March 1949
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
Although the thermodynamic equilibrium distribution of hexenes has been reported (12),the present d a t a are inadequate t o draw any particular conclusions regarding the relative abundance of isomers. ACKNOWLEDGMENT
L. 0. Crockett of the Gulf Oil Corporation supplied the Cg concentrate, and J. E. Walkey, coauthor of this paper, held a Gulf Oil Fellowship from November 1944 through July 1945. The University of Texas Research Institute sponsored the work by the purchase of equipment and by the award of a research assistantship to B. R. Randall, who was active in the work. Many hours of assistance particularly in the analytical distillations were given by H. H. Hurmence, R. H. Bowden, Junam Chew, M. E. Klecka, K. s. McMahon, and E. D. Soltes. BIBLIOGRAPHY
(14) (15) (16) (17)
627
Griswold, Andres, Van Berg, and Kasch, IND. ENG.CHEY.,38, 65 (1946). Griswold and Morris, Ibid., 40, 331 (1948). Griswold, Morris, and Van Berg, Ibid., 36, 1119 (1944). Griswold and Van Berg, Ibid., 38, 170 (1946). Grosse and Wackher, IND.ENG. CHEJI., ANAL.ED., 11, 614 (1939). Hurmence, H.H., private communication, January 1945. ENG.CHEM.,ANAL.ED., 15, 590 (1943). Joshel, L. M., IND. Kilpatrick, Prosen, Pitzer, and Rossini, presented before the Division of Petroleum Chemistry a t the 109th Meeting of the AMERICAN CHEMICAL SOCIETY, Atlantic City, N. J. Lewis and Bradstreet, IND.ENG. CHEM.,ANAL.ED., 16, 617 (1944). Natl. Bur. Standards, American Petroleum Institute, Research Project 44, tables 2a, 6a, 8a, June 30, 1945. Rossini, Prosen, and Pitzer, J. Research Natl. B u r . Standards, 27, 529 (1941). Uhrig and Levin, IND. ENG.CHEM.,ANAL.ED., 13, 90 (1941). Voge, Good, and Greensfelder, IND.ENG. CHEM.,38, 1033 (1946).
(1) Bates, Rose, Kurtz, and Mills, IND.ENG.CHEM.,34, 147 (1942).
(2) Egloff, G., “Physical Constants of Hydrocarbons,” Val. 1, pp. 307-11, New York, Reinhold Pub. Co., 1939. (3) Ibid., Vol. 11, pp. 306-7 (1940). (4) Forziati, Willingham, Mair, and Rossini, Proc. Am. Petroleum Inst., 24, 111, 34 (1943) ; Petroleum Refher, 22, 379 (1943).
RECEIVED October 8, 1946. Presented before the Division of Petroleum Chemistry, 113th Meeting of the AMERICANC H ~ M I C ASOCIETY, L Chioago, Ill. Earlier articles in this series appeared in Volumes 35, pp. 117, 247, a n d 854 (1943); 36, p. 1119 (1944); 38, pp. 65 and 170 (1946): end 40, p. 331 (1948) of this journal.
Fungicidal Treatments for Cork Gaskets SIGMUND BERK Pitman-Dunn Laboratory, Frankford Arsenal, Philadelphia, P a . Growth of four species of fungi on protein bonded cork may deteriorate gaskets. Seven fungicidal formulations applied to protein and resin bonded cork were evaluated on the basis of a number of criteria for moldproofing automotive gaskets. The treated gaskets were incubated in fruit jars, in a cycled tropical humidity chamber, and at a tropical testing station in the Panama Canal Zone. Fungus tests conducted on the treated gaskets conditioned at elevated temperatures and leached with water showed that an aqueous treatment of p-nitrophenol and a fuel oil treatment of p-nitrophenol plus paraffin wax retained
sufficient fungicide to inhibit mold growth. The fungicidally treated gaskets did not disintegrate when immersed in boiling water, hot motor oil, or gasoline. Corrosion studies on the treated gaskets were made by placing the cork gasket between metal strips of aluminum, steel, brass, and zinc plated steel and exposing to 100 YOrelative humidity. Patch tests with gaskets treated with p-nitrophenol in fuel oil showed that this treatment was satisfactory for normal handling. On the basis of all the tests conducted, a 2% aqueous treatment of p-nitrophenol is recommended for moldproofing automotive cork gaskets.
T
gaskets were made by industrial and governmental laboratories, the published literature on the subject is scant (1-8). I n the manufacture of paper and vegetable fiber gaskets, fungicides have for sometime been incorporated in the glue used as binders. Kimberly and Scribner (9) described the use of @naphthol in glue in paper to prevent mildew growth. Delmonte (6) cites the work done by the Forest Products Laboratory on the mold resistance of protein glues treated with chlorinated phenols and their sodium salts. I n a previous report (3) fungicides were evaluated primarily on their ability to impart uniform protection against fungus growth to glue-glycerol bonded cork. Seven fungicidal treatments t h a t showed promise in t h e previously reported results (3) were applied to both protein and resin bonded cork and appraised on the basis of the following criteria: mycological tests in the laboratory and field exposures in the tropics; resistance of the treated gaskets t o fungus attack after storage at elevated temperatures and after leaching by water; physical tests to determine if the fungicidal treatments deteriorated the gasket; corrosiveness of the treated gaskets to metals; and toxicity to personnc.1 on handling the fungicidally treated cork.
HE deterioration of textiles by microorganisms under
tropical conditions is a known phenomenon. However, few realize that other materials, such as cork gaskets, also are attacked by fungi. During the recent war, many recommendations were made as a solution to the problem of controlling mold growth o n cork composition gaskets. One method suggested was individual packaging, b u t this was abandoned because of the scarcity of packaging material. A second method tried was coating the cork composition with a number of fungicides t h a t had been found effecti-re as textile preservatives. Fungus resistance tests conducted on gaskets treated with t h e latter fungicides revealed t h a t most of them were ineffective in controlling mold growth on protein bonded cork composition ( 2 ) . Therefore, a search was made for more potent fungicides and the results of these tests have been reported ( 3 ) . Untreated protein bonded cork is a n excellent source of nutrients for many species of fungi. This source of nutrients for mold growth may be poisoned by a 10-minute immersion of the cork gasket in a number of fungicidal solutions previously reported ( 2 , s). Although many attempts to fungusproof cork
INDUSTRIAL AND ENGINEERING CHEMISTRY
628
Vol. 41, No. 3
UNINOCU-
LATED C 0N T R 0 L
4 S P E RGIL L U S
NIQER
PENICILLIUM SP.
TRICHODERMA
SP.
UNBONDED NATURAL CORK
Figure 1.
RESIN
B 0 Tu-D E D CORK
PROTEI4 BONDED CORK
Comparative Susceptibility of Natural, Resin Bonded, and Protein Bonded Cork Composition to Growth'jof Three Fungi Inoculated strips were incubated over water i n Mason jars for 2 weeks at 85' F.
EFFECT O F FUNGUS GROWTH ON TENSILE STRENGTH OF BONDED CORK
I n order t o study the effects of the growth of pure organisms on the bonded cork, it was necessary t o find a method of sterilizing t h e gaskets without deleterious effects. Strips of protein bonded cork (1 X 3 X 0.126 inch) were sterilized either by using dry heat a t a temperature of 150" C. for 1 hour or by autoclaving at ISpounds pressure for 20minutes. Tensile strength tests conducted with a motor-driven Scott tester ( 7 ) were used as a criterion for t h e deterioration of the cork gasket. The cork strip was placed i n the machine with a distance of 0.5 inch between the jaws and t h e rate of separation of the jaws was 12 inches per minute. All the samples were conditioned at 19" =t 1" C. and 50y0 =t 57, relative humidity for 48 hours prior t o making the tensile strength tests. Table I shows that dry heat sterilization produced a slight loss in the mean tensile strength whereas steam sterilization produced no effect or a slight increase in tensile strength. The cork strips used for this test were sterilized by autoclaving a t 15 pounds pressure for 20 minutes. The sterilized protein bonded cork strips were suspended from the metal tops of 1-quart Mason jars by means of corrosion resistant wire and inoculated by atomization with pure aqueous spore suspensions of fungi as previously reported (3). Four test organisms were used: Aspergzllus niger, United States Department of Agriculture T.C. 215-4247, Chaetomzum globosum,
T.C. 1042.4, Penicillium sp., T.C. 1336.2, and Trichoderma s p . T.C. 6323. Water was poured into the jar t o a 0.5-inch level, the cap screwed on, and the sealed jar incubated for 2 weeks in a room maintained a t 29.4' =t0.6" C. Table I shows the pronounced loss in tensile strengt'h due to the growth of the four species of fungi on the protoin bonded cork. The same cxporiment was repeated with natural cork (3 X 1 X 0.23 inch strips) and resin bonded cork composition. However, no significant loss in tensile strength due to the growth of the fungi was obtained. Figure 1 shows the comparative susceptibility of unbonded natural cork, resin bonded, and protein bonded cork composition t o the growth of three species of fungi. The natural cork had the least mold growth with all three test organisms and showed the greatest susceptibility t o A. niger. The resin bonded cork had slightly more mold growth than the natural cork and also showed the greatest. susceptibility to A . niger. All t,hree organisms made prolific growth on t,he protein bonded cork composition. The data show that the mere presenc'e of mold growth on cork does not produce a loss in tensile strength. I n the case of the protein bonded cork, the fungi probably were not attacking only the cork particles but also the glue binder. On the other hand, with the resin bonded cork composition, the mold probably was confined to the cell walls of the cork particles, since phenolfornialdehyde resins have been reported by Brown (4)to be resistant or slight,ly susceptible to mold growth. It is evident
INDUSTRIAL AND ENGINEERING CHEMISTRY
March 1949 t h a t fungi may deteriorate protein bonded cork gaskets. Also, the great loss in tensile strength in the protein bonded cork is attributed t o the paritial dissolution of the glue binder by the fungi.
AND FUNGUS GROWTHON TENSILE STRENGTH OF PROTEIN TABLB I. EFFECTOF STERILIZATION BONDEDCORK
Mean Tensile Strength, Lb./Sq. In. AQ Ba 136.9 162.8 130.3 147.5 l6O:O
Treatment
A=
..
...
EFFECTIVENESS OF FUNGICIDAL TREATMENTS
Mason Jar Exposure. The treated strips of cork were incubated over water in blason jars as described above. Inoculation
was by atomization with aqueous spore suspensions of Trichodermo sp., A. niger, C. globosum, and Penicillium sp. Four samples of each treatment were used for each organism.
TABLB11.
FUN5ICIDAL
Ba
Fungicide or Chemical Protectant p-Ktrophenol
Since
Concentratim of Fungicide, G./100 M1. Solvent 1.7
p-Ni trophenol 3,5-Dinitro-o-cresol
2.0 1.5
4
3,5-Dinitro-o-cresol
1.5
5
p-Nitrophenol plus sodium alkyl aryl sulfonate p-Nitrophenol plus paraffin wax Malachite green oxalate
1.0 0.6 2.0 5.0 4.5
... ...
bonded cork is a good source of food for fungi, this method of incubation has been reported (3, 3) as a most practicable and highly accelerated test. Table 111shows the results of mold growth on the treated cork after 6 to 26 weeks' exposure in the jars. All the treated gaskets were free from fungus growth except the protein bonded samples given treatment 4 (Trzchoderma) and the gaskets treated with malachite green oxalate which were susceptible t o all four organisms. Observations from this test showed that, with few exceptions, if a specimen were free from mold growth after a 6 weeks' incubation period, i t would remain free from mold for t h e 26-week period of incubation. Tropical Humidity Chamber Exposure. T h e treated cork gaskets in duplicate were suspended by means of corrosion resistant wire from glass rods supported on shelves at the sides of t h e tropical room. The atmosphere of this storage room was controlled t o simulate tropical conditions (3, 6,8). Table 111 shows t h a t there
TREATMENTS APPLIED TO
2 3
I
Standard Deviation, Lb./Sq. In.
.. ..
...
Sheets of bonded cork 0.125 inch thick and cut into strips 1 X 3 inches were used in all the tests. T h e protein bonded cork composition contained 5/10 cork particles-that is, the particles pass through a with No. 5 screen but not through a No. 10 screen-bonded 870 glue and 15y0glycerol. The resin bonded cork composition had 10/20 cork particles bonded with 10% phenolformaldehyde thermosetting resins and 15% glycerol. Weighed strips of the bonded cork attached t o a metal rack were submerged for 10 minutes in the treating solution (3). Table I1 shows the composition of the treating bath, the percentage of wet pickup, and the calculated percentage of fungicide on the treated cork.
(6
Number of Replicates A n Ba 10 18 10 . . 10 10
Untreated control 15.01 8.57 6.26 ._. Dry heat sterilization, 1 hour a t 150' C. Steam sterilization. 15 lb. uressure for 20 min. 16.24 6.25 Steam sterilized and inoculated withb: Aspergillus nioer 79.3 ... 9 5.79 ... C h a e t o m i u m globosum 82.8 9 12.35 ,,. P e n i c i l l i u m sp. 112.6 ... 10 . . 7.51 Trichoderma s p . 98.6 6 16146 ... 161.1 . . 11 8.41 Uninoculated control a Different samples of cork composition were used in A and B. b The inoculated cork strips were incubated for 2 weeks over water in Mason jars a t a temperature of 29.4" C.
CHEMICAL TREATMENT O F CORK GASKETS
Treatment NO. 1
629
PROTEIN- AND
RESIN-BONDEDCORK % Fungicide and Additives on Cork (Calcd. from % Wet Pickup) G' Rb 0.40 0.44
% Wet Pickup
Solvents or Diluents in Treating Bath, M1. Isopropyl alcohol Fuel oil Water (40' C . ) C Isopropyl alcohol Stoddard solvent (42' C.) C Isopropyl alcohol Fuel oil (46' C.)C Water
11 89
Isopropyl alcohol Fuel oil (40' C.)C Water
GJue-glyoerol bonded cork. 5 Rwin bonded cork. C Temperature used t o bring the components of the treating bath into solution. p e r a t m e (25-30' C.).
..
20 80
(ilv. of 6 to 24 Samples) G5 Rb 20.2 22.1
28.2 21.2
30.7 22.4
0.55 0.38
0.60 0.40
20
24.6
24.1
0.44
0.44
..
34.1
36.4
10, 90
25.3
28.5
26.4
28.0
0.33 0.20 0.57 1.42 1.14
0.36 0.22 0.64 1.6 1.21
80
..
Impregnation of cork gaskets, however, was accomplished a t room tem-
OF FUNGUS RESIS'TANCE OF TREATED PROTEINAND RESIN-BONDED CORK TABLE 111. COMPARISON
'Trehemt No. ,/See Table 11)
(Incubated over water in Mason jars and in a osoled troDical humiditv chamber) Test Organismso Type of Aspergillus Chaetomium Penicillium Trichoderma Bonded CorkC ndger globosum SP. SP.
Incubation in Mason Jars, Weeks b
Tropical Humidity Chamber Extent of Exposure, growth No. wk. 34 32 34 34 18 24 22
-
+++ +++ -
+ + + s o t tested Not tested
-
Code for fungus growth:
to entire area moldy.
-
-
-
++++ ++++
no growth:
+ = slight growth t o 25% of area moldy: ++ = 25 t o 50%: + + + = 50 to 75%;
b Where no growth ooourred after 6 weeks' incubation, the sample was incubated C
G
glue-glycerol; R = resin.
for 26 weeks or until moderate growth occurred.
and
++++
24 24 24 6 8
-
75%
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
630
TABLE Iv.
jars for ti t o 26 weeks (as described above) to determine thc loss in fungicidal effectiveness. There was a slight loss in effectiveness of the p-nitrophenol in fuel oil t'reatment on protein bonded cork (treatment 1) after 16 weeks' incubation. The remaining treatments showed no appreciable loss in mold rePistance due to the storage a t 39" C Three treatments were coniplctely resistant to rriold attack by the four tesr fungi: 2 5 p-nitrophenol in water (treatment 2 ) ; a multiple fungicide containing p-nitrophenol and sodium alkyl aryl sulfonate (treatment 5 ) ; and p nitrophenol plus paraffin wax (trratinent 6).
GROWTHON CORK
G.4SKETS (Exposed under shed in jungle of Frankford Arsenal tropical testing station, the Panama Canal Zone) Gaskets Suspended from Gaskets Stored in Waterproof Rafters b Paper RagsC Treatment No. Exposure" Protein bonded Resin bonded Protein bonded Resin bonded Control (unA++ - e - + L e treated: 8 +d 1 A .-..2 A 3 A t4 .A -~ .3 A _ L -e 6 R -t -17 N o t tested COMPdRlSON O F h l O L D
-__
++ + +
+
a
b
I -
I
,
+++
+
+
= from November 15, 194.5, to December 2 5 , 1946 B = from March 6. 1946. to December 2 5 . 1946. Five samples of each treatment were exposed.
4
C Two samples of each t,reatment were exposed. d Code for fungus growth: = no visible growth; = trace to slight g r o w t h ; moderate grou.th, and = moderate t o heavy growth. e Gaskets were' stored in Manila paper bags.
+ + +-
+
is a close correlation in the susceptibility t o mold growth of the treated cork when incubated in the fruit jars and in the tropical room. TROPICAL EXPOSURE
6
-
t =
slight
Vol. 41, No. 3
to
EFFECT OF DYNAMIC WATER LEACHING ON FUNGICIDE RETENTION
The treated cork gaskets with glass sinkers attached w t ' w placed in 1-quart Mason jars which served as leaching vw K a t e r was introduced into the fruit jars through glass tuhc siphons from a thermostatically controlled water source in a 60-gallon tank. The glass tube si?hon extended to within 0 5 inch of the bottom of the leaching vessel. The tenipwatur the water TTas 26" * 1" C, and the rate of flow \\as 10 lit per hour. The pH of the leaching water was 6.6. I n a n attempt to secure data on the effect of leaching time on fungicide retcntion in thc cork, the following brief evpcrimcntal work was carried on. Strips of protein bonded cork treated with p-nitrophenol in fuel oil (treatment 1) were leached for 5 and 30 minutes and for 1, 2 , 4, 8, 16, 24, and 18 hours. The lcachcd strips were inoculated with A nzger, Penzcrllzum sp., and Trichoderma sp., by atomization for the samples incubated over water in Mason jars, and bv pipetting I ml of the spore suspension for those incubated in Petri dishes 011 Sabouraud's dextroie agar The strips t h a t were leached from 5 minutes t o 16 hours and incubated over watclr in Mason jars showed no growth. Thc cork leached for 21 hours showed moderate growth with A . nzger and Trichoderma s p . and heavy growth with Peniczllium ap The samples leached for 48 hours did not shon apprecviably more susceptibility than those leached for 24 hours. Figure 2 shows the effect of leaching time on the amnunt of fungicide retained in the protein bonded cork incubated on Sation-
Cork gaskets, untreated and treated with fungicides, mere exposed during 1945 and 1946 in a shed in the jungle a t the Frankford Arsenal tropical testing site on the Fort Sherman Reservation, Panama Canal Zone. The climate of this region may be described as TTet tropical with a 4-month (January to April) dry season (rainfall less then 2.4 inches per month) each year. I n 1945 the total rainfall was 130 inches and the heaviest rainfall occurred from July to December. During the rainy season the temperature averaged 79" E'. x%-itha daily range of 12" F. The minimum temperature was 72" F. and the maximum temperature was 96" F. The mean relative humidity (per cent) in the rainy season was in the low 90's (ranging from 80 on sunny days to the higher 90's on overcast, cool, rainy days). I n one exposure, five strips of protein and resin bonded cork of each treatment were tacked to a wooden board suspended from the rafters of the shed. I n another te>t, two samples of each treatment were placed in waterproof or Manila paper bags and the bags stored on a shelf in the shed. The duration of exposure for five groups of samples was from Kovember 15, 1045, t o December 25, 1946, and for two groups from March 6, 1946, to December 25, 1946. Table IV s h o w the amount of mold growth on the samples a t the end of the exposure period. On the basis of absence of fungus grom-th, treatment 5 (p-nitrophenol plus sodium alkyl aryl sulfonate) was the best. The TABLE Ti. &;FFECT O F DYR'AMIC \yATER LEACHIZIG ON F U N G U S REsIsT.4NCE O F aqueous p-nitrophenol treated proteinTREATED PROTEINAND RESIN-BONDED CORK bonded gaskets (treatment 2) suspended (Samples leached 24 hours n i t h water f l o w of 10 liters per hour a t temperature of 26O * l o C.' from the rafters had only slight mold Treatment Test Organiamsb growth whereas those stored in the 1-0, Mason Jai (See Table Inrubation. Type of Aspergtllus Chaetomium Penicilldum Trtchoderma paper bags were free from fungiw growth. 11) Weeks Bonded Corka ntger plobosum SP. 8P.
The treated cork strips were stored for 28 days in a constant temperature room maintained at 39" * 1.5" C. and a relative humidity of 25y0 as recommended b y t h e Gasket SubCommittee of the Society of Automotive Engineers Technical Board Committee on Fungi and Their Effects on Xilitary Automotive Vehicles (IO). ..liter this conditioning period the gasket strips were exposed to mycological tests in Mason
G R
2 26 C 26 26 26 26 26 26 2 14 26 24 2 2
FUNGICIDAL EFFECTIVENESS AFTER STORAGE A T ELEVATED TEMPERATURES
a
G = protein; R = resin.
b Code for fungus growth: = 50 to
+++
++
G R
G R
G
R
G
R
G
R
++-+t +(8)$ no growth, + slight growth t u 25010 of area moldy; + + ++-+ 75% to entire area moldy.
G
R
-
-
=
75%: I n all bases where 6-week incubation period is omitted, treated cork was free from mold growth: only maximum number of weeks, samples were incubated are shown d Numbers in parentheses refer t o number of weeks treated samples had lnoiibated when f u n g ~ ~ s grorr-th was recorded. 25 to 50%' c
INDUSTRIAL AND ENGINEERING CHEMISTRY
March 1949
Figure 2.
631
Effect of Leaching Time on Fungus Resistance of Protein Bonded Cork Treated with 1.7% p-Nitrophenol in Fuel Oil Leached cork
strips
i n o c u l a t e d with a upecies of Penicillium a n d i n c u b a t e d on Sahouraud's dextrose a g a r for 2 weeka
raud's dextrose agar. As the leaching time is increased iron1 0.5 hour to 48 hours, the zone of diffusion of the fungicideintotheagar medium is decreased. This is a n approximate measure of the amount of fungicide Dresent in the treated cork. Results of these tests indicate that with aleaching periodof up to 16 hours' duration the amount of fungicide retained is sufficient t o offer resistance to fungus growth with the three species of fungi used. After a 24-hour leaching period, the fungicide content of the cork gasket was inadequate to impart complete mold resistance. A 24hour leaching period is severe and is rarely approached in service unless the cork is exposed to rain or conditions of excessive condensation for extended periods. Comparison of Table V with Table I11 reveals the susceptibility of the treated gaskets to mold growth after a 24-hour Leaching period. The protein bonded cork treated with 1.7% p-nitrophenol in fuel oil lost SO much fungicide that the specimens showed moderate to heavy growth of all four organisms. The malachite green oxalate treated protein bonded cork showed heavy growth nit'h TABLE VI. all the organisms. An aqueous treatment with '2% p-nitrophenol and a 2% p-nitrophenol fuel Treatment oil treatment plus paraffin wax retained a sufficient amount of the fungicide after the 24-hour leach to impart complete resist'ance against fungus attack. Results of leaching tests indicate that whew the treated material will be subjected t o leaching by water, the initial concentration of the fungicide on the cork will have t'o be increased. For p-nitrophenol, this will have
No. (See Table 11) Control (untreated)
1 2 3 4 5
6
7 0
to be greater than 2% with a concentration of the fungicide on the cork greater than 0.55%. EFFECT O F FUNGICIDAL TREATMENTS ON TENSILE STRENGTH
Table VI shows the mean tensile strengths and standard deviations of the fungicidally treated protein and resin bonded cork. With the protein bonded cork all the treatments showed a loss in tensile strength. The aqueous malachite green oxalate formulation showed the least loss in tensile strength; the p-nitrophenol treatment in fuel oil had the highest loss in tensile strength. MTith the resin bonded cork, two aqueous treatments (5 and 7) resulted in increases in tensile strength; treatment 6 caused the greatest, loss in tensile strength. Disintegration Tests. T h e treated cork strips were floated in boiling water for 3 hours, in SAE 30 oil at 100" C. for 2 hours, and in gasoline at, room temperature for 10 days, as provided for in
TENSILE STRENGTH O F FUNGICIDALLY TREATED CORK GASKETS Mean Tensile Strength", Lb./Sq. In. Protein bonded Resin bonded
144.6 111.3 133.1 Not tested
126.9 127.4 118.7 139.5
Average of 10 samples.
'
167.2 148.6 163.1 163.7 158.5 171.4 137.3 184.0
Standard Deviation. Lb./Sq. In. Protein bonded Resin bonded
9.57 11.80 11.89 . .. 9.75 10.74 10.59 13.41
10.84 6.26 10.76 6.32 7.27 7.23 14.65 10.54
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
632 TABLE VII.
CORROSION TESTSON TREATED PROTEIX BONDEDCORKGASKETS
(Metal in contact with cork for 28 days at 37" * 1' C. and 100% relative humidity) Concentration Metals: of Fungicide, Solvents or Treatment Fungicide or G./100 MI. Diluents in Zinc Plated NO Chemical Protectant Solvent Treating B a t h Aluminum Brass Steel Steel 1 p-Nitrophenol 1.7 Isopropyl alcohol 0 0 0 0 Fuel oil 2 p-Kitrophenol 2.0 Water 0 0 3 3,S-Dinitro-o-cresol 1.5 Isopropyl alcohol 0 0 Stoddard solvent 4 3.5-Dinitro-o-cresol 1.5 Isopropyl alcohol 0 0 Fuel oil 5 p-Nitrophenol plus 1.0 Water 0 0 sodium alkyl aryl sulfonate 0.6 6 p-Nitrophenol plus 2.0 Isopropyl alcohol 0 paraffin wax 5.0 Fuel oil 7 Malachite green 4.5 Watec -k oxalate a Code for corrosion: - = less corrosion t h a n control (contlol = untreated protein bonded cork); 0 corslightly more corrosion than control. rosion same as control; t
$ +
+
+
+
-
Federal Specification HH-C-576 ( 7 ) . No disintpxration in the bonded gaskets was observed. Tensile strength tests were conducted on untreated protein- and resin-bonded cork compositions that were boiled for 3 hours in distilled water. One group of boiled cork strip3 was conditioned for 1 week a t 70' F. and 50 to 55y0relative humidity. A second group was dried at 120' F. for 24 hours and conditioned for 96 hours a t 70" F. and 50 to 55yorelative humidity piior t o tensile tests. Each group, including controls, consisted of 25 strips 4 x 1 x 0.125 inch. The results show that the boiled protein bonded cork compositions, which had a density of 16 to 18 pounds per cubic foot, had increases in tensile strength ranging from 38 to 93%. The boiled resin bonded cork composition that had a density of 19 pounds per cubic foot shoued increases in tensile strength ranging from 18 to 23%. However, a resin bonded cork composition with density of 28 pounds per cubic foot showed slight decreases (4%) in tensile strength after boiling. The increase in tensile strength of low density cork compositions is attributed to the loss of glycerol during the boiling process. The lowering of the tensile strength of high density cork compositions after boiling is attributed to the relief of compression which results in the swelling of the material. CORROSION OF METALS
Corrosion tests of the treated gaskets were conducted by making a sandwich of the cork gasket between nietal strips as recommended (IO). A hole, 0.18 inch in diameter, was punched 0.5 inch from one end of strips (3 X 1 X 0.0625 inch) of aluminum, brass, steel, and zinc plated steel. The surfaces of the metal strips were polished with grit No. 3/0emery cloth, cleaned with solvent, and wiped and dried with a clean cloth. The treated cork strip was placed between the two metal strips, and a No. 8 round head screw and nut of the same material as the metal strips were used t o tighten the assembly without deforming the met'al plates. Four samples of each treatment and four strips of Untreated protein bonded cork (controls) were used for each type of metal. The cork-metal assembly was suspended for 28 days in a humidity cabinet a t a temperature of 37" * 1 " C. and 100'% relative humidit.y. At the end of the cxposure period the metal strips were separated from t,he cork. Table VI1 indicates the condition of the metal strips in contact wit,h the treated cork. The corrosion of the metaJ strips in contact with the t,reated cork was compared with the amount of corrosion shown by the metal in contact m-ith a n untreated strip of protein bonded cork. Cork treated with 1.7Y0 p-nitrophenol in fuel oil caFsed no more corrosion than the untreated cork alone. The 270 p-nitrophenol aqueous treatment produced slightly more corrosion than the control did with aluminum and zinc plated steel. However, this slight corrosion does not preclude the use of t.his formulation. Two per cent p-nitrophenol plus 5% paraffin wax protected t h e brass. I n practically all cases the uni,reated cork offered
++ + +
Vol. 41, No. 3 protection to the steel by acting as a mechanical barrier. The malachite green oxalate treated gaskets caused more corrosion than the controls with all four metals. TOXICITY STUDIES
One-inch squares of protein bonded cork treated with 1,7'% p-nitrophenol in Diesel fuel oil and protein bonded cork treated with Diesel fuel oil, were submitted to the Army Industrial Hygiene Laboratory, Edgewood Arsenal, Md., for patch tests. Results of these tests show that approximately 25% of the personnel tested had reactions to both tho control and to the p-nitrophenol treated sampler. It is bclieved that the fuel oil used in the treatment was responsible for the reactions observed although one reaction was believed to represent sensitization of the skin of the volunteer subjcct t o the p-nitrophenol in the samples. It was concluded that cork treated in the same way as the samples tested xould be suitable for items of equipment (including gaskets), provided t h a t their use involved normal handling only. Petroleum products are knov-n to cause skin irritation in a considerable percentage of people. Since the 2y0 aqueous treatment of p-nitrophenol offered superior mold resistance t o t h o fuel oil formulation, the toxicity of the petroleum could be eliminated by substituting the aqueous treatment. p-Nitrophenol has been used on a commercial scale for mildewproofing leather artieles. KO toxicity has been reported so far with the use of p-nitrophenol as a leather preservative (4). Toxicity studies were not conducted on the remaining treatments.
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CONCLUSIONS
KO single fungicidal treat'ment fulfilled all the criteria required for a good fungicide for gaskets. On the basis of field test's a multiple fungicide containing 1 p-nitrophenol plus 0.67,. sodium alkyl aryl sulfonate in water was the best treatincnt.. The 2% p-nitrophenol aqueous treatment showed the best. performance in most of the tests and therefore i t is recorn-mended for fungusproofing automotive cork gaskets. A number of suggestions may be made for future work on pro-venting the deterioration of cork gaskets by fungi. First, the. protein binders used in fusing the cork particles should be re-placed by mold-inert resin binders wherever practicable. Second,. where industrial applications require the use of protein binders,, a fungicide should be incorporated in the binder. Third, a search, should be made for a fungicide that is substantive t'o cork and one that could be added to the cork particles during the manu-facturing of the cork composition. If this fungicide were non-toxic to humans also the cork scraps remaining after fa,bricating: the gaskets could bo used as liners for bottle caps. ACKNOWLEDGMENT
Appreciation is expressed t o C. C. Fawcett, E. R. Rechel,, and 31.Frager of the Frankford Arsenal Ordnance Laboratory for their cooperation, and t o the Ordnance Department for per-. mission to publish this paper. The author wishes to thank L. Teitell for the results on the tropical exposure of t h e cork and the weather conditions a t the Panama Canal Zone tosting site. A joint investigation was conducted by the Pitman-Dunn Labora- -
March 1949
INDUSTRIAL AND ENGINEERING CHEMISTRY
tory and the research laboratories of the Armstrong Cork Company to determine the effcct of boiling water on the tensile strength of cork composition. LITERATURE CITED
Benignus, P. G., and Rogers, D. F., “Mildewproofing Automotive Gaskets,” Monsanto Chemical Co., 1945. Berk, S., Am. SOC.Teeting Materials, Bull. 145, 73-76 (March 1947). ENQ.CHEM.,40,262-7 (1948). Berk, S.,IND. Brown, A. E., Modern Plastics, 23, No. 8, 189-195, 254, 256 (1946).
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(5) Cooke, T. F.,and Vicklund, R. E., IND.ENG.CHEM.,ANAL. ED., 18,59-60,1946. ( 6 ) Delmonte, J., “Technology of Adhesives,” New York, Reinhold Pub. Corp., 1947. (7) . . Federal SDec. Cork ComDosition, Gasket and Sheet, HH-C-576 (1936). (8) Kanagy, J. R., Charles, A. M., Abrams, E., Tener, R. F., J. Research Natl. Bur. Standards, 36, No. 5 , 441-54 (1946). (9) Kimberly, A. E.,and Scribner, B. W., Natl. Bur. Standards, M ~ E Pub. c . M-154,1937. (10) SOC.Automotive Engrs., Tech. Board, Progress R e p t . 2 (October 1946).
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RECEIVED
August 1, 1947.
Dispersal of Triethylene Glycol Vapor with Aerosol Bombs HENRY WISE’ Department of Medicine, University of Chicugo, Chicago 37, I l l . T w o units designed for the production of triethylene glycol vapor. by atomization are studied. The glycol aerosol is produced by the liquefied gas method with Freon-12 and carbon dioxide, respectively, as the propelling agent. Quantitative measurements of the concentrations of triethylene glycol vapor discharged show that the carbon dioxide bomb exceeds the Freon dispense in efficiency of glycol vapor production. The bactericidal effect of triethylene glycol vapor produced by atomization is’ demonstrated in the laboratory on moist airborne droplets containing beta hemolytic %treptococci, Group C. From the standpoint of air disinfection, the use of a single-discharge glycol atomizer will find only timited application under certain specific situations because of the rapid rate of disappearance of glycol vapor from the air.
T
HE successful dispersal of insecticides by aerosol bombs led to the suggestion by Goodhue and McGovran of adapting the liquefied gas method to the production of germicidal aerosols (1). Although propylene glycol aerosols were originally employed by Robertson and co-workers in the early laboratory experiments on air sterilization (8),further studies indicated that rapid killing effect of the glycol on air-borne bacteria could be accounted for only by the interaction of the microorganisms with vapor molecules and not with aerosol droplets (3, 8). In accordance with this hypothesis it was demonstrated that an increase in bactericidal activity was obtained when propylene glycol was dispersed as a vapor instead of an aerosol. This difference in germicidal potency between aerosol and vapor was even more pronounced with triethylene glycol (7), because of the much lower vapor pressure of this compound (6) and, consequently, the less rapid rate of evaporation of its aerosol particles. Thus, for the purpose of air disinfection the physical characteristics of glycol aerosols dispersed into air must favor a rapid production of glycol vapor molecules which are essential for effective collisions with air-borne bacteria. For a liquid with high boiling point such as triethylene glycol, the colloidal particles produced by the dispenser must be small enough t o allow rapid rates of evaporation at room temperatures. The following communication represents a study of two types of liquefied-gas aerosol bombs. They are self-contained units 1 Present
addresa, California Institute of Technology, Pasadena, Calif.
employing compressed Freon-12 (dichlorodifluoromethane) and carbon dioxide, respectively, as the propelling gases which force the liquid triethylene glycol under pressure through a narrow orifice. Observations were made on the physical properties of the aerosols formed, the concentrations of glycol vapor produced, and the bactericidal effect under experimentally controlled and natural conditions. Figure 1 shows a picture of the aerosol bombs used. The large pound-size container is the type generally employed for the production of insecticidal aerosols. It contains a mixture of triethylene glycol and Freon-12 under an initial pressure of approximately 100 pounds per square inch. The container must be kept upright during use, and a knob at the top of the cylinder controls a needle valve. When the knob is turned, a fine stream of liquid mixture is forced through the orifice (0.009 inch in diameter) a t a rapid rate and atomized a t the mouth of the discharge nozzle. The smaller unit utilizes compressed carbon dioxide as the propelling agent for the atomization of triethylene glycol. It consists of a steel cylinder, 65 mm. in length and 20 mm. in diameter, the upper end of which is provided with a sealed orifice. Attached to this outlet and extending almost to the bottom inside the cylinder is a narrow steel tube of O.OO&inch inside diameter (27 gage). When the seal is broken, the mixture of triethylene glycol and carbon dioxide i n the dispenser a t an initial pressure of 900 pounds per square inch escapes through the narrow tube a t a high velocity, and 1s atomized into a fine aerosol. This dispenser differs from the larger one in the much higher pressure used for the production of the dispersoid as well as in the absence of a needle valve to interrupt the process of atomization once the seal has been ruptured. The size of the unit has been designed, therefore, to contain enough triethylene glycol to saturate the air of an average size room (about 2500 cubic feet) temporarily with triethyIene glycol vapor after a single discharge. This aerosol bomb has a total capacity of 10 ml. and contains 0.2 t o 0.5 ml. of triethylene glycol and 0.4 to 1.0ml. of ethanol; the remaining volume is carbon dioxide. Ethanol is added to triethylene glycol in a volume ratio of two to one in order to increase the solubility of triethylene glycol in liquid carbon dioxide. PHYSICOCHEMICAL MEASUREMENTS
The measurements were taken in an air-conditioned chamber of 640 cubic foot capacity (IO). A centrally located fan circulated air gently within the chamber, and the formation of tri-
