0
Flow of Gases through Plastic Membranes a DAVID WILLIAM BRUBAKER AND KARL KAMMERMEYER S t a t e University o f lowa, Iowa C i f y , lowa
M
ANY iniportant technical uses of polymeric substances
number of standard cubic centimeters (0" C., 1 atmosphere pressure) of gas passing through 1 sq. cm. of film, 1 cm. thick, per second, per centimeter of mercury partial pressure difference across the film. The reproducibility, as pointed out in a previous publication, is about 470 when data are taken on samples of the same thickness. When samples of varying thicknesses are used, the precision becomes approximately 10% because of the limitations in the measuring of this dimension.
have heen made possible through the fact that their permeability t o gases is, in general, very low. Recently, several investigators (1, 6-7), using separate experimental techniques, have reported permeability data for a number of gas-film combinations. The investigation reported here v a s undertaken to obtain quantitative data on the rates of gas transmission through a number of polymeric films and to interpret the data in terms of the thickness, the molecular weight, the type of film, and also the effect of gas pressure and of temperature. Fifty-four polymeric membranes were investigated in this study. They are listed with their compositions in Table I, with the supplying company. The gases used in this evperimental work were obtained from commercial sources and were not further purified before use. The purities quoted by the suppliers in terms of percentage were as follows: Helium Hydrogen Carbon dioxide Oxygen Sitrogen
Experimental Results T'arious investigators have made extensive measurements of the permeability of plastic membranes, and their studies have shown that, generally speaking, the passage of gas through a plastic membrane involves several independent physical phenomena. This process of gas permeation may be stated briefly as a sequence of solution, diffusion, and re-evaporation of the permeating gas.
Approximately 100 99.8 99 5 99 6 9s 0
All permeability data reported here were obtained with essentially the apparatus that \vas described earlier ( 3 ) , shown in Figures 1 and 2. For all values of permeability except those taken a t a temperature below 0 " C., the apparatus made use of the principle of measuring the rate of change of volume of the permeated gas a t constant temperature and pressure. The operating technique is described in (5). At temperatures belou- 0 " C. a manometer was substituted for the glass capillary tube and the subsequent change in pressure was observed by means of a cathetometer. The temperature was maintained by using a bath of acetone and dry ice, or dry ice alone. (-4correction was made for the necessary increase in volume of the system due to the changes in elevation of the surface of the liquid in the manometer.) The results obtained by this method are much less accurate than those utilizing the glass capillary. However, as the freezing point of mercury is at -40" C., the glass capillary could not be used a t the lower temperatures. 411 the gas permeability data obtained in this investigation are reported in terms of the permeability constant, P, which is defined as the
Film Sample h-0.
Table I.
1
T r a d e Naine Visking Visqueen Visking Visqneen
5 6
Visking Visqueen Visking Visqueen Visking Visqueen
9
Visking Visqueen
2 3 4
7 8
Composit,ion Polyethylene Polyethylene Polyethylene DE-2500 Polyethylene DE-2400 Polvethvlene DE-2400 Polyethylene Pol yet hylene Polyethylene
......
......
......
10 11
12 13
14 15
16 17 18 19 20 21 22 23
Visking Visqueen Polythene Mylar (polyester) 25-V-200 Mylar (polyester) 25-7'-200 Mylar (polyester) 26-V-200 Mylar (polyester) 25-V-200 X y l a r (polyester) 50-V-200 X y l a r (polyester) 100-V-200 Mylar (polyester) 200-v-200 Mylar (polyester) 500-V-200 LMylar (polyester) (coated) Xylon film 3 Geon 101-EP-100, 261-30
film film film film film film film film film GP-
24
Vinyl chloride type
25 26 27
Trithene Trithene Trithene (plasticized)
28
Trithene (plasticized)
29
Pliofilm 120-P4
1148
List of Films Used
Polyethylene laminate D E 94nn Poiyethylene laminate D E 2400 Polyethylene Polyethylene Polvethvlene tereDhthalate pbly&er Polyethylene terephthalate polymer Polyethylene terephthalate polymer Polyethylene terephthalate polymer Polyethylene terephthalate polymer Polvethvlene tereuhthalate phlyier Polyethylene terephthalate polymer Polyethylene terephthalate polymer Polyethylene terephthalate polymer Fylon Polyvinyl chloride resin 100 Darts. dioctvl Dhthalate . . 30 parts Copolymer of vinyl chloride a n d vinyl maloate Monoohlorotrifluoroethylene Monochlorotrifluoroethylene Monoohlorotrifluoroethylene (plasticized) Monochlorotrifluoroethylene (plasticized) Rubber hydrochloride, 4 units plasticizer
Thickness, In. 0 0 0 0 0 0 0
n
001 003
0015 00156 0013 001 0075 0010
0 0022
Manufacturer Visking Corp. Visking Corp. Plax Corp. Plax Corp. Visking Corp. Visking Corp. Minnesota Mining and Mfg. Co. Visking Corp.
0 0039
Dobeckman
0 0370
0 0010 0 00025
Visking Corp. Du P o n t Co. D u P o n t Co.
0 00031
5,
0 00031
D u P o n t Co.
Co.
Pont ~ o .
0 00066
D u P o n t Co.
0.00075
D u Pont Co.
0 00125
D u Pont Co.
0 00175
D u P o n t Co.
0 00600
D u P o n t Go.
0 00060
D u P o n t Co.
0 001
D u P o n t Co. B. E". Goodrioh Chemical Co.
0 00176 0.00155 0,001 0,002 0.0035
Goodyear Tire R u b b e r Co. Visking Corp. Visking Corp. Visking Corp.
and
0.0065
Visking Corp.
0.00125
Goodyear Tire and Rubber C o .
1149
INDUSTRIAL AND ENGINEERING CHEMISTRY
May 1953
The work reported here was concerned with the correlation of gas permeation with the effects of pressure and temperature of the permeating gas, as well as the thickness, molecular weight, and type of polymeric film. The data are discussed separately under each of the above headings.
Effect of Temperature Permeabilities of four films t o helium, hydrogen, oxygen, and nitrogen have been established for the temperature range of 0' to 50" C. and are presented in Table VII. D a t a for 42 additional films for either helium and hydrogen or hydrogen and carbon
U
Figure 1. Plastic Film-Testing Apparatus 1. 9. 3.
600-pound pressure gage Gas storage tank I 1-inch steel flange Rubber gasket
5. 6.
Glass capillary tube Thermometer
4.
Table 1. Film Sample No.
30 32 33 34 35
36 38 39
40 41 42 43
-
7. 8. 9. 10. 11.
List of Films Used (Confinued) Composition
Trade Name
Rubber hydrochloride, 2 units plasticizer Cellulose acetate CA- Cellulose acetate (dasticized) 48 Cellulose acetate CA- Cellulose acetate (plasti43 cized) Cellulose acetate (plastiCelanese P903 cized) Celanese P911 Cellulose acetate (plasticized) Cellulose acetate (plastiCelanese P912 cized) Celanese S-600 Cellulose acetate (plasticized) Cellulose acetate (plastiCelanese P904 cized) Kodapak I 100 regular Cellulose acetate (plasticized) Kodapak I 100 rigid Cellulose acetate (plasticized) Cellulose acetate butyrate Kodapak I1 regular E a s t m a n Tenite 205-E- Cellulose acetate butyrate 22300-42 100 parts, plasticizer 3 parts Pliofilm 140-N2
44
Bakelite VB-1930
45
Visking Visten A
Figure 2. Gas Permeability Apparatus
Motor-driven vibrator Plastic film Filter paper film support 100-pound pressure gage 50-inch in I-pound manometer graduations'
Copolymer of polyvinyl chloride and polyvinyl acetate (plasticized) Acrylonitrile-butadiene rubber plasticized vinyl halide PI_
Thickness,
In.
0.00125 0.001
0.001
0.00125 0.00120 0.00125 0.00113 0.00125 0.001 0.001
0.001 0.0018 0.00106
dioxide are also given in this table. I n nearly all injtances the logarithm of the ~ermeabilities showed a strict straightline relationship when plotted against the reciprocal of the absolute temperature. These lines were established by taking, on the average, from five to ten readings for each temperature. The data reported in the tables were read Manufacturer from these plots of the actual experiGood ear Tire and mental data. Figure 3 shows a plot of Rugber Co. D u P o n t Co. the permeability constant versus the reDu P o n t Co. ciprocal temperature for a temperature range from -75" t o +50" C, for polyCelanese Corp. of America ethylene film. Although the deviation, Celanesf: Corp. of America or scatter, is much larger a t the lowest Celanese Corp. of temperatures, a straight line may easily America Celanese Corp. of be drawn through the entire temperature America Celanese Corp. of range for all three gases. In order to give America E a s t m a n Kodak Co. a clear picture of the reproducibility of these results a t the lower temperatures, Eastman Kodak Co. the individual determinations are preEastman Kodak Co. sented in Table 11. Tennessee E a s t m a n Corp. Although the straight line presented here is frequently encountered, it is not Bakelite Co. necessarily the rule ( 3 ) .
0.00188
Visking Corp.
0.0026
Visking Corp.
0.00111
Visking Corp.
0.00225 0.00082 0.00206
Effect of Film Thickness
'1'11
Visking Visten C
47
Visking Visqueen
Acrylonitrile-butkdiene rubber plasticized vinyl halide film Polyethylene mol. wt. 17-
48
Visking Visking Visking Visking Visking Viaking Visking Visking Visking
Polyethylene mol. wt. 20 000 Polyethylene mol. wt. 20'000 Polyethylene mol. wt. 21'000 Polyethylene mol. wt 21'000 Polyethylene mol. wt: 21'000 Polyethylene mol. wt. 21'000 Polyethylene mol. wt. 231000 Polyethylene mol. wt. 27,000 Polyethylene mol. wt. 29-
46
49
50 51 52 53 54 55 56
Visqueen Visqueen Visqueen Visqueen Visqueen Visqueen Visqueen Visqueen Visqueen
18,000
30,000
Visking Visking Visking Visking 0.001 Visking 0.0015 0.001125 Visking 0.001125 Visking Visking 0.001 0.00225 Visking
Corp. Corp. Corp. Corp. Corp. Corp. Corp. Corp. Corp.
Permeability data were obtained on five samples of Mylar (polyester) film and on ten samples of polyethylene film as well as on two samples each of plasticized and unplasticized Trithene films of varying thicknesses. These data are shown in Tables 111 and IV. A comparison of the data in Table I11 for samples 15 t o 20 (these samples were obtained a t the same time and thus should
INDUSTRIAL AND ENGINEERING CHEMISTRY
1150
Table II.
Permeability at Low Temperature
[Polyethylene film sample 3. Hydrogen Temp., 0
c.
- 19 - 22 - 22 - 67
- 69 -71 - 72 - 73 - 73 - 73 .~
.-
- 74 -75
- 75
- 75 - 75 - 75
P
x
Permeability, P
sq. c m - c m . Hg)
1
Helium Temp., 0 c. P x 108
100
- 66 -66
0.082 0 070 0.063 0 00219 0.001565
0.00143 0.00131 0.00132 0.00123 0.00106 0.00123 0.00081 0.00065 0.001045 0.00115
108
(P =
CC.-CIII./G~~.-
Nitrogen Temp.,
c.
P
-66.5
x
108
0.000032 0.000025 0.000028 0.000023
- 66 - 67 - 68
- 66 - 66 -67
0.00151
x
0.00162
be comparable) shows that P values varied by approximately 10% a t maximum spread, and that this variation was in no way a function of thickness. The measurement of the film thickness is subject t o variations of about this magnitude, or even more. Thus. the agreement between the data is satisfactorv. The conclusion seems justified that the thickness has no effect on the value of P. The data for sample 14 are included as being of interest, considering t h a t this sample was obtained at a different time than the others, and thus may have been prepared at a different time. The values agree satisfactorily with those of the other films. Sample 16 consisted of two films in series, without any Iaminating compound. Under conditions of the experiment, the two films presented the picture of a film with double thickness. This is in accordance with expectations. Sample 21, a “coated” Mylar (polyester) film, shows somewhat different perme10 ability values. 5 The data on polyethylene films seem to 4 3 bear out the conclusion previously reached P -that is, t h a t the permeability is not affected by the film thickness. Here too, I the variance of the film thickness is much 5 greater than in the case of the Mylar 4 (polyester) film. 3 The data in Table I V indicate t h a t 2 thickness has no effect on the value of the 0.1 permeability constant-that is, the gas 5 5 rate of flow decreases proportionally with increases in thickness. While the varia4 I3 tion in thicknew is not so large as with the g P polyethylene, it is significant t h a t the apu parent effect of thickness is the same on 10-g d such a different type of plastic film. * 5
-
The results obtained for polj-ethylene film with hydrogen gas are presented in Table V. The maximum spread between the values is less than 4%, which is within experimental accuracy. As in the case of the film thickness variations, there is no effect of pressure on the permeability constant, P , a t least for pure gases.
Effect of Molecular Weight
- 68
- 68 - 68 - 68 - 68 - 68
Vol. 45, No. 5
The permeabilities of ten samples of polyethylene film having a variation in nominal molecular weight from 17,000 to 30,000 have been obtained for carbon dioxide and hydrogen and the data are presented in Table VI. ,4 comparison of the data shows that although there are wide differences in the individual permeabilities, there is no definite correlation or trend with molecular weight. This phenomenon may be due either t o inherent difficulties in the determination of the molecular weight, or t o other factors involved in the manufacture of the film. Other investigators also have been unable to observe any definite relation between molecular weight and the rate of gas permeation ( 2 , 4).
Effect of Plasticizer
The effects of plasticizer on the gas permeability ale presented in Table IV for Trithene and in Figure 4 for cellulose acetate. Although data on a variety of plasticizers in varying amounts are to be desired, it is of significance to observe the effects of one plaqticizer on varying amounts, as shown in Figure 4. The effect of plasticizer at different temperatures is obviously not the same. I n general, however, the higher the temperature the greater the change in permeability with plasticizer content. The results also indicate that carbon dioyide permeation is increased much
‘
Effect of Pressure Because of experimental limitations, the effect of variations in pressure at present could be determined only a t superatmospheric pressures. While tests below atmospheric pressure would be desirable, the range of the authors’ present equipment did not allow such measurements. The experiments were carried out with the same gas atmosphere on both the high and low pressure sides of the membrane. This was done for the sake of convenience, as it has been established that the effective pressure difference is the difference in partial pressure.
4
4
I
3
-.
ai Y
10-~ 5
FIGURE 3
GAS PERMEABILITY FOR POLYETHYLENE FILMS
2 10-4
5 4
3 2 10-6
3.2
3.6
4.0 iOO/T
4.4
4.8
5.0
INDUSTRIAL AND ENGINEERING CHEMISTRY
May 1953
Table V.
1151
Effect of Pressure
(Polyethylene film sample 3. Hydrogen gas, temperature 50' C.) High Pressure Hg, om. (gage)
in. Lb./sq. gage
27 51 154 309 4434
53 10 30 60 90
6 7 9 9
a
Low Pressure Lb./sq. cm., Hg,abs. in. gage 74.25 -0 33 74 25 -0 33 74 25 -0 33 74 25 -0 33 74 25 -0 33
Permeability p x 100,cc:Cm./Sec.-Sq. Cm.-Cm. H g
0 258 0 258 0 260 0 252 0 255
more than is that of hydrogen. I n fact, a t 0" C. the carbon dioxide permeability is actually decreased with initial plasticizer addition below t h a t of hydrogen, but then with addition of more plasticizer, the permeability of carbon dioxide becomes greater than that of hydrogen. At both 25 and 50 O C. the permeability of carbon dioxide is less than t h a t of hydrogen initially and then i t becomes greater as the plasticizer content increases. This crossing of the hydrogen line by the carbon dioxide line occurs a t a lesser value of plasticizer content as the temperature is raised.
Table VI.
O ' A '
'
'
'
'
20 '
.
'
'
Va PLASTICIZER IN P L A S T I C Figure 4.
'
30
'
'
'
Effect of Plasticizer Content on Permeability Constant of Cellulose Acetate
Film
No. 47
Effect of Molecular Weight of Polyethylene , . Film on Gas Permeability
Gas
Thickness, In.
xomina1 Permeability, P X 100 Molecular Cc.-Cm./Sec.-Sq. Cm.-Cm: H g Weight 0' C. 25O C. 50° C.
coz
0.00111
17-18,000
coz
0.00225
20,000
coz
0.00082
20,000
cot coz
0.00206
21,000
0.001
21,000
coz
0.00150
21,000
co2
0.001125
21,000
coz H2 cos HZ coz
0.001128
23,000
0.001
27,000
HZ
48
Hz
49
H n
Table 111. Sample
No.
Effect of Film Thickness on Permeability P x 100,
i Thick l ,,ess, ~ Cc.-Cm./Sec.-Sq. Cm.-Cm. Hg In. 25' C. 50' C. Du P o n t Mylar (Polyester) Film
0.00031 0.00031 0.00066 0.00075 0.00125 0.00175 0.00600 0.00060
0.097 0.106 0.105 0.115 0.110 0.107 0.108 0.067
Polyethylene Film 0" C.
0.001 0.003 0.0015 0.00156 0.0013 0.001 0.0075 0.0022 0.0370 0.001
1 2 3 4 5 6 7 9 11 12
Table IV.
26 27
28
0.200 0.220 0.220 0.238 0.230 0 235 0 216 0.180
51
Hz
52
H2
53
HZ
54 55 56
0.0025
29-30,000
Hn
25' C. 1.17 0.95 e.82 0.794 0.855 1.12 1.09 1.250 1.02 1.20
1.85 5.7 1.35 3.85 1.80 '5.30 0.850 2.60 1.40 4.80 0.990 3.00 1.28 4.10 0.930 3.65 4.80 1.60 1.19 3.40 5 98 1.90 1.00 2.90 1.65 4.613 0.830 2.50 1.280 3.135 1.10 3.10 1.15 3.28 1.05 3.85 1.45 4.40 1.05 3.10
50' C.
Effect of plasticizer on Trithene Film
I n Table IV the effect of plasticizer on the rate of carbon dioxide and hydrogen permeation through Trithene is presented. Again the rate of gas permeation increases with the addition of plasticizer. However, in this case the relative rates of carbon dioxide and hydrogen remain in the same order with the addition of plasticizer.
Effect of Polymeric Film
Film Thickness, In.
Permeability P X 109, Cc.-Crn./seh.-Sq. Cm.Cm. H g 0 ' C. 25O C. 50' C.
COz HZ
0,001
0.0035 0.0138 0.0238 0.0322 0.0950 0.2350
COz H2
0,002
0,0032 0,0139 0.0241 0.0320 0.100 0.242
Trithene cized htl%% molecular COz weight Trithene Hn
0.0035
0.0360 0.1820 0.750 0.0775 0.3200 1.080
Conclusions
Trithene plastioised'with low moleoular weight Trithene
0.0065
0.0310 0.1780 0.80 0.0840 0.3720 1.31
Permeabilities have been obtained for a variety of gas-film combinations, including experimental and commercial films and a large number of commercially important compounds.
Sample
No. 25
Ha
~
Gas
He He He He He He He He
14 15 16 17 18 19 20 21
50
0.51 0.40 0.55 0.240 0.37 0.288 0.340 0.28 0.50 0.3555 0.530 0.280 0.510 0.240 0.400 0.340 0,350 0.33 0.400 0.305
Type Trithene, no plasticiser Trithene, no plasticiser
Gas
COz Hz
The permeabilities of various types of plastic membranes are reported in Table VI1 for several different gases. Each type of polymer exhibits its own distinct property toward any one gas, but there is no correlation between the type of polymer and the rate of gas permeation. The rate of permeation for any one gas tends to decrease as the hydrophilic nature of the polymer is increased. This is in agreement with the findings of Reitlinger ( 4 ) .
INDUSTRIAL AND ENGINEERING CHEMISTRY
1152
Table VII.
Permeability Constants of Various Gas-Film Combinations at Ordinary Temperatures P x 108, P x Cc.Hg Gas 0' C. 25' C. 5 0 ° C . He 0.210 0.70 2.00 Hz 0 32 1.17 3.50 0.165 0.62 1.90 He Hz 0.260 0.95 2.95 He 0.163 0.555 1.56 Hz 0.230 0.82 2.46 0 2 0.0695 0 306 1.07 3-2 0.0160 0 093 0 425 COz 0 . 4 0 5 1.32 3.65 He 0.147 0.513 1.47 Hz 0.202 0.794 2.48 Oz 0.0575 0.278 1.06 X z 0 0127 0.080 0.378 COz 0 . 3 2 0 1.18 3.60 He 0.180 0.615 1 74 Hz 0.212 0.855 2.76 0 2 0,0774 0.350 1 26 Sz 0.0178 0.123 0.615 1.40 3 75 COz 0 440 He 0.22 0.68 1.83 Hz 0.33 1.08 3.00 He 0.23 0.82 2.45 Hz 0.32 1.25 4.00 He 0.30 1.00 2.85 1.421 4.40 Hz 0.39 1.02 3.05 Hz 0.290 COS 0.681 1.90 4.73 Hz 0.402 1.20 3.11 Permeability Constant
- Cm./Sec.-Sq. Cm.-Cm'.
Sample Film
NO.
1
Polyethylene
2
Polyethylene
3
Polyethylene
4
5
Polyethylene
Polyethylene
8
Polyethylene
9
Polyethylene
10
Polyethylene
11
Polyethylene Polyethylene
12 13
Mylar (polyester) film 25-V200
He H2
0 042 0.025
COz
O',OO4G
Oz Nz 14 15
16 17 18
19 20 21 22
Mylar (polyester) film 25-V200 Mylar 200 (polyester) film 25-VMylar (polyester) film 25-V200 Mylar (polyester) film 50-V200 Mylar (polyester) film 100V-200 Mylar (polyester) film 2OO-V200 Mylar (polyester) film 5OO-V200 Mylar (polyester) film (coated) Xylon film 3
Vol. 45, No. 5
....
Sample 23
Film PVC with plasticizer
24
Vinyl chloride t y p e
NO.
25
Trithene
26
Trithene
27
Trithene w-ith plasticizer
28
Trithene with plasticizer
29
Pliofilm 120-P4
30
Pliofilm 140-1u2
32
Cellulose acetate
33
Cellulose acetate
34
Cellulose acetate
35
Cellulose acetate
36
Cellulose acetate
37
Cellulose acetate
0.097 0.058
38
Cellulose acetate
39
Cellulose acetate Cellulose acetate
0.200 0.120 . . . . Very low . . , . Verylow 0 . 0 1 1 8 0.027
He
....
0.097
0.200
40
He
...
0.106
0.220
41
Cellulose acetate
42
Cellulose acetate butyrate
43 44
Cellulose acetate butyrate Copolymer PVC and P V
....
0.105
He
....
0.115
0.238
He
....
0.110
0.230
He
....
0.107
0.238
He
..._
0.108
0.216
He COz Hz
....
0.067 0.00272 0 . 0 3 1 0.029 0.100
0.180 0,145
He
0.220
acetate
45
Visten A
46
Visten C
The effect of temperature upon the permeation of gases through plastic membranes is not readily predictable, although usually a straight line is obtained when the logarithm of the permeability constant is plotted against the reciprocal of the absolute temperature. Whenever possible, permeability data should be presented for a t least three temperatures. For polyethylene film, the apparent straight-line relationship seems to hold from -70" to +50" C. for nitrogen, hydrogen, arid helium gas. It has been found that the rate of gas flow decreases proportionally as the thickness is increased. Similarly, the gas rate of flow increases proportionally with increases in the partial pressure difference. Thus, neither the thickness nor the pressure differential has an effect on the permeability constant. -4rather wide range of thicknesses has been used, as well as diversified types of membranes. Unfortunately, there seems to be no apparent correlation between the nominal molecular weight of the membrane and the rate of gas permeation. A wide range of permeability constants was found, but no correlation could be established. The effect of plasticizer is, in general, that of increasing the rate of gas permeation. The presence of plasticizer may also cause a change in the order of gas permeation. The higher the temperature, the less the plasticizer content necessary for the change to occur. The degree of change of permeation is also affected by the nature of the gas. All data available so far indicate the desirability of undertaking extensive studies on the effect of plasticizers on gas permeability.
Constant Cc.Cm.-Cm,' H g 25O C. 50' C. 0.930 2.950 1.290 3 . 0 0 0.80 1.75 1.360 3.22 0 . 0 1 3 8 0.0238 0.095 0.235 0.0139 0.0241 0 . 1 0 0 0.242 0.182 0,780 0.320 1.080 0.178 0.80 0,372 1.31 0 . 1 4 8 0.528 0.226 0,710 0.064 0.230 0 , 1 6 0 0.333 0.630 1.630 0.581 0,170 0.568 0.920 0.800 1.390 1.88 3.30 1.23 2.50 1.21 2.37 0.87 1.95 0.922 2.39 0.880 1.78 0,841 1.82 0.720 1.61 0.732 1.22 0 779 1.43 0.645 0.995 0.800 1.53 1.19 2 23 0.89 1 88 0.821 1 29 0 775 1.42 3.18 5 66 2.10 3 85 1.43 2 75 4.03 5 30 2.80 3.90
He
0.920 0.99 0 27 0.065 1.690 0.200 0.360 0,419 0.360
0.305 0.320 0.061 0.0098 0.480 0.0365 Hz 0.0790 COP 0 . 1 0 0 Hz 0 087
Hz
Oz S z COz COz
0.295
108,
Permeability Cm./Sec.-Sq. Gas 0' C. COz 0.248 Hz 0.480 COz 0.318 Hz 0 495 COz 0 0033 Hz 0 0322 COz 0.0032 Hz 0 0320 Con 0.0380 Hz 0.0775 COz 0.0310 Hz 0.0840 Con 0.0340 Hz 0.0585 COz 0 0143 Hz 0 0875 Con 0 211 Hz 0 260 COz 0.320 Hz 0,320 COz 0.960 Hz 0.545 COz 0 . 5 7 6 Hz 0.338 COz 0 313 Hz 0.398 COz 0 . 3 4 8 Hz 0.280 COS 0 . 4 0 0 Hz 0.379 COP 0 . 3 9 5 Hz 0.376 COz 0 , 5 7 0 Hz 0.370 COz 0 490 Hz 0.380 Con 1 . 7 0 Hz 1.20 He 0.735 COz 2 . 9 8 He 1.89
2.45 2.65 0.95 0.34 4.95 0.84 1 320 1.410 1 350
As has been the experience of other investigators, there appears to be no apparent correlation between the permeability constant and the type of plastic used.
Acknowledgment Most of the work was carried out under sponsorship of the United States Atomic Energy Commission in connection with gas separation studies. Some data, particularly on helium transmission, were obtained for the Aeronautical Research Division of General Mills, Inc., Minneapolis, M n n . The support of these organizations is gratefully acknowledged. Furthermore, the authors wish to express their appreciation to t,he many industrial concerns for their help in supplying film materials so essential to the investigation. The names of the firms whose products were included in the present study are listed in Table I. Literature Cited (1) Amerongen, G. J. van, J. Polymer Sei., 5, 307-32 (1950). (2) Barrer, R. M., "Diffusion in and through Solids," London,
Cambridge Press, 1941. (3) Brubaker, D. W., and Kammermeyer, K., ISD. ENG.Crmhf., 44, 1466 (1952). (4) Reitlinger, S. A,, Rubber Chem. TechnoZ., 19, 385-91 (1946). ( 5 ) Shuman, A. C., IND.ENG.CHEM.,ANAL.ED.,16, 58 (1944). ( G ) Simril, V. L., and Hershberger, A , , Modern Plastics, 27, 95 (July 1950). (7) Todd, H. R., M o d e r n Packaging, 18, 124 (December 1944). RECEIVED for review October 13, 1952.
ACCEPTED J a n u a r y 15, 1953.
