ISDUSTRIAL A S D ENGIA'EERISG CHEMISTRY
600
days during the most trying period of the summer months. The lacquer was of fairly light color and very clear, but possessed a somewhat distinctive aldehyde odor. The durability was good. Similar resins were made from cellulose acetate and other cellulose esters and ethers produced a t this laboratory. The main difficulty in the work was the production of resins of very light color to compare with such resins as dammar and extra pale ester gum* The seemed most interesting, however, and point to the possibilities of producing materials of this character. Chemistry of Process I n the condensation of acetone with aldehydes the first step is a simple additive product as follows: CHI. CO.CHa CH3.CH(0H).CH2.CHO+
+
CH3.CO.CHz. (0H)CH.CHz. CH(0H)CHs
Vol. 20, No. 6
Kater is then lost by heating, and an unsaturated compound, which is in the form of a viscous liquid, is produced: CH3.C0. CH : CH.CH : CH.CH,. Upon further heating there seems to be a polymerization of this unsaturated compound, with the formation of a solid resin of the probable formula CH3 CO.CH.CH:CH.CH.CHs
I
I
CHI. CO.CH.CH:CH.CH.CHa This final product does not add bromine, so it is apparently saturated, but no definite tests could be made to determine its constitution, owing to traces of free acetone and aldehyde in all the final products. This paper cannot be considered as a report of a finished investigation on acetone condensation products, but it is presented as a summary which may be of general interest to investigators in this field.
Adhesion of Films' Further Results on the Adherence of Films to Various Surfaces H. A. Gardner and A. W. Van Heuckeroth IXSTITUTE O F PAINT
A N D V A R N I S H R E S E A R C H , m'ASHINICTON,
OME preliminary results on adhesion were outlined in a recent publication of the American Paint and
S
Varnish Manufacturers' Association.2 In this work the Gardner-Parks tensile strength meter was used for the quantitative determination of adherence. Recently an opportunity has been afforded to determine the adherence by this method of a number of lacquer materiak, when applied to surfaces of black iron, galvanized iron, wood, glass, tin, and aluminum. There has been much discussion as to whether the addition of certain resinous materials to a lacquer would add to or lessen the adhesive properties of the lacquer when applied and dried to a film condition. A number of qualitative tests have been heretofore used to determine this result, but none of them have been entirely satisfactory. Experimental
In the tests made at this laboratory panels 3 by 5 inches (7.6 by 12.7 em.) in size were selected. I n the case of the metal panels it was found necessary to have the surfaces absolutely clean and free from grease. Otherwise comparable results could not be obtained. It was found after considerable experimental work, that the best method of cleansing was to scrub the surface of the panel thoroughly with benzene and later with acetone. Surfaces free from grease are thus secured. In operating the t'est, the lacquer is brushed upon the panel and a piece of silk of the same width as the panel and twice as long is immediately embedded in the coating. There is then applied a second coat of lacquer, which is brushed over the silk before the first coat has a chance to harden. By this means the silk is thoroughly sandwiched in the coating and pressed down with the brush so that no air bubbles are allowed to remain. After drying for 2 or 3 hours, the silk cloth embedded in the film is cut 1 Presented before the Division of Paint and Varnish Chemistry a t the 75th Meetina of the American Chemical Society, Si. Louis, Mo., April 16 to 19, 1928. 2 A m . Point V a r n i s h Mfrs. Assocn. U . S., Tech. Circ. 343 (February, 192R). 8 W. C. Norris, of the Palmerton Laboratory of the New Jersey Zinc Co., has been conducting similar work on the adhesion of films and has devised the use of silk for imbedding in films as outlined also in this paper.
D.
c.
with a sharp razor blade into test strips about 1 em. wide. The test panel is then fastened into the tensile strength apparatus as shown in the illustration, and the end of one of the strips is loosened from the panel t o form a grip for the machine. After the panel is inserted in the machine, the load is applied and the strip slowly and gradually removed from the coated panel. The load usually shows a constant pull all the way down the panel, indicating that the adhesion is the same over the entire surface where normal conditions ( obtain. The results on a number of lacquers upon various types of surfaces are given in Table I. It should be pointed out that the tensile strength machine on which these tests were run is only correct to * 20 grams. It will be noted that on the galvanized iron, tin, black iron, and aluminum panels the adhesion of lacquers 1 to 8 was very low, while that of lacquers 9 t o 14 was comparatively high. This would seem to indicate that the presence of resin in a lacquer gives greater adhesion t o metals of the type mentioned above. Generallyspeaking, the adhesion of the films to the metals increases with the amount of resin, u p to a c e r t a i n percentage. On wood panels comparatively high adFigure e hesion results were shown. This T e n si l e s t r e n g t h Meter would be expected because of the ~~~~~&~~ ~ $ ~ ~ great porosity of wood, which Films Upper portion of picture shows allows-of the-penetration of the steel plate to which lacquer has film material which anchors it- been applied and in which there is embedded a sheet of silk. This self in the pores. The results on has been cut into seven strips, of which have been orlare glass panels were surprisingly three being pulled off, disclosing the high. black metal beneath.
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I A Y D I - S T R I d L1 S D E S G I S E E R I S G CHE.\IISTRI-
June, 1928 LACQCER
SO.
T a b l e I-Adherence R e s u l t s of Lacquers on Various S u r f a c e s GALVAKIZED IRON BLACKI R O ~ GLASS \\-OOD 1 day 6days l d a y 6days l d a y 6 d a y s 1day 6 d a y s
Parls
1
2
3 4
5 6
7
8 9
10
11
Grams 20
Grams 0
Grams Grams Grams Grams 0 20 600 700
13
14
a
.%LZM I S U M
1 day
Interpretation of Results
Query has been made as to whether the results might represent adhesion of the coating to the surface, cohesion of the coating itself, or adhesion of the coating to the silk. When pulled from the panels and examined under the microscope, the silk was found to be well saturated with the coating in practically every instance. In running the tests, it was noted that some of the materials employed were removed from the panels when the silk was subjected to tension, leaving a perfectly clean surface, while the other materids stuck to the panels in spots. It is suggested that when the film is completely stripped, leaving a clean surface, adhesion is less than cohesion, and adhesion is the property being measured; but that when the film is not completely removed, either adhesion or cohesion or both of these factors are variable, or the values lie very closely together. Cohesion should be constant in any test, while adhesion will depend upon the uniformity of the surface of the panel and the method of application of the film. If, in the case of the .potted condition, it were possible t o increase the adhesion, the cohesion remaining constant, the spots would increase in size. At a certain critical ralue, where the adhesion changes quickly, the cohesion spots mould extend entirely across the base panel, and cohesion would then be measured. Any further increase in adhesion would not change the readings, because cohesion would now be less than adhesion. Conversely, if the adhesion be reduced u,hile maintaining the cohesion constant, the sI,ots should decrease in size until ft certain other critical value is reached, at which time there will be no spots left and the film will come off clean from the base panel. At such a point adhesion will be measured. Therefore, when a film comes off clean, it is only possible to state that the adhesion is less than the cohesion. When the entire panel is covered with spots of film, cohesion is probably less than adhesion. For a spotted
6days
Grams Grams
Cotton-base solutionn 100 0 100 Toluene Lacquer No. 1 100 40 50 10 10 600 400 180 300 0 Tricresyl phosphate J Lacquer No. 1 in0 40 40 20 20 160 120 380 290 0 Tricresyl phosphate in Lacquer X o . 1 100 50 80 10 10 300 280 300 360 0 Dibutyl phthalate 5 Lacquer N'o. 1 100 120 280 40 20 320 320 500 460 0 Dibutyl phthalate 10 100 140 100 20 10 480 620 1100 520 0 Lacquer No. 1 Heat-treated t u n e oil 10 100 40 80 380 500 500 420 540 600 Lacquer No. 1 0 Linseed oil (heavy-bodied) 10 Lacquer X o . 1 100 0 10 0 10 160 200 400 500 0 Castor oil (heavy-bodied) 10 Cotton-base solution 100 220 100 380 560 330 200 720 850 40 50% Wax-free d a m m a r (in alcohol) 50 Toluene 50 Dibutyl phthalate 10 Cotton-base solution 100 40 100 220 200 200 220 670 600 30 30Yc Xvax-free shellac (in alcohol) 50 Alcohol 23 Toluene 23 Dibutyl phthalate 10 Cotton-base solution 100 570 600 250 zoo 620 400 520 4so 100 Ester g u m 50y0 (in toluene) 50 Toluene 50 Dibutyl phthalate 10 Cotton-base solution 220 200 360 330 420 300 600 500 380 50'; Irax-free d a m m a r (in alcohol) I 5 Toluene 50 Dibutyl phthalate 10 Cotton-base solution 100 100 100 170 100 300 250 300 200 150 30C0 Wax free shellac (in alcohol) ,a Alcohol 25 Toluene 25 Dibutyl phthalate 10 Cotton-base solution 100 520 340 300 340 300 150 400 380 220 Ester gum solution 50% (in toluene) 75 Toluene 50 Dibutyl phthalate 10 T h e cotton-base solution used contained 32 ounces of 'in-second viscosity nitrocellulose dissolved in 1 gallon of butyl acetate.
10-0
12
Grams Grams 160 180
601
0
1 d a y 6 days Gramr Grams 0 0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
50
60
80
30
20
0
100
20
20
450
300
300
20
20
RO
330
1S0
40
condition, therefore, the values measured lie between the critical values mentioned above. In other words, the value is intermediate between cohesion and adhesion. Actually it is believed that in the case of a spotted condition the two critical values are rather close together. There has been some difficulty in securing the same results with the same lacquer on the same surfaces, after the same period of drying, when the adherence test is made on different days. It is probable that temperature and humidity have a very marked effect in these tests, and that they should preferably be made in a room fitted up for constant temperature and humidity work.
Gas Engineering at Johns Hopkins University Eight men are candidates for the degree of bachelor in engineering in gas engineering in the first class to be graduated from the Department of Gas Engineering a t Johns Hopkins University, a t the close of the fourth year's work. The enrollment for this year shows 30 undergraduate students; 4 graduate students; and 24 extension course students-a total of 58. Nineteen scholarships will be available for the next school year, founded by the Washington Gas Light Co., the Southern Gas and Power Corp., the C. H . Geist Co., Consolidated Gas Co. of New York, Consolidated Gas, Electric Light and Power Co. of Baltimore, the Mobile Gas Co., the Philadelphia Suburban Gas and Electric Co.. The KooDers Co.. and the TamDa Gas Co. With the renewal of the ;&search agreement unde; which the Consolidated Gas e o . of New York, the Consolidated Gas, Electric Light and Power Co. of Baltimore, the Rochester Gas and Electric Gorp,, and the Mars co, have supported full-time investigators, research activities are continuing and give evidence of growth. Some of the problems now under consideration in graduate student work include the purification of gas by means of iron oxide in order to ascertain scientifically the effect of various factorson the activity of the oxide, and the mechanism of the production of organic sulfur in the cracking of oil.
