Karaman D. Resistivity, thermopower and mechanical properties of composite materials on the base of thermally expanded graphite, fluoroplastic and PVH-plastisol

The thesis presents the results of investigation of the correlation between morphology, mechanical and electrophysical properties of composite materials (CMs) on the base of thermally expanded graph-ite (TEG) - polymer. The breaking point and ultimate strain have been investigated as mechanical properties, and resistivity and ther-mopower - as electrophysical properties. Polyvinylchloride plastisol and fluoroplastic-3 have been used as polymer matrix. It has been revealed that within the framework of percolation theory the conduc-tivity of the CMs conforms to the model of 3D conductivity net with blocked sites. For the same CM the percolation threshold for electrical resistivity is lower then for thermopower. It is demonstrated that con-ductivity in the concentration range between the thresholds is caused by the tunneling of charge carriers. The distinction between the threshold volumes is explained by the deficient level of energy of charge carries when these move under temperature gradient to over-come the potential barrier which is formed by the dielectric layer be-tween the TEG particles. Processes in the CMs under the influence of temperature and mechanical tension have been investigated. Recom-mendations for using the CMs as strain gauges and resistors stable to irradiation by electrons and X-Ray quanta are elaborated. It is offered to use the method of thermopower measure to conrol the processes of agglomeration of electial conductivity powder blends and porosity of monolite specimens.