The Measurement of Dielectric Loss at High Frequencies an Under Changing Temperature

1. A method of measuring the properties of a dielectric while its temperature is changing has been developed and applied to certain thermosetting materials under high-frequency heating. 2. The presence of absorbed moisture in small amounts has a pronounced influence on the dielectric properties of such materials. A method for dealing with samples containg moisture is described. 3. Two basic phenomena are active in dielectric heating at high frequencies: dielectric absorbtion (in the Maxwell sense); and some form of molecular polarization. The former is evident in high-stress short-time heating cycles. The latter is the more important for the thermosetting process, and is completely developed in longer lower-stress heating cyc es. 4. The method provides a simple means of determining the total energy input per cycle and per cubic centimeter of the material under study.