Accelerated aging of tires, Part II

The Purpose of this research is to determine the conditions whereby a new tire can be artificially aged in an accelcrated manner, in order to duplicate the actual mechanism of chemical aging observed in field-aged tires. The ultimate goal of the Study is to age tires to a desired level, say equivalent to 4 years old. and then test the tires in various durability, high speed and performance tests. The first step was to determine the aging characteristics of field-aged tires, which has been the Subject of another paper.(1) For this work, tires were statically aged in ovens. Tires were mounted. inflated, then oven aged continuously at temperatures ranging from 40 degrees C to 100 degrees C for various periods of times (from 2 weeks to 12 weeks). Both air and a 50/50 blend of N-2/O-2 were used as the inflation media. The tires were then dissected and analyzed for tensile and elongation properties of the rubber at the end of the steel belts. The results show that as the temperature was increased from 40 degrees C to 70 degrees C. the property degradation of the steel belt rubber accelerated. Shift factors were determined based on time-temperature superposition and the results analyzed by using the Arrhenius methodology. The oven results were similar to the field data, meaning the chemical aging mechanism was the same for both. As the oven temperature increased above 70 degrees C. degradation reactions began to dominate and the apparent aging mechanism changed.