Permeability of Protective Glove Materials to Tetraethvllead and Ethylene Bromide J
GEORGE CALINGAERT AND H Y M I S SHAPIRO Ethyl Corporation, Detroit, Mich.
A
LTHOUGH several new considerable number of plastics and elastomers were high humidity, such as tlic types of protective tested for permeability to tetraethyllead and ethylene Gulf Coast. After this inworkgloves have been manubromide, with a view to the manufacture of better prorestigation n-as statted, a, factured during the past fentective work gloves; t h e principal test employed was a commercial glove of ti-atervears,niost commercial gloves gravimetric disk diffusion test. Several materials were insolubilized PIT-4 was deare unsuitable for the h a w shown to be from 10 to over 1000 times as impermeable to veloped, but this type is dling of inany toxic liquids. these liquids as neoprene. 3Iost of the impermeable difficult to plasticize. Represent,ative of these liqmaterials were unsuited for glovemaking, but t h e nylons Many methods have lwrn uids are tetraethyllead and seemed proinising and were investigated extensive1:-. used for testing permeability, the ethylene halides, the inGloves were fabricated of nylon alone and also of iiylo~i both t,o liquids and gases (3, gredients of the Ethyl brarid compounded with neoprene, and the nylon-neoprene 4 ) . Until recently, horerer, gloves are now in commercial production. A gravimetric felr laboratories have 1)ecii of antiknock compound, n-hich diffuses readily through interested in the permeation method of testing the permeability of whole glores i s described. of organic solvents through the skin. Since there is little in the literature on the gloves, as is obvious from the fact that the glow s p ~ r i pernieation of these liquids fications ( 2 ) of the .Imericaii Standards ,issociation list no t,hrough plastics and elastomers. ii preliminary investigation iras undert,aken t o provide this type of background inforniatiori for specific test method. There appears t o have been practically the development of superior gloves. no experimentation t o relate the extent of permeation of solvents Historically, the paucity of ela,stomers used in glovemaking is with dermatitis or any other physiological consequence of 1x’rworthy of comment. Prior t o about a decade ago, mcation. - . !\-hen neoprene gloves were introduced, natural rubber was the only elasPER3IEABILITY TESTS tomer used, despite the fact that llitchell ( I O ) indicated as far back as 1831 that rubber has high permeabilities for many gases: MATERIALS.I n this investigation the field of commercially before the present investigation it pyas also knon-n that several available plastics and elastomers was surveyed; those matei,ialu synthetic rubbers have high permeabilities tov-ard such coniTrhich n-erc believed promising in any type of application irere pounds as tetraethyllead and the ethylene halides (6). Recently, tested for pernieability toyard tetraethy1lea)d and ethylene commercial gloves have been made of polyvinyl alcohol polymer bromide, and, in many instances, toward ethylene chloridr as well. SelT- types of commercial gloves n-ere also tested as t 11c.y (PS’A). These gloves are linon-n t o be very resistant t o many organic solvents (8) including those n-it11 which this paper is became available. concerned, but they absorb lrater quickly. Consequently, they ~ I C T H O DThrec S. types of gravimctric permeabilit,y tests n-ere used. Tn-o of thesc! a swelling test and a disk diffusion cannot be Trashed conveniciitly aiid ai’e of IitTle use in regions of
15 Minutes
4 Hours
25 Hours
Figure 1. Permeation of Dyed Equimolar Mixture of Tetraethyllead and Ethylene Bromide through Keoprene and Nylon-Neoprene Gloves of Equal Thickness Left glove, nylon-neoprene, approximately 0.5% nylon: center glove, neoprene; right glove, nylon-neoprene, approximately 1.0% nylon
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February 1948
INDUSTRIAL AND ENGINEERING CHEMISTRY
TO TABLE I. DISK PERMEABILITY TESTSO F MATERIALS
INGREDIENTS
OF.ETHYLBR.4ND
OF
333
ANTIKNOCKCOMPOUKD
Total Wt. Loss, Mg. Time, Hr. Permeability4 Specific Permeabilitya ThickMaterial ness,In. T E L CzHiBrz CzH&Iz T E L CzHdBrz CZHICIZ T E L CzH4Brz CzH4Clr TEL CzHaBrz CIH~CII 6b 11 b 22 22 22 .... 0.037 .... ..... PVA-coated cloth 24 24 0,012 28 0.26 ..,. 38 0:35 4.2 3.1 Insolubilized 23 23 0.03 1.0 0.01 0.45 2.5 .... 0.15 PVA A699 d o v e iinsolubilized) 0 . 0 1 5 25 32.5 3616 0.011 ... ... .... 360 ... 1860 10 50 21 21 0.020 0.7 o : i i 1 9 . 7 15:Q 2.2 320’. 390 20 78 7.4 0,020 28.9 150 0.6 0.6 180 24 0.6 8.9 580 82 24.3 164 27 0.75 0,020 48.6 160 8.0 0.75 0.75 970 * 490 R 203 10 20 20 2.3 0.11 793 160 0.070 20 8.8 620 105 20 49 27.2 58,2 0.030 103 33 0.4 1750 1.1 820 0.4 Same 1410 14.9 21 1 . . . c 21 21 890 0.060 0.01 .... 0.6 ... Thiokol 3000-FA2 1210 4 12.8 21 21 21 0.060 1110 0.04 770 11.7 2.4 700 Tbiokol 3000-FA6 12.0 1160 21.5 21.5 21.5 0,0017 616 35 0.61 20 11 0.36 Saran B-115 6.4 23 23 0.12 0.0015 8.6 6.8 0.07 Saran X-366 0.08 .... 0.11 ..... ... ... .... .... ... ... .. ..... Leather glove ...d ..,. ... ... ... ... .. Leather treated with soap in glycerol 22 0.001 33 40 32 22 22 0.40 0.33 0.32 0.40 0.32 Cellophane 0.33 0.001 20 20 20 0.12 0.12 8 20 0.22 Moistureproof cellophane 0.09 0.09 0.22 l1 e 505 , . . 0.003 25 ... 4.5: 75 Patapar PU-0. 35 .... . . ... 406.. 9 61.7 . . 22 0,009 7 4: i Polythene JR-6287 37 2.0 18 ..... 24 109.4 28351 . . 24 0,008 Polyvinylbutyral on cloth 26.3 .... 8 210 1.0 . . . .. 4057~’ .., 24 0.007 338 24 37.6 .... 22 260 Same 3.1 ..... .. 21 3 . 0 2976 21 0.026 0.03 31.4 ... 820 Igelite glove0 .... ..... 0.8 13 223 431 20 0.010 0.55 90 0.14 Vinylite VYNS on cloth 0.55 174 900 1.4 1700 16 155 222 0.135 0.7 0.7 49.1 Koroseal N F W F 0.7 71 6600 5.1 9600 690 142 440, 20 255 45.0 0.012 0.7 140 2.8 1700 0.7 Koroseal 34 540 37 ..... 0,028 20.4 0.6 .... 0.40 Vinyl chloride A-1008 0.6 .... ... 11 3400 14;SOO 24 0.0013 20.7 Pliofilm 20.7 36.5 159 0.26 20.7 0.34 47 210 Vinyl chloride-vinyl acetate 0 024 5 12 384 20 2.1 copolymer 1.3 78 50 I900 1.1 0.06 1.4 Carboxymethocel A 0 , 0 0 3 1 1 . 2 296 24 . . . 24 Low viscosity 2.7 ... 0.10 .... 0.3 8 . 104.2 433.4 24 0,001 24 High viscosity ... 0.96 4.0 .... 4 1.0 Carboxymethoccl S 0,003 14.7 252 . . 24 24 L o w viscosity 0.14 2.3 0.4 7 0.002 70.7 333 21 21 High viscosity 3.5 1.5 7 0.75 0,002 74.0 301.5 24 . . 24 Methocel 1.5 2.8 1.4 0.68 6 0.002 1109 21 188 20.5 Methocel 400 4.0 1.98 12.0 24 0,029 2970 59 44 24 . 28 Neoprene N51 8.7 0.3 810 0.022 12,662 137 24 24 Keoprene 2600 1.3 117 29 .. 0.008 24 24 435 13,836 Neoprene SW 129 ... . . 33 4.1 1000 0.0022 24 80 13 24 Nylon 6.4 sheet 0.12 , . 0.74 0.26 1.6 . . . 0.0022 70 24 24 Cast nvlon GB sheet 8 ... 0.65 0.07 0.15 ... 1.4 ped nylon 0.0015 8.3 79 . . 92 70 0.24 0.02 0.03 0.4 0.0015 13.6 2410 67 ... 68 7.9 0.05 ... 12 0.08 0.037 6 11b 21 9b 21 .... 0.01 21 0.4 leather 1Jnknown 51.9 46 18 17 0.59 glove 0.65 .... , . . ,.. Permeability is expressed as weight loss in milligrams per square centimeter 6 Film disintegrated. of area per hour. Specific permeability is obtained b y multiplying permead Liquid seeped through almost immediately. bility b y total thickness of material in thousandths of a n inch, to convert all Tetraethyllead seeped through in less than 2 hours. permeabilities to a common basis for rough comparison. f Plasticizer extracted.by the ethylene bronude. , b Gain in weight caused b y absorption of water from air. Manufactured in Germany for use in German tetraethyllead plant.
’
....
. I .
...
... ...
...
Q
test, were made on small sections of material, using small amounts of liquid. The third type, used exclusively to check whole gloves, was a diffusion test made by filling a glove with a mixture of tetraethyllead and ethylene bromide and measuring the rate of tetraethyllead permeation. The principal method of test, the disk diffusion test, was carried out as follows: A 25-ml. sample of test liquid was placed in a 70ml. glass bottle, 2.39 cm. in inside diameter, having a screw top, and a wall 0.33 cm. in thickness ai? the lip, which was lapped square to the bottle. A disk of test material, 2.95 cm. in diameter, was pressed against the lip by a neoprene gasket, followed by a copper ring and the plastic screw cap, out of whicha4.5 sq. em. hole had been punched; no sealing compound was used a t the edge of the test disk. The diffusion area of the test piece was a proximately 4.5 sq. em. After the gross weight of the assembfi was obtained, it was inverted for 15 minutes and reweighed. Pinholes or a leaky fit could usually be detected by an abnormal loss in weight during this period. Those assemblies which were not defective were stored in an inverted position, allowing free access of air, and then were reweighedb usually after about 24 hours. The room temperature was 25 * 3” C. Unless there was a detectable leak during the entire period of the test, the loss in weight was regarded as a measure of the permeability of the material. For evaluating whole gloves of experimental production lots, the following procedure was used: The gloves, usually turned inside out if they were not canvas-backed, were suspended from metal ring holders as shown in Figure 1. To each love was added 700 ml. of an equimolar mixture of tetraethJ1ead and ethylene bromide, and the glove was hung in a 2-liter bath of hydrocarbon solvent, which had a negligible effect on the glove. The inner and outer liquid levels were adjusted to equality. The entire solvent bath was replaced a t each sampling period, and the liquid was then analyzed for lead by A.S.T.M. method D52f3-42 (1).
RESULTSOF PERMEABILITY TESTS. The resblts of the swelling tests are not given because they are of less value for predicting the usefulness of a glove material than are the results of the diffusion tests. Although swelling tests are widely used in rubber and plastics laboratories (7), Proske (11) has shown that there is no simple relation between swelling and the deterioration of physical properties, that the tests often give false results because of extraction of ingredients soluble in the test liquid (@, and that both volumetric and gravimetric swelling tests have inherent faults necessitating careful interpretation of the results. The averaged results of the disk permeability tests are given in Table I, which lists, for each material, the thickness of the test disk, the total weight loss for each solvent, the duration of the test, and the permeability for the actual thickness of the test disk. The disk diffusion test is somewhat similar t o B.S.T.11. tentative test D814-44T, which was published after much of the present work was done. Neither test is very reliable, but the present test appears to be better adapted to testing materials for glove use, and certainly it is reliable enough for this purpose. The tests were usually run in duplicate or triplicate, and t h e effect of flaws was minimized by the use of small disks. The A.S.T.M. method requires a disk several times as large, which in an experimental material may be more difficult to cast or dip free of flaws. Moreover, the A.S.T.M. method requires t h a t the disks be held “in contact with the.fluid for five days before starting measurement of the loss in order t o permit the rate of diffusion of the fluid to become uniform.” Although it is known that the rate of diffusion does not become constant in a short
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INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 40, No. 2
over 1000 times as impermeable t o trtraoth\~llratlarid et hvlisrir bromide as is a good grade of neoprene.. REQUIREMENTS OF GLOVE MATERIALS
PIONEER N R W 3 2 NEOPRENE G L O V E , 0.016. THICK
W 4
W K P
40PIONEER
w
EW51
NYLON- NEOPRENE GLOVE, APPROX. 0 . 0 2 5 ” THICK
J
30-
’
-1 j
PIONEER N R W 5 I NEOPRENE G L O I E , APPROX. 0 . 0 2 5 THICK PIONEER E W 3 2 HY LON N E 0 PR E N E GLOVE, ~
IO
20
T & ~ ~ N 0.006‘- 0.00 THICK
25 60
~
8 0 100 ZOO
TIME, HR
Figure 2. Typical Curves for Permeation of Equimolar Ilixtures of Tetraethyllead and Ethylene Bromide through Nylon-Containing Gloi cs
time, the permeability during the initial period is most important, from a safety standpoint’, and in the prebent disk test the factor of nonuniformity of diffusion is minimized by the use of thin disks. With such highly penetrating liquids as tetraethyllead and ethylene bromide, not only is the five-day premea;wrement period time-consuming and inconvenient, but the disk n-ill somet,imes be completely dissolved. For materials of low pernieabilit,y, such as the nylons, the individual \Teight losses in the present tests were so small that in some instances they differed by as much as several hundred per cent. This is not surprising, for minute thin spots and pinholes of a capillary nature are difficult to detect, and very slight leaks at the edges would be significant under these conditions. The tests on materials of high permeability shox a much better reproducibility since the defects had comparatively little cffect. Although the thickness of the test disks varied considerably, for rough comparisons it is quite safe t o consider the permeability as inversely proportional to the thickness (3, 4),so that the results may be compared on the same basis. No attempt \vas made in these tests t o separate the permeability results into the component factors of solubility and diffusivity ( 5 , 2 2 ) . Also, although it is IrnoJTn that the permea,bility of some resins varies somewhat with temperature ( 5 ) , no measurements Irere made except at room temperature. Of the materials tested, the cellophxnes, t,he nylons, polyvinyl alcohol, Compar A-699, Dunnflex, Che IIethocels, the Carboxymethocels, and Saran X-366 have low permeabilities for the two liquids. Leather, the polyvinyl chlorides, polyvinyl butyral, Plygarb, several synthetic rubbers, Patapar, nitrocellulose, the Thiokols, the Koroseals, Saran B-115, Pliofilm, and vinyl chloride-vinyl acetate copolymer have comparatively high permeabilities. ‘l’he relatively impclrineable materials are from 10 to
~
In general, the resu1t.s of the investigation are in ag the current theories of solubility of plastics and c 6, 8 ) . The type of elastomer which is impervious i n tiaturc is characterized by a nonlinear polyin tructure, a considcrabl(~ i hctiyeen the rhains, a amount of crosslinlring and interac tendency to\vard crystallinity and fibrous structure, a high degree of polymerization, a high molecular m i g h t , a,ntl a tnolecula], structure (of the inoiioincric unit) dissiinilar to those of the permeating liquids. Unfortuiiately, the very properties of crosslinking and functional grouping which are vitally rlecrssary for impermeability are the properties \rhich decrease the stretch and flexibility. Therefore, it is patent that materials suitable for thr fabrication of gloves resistant to such liquids as t)c!truethyllead and ethylene bromide are a difficult compromise bctn-een 21 t’hree-dimensional, insoluble, infusible, and intrxtahle material, on the one hand, and a linear, soluble, low melting, riibbery, a,rict rrralr inatrrial on the other. In addition to giving a8dcyuatcprotection against permeating liquids, work gloves must be reasonably durable and cooiiomic:al, and should have thc several eharacieristics n.hich wr! ma:?’ lump toget1ic.r in the term "comfortable." These additional desidrrata malic it impossible t o prcpare or use gloves of many of the most ~imperineable ~ E resins. For t h s e reasons difficulty n in this inve,?tigation in making gloves of such materials as h n r r flex and m~,ter-insolubilized PVA. FABRICATION OF ALL-XYLON AND NYLON-NEOPRENE GLOVES
Of thc Insterials slion-n t o have low permeabilities for tetrarthyllead and ethylene bromidr, the nylons n-ere chosen as the most promising for extensive experimcntation on glove manufacture. After some experimentation on solvents for dipping solut,ions,all-nylon gloves ryere prepared and tested on a laboratory scale. This work was not entirely successful, since the inherent stretch of nylon is much less than that of rubber. Only the nylon type 8 mas comfortable in the finished form, and then only rvhen the gloves m r e thin; the thin gloves m r e too fragile for use on rough jobs. Subsequent cooperative viork with the Pioneer Rubber Company led to the commercial production of gloves compounded of nylon and neoprene. The exposed surfaces of these gloves are all-neoprene, and the gloves have the desired attributes of allneoprene gloves. I n fact, the nylon can be detected only by laboratory methods. Several experiments have indicated that, this type of glove is appropriate for handling hazardous liquids other than tetraethyllead and ethylene bromide. PERMEABILITY TESTS OF WHOLE GLOVES CONTAIYING NYLON
Typical permeability tests of an equimolar mixture of tetra,ethyllead and ethylene bromide through whole nylon and nylonneoprene gloves are shown in Figure 2, in irhich the permeation of tetraethyllead is compared with that of a high quality neoprene glove. The degree of impermeability of such gloves is dependerit mainly on the amount of nylon incorporated. Each of the nylonneoprene gloves tested for Figure 2 coiit,ained about 0.7 gram of nylon, or about 0.5% and 1.0% in the EW51 and EK32 types, respectively. The all-nylon glow neighed about 13 grams. Thin neoprene and nylon-neoprene gloves of the types tested for Figure 2 n-ere filled with a similar mixture of tetraethyllead and ethylene bromide (containing a dye ordinarily used in antiltriock compound) and suspended from metal holdrrs. T h e dye is a visual indicator of the time of safe use of the g10vc:s. h photographic record of the test, is shnan in Figure 1.
February 1948
INDUSTRIAL AND ENGINEERING CHEMISTRY ACKNOWLEDGMENT
The authors wish t o acknowledge the assistance of Wilma J. Reusch and the cooperation of the Pioneer Rubber Company LITERATURE CITED
(1) Am. SOC.Testing Materials, Standards, Part 111, A S T.M. Method D526-42. (2) Am. Standards Assoc., “Ameriran War Standard Specifications for Protective Occupational Clothing, Chemical Resistant Gloves” (July 21,1945). f~, 3) Barrer. R. M..“Diffusion in and through Solids.” Cambridae, Cambridge University Press, 1941. -
335
(4) Carson. F T.. Natl Bur Standards, Misc. Pub. M127 (Aug. 5, 1937) (5) Doty. P M , Aiken, \I‘ H., and Mark, H., IND.ENG.CHEM., 38, 788 (10461 (6) Kehoe, K A.,Univ of Cincinnati,private communication (1941). (7) Kline, G M Martin A R.. and Crouse, W A., Modern Plastics 18,119 (1940) (8) Krebs, H. E. Rubber Aae (N. Y . ) ,51, 299 (1942): Peierls. E.S.. Ibid., 22,315(1943)- M o d e m Plastics, 18,53(1941) (9) Mark, H. i n A Baitsell’s zdSciencein Progress,,7 3rd series, New Haven, Yale Univ Press, 1942 (10) Mitchell, 3. V , J Royal Ins!.. 2 101,307 (1831). (11) Proske, G.,Gummi-Ztg ,54 141-2,167-8 (1940). (12) Van Amerongen, G. J , J Applzed Phys., 17,972 (1946). RECEIVED February 10, 1947.
GUANIDINE SOAPS Properties as Detergents MELVIN Z. POLIAKOFF’ AND GILBERT B. L. SMITH’, The Polytechnic Institute of IJrookZyn, Brooklyn, N . Y . Synthesis and properties of guanidine salts of fatty acids are described. These compounds demonstrate similarity to the usual alkali metal soaps. Detergent ability of the guanidine soaps is compared with the corresponding sodium and potassium compound6 on such points as surface tension, emulsifying power, deflocculating power, and laundering. Possible uses for the guanidine soaps are suggested.
I
NVESTIGATIONS on the nature of guanidine, which have been proceeding a t the Polytechnic Institute of Brooklyn under the guidance of G. B. L. Smith for many years, have uncovered many facts concerning its properties and possible applications (IO). I t s highly basic character led to the prediction that it should be capable of forming soap-type compounds with fatty acids, similar to those formed by the alkali metals.
The appearance and properties of these soaps are not substantially different from the better known potassium and sodium soaps. Guanidine oleate is an amber pasty mass at room temperature, similar in appearance t o potassium oleate. Guanidine stearate is a hard white substance possessing the soapy feel of ordinary cake soap. The soaps dissolve readily in water, yielding clear foaming solutions with good detergent properties. The solubility of the guanidine soaps in organic solvents is considerably greater than that of the corresponding alkali metal compounds. This property would automatically suggest their value as emulsifying agents in water and oil systems. Since these compounds demonstrated the usual properties of soaps, it was decided to evaluate them as detergents. For comparison purposes, stock solutions of the sodium and potassium soaps of the three fatty acids used were prepared by reaction of stoichiometric quantities of fatty acid and alkali metal hydroxide in hot distilled water,
PREPARATION OF GUANIDINE SOAPS
As starting materials, purest available C.P. grades of oleic and stearic acid, as well as a commercial coconut fatty acid, were procured. Guanidine carbonate was purified from solutions of the commercial salt in contact with activated charcoal, by reprecipitation with ethyl alcohol. For the synthesis, the following procedure was found to be simple, practical, and capable of producing almost theoretical yields of the soaps. Fatty acid was first dissolved in about ten times its weight of solvent (ethyl alcohol or acetone). A slight excess of pulverized guanidine carbonate was added, and the mixture was refluxed gently for about 2 hours. To test for completion of reaction, free uncombined alkalinity or acidity was determined by withdrawing a sample, filtering t o remove excess guanidine carbonate, and titrating with standard acid or base as required. With 2 hours of refluxing, an equilibrium state was reached, after which no further reaction took place. The entire contents of the flask were then filtered, the major portionof the solvent was distilled off, and the residue was dried under vacuum. Resultant soaps contained some moisture which was extremely difficult to remove without decomposition, but for the purposes of this study, they were considered to be sufficiently pure. Analyses ‘by standard methods (IS) yielded the results given in Table I. 1 2
Present address, The Penetone Co., Tenafly, N. J. Present address, Naval Ordnance Testing Station, Inyokern, Calif.
TABLE I. ANALYSIS OF GUANIDINE SOAPS 70 Guanidine stearate Free stearic acid Moisture Total (accounted for) Guanidine oleate Free oleic acid Moisture Total (accounted for) Guanidine coconut soap Free guanidine carbonate Moisture Total (accounted for)
97.96 0.56 0.92 99.44 92.68 0.97 5.68 9 i i X 98.04 0.04 1.83 693i
TABLE11. SURFACE TENSION OF OLEATESOAPS IN AQUEOUS SOLUTION AT 25’ C. Concentration % ’ by Weight’
Surface Tension, Dynes per Sq. Cm. Guanidine Potassium Sodium oleate oleate oleate
