INDUSTRIAL A N D ENGINEERING CHEiMISTRY
806
.
Vol. 17, S o . 8
Automobile Finishing Varnishes’ By W. T. Pearce NORTH DAKOTA AGRICULTURAL COLLEGI?, AGRICULTURAL COLLEGE, N. D.
H E writer2 has found that the kauri reduction test varnishes. In general, the directions given in ‘Valentine’s gives reliable information as to the durability of many Materials and Methods of Automobile Painting” were foltypes of varnishes applied on wooden panels. Pulsi- lowed in applying the several coats. When the finishing coat was dry, the panels were exposed fer3 used the elasticity values obtained by this test as a basis for building up proper coats for automobile finishing varn- on a wooden rack, facing south and inclined a t an angle of ishes. He found that the priming materials should have a 45 degrees. This rack was placed on the tower of a high high relative elasticity, and that the elasticity of the materials building in order to prevent any one from injuring the varnish used for the succeeding coats should decrease to the japan coats. April 15 was the date of exposure. This time of the color and then graduallv increase to the finishing varnish. year was selected as varnishes perish most rapidly a t this season. I n this way the color varnishes should Each finishing varnish was applied be less elastic than the rubbing varnish over color and rubbing coats of at least and both much less than the finishing Laboratory and exposure tests two different elasticities. varnish. hlougey4 found that, alwere made on a series of autoThe color and rubbing varnishes though the priming and surfacing mobile varnishes. The varnishes passed the following kauri reduction material were durable, the color and were applied over color and rubbing values : rubbing varnishes frequently were so coats of widely varying elasticity, low in durability that they caused the Black co!or varnish - 50 built upon steel panels and upon Elastic black color varnish - 15 failure of the automobile finish. He one coat of a baking japan. These Black motor chassis varnish +YO showed that the finishing varnish Motor rubbing varnish - 40 panels were fastened to a rack facClear motor chassis varnish +YO should be more elastic than the undering south, inclined at an angle of coats to secure the best results, and By referring to Table I, it will be 45 degrees, and examined weekly that a medium-grade finishing, which noted that the color varnishes of until all the varnishes had failed. dries to a hard film, may give better lowest, medium, and highest elasticities The laboratory examination inresults over color and rubbing varnishes were applied to Panels 1 to 15,16 to 26, cluded elasticity, viscosity, rate of of low durability than a more elastic and 27 to 32, respectively. drying, specific gravity, hot, cold, finishing varnish, which dries to a film I n order to study the durability of and soap water tests, gas and draft less hard. the finishing varnish without reference tests, nonvolatile and acid value. to the different color and rubbing The tabulated data are studied Aims of Work coats, the varnishes were applied over in order to ascertain the relationThis work was undertaken pria coat of baking japan. The japan ship of elasticity, of color and rubmarily to determine the relationship of was flowed on the clean steel panels, bing coats todurabilityof thefinishthe elasticity of the color and ruballowed to drain, and then baked for ing varnish, and the relationship bing varnishes t b the durability of 3 hours in an oven a t 160” C. These of elasticity of the finishing vara u t o m o b i 1e finishing varnishes of were exposed upon the same rack and nishes to their durability. widely varying elasticity, and to secure a t the same time as the series predata upon the relationships of physiviously described. cal tests to the durability of this type Table I-System of Application of varnishes, when applikd over coior coats. Day Coat ~IATBRIALS
T
Outline of Investigation
Several prominent manufacturers donated fifteen varnishes for this study. These were transferred to quarter-pint cans, which were completely filled and tightly stoppered. A freshly opened can was used for each part of the work. For the exposure tests automobile body steel panels, 40.75 by 30.5 cm., were fastened to a wooden frame and not removed until they were ready to be placed out of doors. All panels containing rust spots or dents were discarded. The room selected was nearly dust free a t all times, and by means of a thermostat the temperature was kept at 21 C. Before applying the primer, the panels were washed first with benzene and then with 5 per cent acetic acid, rinsed with water, and washed again with benzene. After consulting many specialists in automobile finishing, the system given in Table I was used to build up the coats upon which to apply the series of color, rubbing, and finishing O
Presented before the Secticn of Paint and Varnish Chemistry at the 69th Meeting of the American Chemical Society, Baltimore, Md., April 6 to 10, 1925. 2 THISJOURNAL, 18, 681 (1924). * J. Sac. AufomofiweEn.?., 11 (1932). Educational Bureau, Paint Manufacturers’ Assoc., Circ. 207, p. 36. 1
1
1
2
2
3
4 5 5 6 8 10 13 17
(A.M.) (P.Y.)
3 4 5 6
7 8 9
10 7
6 9 12
s
16 17
10
6 (r
7 8
12 16 17
10
9
9
A l l Panels Celox primer Blend of equal volumes of Celox primer and rough-stuff Rough-stuff Celox sealer, after sandpaper rub Japan color, after light rub Japan color Panels 1 l o 15 Black color varnish Black color varnish after pumice rub Motor rubbing v a r k h after pumice rub Pumice rub omitting $anel 15 Finishing vAmishes, omitting Panel 15 Panels 1 4 to 26 Elastic black color varnish Elastir black color varnish, after pumice rub Blend of equal volumes motor rubbing varnish and clear motor chassis finishing, after pumice rub Pumice rub, omitting Panel 26 Finishing varnishes, omitting Panel 26 Panels 27 io 32 Elastic black color varnish Blend of equal volumes of elastic black color varnish and black motor chassis finishing, after pumice rub Clear motor chassis finishing, after pumice rub Pumice rub, omitting Panel 32 Finishing varnishes, omitting Panel 32
Physical Examination
The Proposed Tentative Methods for Testing Oleo-ResinVarnishes (D 154-23T) of the American Society for
oils
I N D U S T R I A L A N D ENGIYEERING C H E M I S T R Y
August, 1925
Testing Materials were used for determining the appearance, color, nonvolatile matter, and elasticity (kauri reduction value). For drying time and for hot and cold water, gas and draft tests, the methods given in Circu.Zars 103 and 117 of the Bureau of Standards were used. Viscosities were determined with the Gardner-Holdt viscometer. The thickness of film was calculated by means of the formula
f =
1/2
(10V
+ N)
where f is the thickness of film in microns (or film factor), V the viscosity in poises, and N the percentage of nonvolatile matter. The data secured with these methods are given in Table 11.
Table IV-Durability varnish 61 62 63 64 66 fl7 68 70 71 72 73 75
Panel 33 34 35 36 37 38 39 40 41 42 43 44
807
of Varnishes over BakinQ E n a m e l Appearance oi cracks Complete failure Weeks Weeks I8 23 17 21 19 27 16 22 14 17 16 21 5 11 14 20 16 30 23 24 18 21 26 30
To show the relationship of the durability of the varnishes applied over a properly built-up system of air-dried coats
Table 11-Physical Data' Kauri reduction Film Viscosity Sp. gr. Acid Set to touch Dry hard Varnish value factor Poises Konvolatile 15.5°/15. 5O C. value Color Hours Hours SOAPWATERCOLDWATER 0.60 Passed 8.73 Passed I 1'/2 61 85 44.55 2.35 0.92747 65.61 Passed 7 8.79 Passed 0.60 62 90 33.20 0.91168 57.40 0.90 Failed 12.93 Passed 0.70 20% 63 70 63.85 39.42 1.50 0.92641 9.66 Passed Passed 0.50 24 90 65.92 64 40.71 1.55 0.93553 Passed Passed 0.50 10.79 17l/z 65 42.03 2.10 0.92581 140 63.07 Passed Passed 0.50 7.69 33/r 35.35 2.30 0.89240 47.71 66 60 Passed Passed 0.50 6.57 53/4 38.89 0.89415 54.28 67 65 2.35 Passed Passed 1.75 15.52 83/r 0.89577 68 00 30.26 0.80 52.52 Failed Failed 0.70 17 17.79 0.94180 69 10 41.57 2.45 58.65 Failed Passed 0.50 8 5.61 0.92737 38.12 30 1.40 62.25 70 Passed Passed 0.40 10b 10.45 0.91446 2.25 59.70 41.10 71 190 Passed 11.34 Passed 1.00 3'/2 1.50 0.90300 65.02 40.01 72 80 Failed Passed 0.60 11.89 101/2 0.93438 37.13 73 55 1.40 60.26 Failed Passed 0.60 10 16.75 0,92980 74 35 61.73 38.86 1.60 Passed Passed 6 6.33 0.50 0.90546 41.53 75 135 1.75 65.57 a All varnishes were clear and all passed the gas and draft tests except No. 72, which gave a silking effect, owing to its rapid drying. b Tacky for 24 hours.
Exposure Data
The panels were examined a t intervals of 7 days from the date of exposure, noting loss in luster, first signs of cracking, scaling, and the time of complete failure. Table I11 gives the weeks' exposure of each varnish over the color and rubbing coats and over the baking enamel, before cracking and before the finish failed. Table 111-Exposure D a t a Appearance of Complete failure Varnish Panels cracks, in weeks in weeks A B C . A B C 1 and 16 26 61 18 18 26 2 a n d 17 62 17 17 22 24 63 I9 26 24 19 3 and 18 64 26 26 4 and 19 16 16 65 26 5 and 27 24 16 16 16 6 and 20 17 66 11 10 67 7 and 21 I!? 14 14 20 68 8 and 28 9 5 4 10 9 and 22 15 69 14 6 5 70 10 and 23 13 12 16 26 27 71 11 and 29 10 17 23 24 26 72 12 and 30 18 18 20 73 13 and 24 14 14 17 17 74 14 and 31 12 10 16 27 75 25 25 17 4 7 15, 26, 32 2 7 10 A = over least elastic color and rubbing varnishes. B = over medium elastic color and rtibhing varnishes. C = over greatest elastic color and rubbing varnishes.
Varnishes 66, 68, 70, and 74 began to fail sooner over the more elastic color and rubbing varnishes than over the less elastic coats. The kauri reduction values for these varnishes are 60, 00, 30, and 35. Varnishes 67 and 73, having kauri reduction values of 65 and 55, began failing a t the same time in both sets. It will also be noted that Varnish 71, with a kauri reduction of 190, gave much greater durability over the most elastic undercoats. (A difference of 7 weeks in time of appearance of first cracking, and of 4 weeks in time of complete failure.) Panels 15, 26, and 32, containing no finishing varnish coat, perished in the order of the elasticity of the color and rubbing coats. The times of appearance of first cracking were 2,4, and 6 weeks, respectively, and the times of complete failure were 7, 10,and 17 weeks. The time of failure of the varnishes amlied _ - over the bakingenamel is given in Table IV.
and over a baked enamel coating, the time of failure given in Table IV and the highest figures given in Table I11 are tabulated along with the kauri reduction values and thickness of films of the finishing varnishes. This is shown in Table V. Table V-Comparisons
Varnish 61 62 63 64 66 67 68 70 71 72 73 75
Film lactor 44.55 33.20 39.42 40.71 35.35 38.89 30,26 38.12 41.10 40.01 37.13 41.53
of Durability Data, Film Thickness, and
Elasticity FIRST CR.4CKING OVER Air-dried Baked Kauri coats coat reduction Weeks Weeks R5 IS 18 17 17 90 70 19 19 16 1B 90 14 on 11 16 65 1; 5 00 14 30 13 100 I6 17 18 80 23 14 55 18 25 135 26
COMPLETE FAILURE OVER
Air-dried Baked coats coat Weeks Weeks 26 23 24 21 27 2R 22 26 17 17 20 21 11 10 26 20 27 30 25 26 21 20 27 30
It will be noted that first cracking was observed from 1 to 5 weeks earlier over the air-dried coats in the case of five of the varnishes, a t the same time for five, and 1 week later for one. Over the air-dried coats complete failure was noted from 1 to 3 weeks sooner for six of the varnishes and from 1 to 4 weeks later in the case of five. Table VI-Initial Loss in L u s t e r a n d First Cracking, in Weeks Initial loss in luster First cracking Kauri Varnish (a) (a) (a) (b) reduction
72 12 14 73 11 11 75 12 12 ( a ) Oven air-dried coats. ( b ) Over baked coat.
18 14 2.i
23 18 26
SO 55 135
First observations of loss in luster, as noted by the eye, are given in Table VI along with the time of initial cracking. I n most cases loss in luster was noted 3 or 4 weeks before first signs of cracking. Two varnishes showed loss in luster
iiiileh
sooner w c r buth types of routs and two silowed mark-
iitg and loss in luster at tlie same time.
Hy grouping tho vnriiishes according t o their elasticity mid tivcraging their dnraljility, tlre following data are obt,nincd: No. of v:f tire time recorded. The average durability measured in this way is in all cases greater over the more elastic color and rulhing varnish coats. BAKEDUXDERC~ATS FOR EXPOSURE T~s~s.--The relative iliiraitiity of the varnislies over the system of air-dried coats and over a baked coat has already been noted. The data of the finishing varnish over the best suited unden:oats were .imilar to those found over the baked coat. Therefore, for .studying tlie diirability of automobile finishing varnishes xit,tiout relation to the undercoats, the one baked coat seems t u be quite as satisfactory as tlie system of built-up air-dried coats. These conclusions are tentative ones, and the study will be continued. A larger number of varnishes, having a kauri reduction of over 100, will be used over a larger number of color coats and over several baking enamels. If it is possible, varnishes varying more widely in othcr plrysical cliaracteri.stics, such as film fartor and watcr resistance, vdl be ineludcd.
..
Acknowledgment
l'ire writer wishes to express his tEinnks to the Edut~atioiial liiireau of the Paint Xanufacturers' Associrttion for doiiating ' 1 I'ulsifcr, of Vttlentine lirnds to eonduct this study and t o I,. . & Company, for his advice and interest in t,lie work. He Jvislies also to express appreciatioii t o A. S . Loudon for valiirtble assistance and t.o several manufaeturcrs for suggestions snd donations uf rarnislies. Fuel Oil Made Dutiable in Antigua~ -Accurding t o T r a d e Commissioner H . P. hfacgowan, Antigua has passed an o r d liaiice removing from her free list of imports oil to be used as fuel io oil engines for industrial purposes, and imposts an import duty on such goods a t tlic rate of 15 per cent ad vdorcm uiider t h e griieiai tariff and 10 per cent ad illo ore in under t h e Rritisk preferential tarifl.
diortening the analytical time the progress of the merchandise tlirougli the plant is facilitated, equipment can be used more times around-in general, many savings can be accoin~~lislied.The microscope has its place in certain types of con!rol xork and is becoming more useful daily, particularly in the metals indiistries. J3ut for average analytical control work it cannot conveniently he used-nly chemical methods can 1)eused. Jlicrochemical analytical technic is simply a refinement of the ordinary macro metliods for tile purpose of assaying accurately small amounts of substance. The pioneer in this speri,liized field d cliernicd analysis is Prof. Fritz Pregl, of the University of Graa. The stimulus to his ~ o r on k micro&
R c c e i v e d June
2. 1923.
