LNDUSTRIAL I S D EA-GISEERISG CHEMISTRY
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O X Y G t N B O M B 4- G E E R O V E N
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Accelerated Aging vs. Shelf
Aging
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Everett M . Follansbee
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SIXPLEXM'IRE & CABLECo., BOSTON, MASS. 24
AMPLE8 of rubber-insulated wire were aged by exposing
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to the diffused light in the physical testing laboratory. The thickness of wall of rubber surrounding the tinned copper wire showed a variation from 0.030 t o 0.065 inch (0.76 to 1.65 mm.). The samples were tested for tensile strength and elongation during the aging interval and the results werd then compared with accelerated life teats obtained on the same samples when new. Average results on 480 different compounds, ranging i n quality from a low-grade compound to a compound containing 60 per cent by weight of crude rubber, show the following relationship between shelf aging and accelerated aging.
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Tensile strength Elongation
D A V 5 IN O V C N
Acknowledgment
Acknowledgment is due B. N. Larsen for his valuable assistance in preparing this paper. Literature Cited (1) Bierer. IND. ENG. CHEM.,16, 711 (1924). ( 2 ) Geer, I n d i a Rubber W o r l d , 64, 887 (1921).
E q u i v a l e n t Y e a r s of Shelf Aging HEATED24 HOURSIN OXYHEATED96 HOURSAT GEN AT 60' C. A N D 300 L B S 70" C. IX AIR (21.1 KG.) PRESSURE Years Years 1.43 1.37 1.00 1.18
Both of theqe accelerated aging tests give a longer shelfaging time equivalent for tensile strength than is given for elon gat ion. The Geer test (96 hours a t 70" C. in air) on the average represents the same shelf-aging time regardless of the type of compound. The oxygen test, however, in the case of elongation, represents a much shorter shelf-aging time for the lower grade compounds. Both of the accelerated aging tests gave results that varied considerably in equivalent time for shelf aging, and it should be emphasized that the above equivalent aging results are only awrage figures.
