Development of a service-simulating, accelerated aging test method for exterior tire rubber compounds II. Design and development of an accelerated outdoor aging simulator

Abstract

During storage and service, exterior tire rubber compounds are subject to aging due to multiple factors. This process cannot be accurately represented by conventional single factor tests. The overall goal of our research is to develop an accelerated, service-simulating, artificial aging test for exterior rubber compounds. During the first part of this work, a cyclic test consisting of a series of single factor sub-tests was proposed and compared to dynamic outdoor aging and two standard single factor test: thermal aging and dynamic ozone aging. Although this cycle test shows promise, it does not account for interactions and is time consuming and inefficient making it unattractive for industrial use. In the present paper, an outdoor accelerated aging simulator is designed, build and tested. It includes the aging factors of heat, ozone, ultraviolet light, dynamic stretching, and aqueous solutions. The chamber is compared against dynamic outdoor aging and the above-mentioned cyclic aging test by characterizing the degradation as a function of aging time. Four formulations of exterior tire rubber compounds are used as experimental materials. The experimental results demonstrate that the chamber runs show excellent correlation with the cyclic and dynamic outdoor aging test. For all the tests completed, the static modulus initially increases, then reaches a maximum, and then decreases. The final chamber test run provided an acceleration factor of roughly 7.5 times the rate at which aging occurs in the dynamic outdoor aging test. It was found that the size of the specimen has a significant affect on the aging rate, which can be utilized to accelerate the aging without elevating the temperature.