The confirmation of UL standard temperature grade is determined according to Formula 1.1 (see UL 2556-2007, part 4.3 materials aged for a long time). The specific process is to first give the heat resistance level of the material, such as 105℃, then calculate the oven temperature of 1.1 test at 112℃ according to the formula, and get the tensile rate change rate and aging data of the sample at the test temperature of such a local sample for 90 days, 120 days and 150 days respectively, and then calculate the linear relationship between the daily aging and the elongation at break by the least square method. Based on the linear relationship, the sample of elongation at break aged for 300 days at oven temperature (112℃) is obtained. If the change rate of elongation is less than 50%, it is assumed that this material can reach the rated temperature. If the change rate of elongation at break is more than 50%, it is considered as the bottom that the rated temperature of the material cannot reach.