The TR test is a standard testing method for evaluating rubber properties at low temperatures. The test is mainly used to determine the brittleness point or the compression set and recovery behavior of elastomers. Normally, these tests will be performed in tensile mode in a thermomechanical analyzer (TMA).
The TR test is used for vulcanized rubber products like O-rings. The tensile mode delivers best results. Prior to the cooling procedure, the sample will be stretched from the initial sample length of 100% to a given extension, e.g., 150%. During the second step, the sample will be cooled down 50 K below the estimated TR10 point. Then, the sample is released and heating starts at 2.5 K/min until the specimen reaches room temperature.
The stretch is recorded versus time, and the temperature at which the sample recovers 10% or 20% of the initial extension is referred to TR10 or TR20, for example. Those points are marked in the graph below showing the elastic behavior of an elastomer at low temperatures.