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DEVELOPMENT OF HIGH-TEMPERATURE STRAIN-GAGE BONDING MATERIALS CURABLE AT LOW TEMPERATURES (PART IV)
NAVAL AIR ENGINEERING CENTER PHILADELPHIA PA AERONAUTICAL STRUCTURES LAB
Compositions were prepared for strain gage bonding. A low-temperature formulation of tubular alumina in a potassium silicate sol with suspending agent will cure to a high degree below 200 F if presealed with silicone between air setting and heating, and is electrically serviceable to 800 F. A high-temperature composition, designated formulation B52, based on the monoaluminum dihydrogen phosphate-silica mixture, but with chromic anhydride and alumina hydrate additions, cures adequately at 400 F or below and is useful even above the limiting service temperature of present strain-gage alloys, ca. 1600 F. Both cement types display good resistance to thermal shock and repeated rapid cycling they are adequately strong for normal strain transmission purposes. The low-temperature cement is mechanically the stronger at all temperatures. Differential thermal analyses verified curing temperatures and suggest the possibility of low-temperature vacuum curing of phosphoric acid compositions. Author
See also Part 5, AD-276 261.