Space Quantitative Analysis And Interphase Effect Of Rubber Composite On Thermal Conductivity

Along with the rapid development of science and technology, polymer composite with high thermal conductivity is applying to more and more fields, which has been a hot research topic among scholars. AlN/EPDM composites were prepared and the thermal conductivity was experimentally measured at different filling fraction with the heat probe. We also observed the surface topography of the samples with the 3D measuring laser microscope. Besides, the effect of the spatial distribution, particle size, particle Gaussian distribution and interphase properties on thermal conductivity of composites were studied by using ANSYS finite analysis software. At the same time, a mathematical analysis was taken on quantitative analysis of space with same particle size and AlN/EPDM composite with an interphase model.It was reported that:the thermal conductivity of composites presented a linear rise trend with the increasing of AlN filling fraction, which drew a conclusion that thermal conductivity of composites would be greatly improved by filling AlN particles. Due to several kinds of reflective materials included in composite, distribution of AlN in the rubber that was prepared in the present ingredient could not be observed with 3D measuring laser microscope.Spatial distribution had a tremendous effect on thermal conductivity of composite at filling particles with identical size. The thermal conductive pathways or networks would be formed if filler particles had a better distribution in the rubber, in other words, filler particles might be in a line in the rubber, as a result, the thermal conductivity of composite would be enhanced greatly. However, there was a volatility of thermal conductivity which was attributed to aggregation or over dispersion of filler particles in the rubber. We have got a parameter-heat flow synergy degree by quantitative analysis on two-dimensional random distribution, which can be used to describe the thermal conductive networks in the composite. The thermal conductivity of composite can be predicated by the value of this parameter. The conductive pathways or networks which were in favor of heat transport would be easier to form when smaller particles were filled in the rubber.If the radius square conforms to normal distribution at the same filling rate, the lower the standard deviation is, the higher thermal conductivity of the composite material will get. However, when the standard deviation is 0.05, thermal conductivity of the composite is the most stable. Therefore, the optimal conditions of particle size are that the standard deviation of filling rate should be between 0 and 0.05.Comparing the experimental value of AlN/EPDM composite and simulation results on thermal conductivity, it was found that the effect of interface on thermal conductivity cannot be ignored. The modified Maxwell model was obtained by correcting the two-phase Maxwell model. The interface thickness between phases can be countered by formula resulted from correcting the Maxwell model.From the simulation that how the interface affects the thermal conductivity of nanotubes/EPDM composites, we can find that:a thin interface can improve the efficiency of heat transfer to the carbon nanotubes, but tends to debond; interfacial adhesion can be increased by a thick interface, but the efficiency of heat transfer to the carbon nanotubes will be low. So when we attempt to optimize the filled composites, we should also control the interface thickness reasonably. We can increase the thermal conductivity of composite filled with carbon nanotubes by both enhancing its filler fraction and improving its interfacial thermal conductivity.