Effect of Chemicals on Fluorothene SHELDON E. FREY, J. DONALD GIBSON, AND ROBERT H. LAFFER",
JR.
Carbide and Carbon Chemicals Division, Union Carbide and Carbon Corporation, K-25 Plant, Oak Ridge, Tenn. Ruorothene, the plastic polymer of chlorotrifluoroethylene, has a specific gravity of 2.111 at 25' C., is selfextinguishing, and has very low water vapor permeability and no water absorption. Fluorothene was found to be very resistant chemically and was not dissolved by any reagent at ordinary temperatures. A few reagents are abeorbed by the plastic and this absorption is facilitated hy an elevation of temperature. The absorption may reach a saturation value after which further changes are not observed. Logarithmic expressionswere found for the rate of absorption of reagents by Fluorothene and for the swelling of the samples during absorption of the reagents.
F
LUOROTHENE is produced for the Atomic Energy Commission by the Carbide and Carbon Chemicals Division, Union Carbide and Carbon Corporation; the M. W. Kellogg Company produces this same plastic commercially under the name Kel-F. Some properties of Fluorothene have been determined by Miller (4). Some of the data included in this paper have been issued in a preliminary report (6) by this laboratory. The following study waR made in order to have more complete information concerningthis recent addition to the field of plastics. A.S.T.M. TESTS
The results observed for four A.S.T.M. tests ( I ) are summarized in Table I. For the water vapor permeability test the increases in weight observed were within the error of weighing. If a gas flame is held on Fluorothene, the plastic decomposes and burns with a smoky flame which has a faint tinge of green at the surfacc of the plastic. No water absorption was observed at 60" C. for an immersion time of over 900 hours.
data observed were similar to those reported by Kline and others All percentages are based on the observations made on the untreated sample. ( 8 )for several plastics.
TABLE11. REAGENTS PRODUCING LESS THAN0.02% WEIGHT CHANGE AFTER IMMERSION FOR 7 DAYSAT 25' C. Acetic acid Acetic acid, 5% .4cetio anhydride Acetophenone Ammonium hydroxide. 10% Amyl acid phosphate Aniline Antimony pentachloride Aqua regia Aroclor 1242 Aroclor 1248 hroclor 1254 Benzaldehyde Bensonitrile Benzoyl chloride Benzyl alcohol Butyl alcohol Carbitol acetate Cellosolve 1-Chloro-1-nitropropane Chlorotrifluoroethylene liquid poly mer Chromic acid cleaning soltit,ion Cresol Cyclohexanone Dibutyl phthalate Dibutyl sebacate 1,2-DichIorobutane &Dichloroethyl ether 2 4-Dichlorotoluene 3:4-Diohlorotoluene nicyclopentadiene niethylenetriamine Dioxane ~ . - . . Ethyl alcohol, 50% Ethyl alcohol, 96% Formic acid
Halowax 1000 n-Heptane Hydrochloric acid, 10% Hydrogen peroxjde, Hydrofluoric acid, 50% 3% Hydrogen peroxide, 30% Methanol Mineral oil Naohtha solvent Nitric acid Nitricacid, fuming, 89 to 95% Nitric acid. 10% Nitrobenesne . Nitromethane Oleic acid Pentaohloroethane Perfluorotriethylamine Santicizer B-16 Santicizer E-15 Santicizer M-17 Santiciaer 8 Bantolube 31 Sodium carbonate 2 ?6 Sodium chloride io% Sodium hydroxide 1% Sodium hydroxide: 10% Stannic chlonda Sulfuric acid Sulfuric acid, 3% Sulfuric acid 3 0 9 Sulfuric acid: 20% free SOa sym-Tetrachloroethane 1 1 2-Triohloroethane 1:2:3-Trichloropropane Trichloropropane" Water, distilled
Supplied by Shell Developnient Company; distillation indicated a mixture. Q
~~
TABLE
TABLEI. SOMEA.S.T.M. TESTS Teat
Designation D 697-42T D 370-42 D 635-44 D 792-44T
Property Determined Water vapor permeability, g./sq. m./24 hours Water absorption, % Flammability rate Speclfic gravity, 25/25' C.
111. REAGENTSPRODUCING 0.02 TO 0.37% WEIGHT CHANGE AFTER IMMERSION FOR 7 DAYSAT 25' C. Reagent
Result
Hydrofluoric acid, anhydrous Pvridine
CeiiG&e acetate Ethylene chloride Propylene chloride Bromobenzene Piperidine n-Butyl ether Bromine a-Chlorotoluene p-Chlorotoluene Amyl acetate Ammonia anh drous Carbon d i h f i & Acetone 1 2-Dichlorohexafluorocyclohutane Bhfur dioxide, anhydrous Meth lformate Acet Tchloride D i e t h Carbitol 1 1 1-Trichloroethane hi&hall 1 chloride n-Propyl'f ormate Methyl ethyl ketone Methylene chloride Triethylamine Ethyl formate Isopro yl ether Allyl ctloride Benzene 2-Chloropropane n-Prop 1ether n-Butyf acetate
Lees than 0 . 4 0.00 Self-extinguishing 2.1115
ONE-WEEK IMMERSION TESTS
hpproximately 125 tests were performed for a 1-week immersion eriod at 25" C. in accorddnce with the A.S.T.M..method for ctemical resistance. The samples tested were 1 X 3 inch rectangular pieces cut from 0.125-inch sheets, molded from coarse granules of the polymer in a press a t 300" to 305' C. They were quenched in water at 16" C. to form the transparent sheets urlth a no-strength-temperature of about 320" C. with low crystallinity. The no-stren h-temperature is defined by Miller ( 4 , p. 103) &s the Centigrag temperature at which a notched strip of plastic . 2 inch essentially loses its strength properties. The 1/18 X l / ~ X strip with the lower portion below a notch of 1/18 X 8/64 inch cross section weifhted to 0.5 gram was heated a t an increase in temperature of 1.5 per minute over the critical range until the plastic pulled in two. The reaulte are summarized in Tables 11, 111, and IF'.
The 2314
Weight Change, % 0.02 0.02 0.02 0.02 0.02
0.02 0.04
0.04 0.04 0.05 0.06 0.06 0.09
0.10 0.11 0.11 0.12
0.13
0.13 0.14 0.15 0.16 0.16 0.22
0.23 0.24 0.24 0.25 0.26
0.29
0.33 0.34 0.37
INDUSTRIAL AND ENGINEERING CHEMISTRY
November 1950
231s
TABLEIV. REAQEXUTSPRODUCING GREATERTHAN0.38% CHANQE AFTER IMMERSION FOR 7 DAYS AT 26" C. Ori inal Thicfnass, Reagent
Inch
Change. % Thicknees Width Length
Weight
0.1275 0.1255 0.1208 0.1228
0. iaoe
0.1311 0.1204 0.1292 0.1302 0.1281 0.1244 0.1239 0.1252 0.1300 0.1280 0.1241 0.1244 0.1236 0.1281 0.1254
to00 IMYERStON T I M E ,
4000 HOURS
Figure 1. Effect of Reagents at 25' C. Although the work reported here was with quenched sheet of low crystallinity, it is interesting to note that Miller (4, p. 107) found the absorption of reagents varied with the no-strengthtemperature of the plastic. The degrees of absorption have been attributed to differences in crystallinity due to the heat treatmente. Increased crystallinity of the polymer causes lower absorption. In general, it may be said that as Fluorothene absorbs reagents and gains in weight, the flexibility and swellingof the sample increase. Drying the treated samples for 7 days at 50" C. as a rule caused a loas of approximately 50% of the absorbed reagent. It was obeerved, however, that for several samples nearly loo0 hours of drying at 115" C. were required to bring the weight of the sample back to ita original weight. Chlorine waa the only reagent observed to produce a color change in the tested sample; the Fluorothene sample turned yellow.
0.12b3
9.5
2.2
1.0
9.18
0.1262
8.6
6.0
4.8
12.31
It ie significant that the reagents producing the greatest change on the Fluorothene aample are those with low dielectric oonstanbs, although some reagents with a low dielectric constant produce little change. Perhaps this general observation could have been readily predicted on the bash of earlier observations (6). In order to determine whether mixtures had an increased effect on the Fluorothene, four binary mixtures were tested at 25 C. for 8 days. The binary mixtures of ethyl ether with trichlomthylene, ethyl acetate, and carbon tetrachloride caused weight increases approximately equal to those predicted by a straight-line plot with composition. The other mixture of ethyl acetate and trichloroethylene indicated a greater weight increase than that predicted, but not higher than the increase of 2.7% for trichloroethylene alone. Fluorothene waa tested with several reagents at 70" C. for tin immersion period of one week. The results are given in Table V, Inaamuch as the iirst six or eight samples listed in Table V gained little or no weight, it may be concluded that the tlinieir-
Y
y
IO
4
0
c
'I
I
I
s 5
4
w FREON - I N
I
I
-I
DIETHYL CELLOSOLVE
I
200
I
I
400
600
STANDING TIME. HOURS
Figure 2.
Effect of Reagents at Their Reflux Temperatures
Figure. 3. Desorption at Room Tem ratuw after Immersion for 277 Hours at Reflux Emperaturea
Vel. 42, No. 11
INDUSTRIAL AND ENGINEERING CHEMISTRY
2316 24
1
able absorption could be obtained at 110" C. The rate of loas of this polymer from Fluorothene was very slow. On standing for 504 hours at room temperature the weight change of 19.01% decreased to 18.30%. Probably none of this change is due to evaporation, as the sample was wiped before each of the six determinations during the period. CORRELATIOS O F DATA
The swelling of Fluorothenc by various reagents was readily correlated by Equations 1 and 2.
v
=
UCk
log V = k log C IMMERSION TIME, HOURS
Figure 4.
Effect of Light Fraction of Chlorotrifluoroethylene Liquid Polymer at 110" C.
sional changes observed were produced thermally rather than by any action of the reagents. EXTENDED IMMERSION TESTS
The results for several extended immersions at 25" C. are given in Figure 1. Data were observed for the dimensional changes of the various samples and though in general the per cent thickness change paralleled the per cent weight change, the corresponding values for the width and length were much smaller. For example, with the trichloroethylene-treated sample after 5358 hours' immersion, the weight, thickness, width, and length per cent changes were, respectively, 7.96, 6.2, 2.9, and 1.5. Toluene produced effects very similar to carbon tetrachloride and these data are not included in Figure 1. In the case of the extended immersion of Fluorothene in ethyl ether at 25 C. a limiting value was reached after which no further changes were noted (Figure l). A few tests were performed at the reflux temperatures of various reagents to observe if similar effects were produced at elevated temperatures. This experiment was performed by placing the sample in the liquid in a flask connected to a reflux condenser. The results of these tests are shown in Figure 2, which indicates that an elevation of temperature very greatly facilitates the absorption of reagents. The limiting saturation value is readily attained. By measuring the weight change of the treated samples on standing it was observed that the liquids which are most rapidly absorbed are those which will be most rapidly losf. This is illustrated by a comparison of Figure 3 with Figure 2. The changes are based in both cases on the weights of the untreated samples. Although it was shown in Table I1 that chlorotrifluoroethylene liquid polymer was not absorbed by Fluorothene at 25' C., Figure 4 shows that by using a light fraction of this polymer appteci-
TABLE v. Reagent Sulfuric acid, concd. Phenol Butyl alcohol Aniline Nitric acid Trichloroacetic acid Acetic anhydride Acetic acid Amyl acetate Ethylene chloride Bromobensene Ethyl acetate Toluene Carbon tetrachloride Trichloroethylene
IMMERSION FOR
7 DAY$ AT 70" C.
Ori inal Thictness, Change, % Inch Thickness Width Length 0.1217 1.6 -0.7 -0.8 0,1226 1.5 -0.7 -0.7 0.1216 -0.8 -0.8 1.5 0,1219 -0.7 -0.8 1.7 0.1228 -0.7 -0.8 1.6 0.1232 -0.7 -0.7 1.5 1.7 0.1223 -0.7 -0.7 0.1211 1.8 -0.7 -0.8 0,1223 3.0 -0.5 -0.6 0.1216 3.0 -0.4 -0.5 0.1208 -0.4 -0.4 4.1 0,1224 3.2 3.3 6.5 3.7 0,1224 3.6 7.3 0.1217 1.4 1.1 9.9 0.1220 4.1 4.1 8.6
WeighT 0.00 0.00 0.01 0.01 0.01 0.03 0.10 0.23 0.87 1.21 1.90 6.49 6.76 9.73 13.54
+b
The percentage of the reagent in the swollen Fluorothene is given as C, V is the volume per cent increase, a and k are constants, and b is equal to log a. Figure 5 shows a typical plot from which the constants were calculated. A study of this figure shows that it is an adequate definition of the reagent used, because all the data for a given reagent fitted well regardless of the time or temperature of the test. Table VI gives the constants for other reagents and it is seen from the values found fork that swelling is nearly a linear function of concentration. The conscant a gives the value of V for unit per cent concentration change and is a measure of the relative swelling power of the reagent.
0:
0,s W
z
3 P b e 9
o c - - P 5 OC & F E R REMOVAL o--- REFLUX n---REFLUX AFTER REMOVAL x---70eC. FOR 7 DAYS
LOG OF PER C E N T CONCENTRATION
Figure 5.
Swelling during Absorption of Carbon Tetrachloride
TABLE VI. CONSTANTS FOR
EQUATIONS
Reagent
k
Ethyl ether Freon- 113 Carbon tetrachloride Ethyl acetate Trichtoroethylene Toluene Diethyl Cellosolve Light fraction of chlorotrifluoroethylene liquid polymer
0.933 1 000 1.008 1.028 1.090 0.990 1.096 1.141
1 AND 2
b 0.462 0.092 0,143 0.315 0.089 0.397 0.343
-0.070
a
' 2 90 1.24 1.39 2.07 1.23 2.50 2.20 0.85
Equations similar to 1 and 2 were found to be applicable for the rate of absorption of various reagents by Fluorothene. Equations 3 and 4 are similar to those given by Miller ( 4 , page 107).
w = ntm
log W = m log t
+d
(3) (4)
where W is the weight per cent increase, t is the time in hours, n and m are constants, and d is equal to log n. The equation prior to saturation would obviously not continue to be valid after saturation. Table VI1 gives the constants for Equations 3 and 4.
INDUSTRIAL A N D ENGINEERING CHEMISTRY
November 1950
FOR EQUATIONS 3 AND 4 TABLE VII. CONSTANTS
Reagent
m
0.593 0.630 0.284 0.413 0.440 0 . ~ 5 0.450
At reflux temperature Freon-1 13 Carbon tetrachloride At l l O o C. Li t fraction of chlorotrifkoroethylene lisuid polymer
0.324 0.607 0.490
d -0.762 -1.705 -0.643 -1.346 -0.768 -1.153 -1.160 0.126 0.026
-0.223
n
0.177 0.020 0.288 0.045 0,175 0.070 0.069 0.34 1.06 0.598
In a study which Irany ( 8 )made of water absorption of various resins, he found that a diffuaion-typeexpression 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., IND. 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 Chloroperfluorwlefinsin 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 of the AMERICAN CREVXCAL SocxmY, Atlantio City, N. J. Work wrformed 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-
