Conductive Response Properties Of Silicone Rubber/ Silver-coated Fly Ash Cenospheres Composites Under External Field

With the rapid development of information technology and microelectronic technology, the application of electrical conductive polymer composites have become more and more wide, while the environmental conditions become more and more rigorous. In this paper, we studied on silicone-rubber/ silver-coated fly ash cenospheres conductive composites prepared with silicone rubber as matrix and silver-coated fly ash cenospheres as fillers, especially on resistance responses of the conductive composites under external field. The results show that:(1) A integrate and dense layer of silver were plated on the surface of fly ash cenospheres after roughtening and alkali treatments that contributed to the new nuclear Ag adsorption on its surface and reduced plating bath from self-decomposition. The pH value of the plating bath had a great influence on its stability, but little effect on the grain size of Ag, and the optimum pH value was 12.9.(2) With the volume fraction of conductive fillers increasing, the conductive percolation phenomenon occurred in the composites, and its percolation threshold was 62.6%~65.3%. In addition, comparing the percolation theory of phase transitions, GEM equation and Mamunya model used in the experimental results, it's suitable for the conductive percolation phenomenon of silicone-rubber/ silver-coated fly ash cenospheres conductive composites by Mamunya model.(3) Silicone-rubber/ silver-coated fly ash cenospheres conductive composites exhibited negative temperature coefficient effect (NTC) and positive temperature coefficient effect (PTC) between -200℃and 200℃. However, the effect of temperature and concentration of conductive particles on PTC of the composites attributed to the influence of the coupling on its microstructure.(4) The electrical resistance change presented linearly with the geometrical deformation of the composites when the strain is small, while it increased in exponential way beyond the critical strain, which depended on the frequency under the cycle alternating stress field. The resistance curves of the composites were similar to the polymer materials'stress relaxation and creep curves under mechanical relaxation, moreover, the resistance change appeared viscoelastic propertie since conductive networks within the composites and silicon rubber matrix network were not only independent, but also interrelated.(5) The resistance change of the composites coincides with Ohm's law when the volume fraction of conductive fillers is small and the electric current is low, however, with the conductive filler and electric current increasing, the resistance change deviates from Ohm's law, showing nonlinear behavior originate from the conductivity and electric field stimulate the tunneling effect between conductive particles, which yield a large amount of tunneling current.(6) Silicone rubber matrix was damaged greatly by strong acid and alkaline solutions, but little by organic solvents, however, due to its swelling in organic solvents, conductive networks within the composites may be destroyed, which causes lower electrical conductivity of the composites,or even non-conducting transition.