Permanent Effect of Heat

Permanent Effect of Heat is of particular value in connection with established or potential applications which involve service at elevated temperatures. It permits comparison of various plastics and grades on one plastic in the form of test specimens, as well as molded parts in finished form.

Specimens are placed in an air circulating oven at a temperature (multiple of 25 °C) which is thought or known to be near the temperature limit of the material. If, after four hours, there is no change observed, the temperature is increased in increments of 25 °C at four hour intervals until a change does occur.