One way to measure this effect on the elastomer is to conduct a compression test. Compression testing is useful for comparison studies within a sample set, but it is very important to maintain the same time, temperature, and deflection force for each sample within the study. These three factors have an effect on recovery results, and they make comparisons invalid if test conditions are not controlled. The other process that occurs during contraction is stretching. When a rubber is stretched, the molecules slip alongside each other, distributing the stress evenly among themselves.
Energy is absorbed and only partially regained upon retraction.
This loss in energy is measured as hysteresis, which can be correlated to the resilience of the rubber. The higher the resilience, the lower the hysteresis. Hysteresis is calculated from a stress-strain curve, as shown in Figure 1. The marked area represents the hysteresis, or the measure of work lost. Percent hysteresis is the difference between the loading energy and the unloading energy, expressed as a percentage of the loading energy.