UL Materials Testing and Certification (English)
Hot-air aging in a load-free state
UL Solutions has more than 150 hot-air cabinets for thermal aging and determining the RTI (relative temperature index) of a material. These cabinets were developed in close cooperation with the manufacturer to guarantee maximum precision and reproducibility.
All our hot-air cabinets are measured and monitored continuously with the help of a software system on which UL Solutions likewise collaborated extensively. The test specimens are aged in a load-free state at different temperatures in forced-ventilated hot-air cabinets. The change in specific properties in relation to the aging period can subsequently be calculated at room temperature.
Standards for Hot-Air Aging (RTI)
UL 746B or equivalent standards
These property changes are generally investigated by means of a mechanical shock test and quasi-static and electrical measurements.
The test ends when the property value in question falls below the minimum threshold (50% of the original value). The time until the property limit is reached is calculated for each individual property (temperature/time pairs) on the basis of the results obtained. These pairs are then used to generate a thermal resistance diagram for the material being tested. By extrapolating the results over time, a temperature index (TI, normally after 5,000 and 20,000 hours) can be determined according to (IEC) DIN EN 60216-1.