Study On The Conductive Properties Of Two-component Vulcanized Conductive Silicone Rubber

With the rapid development of robotics, researches on intelligent robot is more and more extensive, tactile sensors applied to robot intelligent skin are gradually progressing. As the main material of tactile sensor, conductive silicone rubber is made from rubber matrix with conductive filler particles filled into it, and it has both the pliability of the rubber and a certain conductivity. Carbon black and copper are used as conductive filler materials to test the properties of conductive rubber with different content of the two fillers. The main contents, analyses and conclusions are as follows:(1)Based on the conductive path theory and tunneling effect theory, conductive mechanism, piezoresistive property and relaxation property of conductive silicone rubber are studied as well as three seepage models forming circuits. Studies show that the tunneling effect theory plays a leading role when conductive filler is in low concentration, while the conductive path theory plays a leading role when it’s in high one. The conductivity of conductive silicone rubber is the result of the two theories.(2)Through the analysis of the type and content of raw materials, with two-component RTV silicone rubber as matrix material, carbon black and copper powder as conductive fillers, simethicone as diluent, ethyl silicate as crosslinking agent, dibutyltin dilaurate as catalyst, silane coupling agent as coupling agent, n-hexane as organic solvent, different experimental samples are made through solution co-blended process and their properties are tested as well. By comparing and analyzing the result of the experiment, the best proportion solution is achieved so as to prepare conductive silicone rubber with good comprehensive properties.(3)The conductivity and piezoresistive property of different samples are studied. Analysis of conductive property shows that resistance of the sample with copper powder is obviously lower than that without copper powder when total content remains constant. It indicates that the mixture of carbon black and copper powder can improve the conductivity of conductive silicone rubber. So the cost can be reduced by reducing the amount of carbon black. Analysis of piezoresistive property shows that samples with different content of carbon black and copper powder have almost the same curves of piezoresistive property. Through comparison, the samples of B2(15% carbon black + 9% copper powder)and C2(18% carbon black + 9% copper powder)have not only good conductivity, but also a wide range of piezoresistance. In the experiment of relaxation property, the resistance change with time of the sample under constant external force is studied, and the mechanism of relaxation phenomenon is analyzed as well as the influence on internal structure of conductive silicone rubber under different external force. The study of relaxation phenomenon has vital significance to improve the stability and sensitivity of conductive silicone rubber.The properties of the filler particles are the main factors influencing the conductivity of conductive silicone rubber, but commonly used carbon-based fillers are not easy to diffuse, metal-based fillers are easy to be oxidized. By using the two kinds of fillers together, shortcomings of the single filler are overcome and the comprehensive properties of conductive silicone rubber are improved. The study is of great significance to the tactile sensors for further practical applications.