UL758 UL2556 This equipment is used to test the degree of thermal deformation of materials such as plastics and wire rubber. At a specific temperature, place the test piece freely in the testing apparatus for 30 minutes, then sandwich it between the parallel plates of the machine, add the specified load, and place it at the same temperature for another 30 minutes, use a scale to measure the thickness difference between before and after heating. The thickness difference divided by the thickness before heating, which is the deformation rate.