Effects of oven aging on ABS, poly(acrylonitrile‐butadiene‐styrene)

Tensile properties of injection and compression molded ABS, terpolymer of acrylonitrile, butadiene, and styrene, were measured as a function of aging time at 40 to 90°C. Both air and nitrogen atmospheres were employed to separate the oxidative and thermal effects. Results demonstrate that tensile elongation is drastically reduced by oven aging at 50 to 90°C, even when a nitrogen atmosphere is employed. Aging in air causes changes in the infrared spectra of ABS and these changes can he monitored in thick samples using the frustrated multiple internal reflection (FMIR) technique. The FMIR technique also provides information on the changes in polybutadiene distribution near the surface of molded parts. The loss of tensile elongation after oven aging is attributed to annealing of the glassy styrene‐acrylonitrile matrix. This is supported by differential scanning calorimetry. The tensile elongation is found to he recoverable by reheating to processing temperatures.