Thermal Conductivity And Its Characterization Of PP/Al(OH)₃/Mg(OH)₂ Composites

Polymer materials with high thermal conductivity has good thermal capability, excellent resistance to chemical corrosion and high temperature performance, which was widely used in the modern industrial and high-tech. However, the vast majority of polymer materials are low thermal conductivity material. Filling polymer with high thermal conductivity filler could obtain high thermal conductivity composites. It is very important to study on heat conduction mechanism of filled thermal conductivity polymer composites.Derived from Fourier's law, a particle filled polymer composites thermal conductivity theoretical model is based on the law of minimum thermal resistance, the law of the same specific equivalent thermal conductivity and the homogenization theory. The corresponding thermal conductivity prediction formulas are derived. Reference literature experimental data were compared with the thermal conductivity prediction formulas, results show that the calculations and measurements are close to each other, especially in the case of the filler content is low. Preliminary verification of the correctness of the thermal conductivity prediction formulas which derived in this paper.According to the mechanism of heat transfer, the heat transfer in a composite unit is simulated by using a finite element analysis software ANSYS. A 3-dimension model of the composites was structured by finite element software ANSYS, meshed, loaded boundary conditions and solved. According to the simulation results, analysis of the element body's temperature distribution and heat flux distribution, and obtain thermal conductivity of simulated values of PP/Al(OH)3/Mg(OH)2 composite. The result shows that the composite's thermal conductivity with the increase of filler content; Thermal conductivity of simulated values of composites which filled with larger size particle are slightly higher.Polypropylene (PP) thermal composites filled with Al(OH)3 and Mg(OH)2 were prepared. The thermal conductivity coefficient of the composites was measured by stable flat measuring instrument NF-7 for thermal conductivity in different testing temperature. The effects on thermal conductivity property of the filler content, testing temperature and filler particle size were analyzed. The results show that the addition of Al(OH)3 and Mg(OH)2 increased thermal conductivity of PP. Thermal conductivity coefficient of PP/Al(OH)3/Mg(OH)2 composites presents a nonlinear increase with an increase of the filler content, a nonlinear increase with an increase of the testing temperature, as well as a nonlinear increase with an increase of the filler diameter. Experimentally measured thermal conductivity coefficient of the PP/Al(OH)3/Mg(OH)2 composites were compared with the predicted. The results show that the predicted and measured values matched well when the filler content is low. Experimentally measured thermal conductivity coefficient of the PP/Al(OH)3/Mg(OH)2 composites were compared with the simulated. We can simulate the thermal conductivity coefficient of composites when filler content is low, thus reducing the cost of experiments and material development.The photos of impact fracture section of specimens are taken to study PP/Al(OH)3/Mg(OH)2 composites'microstructure by using Scanning Electronic Microscopy (SEM). The photos show that small particles more easily dispersed within PP, large particles are more likely to touch each other, accumulate into particle groups. The particles are dispersed more evenly in PP when Filler content is low. The probability of the particles contact with each other and then accumulation into particle groups is increase with increase of the filler content.