INDUSTRIAL A N D ENGINEERING CHEMISTRY
November 1950
FOR EQUATIONS 3 AND 4 TABLE VII. CONSTANTS
Reagent
m
At reflux temperature Freon-1 13 Carbon tetrachloride At l l O o C. Li t fraction of chlorotrifkoroethylene lisuid polymer
d
n
0.593 -0.762 0.630 -1.705 0.284 -0.643 0.413 -1.346 0.440 -0.768 0 . ~ 5 -1.153 0.450 -1.160
0.177 0.020 0.288 0.045 0,175 0.070 0.069
0.324 0.607
0.34 1.06
0.490
0.126 0.026
-0.223
0.598
In a study which Irany ( 8 )made of water absorption of various resins, he found that a diffuaion-type expression held very well for a homogeneous resinous substance. He considered the onedimensional diffusional case. Although the present work would involve a three-dimensional case, many of the curves obtained are of a type similar to those which Irany obtained (Figure 2). PENETRATION AND ORIENTATION
It was possible to follow the penetration rates of a few reagents qualitatively by observing the demarcation between the Fluorothene rich in reagent and the Fluorothene poor in reagent. For example, with the trirhloroethylene-treated sample this demarcation appeared parallel to all edges which on further treatment moved inward and finally disappeared. While the rates of penetration for ethyl ether and trichloroethylene appeared to be the
2317
aame along the lengtb and width, it was much less along the thickness. The observations suggest an orientation of the p l y mer chains which is possibly due to technique of molding the sheets from which the samples were taken. A test was performed with refluxing trichloroethylene tQ determine if removal of the natural gloss of the sample had any effect ion this penetration. A sample whose surfaces were roughened with fine sandpaper gave results very similar to one not so treated. It still may be possible that the absorption of liquids may take place more rapidly through the cut edges than through the molded surfaces of a specimen. LITERATURE CITED
(1) Am. Soc. Teeting Materials, Philadelphia, Pa., ”1946 Book of A.S.T.M. Standards, Part 111-B,Nonmetallic Materiala,” 1947. (2) Irany, E.P., fm. EN^. CHEM., 33,1551-4(1941). (3) Kline, G. M., Rinker, R. C., and Meindl, H. F., Proc. Am. SOC. Testing Materials, 41, 1246-60 (1941). (4) Miller, W. T., “Use of Perfluoro- and Chloroperfluorwlefins in the Synthesis of Fluorocarbon Materials,” Columbia University, SAM Laboratories, Atomic Energy Commission, MDDC 1177 (1946). (5) Reysen, W. H., and Vanstrum, P. R., “Properties of FLuorothene,” Carbide and Carbon Chemicals Corp., K-25 Plant, Oak Ridge, Tenn., Atomic Energy Commission, AECD-2032 (Sept. 22,1848). (6) Weiser, H. H., “Colloid Symposium Monograph,” Vol. 4,pp. 20314,New York, Chemioal Catalog Co.,1926. RXNJEIVWI December 22, 1949. Presented before the High Polymer Forum, Division of Paint, Varnish, and Plastics Chemistry, at the 116th Meeting SocxmY, Atlantio City, N. J. Work wrformed of the AMERICAN CREVXCAL at carbide and Carbon Chemicals Division, Union Carbide and Carbon Corporation, Oak Ridge, Tenn., under contract with the Atomio Energy Commiemion.
Phase Equilibria between Fluorothene and Solvents RAYMOND E. McHENRY, SHELDON E. FREY, J. DONALD GIBSON, AND ROBERT H. LAFFERTY, JR. Carbide and Carbon Chemicals Diubion, Union Carbide and Carbon Corporation, K-25 P l a n t , Oak Ridge, Tenn. A n investigation of the phase equilibria between Fluorothene (chlorotrlfluoroethylene solid polymer) and a number of high boiling solvents was made for the purpose of finding a good solvent for Fluorothene. Of the reagents tested, chlorotrifluoroethylene liquid polymer wae found to he the best solvent. A n increase in molecular weight of Fluorothene had little effect on the solubility. Other materials gave phase diagrams showing a maximum solution temperature.
A
N INVESTIGATION of the phase equilibria between Fluorothene (chlorotrifluoroethylenesolid polymer) &nd a number of high-boiling solvents has been made for the purpose of finding a good solvent for Fluorothene. This work is an outgrowth of previous work in this laboratory ( 1 ). The usefulness of Fluorothene has been limited by the fact that there were few solvents for it. Miller (9,p. 106) reported that the solid polymer was soluble in the liquid low polymer at high temperatures. Richards (4) has made an extensive investigation of the phase relationship between polyethylene and a number of solvents. In this study, he determined quantitatively the solubility of polyethylene in several compounds, showing that there were two dis-
tinct relationships between polyethylene and solvents. For good solvents, there waa an almost linear relation between the composition of the solution and the temperature a t which the plastic dissolved. With poor solvents the composition-temperature diagram showed a maximum. This work has been undertaken to determine the similarity between the behavior of Fluorothene and polyethylene with various solvents. From the relationship which exists between the two plastics it should be possible to extrapolate the knowledge obtained for solvents of polyethylene to solvents for Fluorothene. APPARATUS AND TECHNIQUES
The temperatures at which mixtures of Fluorothene and a solvent form a single liquid phase were determined by heating the mixture in a test tube immersed in a suitable liquid contained in an electrically heated Thiele tube. The temperature of the sample waa raised as rapidly as possible to avoid decomposition due to prolonged heating until a single homogeneous liquid phase was formed. The resulting solution was cooled until a second ,phase reappeared. The sample waa then reheated, and the temperature at which this second phase disappeared was taken as the border temperature. The proce-
2318
INDUSTRIAL AND ENGINEERING CHEMISTRY
durr followed in determining any liquid-liquid to liquid-liquid-solid border temperature was the same as described above for a liquid to liquid-liquid or liquid to liquid-solid point. M'hcsn a mixture of Fluorothene and a solvent was heated initially, the polymer gradually softened and diasolved, usually without the formation of a second liquid phase. The initial solution temperature was above 285" C. for all solvents a t all cancentrations for heating periods of less than a half hour. All measurementa of the border temperatures were reproducible within 2 " C. 300
p
Vol. 42. No. 11
In addition to these complete phase diagrams, individual tests with poor solvents are summarized in Table I. The first four reagents have no effect on Fluorothene up to the boiling point of the reagent or the decomposition point of the reagent or the decomposition point, of Fluorotherie. A GOOD SOLVENT
The phase diagram of Fluorothene and chlorotrifluoroethylene liquid polymer shown in Figure 3 is a typical "good solvent type" diagram. Such diagrams show no maxima. When a single phase is cooled at any concentration, solid polymer will be precipitated. Richards interprets this to mean that the critical solution temperature of thesolvent and a hypothetical polymer-rich liquid phase is below the temperature at which solid polymer is formed.
250
ABSORPTION
W
LIOUIO- LlOUtD
If the loop of a i'poor solvent type" curve is extended to lower
t3 W (L
4 zoo
I50
40 00 COMPOSITION, PER CENT FLUOROTHENE
0
Figure 1. Fluorothene-Dibutyl Phthalate System except where the border temperature was depressed a few degrees owing to decomposition of the sample each time it was heated to ita border temperature. In the case of dibutyl phthalate it was observed that a t temperatures above 260' C. decomposition of the sample occurred, which resulted in the second phase dissolving at a slightly lower temperature than that at which it appeared. When a solution of Fluorothene waa cooled until a second phase appnred and was reheated until this second phase dkolved, a difference in the temperatures was observed. This supercooling was more pronounced in dilute solutions.
temperatures and higher concentrations, the extrapolation will represent the absorption curve. Data on the absorption by Fluorothene of dibutyl phthalate, dibutyl sebacate, and chlorotrifluoroethylene liquid polymers obtained by this laboratory are in qualitative agreement with the expected values from the phase diagrams. There was practically no absorption of dibutyl phthalate or dibutyl sebacate at 25" C., whereas 19% chlorot~ifluoroethylene liquid polymer was absorbed after 1149 hours at 110"C. without any indication that equilibrium was being approached. This is in agreement with Figure 3, inasmuch aa the polymer-rich solid phase could have any composition from 0 to 100% solvent, depending on the quantity of solvent present. NO-STRENGTH-TEMPERATURE AND SOLUBILITY
The no-strength-temperatre is defined by Miller (9, p. 103) as the Centigrade temperature at which a notched strip of plastic easentially loses ita strength properties. The X '/a X 2 inch strip with the lower portion weighted to 0.5 gram was heated at an increase in temperature of 1.5" per minute over the critical range until the plastic pulled in two.
POOR SOLVENTS
The phase diagram shown in Figures 1 and 2 for dibutyl phthalate and dibutyl sebacate system, respectively, with Fluorothene powder having a no-strength-temperature (9, page 103) of 310' tQ 315' C. (as defined below) represent what Richards refers to rn "poor solvent type" diagram. The straight portion of the curve at concentrations higher than that of the minimum point represents the lowering of the transition point of the Fluorothene by the solvent. When a single phase in this region is cooled, solid polymer will be precipitated. The loop exhibited by poor solvents at lower concentrations of polymer represents the formation of two liquid phases, one predominantly solvent and thc other a polymer-rich liquid phase. On cooling a polymer-rich liquid phase, solid polymer will be precipitated. This is represented in Figures 1 and 2 by the lower curve at low concentrations. COYPOSITION, PER CENT FWOAOTHENE
TABLE
I.
CHAHACTERlSTICB OF VARIOUS
Reagent Ammonium aoid sulfate Glycerol Carbowax eo00 Diphenyl ether Arwlor 1254 Aroclor 1242 Stearic acid
Fluorothene in Mixture, %
MIXTURES
Liquid to Liquid-I.iquid Border Tzmperature, C.
19.0
D
0.8and46.7
1.0 19.0
12.2 12.1
7 . 1 and 26.5
(I
D
364 334
300 to 335
Figure 2.
FluorothenwDibutyl Sebacate System
Miller considered that the no-strength-temperature was a rehitive measure of the molecular weight but was not related to the transition point of the plastic. Because the transition temperature is a point on the curve of a phase diagram, it might be espected that the no-strength-temperature is not related to solubility. The data in Table I1 qdicate that for the range of nostrength-temperature, 180' to 320' C.,the no-strength-temperature is not measurably related to the solubility. Powibly lower
. 2319
I N D U S T R I A L A N D BNGIWEERIWQ CHEMISTRY
November 19s
I
TABLETI. BORDERTEMPERATURES FOB FLUOROTHENE MIXTURES WITH 367, DIBUTYL PHTHALATE No-Rtrongth-Temperature,
c.
Liquid to Liquid-? Temp.,
Falling
320( owder) 310-815 (powder 226-280 (powder]
>300 molded) < 180 lpowdcr)
254 268
249 261
...
I
I
I
I
40
60
00
100
260
3
uid Border
8.
280
W
Ridng 264
D ieo
eK
864 263 260 262
-~
0
5
60
L.
to -PO
20
0
COMPOSITION, PER CENT POLYMER
Figure 4. Dibutyl Phthalate-Chlorotrifluoroethylene Polymer System high molecular weight the increase in the critical solution tempera‘ture is negligible. As the critical solution temperature increases, the critical concentration of the polymer in the solution decreasea (Figure 4). CONCLUSIONS
values of the no-strength-temperature might be related to solubility and also the transition point. However, no plaatic samples of lower no-strength-temperature were available. Solubility tests were made on a sample of polymer, Table 11,which was obtained from the uncatalyaed polymerination of monomer at 125” C. The value of no-strength-temperature for this sample wits not known, but it would he below the melting point, which was 180° c. 4 solubility determination was mude on a sample of molded Fluorothene and it was observed to have the Rame solubility as the powder (Table 11). MOLECULAR WEIGHT AND SOLUBILITY
As stated previously, the no-strength-temperature is considered to be a relative measure of molecular weight. Because the nostrength-temperature for the range investigated is not related to solubility, it may be concluded that the molecular weight for that range also is not measurably related to solubility. The phase diagrams for two samples of chlorotrifluoroethylene liquid polymer ( 8 ) of molecular weights 672 and 1027 are shown in Figure 4. The results of these tests indicate that for polymers of low molecular weight an increase in molecular weight causes an irirreatse in the critical solution temperature, but for polymers of
The following conclusions may be stated from the above work: The same type of relationships which Richards found between polyethylene and solvents holds for Fluorothene. Extrapolation of the work of Richards indicates that a search for materials which will dissolve Fluorothene at room temperature will probably be fruitlesa. Chlorotrifluoroethylene liquid polymers are good solvents for Fluorothene at elevaM temperature. The solubility curve haa no maximum and represents the depression of the transition point of Fluorothene by the solvent. An aliphatic chlorofluorocarbon having a boiling point, or ahout 300“ C. is the ideal solvent for Fluorothene. LITERATURE CITED
Frey, S. E., Gibson, J. D., and Lafferty, 3%. H., Jr., IND.ENO. CRnat., 42, 2314 (ISSO). (2) Oabbsrd, J. L., et al., “Physical Properties of Chlorotrifluoroethylene Polymers aa a Function of Molecular Weight. XI. Molecular Fractionstion, Density, Viscosity, Molecular Weight, and the Correlationof These Properties of Chlorotrifluoroethylene Polymers,” Carbide and Carbon Chemicala Corp., K-26 Plant, MDDC-1724 (Jan. 16, 1948). (3) Miller, W. T., “Uae of Perfluoro- and Cbloroperfluoroolebs in the Synthesis of Fluorocarbon Materials,” Columbia University, SAM Laboratories, Atomic Energy Commission
(1)
YDDC-1177 (1946).
(4)
Richards, R. B., Traw. Faraday Soc., 42, 10-28
(1946).
R~CEIVED December 22,1949. Presented before the Southeastern Regional )Meeting of the AYBBICANCBBMICAL SOCIBTY, Oak Ridge, Term.,June 1949. Work performed at Carbide and Carbon Chemical8 Divieion, Union Carbide and Carbon Corporation, Oak Ridge, Tenn., under contract with the Atomia Energy Cornmimion.
* * * * * Another report froni the Union Carbide and Carbon Corporation plant at Oak Ridge, Tenn,, where chlorotrifluoroethylene polymers are made for the Atomic Energy Commission, will be published in the DeAND ENGINEERING CHEMISTRY. cember issue of INDUSTRIAL The paper, “Physical Properties of Chlorotrifluoroethylene Polymers” b y R. H. Reysen and J. D. Gibson, summarizes the properties of the chlorotrifluoroethylene liquid polymers in a form suitable for use in the solution of lubrication and oil-blending problems, The data included in the paper were originally accumulated by J. L. Gabbrard and co-workers and published in five A.E.C. reports. 0
