.32 0.0739 8.00 0.0742 8.90 0.0745 10.22 0.0748 12.37
of Table 111 are shown graphically on Figures 7 to 11, inclusive. The heavy lines connect the points representing the viscosities of solutions involving only pure solvents, whereas the lighter lines show the variations in viscosity of solutions ihvolving mixtures of the pure solvents and different alcohols. The commori abscissa of all curves on Figures 7 to 10, inclusive, is the mean molar volume of the solvent or solvent plus coupler. The per cent composition by weight of any mixture of solvent and alcohol (Figures 8 t o 10, inclusive) may be obtained from Table 111,but the reading of these data from the curves has been simplified by placing dots on these curves at intervals of 10 per cent in composition by weight. Thus the circle towards which each group of light line curves converges represents 100 per cent, or pure solvent. The first dot is 90 per cent solvent, the next 80 per cent, and SO on. Figures 7 to 11 present some interesting comparisons with
100 Methyl Cellosolve 100 80 60 40 20 Cellosolve 100 90 80 70 60
0.2058
108
...
n-Butanol 0.0789 67.0 0.0815 60.0 0.0840 58.6 0.0865 60.3 0.0889 77.3
Methyl Cellosolve acetate 0.0789 67.0 0.0842 61.9 0.0904 57.2 0.0978 53.2 0.1066 52.7
n-Butanol 0.0970 77.4 0.0963 73.0 0.0957 71.6 0.0951 71.0 0.0945 70.8
Cellosolve acetate 0.0970 77.4 0.0999 71.8 0.1026 68.9 0.1057 66.6 0.1091 65.0
..
.. Butyl Cellosolve 0.0789 67.0 0.0862 70.8 0.0946 75.7 0.1046 83.1 0.1166 93.6
.... .... .... ....
.. .. .. ..
Figures 1 to 6 . Figure 7 shows that in the case of each homologous series, solutions in pure compounds of the lowest molecular weight give the least viscosities. This is at variance with the picture presented in Figure 1, where it is shown that in the case of both the ether-alcohols and the normal acetic esters the dilution ratio values pass through maxima as the size of the molecules increases. If we are to accept the tolerance for diluent as a practical measure of solvent strength, therefore, we must abandon the conception that the maximum solvent strength is associated with the least viscosity of solutions involving the undiluted solvent. With mixtures of solvent and coupler, however, there is more justification for the belief that a low viscosity of solution indicates a high solvent strength in the solvent-coupler mixture, although in only one case among the twenty-six combinations studied did the mixture of maximum solvent strength have the same composition by both methods. This was a mixture of 92 per cent methyl n-butyl ketone and 8 per cent isobutanol. A notable exception to the supposed rule that the least viscosity represents the maximum solvent strength may be observed in the case of acetone. No mixture
FEBRUARY, 1938
INDUSTRIAL AND ENGINEERING CHEMISTRY
197
A comparison of the curves of Figures 8 and 9 indicates that, in general, the viscosities of solutions involving esters can be considerably reduced by coupling the esters with alcohols, whereas with ketones very little lowering of viscosity results. An unexpected phenomenon was observed in the case of the n-butyl and n-amyl acetates (Figure s), coupled with alcohols of the corresponding number of carbon atoms. I n both of these cases the secondary alcohols gave lower viscosities than the normal alcohols. With methyl n-butyl ketone (Figure 9), however, sec-butanol was less effective in reducing the viscosity of the nitrocellulose solution than either n- or isobutanol. Figure 10 is of interest in that the point representing the viscosity of a solution involving pure Cellosolve lies on the curve connecting the viscosities of solutions made with various mixtures of methyl Cellosolve and butyl Cellosolve. I n the case of the dilution ratio studies (Figure 4) it was shown that the mixture of methyl and butyl Cellosolves passed through a composition of maximum diMOLAR VOLUME OF SOLVENT INLITERS lution ratio, but the value of the dilution FIGURE7. VISCOSITIES OF EIGHTPER CENTNITROCNLLULOSE SOLUTIONS ratio a t a mean molar volume of 0.0970 (the IN NORMAL PUREKETONES, ESTERS, AND ETHER-ALCOHOLS AT 20' C. molar volume of Cellosolve) was considerably 1. Methyl Cellosolve 9. Acetone 2. Cellosolve 10. Methyl ethyl ketone less than the dilution ratio of Cellosolve. 3 But 1 Cellosolve 11. Methyl n- ropy1 ketone 4: M e t h acetate 12. Methyl n-gutvl ketone Since isopropyl acetate is not a normal 5. Ethyf acetate 13. Methyl n-amyl ketone compound, the viscosity data involving this 14. Methyl n-hexyl ketone 6. n-Propyl acetate 15. Methyl n-nonyl ketone 7. %-Butylacetate solvent could not be presented on Figure 8. 8. n-Amyl acetate A comparison between isopropyl acetate and ethyl acetate, each couded with the same alcoof acetone and coupler (Figure 9) gave a lower viscosity soluhols, is made on Figure 11; using per cent composition by tion than the solution made with pure acetone, yet Figure 3 weight of the solvent-coupler combination as the common shows that the dilution ratio values pass through maxima with abscissa. Inspection of these curves indicates, as pointed out each of the combinations of acetone with methanol, ethanol, in the first section of this paper, that isopropyl acetate-ethanol and isopropanol. makes a better solvent than isopropyl acetate-isopropanol.
.050
.050 .060 .070 ,080 .090 .IO0 .I 10 .I20 ,130 .Id0 . I MEAN M O L A R VOLUME. oc SOLVLNT ( + C O U P L E R ) IN L I T E R S
FIGURE 8. VISCOSITIES O F EIGHT PERCENTNITROCELLULOSE SOLUTIONS IN NORMAL ACETICESTERALCOHOL COMBINATIONS AT 20" C. Methyl acetate-methanol Ethyl acetate-methanol Ethyl acetate-ethanol Ethyl acetate-isopropanol n-Propyl acetate 6. n-Butyl acetate-n-butanol 7. n-Butyl acetate-isobutan 1 1.
2. 3. 4. 5.
.060 .070 .080 .090 .IO0 . I 10
MEAN MOLAR VOLUME
IO
n-Butyl acetate-sec-butanol n-Butyl acetate-sec-amyl alcohol 10. n-Amyl acetate-n-amyl alcohol 11. n-Amyl acetate-sec-amyl alcohol 8.
9.
.I20
.I 30
.I40 . l 5 0 . .I IN LITER
ow SOLVENT C+COUPLLR)
FIGURE9. VISCOSITIES OF EIGHT PER CENTNITROCELLULOSE SOLUTIONS IN NORMAL 2-KETONE-ALCOHOL COMBINATIONS AT
1. 2. 3. 4.
5. 6.
panol Methyl n-propyl ketone 8. Methyl n-butyl ketone-sec-butanol 7.
20"
c.
Methyl n-butyl ketone-n-butanol 10. Methyl n-butyl ketone-lsobutanol 11. Methyl n-amyl ketone-n-amyl alcohol 12. Methyl n-am 1 ketone-methyl n-amyl alcolol 13. Methyl n-hexyl ketone 9.
INDUSTRIAL AND ENGINEERING CHEMISTRY
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VOL. 30, NO. 2
TABLEIV. RELATIVE VISCOSITIES Molar Vol. 0.0793 0.0978 0.1150 0.1317 0.1482 0.0733 0.0897 0.1062 0.1222 0.1400 0.1568 0.2058 0.0789 0,0970 0.1312
Methyl acetate Ethyl acetate n-Propyl acetate n-Butyl acetate n-Amyl acetate Acatone ...~~. Methyl ethyl ketone Methyl n-propyl ketone Methyl n-butyl ketone Methyl n-amyl ketone Methyl n-hexyl ketone Methyl n-nonyl ketone Methyl Cellosolve Cellosolve Butyl Cellosolve ~~
Viscosity Viscosity of Soin., of Solvent, Relative Centipoises Centipoises Viscosity 16.4 0.38 43.2 20.0 0.45 44.5 26.4 45.5 0.58 47.3 36.0 0.74 46.3 0.95 48.7 0.32 6.83 21.2 0.42 10.1 24.1 0.50 14.0 28.0 19.0 30.2 0.63 27.0 33.3 0.81 38.7 36.5 1.06 45.5 2.40 108.0 1.72 67.0 39.0 2.09 77.4 37.0 3.31 109.3 33.1 ,
fore, we might propose the following formula to express the new relation, based on the experimental evidence presented here : viscosity of solution = aV viscosity of solvent 5 O ~ " " ~ " " " " ' " " ' " " ' " " " ' " ' " " ' " " " ' ' " " " " ' " ~ .075 .080 .085 .090 .095 .I 00 .I05 . I IO . I I 5 . I 2 0 .I25 .I30 . I MEAN MOLAR VOLUME OF SOLVENT (+COUPLER) I N LITERS
+
(5)
,
FIGURE 10. VISCOSITIES OF EIGHT PERCENTNITROCELLUSOLUTIONS IN NORMAL ETHERALCOHOL-COUPLER COMBINATIONS AT 20" C.
LOSE
1. 2. 3. 4. 5. 6.
Methyl Cellosolve-n-butanol Methyl Cellosolve-methyl Cellosolve acetate Methyl Cellosolve-butyl Cellosolve Cellosolve-n-butanol Cellosolve-Cellosolve acetate Butyl Cellosolve
Furthermore, the viscosity curves of isopropyl acetate-ethanol and ethyl acetate-ethanol converge as the proportion of coupler increases; the difference in viscosities is only 1.3 centipoises with equal parts of solvent and coupler in each case. An empirical mathematical expression was given in the first section connecting the dilution ratio values of the members of homologous series of solvents with the molar volumes of the solvents, and it was shown (Figure 1) that the experimental data were expressed by the formula with surprising accuracy. Perhaps the most significant contribution from the theoretical Doint of view arising of the viscosity studies presented in this section is the fact that the members of these same homologous series may be connected by straight-line relations when the relative viscosities of their 8 per cent solutions are plotted against the molar volumes of the solvents. These lines, shown on Figure 12, are plotted from the data of Table IV. Relative viscosity is the viscosity of the solution divided by the viscosity of the solvent. This conception was advanced by Einstein (23) in the well-known formula: viscosity of solution = KF) (4) viscosity of solvent where K = a constant F = fraction of solid present by volume
r
%SOLVENT-BvWT. t~ 30LVLNT-COUPLLR MIRTURL
FIGURE11. VISCOSITIESOF EIGHT PER CENT NITROCELLULOSE SOLUTIONS IN ETHYLACETATE AND IsoPROPYL ACETATE MIXTURESWITH ALCOHOLS AT 20" C. 1. Ethyl acetate-methanol 2. Ethyl acebate-ethanol 3. Ethyl acetate-isopropanol 4. Isopropyl acetate-methanol 0. Isopropyl acetate-ethanol 6. Isopropyl acetate-isopropanol
+
This formula relates relative viscosity with the solids content of the solution and has been applied satisfactorily to many colloidal solutions over a range of low solids concentrations. I n the present i n s t a n c e , h o w e v e r , t h e s o l i d s c o n c e n t r a t i o n is fixed in all cases while the solvent itself is varied. There-
MOLAR VOLUME
OF
SOLVENT
IH
LITERS
VISCOSITIES OF EIGHT PERCENTSITROCELLUL FIGURE 12. RELATIVE SOLUTIONS IN PUREKETONES, ESTERS, AXD ETHER-ALCOHOLS AT 20" C. 1. Methyl acetate 2. Ethyl acetate 3. n-ProDyl acetate n-Butj;l acetate n-Amyl acetate 6. Methyl Cellosolve 7. Cellosolve 8. Butyl Cellosolve
2:
Acetone Methyl ethyl ketone Methyl n-propyl ketone 12. Methyl n-butyl ketone 13. Methyl n-amyl ketone 14. Methyl n-hexyl ketone 15. Methyl n-nonyl ketone 9.
10. 11.
FEBRUa4RY, 1938
where V
= size of solvent a, b = constants
INDUSTRIAL ARTDENGINEERING CHEMISTRY
molecules
199
The compositions giving the minimum viscosity as revealed by this work rarely coincide with the compositions giving the maximum dilution ratio as determined in the first section of the paper. 3. The viscosities of solutions involving esters can be considerably reduced by coupling the esters with alcohols, but very little reduction in viscosity can be effected by coupling ketones with alcohols. 4. Secondary alcohols are more effective in reducing the viscosities of solutions made with n-butyl and n-amyl acetates than are the corresponding primary alcohols, although the differences are very slight. On the other hand, ethyl alcohol, a normal compound, is more effective in reducing the viscosity of solutions made with isopropyl acetate, a secondary compound, than is the corresponding secondary alcohol, isopropanol. 5 . The relative viscosities'of solutions of nitrocellulose in the pure members of homologous series fall on straight lines when plotted against the molar volumes of the solvents.
Figure 12 shows that the relative viscosity increases ( a is plus) as the size of the solvent molecules increases in the case of both normal esters and normal 2-ketones, but decreases (a is minus) in the case of the normal ether-alcohols. The reversal of the slope in the case of the ether-alcohols is due t? the fact that the viscosity of the solvent increases faster than the viscosity of the solution as we ascend the homologous series.
Summary 1. The viscosities of 8 per cent solids solutions of nitrocellulose in the pure solvents belonging to homologous series of normal acetic esters, normal 2-ketones, and normal etheralcohols increase continuously as the size of the solvent molecules increases. 2. Data showing the relation of the viscosities of 8 per cent solids solutions of nitrocellulose in mixtures of solvent and coupler to the composition of the mixtures are given for twenty-six different combinations of solvent and coupler.
RECEIVEDDecember 13, 1937.
Phase Diagram Method of Solvent Evaluation
I
cosity method and the dilution ratio method are combined on a single chart or phase diagram. This method of evaluation defines precisely the regions (compositions) in which it is more desirable to formulate and the regions that must be avoided, and has the advantage of expressing quantitatively the physical state of complete systems involving the resinous material, solvent (plus coupler), and diluent. The phase diagram method was developed in connection with a study of solvents for Vinylite3 resins, which cannot be evaluated satisfactorily by dilution ratio comparisons. The general usefulness of the method was a t once apparent, however, and the study was extended to include solvents for other resinous materials besides Vinylite resins. I n this section, therefore, the application of the phase diagram method of solvent evaluation to solvents for nitrocellulose will be given. The dilution ratio is defined as the ratio by volume of diluent to solvent when a mixture of two such liquids just fails to dissolve nitrocellulose. The determination is usually carried out by titrating a solution of nitrocellulose in the solvent with
N T H E preceding sections, solvents and solvent-coupler
mixtures were compared by means of their toluene dilution ratios and by the viscosities of their nitrocellulose solutions. Neither of these methods is adequate to evaluate the strictly solvent characteristics of these liquids, as distinguished from their use characteristics such as evaporation rate, stability, blush resistance, color, and odor. A system for the complete evaluation of the solvent characteristics of solvents for resinous material has been worked out in this laboratory whereby data determined by both the vis-
I60
I40
2 t
120
a
Trade-marked name.
#
3
%OF 85%ETHYL ACETATE IN THINNLR- BV W T .
FIGURE 13. EQUILIBRIUM VISCOSITY DIAGRAM O F hTITROCELLULOSE IN 85 PER CENT ETHYL ACETATE-TOLUENE MIXTURESAT 20" C .
0
-0
IO
10 30 40 50 % OF 85 % ETHYL ACETATE
60
70
IN THINNER
80
-.
90
100
6 Y WT.
OF NITROCELLULOSE IN 85 PERCENTETHYL FIGURE 14. PHASEDIAGRAM ACETATE-TOLUENE MIXTURES AT 20" C .
