Document 85EYDppkVGjzVQRKXQwnggLEk

94 Hoe w-588 ufNRIrXFDw Dr. 1. A* Fluevog, Toledo Mr* B. Bullitt. Lab. Mr. a*. W, niff, tab. Dr. P. B. Evans, Lab. Dr. S, Horning, Lab. Ji 10 MARSHALL LABORATORY LM majustaui ` 'mmmh COLOR DRIFT OF IRON BLUE PIGMENTS IN 94 AND 194 LINE BAKING "DULUI" CHEVRON BLUE AND DARK BLUE ENAMELS This investigation of overnight oolor drift ooo tiring after baling 94-23150 Chrysler-Plymouth Chevron Bine and 194-22074 Dark Blue Baking "DULUX" really consists of two separate problems brought to our attention by customer complaints and the Prodaction Department respectively. The first is excessive difference in color caused by a difference in baking schedule and the second is a change in tone from green-blue to red-blue in a twelve to twenty-four hour period after baking. Conclusion? The existence of the first problem was verified by gluing a panel of 94-23150 the regular bake of 25* z 275*F., and a similar panel a bake of on hour at 225F. The panel baked at the higher temperature was considerably more yellow in tone than the panel baked at the lower temperature, showing this difference in color to be related to the amount of heat used. It was found that the color drift phenomena was essentially a chemical-oxidation reaction and that a gaseous oxidising agent was needed to accelerate this reaction. A 27.5# solution of hydrogen peroxide was found to produce the same change in about 1-1/2 hours that occurred overnight in the laboratory. On the basis of this work, a hydrogen peroxide dip process oould probably be set up for accelerating this "color drift" so the batches oould be checked more q.uiokly against standards for oolor match. Experimental} This color' drift, which occurred with both W-5S2 and W-586 Iron Blue pigments did not occur in the same product when the iron blue pigment was replaced by W-505 Monasfcfeal Blue, indicating that the change was in the pigment and not the vehicle. 0van ventilation had no effeot upon the oolor drift-nordid exposure of tli panel to sunlight, although the latter effected a sort of fading In color* Panels of the Iron blue products kept for an over* night period In a vacuum dessieator in an atmosphere of OO2 gas and those kept at a very low temperature did not redden in tone overnight like the control panel, suggesting that the reaotlon was one of oxida tion. However, dipping the panel in acid solutions of potassium per manganate Or potassium dichromate did not aooeler&t the color drift even when the panel was left in the solution several hours. However, when the panel was allowed to stand in a 27,5% solution of hydrogen peroxide, oxygen wfs slowly evolved and the color change took place in less than two hours. Considerable work was done originally along the line of this being a physical problem based on dispersion. Flocculation of the pigment seems to have a very slight effect on "color drift", but this problem is mainly one of a chemical reaotion. With the idea that varying film acidity at different stage of dry might be affecting the color, enamels ware doped with phosphor ic acid to maintain a definite acidity* Sfhese enamels baked out much greener in color than the controls, but drifted to about the same ex tent after baking. Details of experimental work on this problem are found in Notebook 2972, pages 5-43. FSHLAHELHilA lABOBATOflY LC,$W9cJ joc/mhl C. CARVES DUP030002956