TENSILE BEHAVIOR AFTER OXIDATIVE AGING OF GUM AND BLACK-FILLED VULCANIZATES OF SBR AND NR

Typical sulfur-Cured vulcanizates of slyrene-butadiene rubber (SBR) and natural rubber (NR) were prepared, and subjected lo air-oven aging at 100 °C. Gum specimens exhibited an initial aging period in which stiffness was unchanged, while tensile strength and strain-to-break were significantly reduced. In contrast, black-filled vulcanizates stiffened during early aging. After intermediate aging times, NR specimens softened, while SBR stiffened. With prolonged aging, all compositions became hard and incxtensible.