ASTM D573 test provides a method to determine the physical properties of vulcanized rubber under accelerated conditions of elevated temperature. The physical properties of rubber and rubber goods may deteriorate with time due to oxidation and thermal aging. The test is useful for measuring how the sample reacts to thermal changes by examining the change compared to the original sample before temperature exposure. ASTM D573 helps to assess the change in physical and chemical properties of the sample. This test may not provide the required correlation with service performance as the performance conditions differ in a wide range; however, this test helps evaluate rubber compounds on a laboratory comparison basis.
The samples are preheated to the operating temperature as specified by ASTM D573. Then, the samples are placed for aging in the oven. If possible, the simultaneous exposure of a varied group of different compounds is avoided. The aging interval is started at the time the samples are placed in the oven for a certain mentioned time interval. Then, appropriate time intervals are selected based on the rate of deterioration of the specific material being tested. The frequently used time intervals are 3, 7, and 14 days. The samples are removed from the oven at the end of the aging interval. Then, the samples are cooled to room temperature on a fate surface and allowed to rest between 16-96 hours before evaluating the physical properties. Finally, gage lines are applied for determining elongations to the samples.
The standard samples for ASTM D454 are dumbbell-shaped, as described in ASTM D412. The most typical tested shape is a die-cut C dumbbell sample that has an overall length of 115 mm (gauge length of 25 mm), a width of 6 mm, and a thickness of 3 mm. The thickness of the sample is measured three times, and the median value is calculated.
The results of the aging test in each physical property are expressed as a percentage change as follows:
P= percentage change in property,
O= original value, and A= value after aging or exposure.