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During the Spring Meeting of ASTM Committee D-11 on Rubber and Rubber-Like Materials held in Chicago in March, 1949, there was held a Symposium on Aging of Rubbers. That symposium covered the effects of oxygen, light, ozones and heat on rubber. The effects of light and ozone were covered by John T. Blake of Simplex Wire & Cable Co. Since 1949, the interest in ozone and its effect on elastomeric polymers has become an item of prime importance to rubber technologists, and because of this intense interest, it was thought advisable to present several papers covering the several facets. By so doing, it is possible to consider in greater detail the subjects which, of necessity, could be given only passing mention in 1949. For many years, technologists were concerned with “light aging,” which had been recognized as a destructive force by Burhardt as early as 1883. However, it was not until 1926 that Ira Williams observed that “in an atmosphere of ozone cracks appeared on all sides of a stretched sample regardless of light exposure. Unstrained rubber is not affected by ozone.” He also observed that “the greater the stretch the smaller the cracks and the greater the number.” Williams thus differentiated between light aging and ozone aging. Van Rosen and Talen6in 1931 observed that on outdoor exposure tests of stretched rubber samples cracks formed at a lower elongation on the shady side than on the side directly exposed to the light. Further, it was learned that cracks could be formed in stretched samples when samples were exposed to the atmosphere only at night. This eliminated sunlight as being necessary for the formation of cracks.
Maassen, G. C.
Laboratory DirectorChairman of Symposium Committee, R. T. Vanderbilt Co., Inc., New York, N. Y.