Conductive thermoset composites: PTC effect

Positive temperature coefficient (PTC) materials art: characterised by a re versible metal to insulator transition at a defined temperature Tc. This ph enomenon has been widely observed in conducting polymer composite materials such as carbon black / polyethylene compound. From a fundamental point of view, the mechanisms are still not fully understood, especially in conducti ve filled thermosets, which do not present a large volume expansion compare d to a semicrystalline: polymer matrix. The aim of our work consists to study the properties of different conductiv e: epoxy composites based on mono or biphasic matrix and filled with carbon black or metallic particles. Wt: attempt to contribute to a better underst anding of the: electrical non-linear phenomena in such conductive: disorder ed composite: materials. Analysis of the thermo-mechanical properties, percolation and conduction me chanisms are important and appear to be essential to the understanding of t he PTC effect in such composites. Theoretical interpretations of the PTC an omaly will be advanced.