was disclosed by Ralph F . Nickerson, group leader in t h e textile chemical research laboratory of Monsanto's Merrimac Divi sion. T h e test method recommended b y Mon santo specified placing equal quantities of Danger of introducing abrasive particles in a metal f l a w detection procedure concentrated urea resin solutions in watch is eliminated . . . Method developed by N a v y is suitable for field work classes or foil cups. T o o n e glass, 5Ve uf catalyst AC based on the urea formal d e h y d e solids present is added. O n t h e ituilticylinder Diesel engines. in such AΝ OIL-POwder method has been chsame basis 3 ' ν of D A P is a d d e d to t h e structures t h e magnetic powder flaw-de **· vcloped by t h e Naval Engineering other. Both arc evaporated to dryness on tection method is difficult to apply, and K \ p e n m e n t Station, Annapolis, Md., for the use »>t fluorescent oils w a s found im a hot plate. detection of surface flaws a n d cracks in practical because of t h e requirement tor W i t h the DAP. t h e resin soon starts to dense materials. T h e inspection method use of ultraviolet light in detection. T h e .N applicable to both ferrous a n d rionsolidify and forms a thick mush in solu h-rrous metals, vitreous enamel, a n d non- method provides detection regardless of the tion. In the case of catalyst AC, t h e resin geometry of the structure, without auxiliary porous plastics. remains in solution until t h e mixture is devices such as ultraviolet light. •practically dry. W h e n this stage is A film of penetrating oil is applied to the surface being inspected, then removed reached, both are cured for 15 minutes at The single disadvantage is said to b e itter a brief period. T h e area is dusted lowered speed in the procedure; • > to 5 >00° F . T h e disk containing DAP appears with a nonabrasive detecting powder. minutes are required to develop signals .is a light, frosty, porous cake. T h e catalyst Defects show up as a colored tracery on at one application. AC disk is dense, glassy, a n d translucent. a dull white background. T h e disks are broken up in water a n d Tracery of t h e flaws can be photo T h e penetrating oil used is c o m p o u n d e d graphed by normal procedures. By reason allowed to stand for several hours, after of Diesel fuel, oleic acid, a n d a cutting ot deep penetration often t h e tracery can which t h e pi I of each solution is measured. fluid. An alizarin type d y e is dissolved be redeveloped hours after application Average p H of t h e D A P sample is 2.9; in this mixture, which is proprietary. T h e of penetrating oil without loss ot detail. that of the catalyst AC solution, 4 . 5 . detecting powder used is fine ( nursery T h e s e solutions are then made alkaline grade ) talcum powder. with soda ash 'solution. T h e D A P sample C a t a l y s t in Urea Resin Finishing T h e combination of fluids provides a has a fishy, amine odor as well as t h e penetrant whose high capillary force is Laboratory experiments for mill-testing odor of formaldehyde. A formaldehyde maintained in the presence of moisture; the efficiency- of a catalyst in eliminating odor is obtained from the sample cured thus this product is suitable regardless two known causes of odors trom urea resin with catalyst AC. of the presence of entrapped moisture finishing h a v e been recommended by Mon Dr. Nickerson h a s suggested t h a t D A P in cracks of fissures. santo Chemical Co. causes resin to solidify during t h e early T h e method was developed for use in T h e know-how of comparing catalyst stages of the drying operation, whereas intricate structures, such as t h e frames of AC with diammonium phosphate ( D A P ) w h e n catalyst AC is used, t h e resin prob ably remains in solution until t h e fabric is nearly dry a n d consequently c a n adapt g ^ ^ S T T ^ ^ y ^ " ^
