The glass transition temperature is the temperature obtained from a transition point of the polymer material from the glass state to the rubber state. It only represents a point, only that the intensity is stable before this temperature, but it does not mean that it will not work or exceed this temperature intensity.
Thermal stability refers to how long the polymer material can work at a certain temperature and the strength cannot be reduced to a certain limit, so it refers to the thermal stability at this temperature. To give an example: the glass transition temperature of material A and material B are both 100 degrees, which shows that the strength of the two materials is stable before 100 degrees, and it cannot be said how long it can be used after 100 degrees. Now suppose that material A is grade H, that is, this material can work at 180 degrees for 10,000 hours. The bending strength is not less than 50% of the original. Conclusion: Its heat resistance is H grade, also 180 degrees. At the same time, the B material is F grade, that is, this material can work at 155 degrees for 10,000 hours. The bending strength is not less than 50% of the original. Conclusion: Its heat resistance is F grade, also 155 degrees.