Relative temperature index


The Relative temperature index is a characteristic parameter related to the thermal degradation of plastic materials.
The RTI is part of the thermal-aging program of the UL 746B standard from UL.
During the process of the UL 746B program, the degradation of certain properties of the material like dielectric and mechanic strength, is investigated with regards to thermal-aging. The RTI is the temperature in degrees C, at which the properties have decreased to 50 percent of their initial value after a long-term exposure to this temperature.
Though the RTI is an index, it is given in Celsius units.
The UL 746B standard distinguishes between three sub-categories of the RTI: