Study of polymer composites for temperature and current sensors

Study of electrical resistivity of polymer composites as a function of temperature (t) in the temperature range 20 less than or equal to t less than or equal to 300 degreesC has been presented. The room temperature resistivity (RT) of the various composites lies in the range of 0.1 - 1.0 Omega cm. Extremely high positive temperature coefficient (PTC) of resistance (depending on the type of filler, its distribution and volume fraction) has been observed. Both melting and recrystallization behavior are responsible for PTC effect. Influence of a variety of conducting filler materials and polymers on RT resistivity, magnitude of resistivity increase and transition temperature (T-c) are investigated. The transition from low RT resistivity to high resistivity can be utilized for current limitation. The T-c is related to curing temperature for thermoset polymers and to melting temperature in case of thermoplastic polymers. Choice of polymer and its processing history determine the T-c. Polymer composites having very low resistivities and high T-c is extremely suitable for their application as current sensors and temperature sensors.