Research On Effective Thermal Conductivity And Temperature-Resistivity Behavior Of Conductive Polymer Composites

Since the 1980 s,some researchers have paid great attention to the conductive polymers as functional materials and structural materials.Besides,it's one of important research in the field of materials science and engineering.Because the conductive polymer possesses both electrical conductivity and load-bearing capacity,it is also widely used as various kinds of sensors,electromagnetic shielding apparatuses,aerospace materials and so on.Up to now,studies on conductive polymer composites mainly include the following two aspects: 1.Some of studies are about the effects of inclusion size,shape and content on electrical resistivity.2.The others are about the influences of piezoresistive effects on conductive polymers.Although there are also studies on the effects of temperature on conductive polymers,they are still insufficient on the studies of heat conduction and interfacial debonding.Furthermore,the damage will appear in the conductive polymer composites under the stress or temperature load.However,there are few researches on the effect of the damage on the conductive properties.Conductive polymer is also one of viscoelastic materials.The present study does not relate to connection between internal damage and viscosity.Therefore,the relationship between the thermal conductivity and the temperature-resistance effect of conductive polymers was studied in this paper.They are reviewed in the chapter 1 included the thermal conductivity of conductive polymers,PTC/NTC effect and interfacial debonding.In the chapter 2,it is difficult to accurately measure its thermal conductivity because of the low thermal conductivity.This chapter has designed a more precise experiments and carried out more accurate measurements within a relatively large temperature range according to the plan.In the chapter 3,experimental results of the composite are processed and analyzed about the effective thermal conductivity and thermal expansion coefficient.Moreover,the conductive properties of the conductive polymers during the heat conduction process are studied.Then,the effect of heat conduction on the resistivity of the composite system is discussed.By the test of heat conduction and electrical conductivity,it was found that the electrical resistivity of the material increase with the increase of temperature and showed PTC behavior.The viscosity of the conductive polymer is related to the critical debonding strength by establishing a constitutive relationship between the matrix and the particles in the chapter 4.It's proved that the interfacial strength increases with increasing relaxation time by changing the way of load loading.It's shown that the material tends to be linear elastic material when the relaxation time continually increases.In the meantime,it's also demonstrated that the relationship of relaxation time and interface strength are the same as before considering the cohesion force model.However,the interfacial strength is obviously improved.Chapter 5 summarizes the full article and the outlook for research contents.