Fungicide-Treated Cotton Fabric OUTDOOR EXPOSURE AND LABORATORY TESTS S. S. BLOCK Engineering and Industrial Experiment S t a t i o n , University of Florida, Gainesuille, Flu. Results are presented of two years of outdoor shade exposure, in Florida, of cotton fabric treated with fungicidal preservatives. Untreated 10-ounce cotton duck lost 67%of its tensile strength in one year and 939%in two years. Of the different fungicides applied to the fabric on a concentration of 1% of the dry weight of the treated fabric, only the copper and silver compounds stood up well after two years in the field. With the copper group the copper ion, rather than the anion or whole molecule, appeared to be the protecting agent. The mercurials and other heavy metal fungicides did not afford protection for the two-year period. The phenolic group were the only purely organic fungicides that rendered the fabric appreciably resistant to microbial decomposition. Waterrepellent treatment improved the performance of the phenolic but not the copper fungicides. Laboratory soil burial tests were, in general, in agreement with the outdoor exposure tests.
I”
u
in New Orleans lost 60 to 65% of its strength. The damage was attributed t o the action of sunlight rather than microorganisms. Armstrong (3) investigated the rotproofing of sandbags. He recommended for inexpensive, effective treatments: organic copper soaps (0.8 to 1.0% Cu), cuprammonium hydroxide (1.0 t o 20% 1.5% Cu), creosote (25%), or copper creosote (0.5% Cu creosote). In service tests of copper-treated sandbags, Dean, Strickland, and Berard (6) rated different copper treatments and found copper naphthenate most effective, on a basis of 1% copper. They reported the results of their outdoor tests t o be in good agreement with accelerated, laboratory, soil burial tests. Fargher (8) observed that the loss of copper by leaching after 3-month outdoor exposure with 5.4 inches of rainfall was as follows: copper hydroxide, 97 yo; copper carbonate, 96%; cuprammonium hydroxide, 96%; copper oleate, 70%; copper naphthenate, 62%; and copper ricinoleate, 45%. Barghoorn (6) made extensive field tests in the Panama Canal Zone, Florida, and New Guinea. I n the Canal Zone cotton duck lost about 7070 of its tensile strength when exposed in the shade for one year; in soil burial, 100% loss occurred in 6 t o 7 weeks. On 42-week exposure in Florida, cotton duck lost approximately 40% of its initial tensile strength in the shade; in the sun for the same period, the loss was approximately 7070. In sun exposure the presence of fungicides invariably brought about a greater loss in tensile strength than their absence, except where a protecting, mineral, sun screen was employed. Copper naphthenate, copper 8-quinolinolate, copper ammonium fluoride, and dihydroxydichlorodiphenylmethane were the most effective fungicides in soil burial tests.
+
T H E past several years there has been a surge of interest in the preservation of fabrics from the deteriorating effects of rot and surface molds. This interest has resulted from the wartime need for military equipment that would stand up under tropical conditions. Protection from the deleterious action of microorganisms, however, is not only required in tropical climates but is important in may areas of the United States. Treatment of fabric with chemicals toxic to microorganisms, particularly fungi, was found to be an economical and satisfactory method of protection. The recent literature contains many references to new fungicidal treatments and laboratory tests but few reports of actual service tests of different treatments in outdoor field exDosure. This research was conducted to obtain such information. Thaysen el al. ( 1 1 ) in 1939 made the first comprehensive study of the effects of weather on exposed fabrics. They found that fabrics composed of cellulose, cellulose rayons, wool, and silk disintegrated rapidly on soil exposure. Cellulose and wool fabrics exposed in the shade to very humid tropical conditions were damaged much less rapidly than when exposed in the soil, although there was extensive surface mildewing. In subtropical or temperate climates with rainfall about 30 inches per year, the microbiological damage to fabrics exposed in the shade for one year was considered insufficient to affect the strength of the fabric. Fabric exposed in sunlight showed less microbiological damage than that in shade but suffered from loss in Copper n a p h - T e t r a b r o m o Mercuric Lauryl pyriB a r i u m flu8-Quinolinol tensile strength resulting from chemical thonate o-cresol pentad i a i u m brosilicate degradation of the cellulose. Dean and chloromide phenate Worrier (‘) showed that cotton Figure 1. Range of Mold Staining of Fungicide-Treated Cotton Strips after duck exposed t o sunlight for one year One Year of Outdoor Exposure 1783
INDUSTRIAL A ND E N G INEERING CHEMISTRY
1184
Vol. 41, No. 8
OUTDOOR AND LABORATORY TESTING
2
Figure 2. Cotton Strips without Fungicide Treatment, after One Year of Outdoor Exposure
Outdoor exposure tests were carried out aboveground in the shade for two years. hccelerated laboratory tests consisted of 2-month soil burial of similarly treat,ed strips. To determine t,he comparative 'effectiveness of representative treatmcnts, the fungicidal agents were applied as 1yo of the total dry veight of the treated fabric. (Tn a few cases higher concentrations were also tested.) Each outdoor-exposed sample mxs tested with and without water-repellent. A 10-ounce cotton duck was thoroughly n-ashed and extracted with hot ethyl alcohol to remove sizing materials and Tvaxes that might interfere n-it,h application of the treat,ments. The cloth was then cut into &ips 18 inches long and 4.6inches wide. These strips mere dipped into solutions of the fungicidal chemicals of such concentration that when the fabric had taken up 60y0of its weight of solution, the dry weight of the chemical was 1% of the dry weight of the treated fabric. When t,wo-bath treatments were used, the concentrations of the solutions were calculated to give 1% of the protective chemical on the fabric. Whenever the chemical manufacturer recommended specific t,emperatures and times in applying a product,, t'hose directions were followed. The wet strips were placed between blotting papers and put through metal rolls adjusted to squeeze out all but the desired quantity of solution. The strips were air-dried, rinsed in water to remove the excess soluble chemicals, and then dried again. The samples receiving an additional water-repellent treatment were passed through an aqueous emulsion of Fabricsec AA waxaluminum acetate (Socony-Vacuum Oil Company); they were allowed to take up enough to have a dry weight of 4.5y0 of the water repellent on the fabric. The repellent was cured on the fabric in an oven a t 140 C . The treated &ips were stretched on frames, the ends being clamped tight between wooden strips so that the fabric strips were not in contact with any metal, and were spaced from one another. The outdoor-exposed strips mere placed in a forest in Gainesville, Fla., mounted 3 feet off the ground, at an angle of 45" facing north; i t was thought that mold damage would be greater if the strips faced north. The appearance was recorded when the &rips TTerc set out and after each year of weathering, from August to August. Photographs viere taken after each year to demonstrate the mold spotting. The extent of mold spotting was recorded on a scale of 0 t o 5, as indicated in Figure 1. Tensile strength was measured by the A.S.T.M. breaking strength method ( 1 ) in a Scott test'er (Table 111). Strips were cut off the side of the samples for tensile strength measurements; therefore, the two-year samples were not so wide as the one-year samples (as shown in the photographs). Soil burial tests were run according to t,he A.S.T.M. method ( 9 ) with strips removed from the soil and tested a t regular intervals up to 8 weeks. Copper analyses were made by the colorimetric method, using sodium diethyl dithiocarbamate reagent according to McFarlane (IO). Mercury analyses were run by titration with dithizone (4). CLIXIATIC CONDITIONS
Figure 3.
Cotton Strips Treated with Phenolic ExposureCompounds, after Two Years of Outdoor
Table I gives the n~onthlytemperat,ure and rainfall data for Gainesville over the period of the tests. Conditions of high temperaturc and rainfall prevail from May through October with the most favorable conditions for microbial activity in the suninier months of June, July, and August. Compared
INDUSTRIAL AND ENGINEERING CHEMISTRY
August 1949
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with silver pentachlorophenate (Table 11). The mercury group decreased E BN gy, @ %e 5 5 .e in strength from 13 to 32% loss in 9, 7 ?.a .:A 86% %g 4; strength the first year to 64 to 88% CJP, SP, obq -9 a 5 dY a 3 k k i I 8 p. k k loss the second year. The zinc.* g4 $1 $I g d &U 0 treated strips were variable in B 8" i 8 t 8 k 8 strength the first year, but after the ci U U u U u 3 second year all evidenced over 60y0 loss in strength. Of the purely organic treatments, the phenolics protected from 0 to 79yo loss the first year; after the second year all showed 61 to 95% loss. The quaternary ammonium compounds allowed only 23 to 37% loss the first year but 74 to 90% the second year. Figure 3 shoFs two-year weatherexposed strips treated with p e n t a chlorophenol and metal pentachlorophenates. Only silvcr and copper pentachlorophenates afforded protection for two years from rot and surface mold. The heavy metals salts, like the compounds of mercury, were surprisingly ineffective. The loss of strength of the fabric treated with pentachlorophenol and the zinc salt Figure 4. Cotton Strips Treated w i t h Copper-Containing preservatives, after was greater than that of the controls Two Years of Outdoor Exposure after the first and second years, an indication that another agency was with a 45-year average, the temperature during the test period active in deteriorating the fabric. The deteriorating agent was would be considered normal. The rainfall, however, was considerprobably hydrochloric acid, resulting from decomposition of the ably greater than average the first year but normal the second chlorinated phenol. year. I n considering the microbial activity, the total rainfall may Strips treated with copper preservatives and exposed for two not be so important as the frequency of rainfall. Frequent rains, years are shown in Figure 4. With the exception of the strips conparticularly in the late afternoon, which are common in Florida taining 1% copper naphthenate, none had a surface stain rating of during the summer, often keep the cloth wet overnight and more than 2. None had lost as much as one half their initial tensile produce the moist conditions necessary for fungal growth. The strength and some less than one fifth. Table I11 gives analyses data show that rains occur more frequently during June through for copper and mercury on treated samples during the test August. Inasmuch as the test strips were sheltered by trees, period. The superiority of copper to mercury was not only a the saturating effects of beating rains were reduced. On the other result of the severe leaching of the latter (copper was also badly hand, the drying of the strips when wet was retarded. leached as shown), but of the greater fungicidal activity of the copper. The residual mercury in several cases was greater than
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OUTDOOR EXPOSURE T E S T S
After one year of weathering, control cotton duck strips with-
out fungicidal or water-repellent treatment had deteriorated to the point where they could no longer be considered serviceable. They lost an average of two thirds of their original tensile strength, were gray-brown in color, and completely covered with mold stains (Figure 2). After two years they had practically no tensile strength and were even more badly mold-stained. Samples having only a water-repellent treatment lost half of their initial strength the first year and were not so badly spotted as the controls (Figure 2). After two years, however, there was little difference between those with and without water-repellent treatment. The deterioration of fungicide-treated strips varied considerably. Table I1 shows a range of tensile strengths from 0 to 88% loss the first year, and 12 to 100% loss the second year, for samples containing 1% of fungicide. Table I1 and Figures 1 to 6 show a range from no mold spotting to complete mold staining after one- and two-year exposure. The surface appearance demonstrated that the deterioration resulted primarily from microbial rather than other action. The copper group gave best performance with loss of strength of 0 to 19% the first year and 12 to 45% the second year (for those samples having 1% of fungicide). The only other strips that stood up well after two years of weathering were those treated
TEMPERATURE AND RAINFALL FOR PERIOD TABLE I. MONTHLY OF EXPOSURE TESTS Rainfall Mean Temp., Month Max.
F. Min.
inches
No. of Days over 0.01 inch 1.0 inch
FIRSTYEAR Bug. Sept. Oot.
Nov.
Dec. Jan. Feb. Maroh April May June July Aug. Sept. Oct. Nov. Deo. Jan. Feb. March April May June July
89.9 89.3 82.3 79.6 67.1 70.0 71.0 77.4 82.3 86.0 88.1 89.5 89.2 87.1 82.9 78.5 73.9 76.1 62.9 70.3 85.3 88.2 84.0 88.1
71.4 71.7 61.0 62.9 43.6 49.9 48.3 55.1 58.5 66.5 69.0 71.5
15.2 4.26 1.39 2.00 9.32 1.95 2.74 2.87 1.70 7.00 11.6 10.3
SECOND YEAR 5.72 71.6 4.13 69.8 4.57 62.9 1.28 61.5 49.8 0.19 56.7 1.40 4.67 40.2 8.75 47.7 1.70 63.2 4.16 64.8 5.52 68.9 10.00 68.6
19 15
5
1 0 1 2 0
0 4 14 13 19 17 11 7 5 2 12 10 10 8
a
13 18
1 0 2 4
3 2 1 1 0 0 0 1 3 0 2 0 3
INDUSTRIAL AND ENGINEERING CHEMISTRY
1786
TABLE 11.
LOSS OF
TENSILE STRENGTH I X
Vol. 41, No. 8
OUTDOOR \vC.4TIIERISG APiD LABORATORY SOIL Loss of Tensile Strength, 70 Outdoor Weathering Without With Roil Burialb repellent repellent -- 1 2 3 ___ 1%. k . 1 yr 2 yr. ' 1 yr. 2 yr. wk. wk. Oi 93 49 90 69 1co
.
~~~
BURIALTEST^ -
_ _ I _
Chemical Type Controls Copper compounds
Protectant= S o treatment C u chromate Cu pentachlorophenate Cu ammonium fluoride Same, 2% Same 57& Cu d p h t h e n a t e Same, 2% Same, 5% C u 8-quinolinolate C u undecylenate C u diethyl bamate
Zinc conipoundv
Meroury compounds
ditliiocar-
Zn 8-yuinolinolate
Cupric acetate chromate Cupric acetate cide G Protela S B Protela SB Protela SB S u o d e x copper Nuodex copper Nuodex copper Cupric acetate olinol acetate Cupric acetate decylenate
t .
+ Na + Dowi-
Mercuric chloride+ Dowicide G Pyridose N a oleate IN-2555
Pyridyl mercuric oleate Phenyl mercuric oleate
Uranyl pentachlorophenate B a fluosilicate R a r e e a r t h hydroxides T1 stearate Pentachlorophenol Dihydroxydichlorodiphenylmet hane Salicylanilide Tetrabromo-o-cresol
3
5
5
30
27
34
50
l00d
0
1
1
1
25 24
2 8
0 54
0
94 e
2
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0 1 0
2
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ii
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3 7 4
0 31
0
0 4
4
4
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0
12
25
is
0
0 0
2
35
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44
33
66
9.5
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0
2
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1
7
17
19
5
38
48
9Od
0
1
2
2
19
24
I0
31
0
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17
906
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0
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16 57 42
78 89 92
8
63
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3 4
4
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100 94
2
,.
73 79
5
..
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4
5
19 88
16 9
71
27 0
38
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3
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1 2
5
100
21 13
64 67
32 26
28
92 100
2
5
0
2
0 2
5 5 5
81
..
+ ++ + ++ Uranyl acetate + Dowicide G Ba chloride + Na fluosilicate R a r e e a r t h chlorides + NHaOH
..
, .
-4
..
,.
80
88
8
74 72
54 100
..
21 54
..
67
, .
100
..
.. ..
0
0 6
,.
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.. .. ..
,.
0 69
11; 100
,.
13 69 88
12 22 37
11 65 82
-3 5 21
29 84
20 21
84
12 12
74 70
19 24
69
93
46
95
23
76
36
77
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71
82
66
73
19
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47
85
46
88
92
100
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20
26
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67
80
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97
37
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33
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79
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30
77
46
100
..
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42 34 -1
91 89 74
9 15 8
62 61 84
8
25
79
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Na
Dowicide 7
Dodecyl isoquinolonium bromide Isothan Q-15 Lauryl pyridinium bromide Isothan Q-4 Trimethyl cetyl ammoniuni pentachloroHyamine 3258 phenate Alkyl dimethyl benzyl Benzalkonium chloride ammonium chloride
..
92
100 80
, . I .
2 1
5
5
0
3 3
0
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0 0 3
0 4 5
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3 4
5 5
2 4
4 5
4
5
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4
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3
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5
5
5
3
5
4 4
5
0 0 0
4 4 5
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L
5 5
29
90
33
90
27
90
3
5
4
5
86
26
76
54
93
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37
, .
3
5
2
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24
89
23
80
64
82
100
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2
4
4
5
37
86
2.5
74
80
82
100
, .
3
5
1
5
94 93 100
100 100
5 ? 3 5 5 After 8 weeks.
4 0 4
4 5
8-Quinolinol 8-Quinolinol 57 Phenothiazine 31 Phenothiazine Undecylenic acid Undecylenic acid 72 Scale of increasing 1% unless specified. b Samples without repellent,
the residual copper in treated strips; yet in all cases the mercurytreated samples had less residual strength and more mold stain than the copper-treated strips after two years in the field. The molds on the fabric strips were identified by H. D. Barker and associates of the Bureau of Plant Industry, U. S. Department of Agriculture, as belonging to a group of angiocarpous forms falling piimarily into the sphaeropsidales of the fungi imperfecti as reported by Zuck and Diehl ( l a ) . Apparently these fungi are much mole susceptible to copper and resistant t o mercury than the Penicillium and Aspergillus types commonly associated with mold spotting. Table 111 demonstrates how little copper is necessary for protection against fungal deterioration. With several samples a mean of approximately 0.01 % copper during the second year was sufficient to restrict deterioration to no more than 10% decrease i n tensile strength from the end of the first year to the end of the
83 58
0
.. -1' 1
2 11 27
Miscellaneons
4
w.
5
0 7
H g nitrate Dowicide G P b acetate Dowicide G N i nitrate Dowicide Q Chrome alum Dowicide ci Co nitrate Dowicide G Ccl:chloride Dowicide
Fungicide G-4 Shirlan Fungicide 242
J
w.
12
+
+
, .
yr.
25 45 18 9 39 24 13
+ +
Thallous sulfate stearate
yr.
16
+ 8-quin+ N a unCupric acetate + N a diethyl dithiocarbamate Zn sulfate + S-quinolinoliate acetate
H g pentachlorophenate
1
Final
15 -3
19 0
Nuodex zinc Nuodex zina N a diethyl Zn sulfate dithiocarbamate Zn sulfate Dowicide G
Co pentachlorophenate C d pentachlorophenate
Quaternary ammonium compounds
..............
Zn naphthenate Same. 2 % Zn diethyl dithiocarbamate Zn pentachlorophenate
Miscellaneous metal compounds Ag pentachlorophenate P b pentachlorophenate N i pentachlorophenate C r pentachlorophenate
Phenolic compound8
Chemical or Proprietary Products Applied
93 91 43 92 0 71 24 99 74 mold growth, 0-5.
..
After 6 veeks.
..
5
second. These samples were treated with copper pentachlorophenate, copper undecylenate, and 2% copper ammonium fluoride. Although a high percentage of copper was lost the first year the sainples were exposed, the mean quantity of copper during that year was sufficient to limit deterioration. The mean quantity of copper present t'he second year was much less, and the second-year tests showed decided advances in deterioration of some of the samples. That the criterion of protection or deterioration was the quantity of residual copper is indicated in Table IV. When the copper-treatcd samples were arranged in order of residual percentage of copper a t the end of the second year, the residual tensile strengths followed the same order in eight out of ten casesb This does not mean that all the compounds had the same fungicidal potency. I t does indicate, however, that with thc fungi responsible for the detcrioration of the fabric, t8he copper ion had so much greater fungicidal po-
INDUSTRIAL A N D ENGINEERING CHEMISTRY
August 1949
1187
tency than the anions in combination with it, that the copper, rather than the anion or whole molecule, was the limiting factor in protection. If it is true that the quantity of copper in the fabric is the limiting factor in protection against fungal deterioration, then the obvious means of affording protection is to conserve the copper which has been applied or to use a greater quantity of copper at the start. Two methods are possible to conserve the c o p per. The first is to employ a compound in which the copper is resistant to leaching; the second is to add a water repellent. Whereas Fargher (8) showed distinct differences in leaching rate of different copper com-’ pounds when exposed for 3 months to 5 inches of rainfall, the effect of more than 60 inches of rain in one year leveled any differences that may have existed, since all the samples approached 100% loss of copper by leaching. Table I11 shows that 9 the use of a water repellent ‘5 was definitely helpful in restricting the leaching of copper. It was surprising, however, that the greater concentration of residual copper was not accompanied b y greater residual tensile After Two Years o f Outdoor Exposure After o n e year of outdoor weather exposure strength. After two years Figure 5. Effect of Water Repellent on Cotton Strips Treated with Phenolic Preservatives most of the strips with water repellent had iower tensile strengths than those without, in spite of their greater copper conTABLE 111. EFFECTOF COPPER AND MERCURY I N FUNGICIDEtent. I t is possible that the wax in the water repellent may have ON OF STRENGTH AFTER occluded particles of copper compounds and thus made them unOUTDOOR EXPOSURE Loss of available for protection; however, a more probable explanation Metal, % Water for the apparent ineffectiveness of the extra copper when the gtrength, Tensile % Gr--Repellent tis1 1 yr. 2 yr. 1 yr. 2 yr. water repellent was used is that another agency was operative in Copper compounds deteriorating the fabric. With wax-aluminum acetate the agent Chromate O.” 0.07 0.02 may have been acetic acid from hydrolysis of aluminum acetate. Chromate 0.08 40.51 0.12 Pentachlorophenate 0.11 0.01 0.003 15 25 Pentachlorophenate 40.11 0 . 0 8 0.03 0 25 -3 45 Ammonium flu0rid.e 0.28 0.007 0.003 40.26 0.11 0.05 Ammonium fluoride 24 TABLEIV. RELATIONBETWEEN RESIDUAL COPPERAND Loss 0 . 1 1 0.01 0.004 3 39 Naphthenate 0.11 0 . 0 1 0.004 13 44 OF TENSILE STRENGTH OF WEATHERED COTTON FABRIC TREATED Naphthenate 8-Quinolinolate 8-Quinolinolate Undecylenate Undecylenate Diethyldithiocarbamate Diethyldithiocarbamate Ammonium fluoride, 2 Ammonium fluoride, 5 % Naphthenate 2% Nephthenate: 5% Mercury oompounds H g pentachlorophenate H g pentaehlorophenate Pyridyl mercuric oleate Pyridyl mercuric oleate Phenyl mercuric oleate
2+ +-+ -
--
-
++ +
0.18 0.18 0.15 0.15 0.22 0.22 0.52 1.30
0.02 0.14 0.02 0.15 0.05 0.12 0.02 0.20
0.22 0.55
o:io
0.27 0,27 0.36 0.36 0.36
0,025 0.023 0.021 O:Oi4 0.012 0,027 0.025 0.002 0.002
0.004 0.03 0.01 0.03 0.008
0.03 0.005
0,07 0.004 0.03
‘g
ig
. .2
35 44 17 19 24 31 18 9 24 13
7 -4 19 10 19 0 7 4 21 32 13 26
64 88 67
8
72
74
WITH
COFPERPRESERVATIVES
Compound (No Water Repellent) Copper ammonium fluoride, 5% Copper naphthenate, 5% Copper chromate Copper undecylenate Copper diethyldithiooarbamate Copper ammonium fluoride, 2% Copper 8-quinolinolate Copper naphthenate Copper pentachlorophenate Copper ammonium fluoride
Copper after 2 Yr., %
0.07
0.03
0.02 0.01 0,008 0.004 0.004 0.004 0.003 0.003
Loss of Tensile Strength after 2 Yr., % 9 12 18 17 24
18 35 39
25 45
1788
'
INDUSTRIAL AND ENGINEERING CHEMISTRY
The other alternative, of employing a greater quantity of copper on the fabric, was more effective than attempts to conserve the fungicide. Where the initial copper applied \\-as approximately 0.5% (no repellent treatment), the loss of strength after two years was 12, 13, and 18% (Table 111). A sample which received 1.30% copper lost only 9 % of its original strength in two years. The different copper fungicides are compared, not on a basis of equal percentage of copper, but on that of equal percentage of fungicide. The question t'o be decided in these tests was not whether copper was more effective as the chromate or the naphthenate, etc., but whether copper chromate was more effective than copper naphthenate, etc. This method of coniparison favors the conipoiinds having the grea,ter percentage of copper in the molecul~,but it has justification. If copper is the protect,ive ingredient, as has been found, then it is the elempiit to be desired. If t'wo copper compounds are equal in cost and resistance t,o leaching, but one contains 10% copper by weight while the other cont,ains 50%, the latter should have a much bet,ter protective value. I n addition, the former adds five times as much weight of fungicide per weight of copper to the treated fabric as the Iat't'er, and thus changes the physical properties of the fabric by increasing its weight., stiffness, color, and possibly odor. An example of t,he latter type of compound is copper chromate, which contains 51% copper and gave excellent protection for two years when used as 1% of the weight of the fabric, I n many of the fungicides the copper was the least erpensive part of the molecule. None of the completely organic fungicides gave as effective protection after two years as the metallics just discussed. Of the organic fungicides, the phenolics gave best results. Figure 5 shows strips treated with phenolic compounds, with and without water repellent. The appearance and tensile strength data show the necessity of employing a water repellent with these compounds. Except for pentachlorophenol, the phenolics gave excellent protection the first year when used with the water repellent.. Although the t'rend was the same the second year, even those wit,h the water repellent' exhibited advanced detprioration and mold spotting. I n view of the excellent results in the first year of exposure, i t appears that these compounds could be expected to give satisfactory protection if used in sufficiently high concentration and in conjunction TTith a permanent wat'erproofing agent, such as one of the resins. Although the quaternary ammonium salts have the desirable property of being adsorbed on cellulose because of their positive charge, t,hey did not show up well in these tests. They afforded only fair protection the first year and little protection tmhesecond year of exposure. Undecylenic acid and 8-quinolinol (sometimes called 8-hydroxyquinoline) offered practically no resistance t o deterioration; this is further evidence that the copper in copper undecylenat,e and copper 8-quinolinolate was responsible for the protection giver1 by those compounds. Phenothiazine is of interest, for it is not a fungicide itself but is oxidized upon n-eather exposure to products which are highly fungicidal ( 9 ) : Phenothiazine-treated strips developed a dark reddish-brown color 011 the top side, which is the color of phenothiazone, the most highly fungicidal of the oxidation products. The presence of this fungicide was evidenced the first year by the strength and freedom from surface mold of the strips treated with water repellent. SOIL BIIRI k L TESTS
Burial of fabric strips in soil rich in microorganisms has often been used as an acccleratcd tcst to predict the effectiveness of new rotproofing chemicals. Theie is a general lack of agrecment, however, as to how accurately such 3. test forecasts the future of a fabric preservative in actual above-ground weathering tests. Since all of the treatments received both an outdoor weathering and a soil burial test, it is possible to check the accuracy of the soil burial method. Table I1 shows that, in
Vol. 41, No. 8
general, there was excellent agrecmcnt between the actual shade exposure and soil burial tests. The fabric strips buried in moist, warm soil for one and two weeks were deteriorated to about' the same degree as strips exposed to the weather for one and two years, respectively. The value of the soil burial test may be judged h y loss of tensile strength of weathered samples and those subjected i o ilie laboratory accelerated test (Table 11). For a, more ready comparison, t'he treated strips shown in Figure 3 are listed in Table T' in order of increasing loss of tensile strength in the outdoor exposure t'est and compared with the soil burial test. TVith two exceptions out of eleven, the correlation between the weathering and soil burial tests was good. There mere a sufficient number of exceptions, hon-ever, to prevent definite conclusions on the serviceability of a.ny product based merely on the soil burial test. On t,he other hand, it is a useful tool in roughly evaluating new preservatives.
TABLE 17. RATING O F k1ETAL PEST.4CHLOROPHEPiATES I X ORDER OF DECREASING TEKSILE QTREXGTH OF TREATED FABRIC SairPms Compoiind Sil\.er uentach1oroDhenate Copper pentachloiophenate Lead pentachlorophenate N e r c u r y pentachlorophenate Cadioium pentachlorophenate T,-ianyl pentachloropheiiate Chromium pentachlosophenate Nickel pentachlorophenate Cobalt pentachlorophenate Pentachlorophenol Zinc pentachlorophenate
Outdoor Exposure 1 2 3
+ 6 7 8
Lab. Soil Burial 1
2 3 10 6
z
9 10
8 9 11
11
4
,In interesting observation is the unusually high resistance to deterioration of strips t,reated wit,h silver pentachlorophenate. The resistance was confirmed in the exposure tests. Although silver pentachlorophenate gave t'he best resuks of any of the fungicides employed in thesc tests, it is doubtful whether t.he high Cost of silver would permit its use in any but special applications. SUMMARY AND CONCLUSIOKS Fungicide-treated cotton fabric strips were given outdoor shade exposure tests for two years in Florida. The rainfall mas 70 inches the first year and 52 the second. All preservative-treated strips contained 1% by weight of fungicide when dry. One series had an additional water-repellent treatment. L-ntreated controls lost an average of 67% initial tensile strengths the first year of weathering and 93% the second year. Controls treated only with wax-aluminum acet,atewater repellent lost 49% tensile strength the first year and 90% the second. The surface mold st*aingave a visual indication of the extent of deterioration of the weathered strips. The only strips that withstood t'wo years of weathering without eonsiderable deterioration 7%-erethose treated with copper and silver preservatives. The copper group had a tensile strength loss o€ 0 t o 19% t'he first. year and 12 to 45% the second. Residual strength after two gears was correlated with the residual percentage of copper. Copper chronmte, having a high initial copper content, gave excellent,protection over the two-year period. Mercurials and other heavy metal compounds did not give the anticipated protection. Even where the residual concentration of niercury was greater than that of copper, the deterioration of the treated fabric was much greater than that with the copper. The phenolics, used with water repellent, were the only organic fungicides that rendered the fabric appreciably resistant to microbial decomposition. For longer service life, however, it appea,rs that the phenolics should be used in higher concentration than 1yoor in conjunction m-ith efficient waterproofing agents. The laborat,ory soil burial tests were, in general, in agreement with the out,door exposure t.ests. Soil burial for one and two weeks deteriorated the fabric to about the same degree as one and two years of outdoor weathering, respect,ivcly. Fabric treated with
INDUSTRIAL AND ENGINEERING CHEMISTRY
August 1949
silver pentachlorophenate had unusually high resistance to deterioration in soil burial compared to the other treatments. LITERATURE CITED
(1) Am. Soo. Testing Materials, “Standard General Methods of
Testing Woven Textile Fabrics,” Designation D 39-39. (2) Am. SOC. Testing Materials, “Tentative Methods of Test for Resistance of Textile Fabrics to Microorganisms,” Designation D 684-42T. (3) Armstrong, E. F., Chemistry &,!ndustry, 60,668 (1941).
(4) Assoo. Official Agr. Chemists, Methods of Analysis,” 5th ed., p. 409 (1940).
1789
(6) Barghoorn, E. S., Office of Quartermaster General, Teztile Beries Rept. 24 (1946). (6) Dean, J. D., Strickland, W. B., and Berard, W. N., Am. Dyestuff Reptr., 35, 346 (1946). (7) Dean, J. D., and Worner, R. K., Ibid., 36,405 (1947). (8) Fargher, R. G., J.Soc. Dyers Colourists, 61, 118 (1945). (9) Goldsworthy, M. C., and Green, E. L., Phytopathologg, 29, 700
(1939).
(10) McFarlane, W. D., Biochem. J . , 26, 1022 (1932). (11) Thaysen, A. C., Bunker, H. J., Butlin, K. R., and Williams, L. H., Ann. Applied Biol., 29, 750 (1939).
(12) Zuck, R. K., and Diehl, W. W., Am. J . Botan?~, 33, 374 (1946). RECEIVED August 11, 1948.
Film Coefficient of Condensing Vapor JU CHIN CHU, R. K. FLITCRAFTI, AND M. R. HOLEMAN2 Washington University, S t . Louis,M o .
A
modified method of measuring the heat transfer coefficient of a condensing organic vapor on a single horizontal tube is presented. The method of Wilson is not fundamentally sound in t h a t i t assumes t h a t the heat transfer coefficient is independent of the rate of heat transfer. It is shown theoretically t h a t the heat transfer coefficient is a function of the rate of heat transfer; therefore, the correlation of data obtained a t a constant value of rate of heat transfer will place Wilson’s method on a rigorous basis. This involves a major modification of the Wilson method. Experimental conditions of rate of water flow and over-all temperature difference are varied 80 t h a t data are obtained a t a constant rate of heat transfer under two or more conditions. The value
of the heat transfer coefficient a t a constant value of t h e rate of heat transfer is calculated according to the modification of the Wilson method. The over-all temperature difference is varied by changing the vapor system pressure. The experimental values of the heat transfer coefficient obtained a t low rates of heat transfer check those calculated from the Nusselt equation. The deviation of the experimental values from the calculated values increase as the rate of heat transfer increases. This may indicate turbulenoe i n the condensate flow a t high rates of heat transfer. The theoretical derivation of the relationship of the heat transfer coefficient and rate of heat transfer is confirmed by experimental data obtained on ethyl acetate and benzene.
T
the wall. The thermocouples measure only isolated point temperatures, and then i t is necessary to make certain assumptions in calculating the wall temperature. Baker and Mueller ( 1 ) later proved that there is no point at which a thermocouple can be located in a tube wall and obtain the true surface temperature of the tube wall. Rhodes and Younger (12) avoided the use of an embedded thermocouple by applying Wilson’s method. Checked experimental values with Nusselt’s equation have been obtained with the exception of benzene and toluene. I n an effort to obtain further information on the subject of film coefficients of condensing organic vapors and to determine, if possible, the reason for the discrepancy in the values of toluene and benzene, i t was proposed that a modification of the Wilson method (12, 1 4 , based on a rigorous theoretical analysis, be employed. Wilson’s method (14) has been well discussed by Mchdams (6, 7) and by McAdams, Sherwood, and Turner (9). It is based on the following equation of over-all thermal resistance for the transfer of heat from condensing vapor t o cooling water through a tube surface when the flow of water is inside a tube in turbulent region.
HE Kusselt equation (7, 10) is usually used in predicting
the rate of heat transfer between pure condensing vapor and a colder surface. The Nusselt equation for a single horizontal cylindrical tube is
ho
x
=
0.725(K,33;2gX/D#,
(11
The equation assumes that streamline motion exists throughout the continuous film of condensate and that gravity alone causes the flow of condensate over the surface. The possible effect of vapor velocity upon the film thickness is neglected. The theoretical equation is based on the assumption that the total thermal resistance is in the condensate film. The film coefficients for benzene and toluene have been investigated previously by using an embedded thermocouple (6,8, la). The data do not check well among themselves, and in some cases the agreement between the theoretical ho value and the observed value is not good. There appear to be no previous experimental data on the film coefficient for ethyl acetate on a horizontal tube. Rhodes and Younger (1%’)pointed out that the use of thermacouples embedded in the tube to obtain the wall temperature had several disadvantages. There is likely to be disturbance of the fluid film on the tube surface due to irregularities; however, with the present advanced techniques i t is probable that the surface can be smoothed properly. The introduction of a foreign metal in the tube wall will be likely to disturb the flow of heat through address, Monsanto Chemical Company, St. Louis, Mo. 1 Present address, Fouke F u r Company, St. Louis, Ma. 1 Present
ZR
=
Re
+ R w + CL/VO.’
(2)
where a = a constant. It was then assumed that if R, R , was independent of the cooling water flow rate, a linear equation would result between R and 1/Vo.8. Using a condenser with a tube of known thermal
+
