NOTES
636 Hence =
-~
~ 1 1 ,
Approximating (1+KU)-’ can be simplified to Ah = do
+ K a ) - ~ + ~ / 2 1 (34) by (1-KU + ~ ~ a (34) ~ ) ,
- BC’/,(l - Ka + H / 2 ) - &‘/%‘a2
Vol. 63
shows that it usually can be neglected, provided ~a < 0.2. Replacing H by its explicit value, we have finally =
- Bc,,,
+
Bc’/*~a[ll/l2- ( b / S ) ( l n rta
(351
+ 1.0172)]
(36)
When combined with the other relaxation terms, The last term of (35) gives the major part of the (36) will then give the final conductance equation.6 former term J2c’’’; comparison with experiment (a) R. M. F ~ibid.,~ so, 3163 ~ (1958). ~ ,
NOTES THE ACTION OF REACTOR RADIATION ON SATURATED FLUOROCARBONS BYJ. H. SIMONS AND ELLISON H. TAYLOR University of Florida, Q a h m d l e , Florida, and Chemist?# Diviaon,
Oak Ridge National Laboratory,1 Oak R&e, Received September 1.5, 1068
Tennessee
The extraordinary stability of fluorocarbons to heat and to most reagents led to early hopes of a similar high stability to ionizing radiation. Experimenh upon fluorocarbon polymers,2 however, indicated a greater than average sensitivity to radiation. Interest in these materials for applications involving radiation therefore waned, despite the fact that non-polymeric saturated fluorocarbons would be expected to act differently. Other radiation studies of fluorocarbons have been motivated by interest in radiation polymerization of some unsaturates, and have shown that these can be polymerized when irradiated in glass.’ On the hypothesis that the observed radiation instability of the polymers and the polymerizable monomers might result from impurities (residual H in impure fluorocarbons), reaction with the container (glass), or from innate instability of particular compounds (polytetrafluoroethylene), the present experiments were initiated. Fluorocarbons and fluorocarbon derivatives of low hydrogen content had become available, and it was therefore thought possible finally to establish the degree of radiation stability of this class of compound. ~
Experimental Materials.-GFl~less than lo-*% hydrolyzable F; b.p. 82’; optical density 0.51 at 2700 b.; 0.23 at 2460 A.; 0.67 a t 2206 b. C8F16Q-a mixture of cyclic fluorocarbon oxides of this comDosition but undetermined structure; b.P. 101’ (constant over whole sample); optical density 0.5i at 2536 ‘il. (C,Fp)aN-purified to remove H-contahing compounds; b.p. 177’. Methods.-Each sample waa further purified by evacuation while frozen, melting, refreezing, and further evacuation, followed by distillation through PaOsi?to the irradietion vessel. This was a 4.inch length of 1-mch aluminum (2 S) tube with a flat bottom and a * #-inch aluminum tube a t the top, fabricated by heliarc weding. It was attached (1) Operated by Union Carbide Corporation for the U. 8. Atomic Energy Commiseion. (2) 0. Sisman and C. D. Bopp, Physical Properties of Irradiated Plastics, USAEC Unclassified Report, ORNL-928 (June, 1951). (8) D. 8. Ballantine, A. Glines, P. Colombo and B. Manowits. “Further Studied of the Effect of Gamma Radiation on Vinyl Polymer Bye-,” BNL-294 (March, 1954).
to the vacuum system through a Kovar-to-PFex seal. After being filled, the vessel was sealed off while frozen, first in the glass and then by pinching and welding the aluminum. The samples were irradiated for 4 weeks in the Oak Ridge Graphite Reactor a t a neutron flux of 5.5 x 1011 cm.-2 sec.-l and a t a maximum temperature of 110’. The total energy absorption a t this position should have been 3.6 X lo-‘ cal./g., sec., for a ample composed of graphite, based upon calorimetric measurements by Richardson and Boyle‘ corrected for the flux ratio between their position of mesaurement and the resent location. About 82% of the energy (in graphite7 arises from absorption of y-rays and the remainder from stopping of fast neutrons.4 The samples were opened by attaching them to a vacuum system, cooling in liquid air, and then drilling a small hole in the top of the entrance tube by hand with a steel twist drill. The first sample opened was completely removed from the am o d e by vaporization. Because of the formation of hi h-toiling substances this became a len thy procedure. ‘%heother samples were similarly opened lut,.after the low-boiling material was removed, air was adrmtted, the ampoule removed from the system, and the content@ poured into the distillation apparatus.
Results There was no evidence of corrosion, the inner wall of each capsule being clean and bright after irradiation. There was no large amount of gas in any case, and in particular no F2 or CF4. Each irradiated sample was clear and colorless. The results of distillation and other examination of the samples are given in Table I, and the distillation curves (5 to 10 theoretical plates) in Fig. 1. Discussion The irradiation effected chemical changes in these three materials. Thermal changes cannot have contributed since the compounds are stable to 50O0. The yield, G, can be estimated from the distillation analyses and the energy absorption in graphite, assumed equal to that in the fluorocarbons. This assumption is probably accurate to f 20% except for (C4F&N, in which the reaction N14(n,p)C14increases the energy absorption appreciably. For CTFls, with 35% of the molecules transformed for a total energy absorption of 2.2 X e.v./g., G = 2 to 3 molecules transformed per 100 e.v. absorbed. This value is based only on the total energy absorbed, since such reactor experiments give no way for separating the effects of the different kinds of radiation. If the relatively (4) D. M. Richardson, A. 0. Allen and J. W. Boyle, “Calorimetric Meaeurement of Radiation Energy Dissipated by Various Materish Placed in the Oak Ridge Pile,” USAEC Unclassified Report, O R N L 129 (December, 1848).
.
+
4
NOTES
April, 1959
637
TABLEI OF IRRADIATED FLUOROCARBONS EXAMINATION Sample
Wt. sam le
k.Zi
C&
23.1
Cd&sO
26.5
(CIHJ~N
of produot boilinBelow Near Above original original original
7%
Gas
Less than 1%
Liquid
of
-
12
65
23
total sample Acidic." Smells like Acidic" 12 42 46 low mol. wt. fluorinated carboxylic acids 26.2 2 ml. boiling below 25" Neutral" 40 7 53 " To moist litmus paper. * Residues represented about 10% of total sample.
B.P. residue, b OCa
185-192
300 >300
produced in moderate amounts, without detectable corrosion or production of Fz, CF4, carbon, or of tars. The chemical changes here reported as the result of reactor radiation have not been reported to be produced in saturated, hydrogenfree fluorocarbons and their derivatives by heat, electromagnetic radiation, or by electrical discharge. Acknowledgment.-The authors wish to thank the Minnesota Mining and Manufacturing Company for providing the pure samples of hydrogenfree saturated fluorocarbons. The authors also wish to thank Drs. Christie, Dresdner, Shults and Wetbington for permission to refer to the results of their experiments. FILM AND SUBSTRATE FLOW IN SURFACE CHANNELS' BY ROBERT S. HANSEN Contribution from Inttitute for Atomic Research and Department of Chemistry, Iowa State COZZ~Q~, Ames, Iowa Receive3 July Si, 1068
Fig. 1.-Distillation curves for irradiated fluorocarbons.
great stability against y-rays which has been observed in certain experiments with other fluorocarbons6-' applies under the present conditions, then of course the G value for neutrons would be proportionately higher. The absence of FZand of CF, suggests that the primary chemical effect is the breakage of C-C rather than of C-F bonds. The greater instability of the 0- and N-containing compounds can be explained by the lower strength of C-N and C-0 bonds compared with C-C, as demonstrated by the relative thermal stabilities of the compounds in question. Dried, highly pure samples of C7FI6,CeFlsO and (CrFe)aNin aluminum were irradiated in a nuclear reactor. Higher and lower boiling materials were (5) J. A. Wethington and W. H. Christie, peraonal communication. ( 6 ) R. D. Dresdner, personal oommunication. (7) Allan R. Shultz, personal communioation.
LaMer and Blank have recently published two studies of the transfer of monolayers in surface channels2sain which the transfer rate is interpreted in terms of a geometric resistance factor and a rate constant. Transfer of appreciable quantities of substrate was observed.a The purpose of this note is to point out, as has indeed previously been done by Harkins and Kirkwood4 that an idealization of this problem (film flow in a rectangular channel) can be solved by conventional hydrodynamics, and to give results pertinent to experiments such as those performed by LaMer and Blank. Consider a long rectangular trough of depth h and width 2a, filled with a liquid of viscosity q on top of which rests a film of surface viscosity rr; the film is subjected to a 6lm pressure gradient K along the axis of the trough. We choose the film surface as the zy-plane, the y-axis as the trough axis, and the z-coordinate as the depth coordinate. For steady flow, let L, (z,z) be the fluid velocity at x,z. Then V U = 0, - a _LzL a , O Lo L h (1) U(*a,z) = U(Z,h) = 0 U ( z , z ) = V( -z,z) (by symmetry)
dJ..(Z,O)
+ rlu. (2,O)
= -K
(2) (3) (4)
(1) Work was performed in the Amea Laboratory of the Atomic Energy Commission. (2) V. K. LaMer and M. Blank. J . Colloid Sei., 11, 608 (1956). (3) M. Blank and V. K. LaMer, THISJOURNAL, 61, 1611 (1957). (4) W. D. Harkina and J. G. Kirkwood, J . Chem. P h w , 6 , 53 (1938).
