Isothermal Differential Calorimetry as a Means to Measure Insulation Aging Rate down to the Operating Temperatures

A new calorimetric method for measurements of insulation aging rate is introduced. The method is based on measurements of the heat flow caused by the heat absorbed or liberated in aging reaction. In isothermal conditions, this heat flow is proporticnal to the reaction rate. The instrument is sensitive enough for reactionrate measurements down to the service temperatures of materials. Using an appropriate gas circulation system, the tests can be performed in different atmospheres. In this way, the competing reactions in an aging process can be observed separately. Any type of solid material can be tested: solid block, film, powder, etc. Some test results on a few well-known insulating materials are described. A new procedure for aging tests, based on the use of isothermal differential calorimetry, is proposed.