Most PTC tapes are based on carbon loaded polyethylene. This is extruded around the two conductors and then crosslinked for thermal stability. Additional layers of insulation and protection will be added according to the end use. As the material heats up it expands reducing the contact between the carbon particles hence increasing the resistance. The tape will find its own balance point reaching a resistance where the heat generated (V²/R) matches the heat flow out. The art of these is selecting (and manufacturing) a suitable carbon loading. Some self resetting fuses use the same technique.
Most PTC tapes are based on carbon loaded polyethylene. This is extruded around the two conductors and then crosslinked for thermal stability. Additional layers of insulation and protection will be added according to the end use. As the material heats up it expands reducing the contact between the carbon particles hence increasing the resistance. The tape will find its own balance point reaching a resistance where the heat generated (V²/R) matches the heat flow out. The art of these is selecting (and manufacturing) a suitable carbon loading. Some self resetting fuses use the same technique.
