A novel approach to addressing the problem of temperature variation in laboratory thermal ageing experiments

For many years now, the accuracy of data used for thermal evaluation of insulating materials and systems has been grossly impaired by systematic errors inherent in the degradation process itself. The most significant of these are the errors due to temperature variation within the oven chamber used for thermal ageing experiments. It is important to be able to declare within acceptable tolerances that the temperatures reported are actually those which the test materials were subjected in the course of ageing. Not only do test materials suffer wide variations about the nominal average temperature setting of the oven, they are also exposed to unknown temperatures that may be above or below the average value as the temperature profile within the oven is non-uniform. This becomes imperative when accurate comparison is required between two or more alternatives. This paper describes the improved processes and testing procedures required to address the problem.