Heating equipment high-frequency dielectric

A low dissipation factor is important for plastic insulators in high-frequency applications such as radar equipment and microwave parts smaller values mean better dielectric materials with less dielectric heating. A high dissipation factor is important for polymers that are to be heated in a radio frequency or microwave oven for welding, drying, etc. 

A common cause of RF contact burns is from the metal electrode jigs of dielectric heating and plastics welding apparatus, operating at radio frequencies. Unless the output is pulsed there is unlikely to be a shock risk, but an accidental hand contact, for example, will draw out an arc when the hand is removed and a high frequency burn will result. The burning is a function of the arc energy, and for low power apparatus only a minor burn is likely. More powerful equipment, above about 1 kW, can inflict more serious burns. 

It heis long been established that a dielectric material, such as many types of ceramics, can be heated with energy in the form of high frequency electromagnetic waves. The frequency range used for microwave heating lies between 400 MHz and 40 GHz, however the allowed frequencies are restricted to distinct bands which have been allocated for Industrial, Scientific and Medical (ISM) use, as shown in Table 1. The principal frequencies are centred at 433 MHz, 915 MHz (896 MHz in the UK) and 2450 MHz since specific industrial equipment can be readily purchased. 

---