Preparation And Properties Of Li Min And Wen - Min Conductive Silicone Rubber

Conductive rubber belongs to the conductive polymer composites. It is a new type of semiconductor functional materials with conductive filler uniformly dispersed in the polymeric elastomer matrix, which has both elasticity and conductivity. Conductive rubber is used to prepare flexible tactile sensor force-sensitive components and temperature-sensitive components because of its good force-sensitive and temperature-sensitive properties. There are a lot of factors about the effect of force-sensitive and temperature-sensitive of conductive rubber. Although the mechanism of force-sensitive and temperature-sensitive of conductive rubber is based on conductivity mechanism, its essence is not the same. This paper described the conductivity mechanism of conductive polymer composites, analyzed the mechanism of force-sensitive and temperature-sensitive based on conductive path theory and quantum mechanical tunnel effect theory, summarized some representative mathematical model of force-sensitive and temperature-sensitive, improved and optimized the preparation of conductive silicon rubber, studied force-sensitive and temperature-sensitive of conductive rubber of the influence factors about viscosity and components of rubber matrix, vulcanization, the content of carbon black, etc. In this paper, the preparation and properties of conductive rubber were studied from force-sensitive and temperature-sensitive effect respectively.A pretreatment method was presented which eliminated the agglomeration phenomenon, and improved the dispersion of the filler in the rubber matrix. A new way was presented which used silane coupling agents to modify filler powder. It is about 12 hours for conductive silicone rubber curing after mold release. A new preparation of conductive silicon rubber was proposed. It is refining and quantifying parameters such as the addition order of raw materials, stirring speed and stirring time. The dispersibility of the conductive filler was improved. The percolation threshold was reduced (dropped from 6% to 4%).The effect of viscosity and components of conductive silicone rubber matrix, vulcanization and modified materials on the piezoresistive effect, relaxation effect and hysteresis characteristic of the force-sensitive were studied. Research showed that, the viscosity of silicone rubber matrix (from 1500 to 10000 mPa.s) was higher, the better piezoresistive characteristic, the shorter resistance relaxation time, and the smaller coefficient of resistance hysteresis. Two components RTV silicone rubber matrix had better smoothness piezoresistive characteristic curve, the shorter resistance relaxation time, and the smaller coefficient of resistance hysteresis than single component RTV silicone rubber matrix. Silane coupling agent could be used alone as a vulcanizing agent. It was shorter vulcanization time and resistance relaxation time, larger pressure-sensitive range and piezoresistive range, better regularity of the piezoresistive curve with a blend of silane coupling agents Si-69 and ethyl orthosilicate. The force-sensitive effect of conductive rubber was better. Vulcanization rate was accelerated by improving vulcanization temperature, but it had a negative impact on the internal structure and the stability of conductive silicon rubber. The piezoresistive range increased significantly, and the resistance relaxation time reduced with the addition of multiwalled carbon nanotubes modified material. It had good force-sensitive effect. It could be used as a flexible force-sensitive component in the 0-50N pressure range for force-sensitive sensor.The temperature-sensitive effect of different acetylene black content filled RTV conductive rubber was studied. Research showed that, the percolation range was between 4% and 12%. Conductive rubber exhibited a positive temperature coefficient effect when the content of conductive filler was close to the 4%percolation threshold. Conductive rubber exhibited a positive temperature coefficient effect at first, and then a negative temperature coefficient effect when the content of conductive filler was increased to 8%. There was a temperature critical point 80℃. Conductive rubber exhibited a negative temperature coefficient effect when the content of conductive filler was increased continually. Conductive rubber could be used as a flexible temperature-sensitive component in the 20℃-120℃ temperature range for temperature-sensitive sensor with 4% content of carbon black filler.The negative temperature coefficient effect of conductive rubber was more obvious with smaller viscosity for the same RTV silicone rubber matrix (from 1500 to 10000 mPa.s). Conductive silicone rubber exhibited a negative temperature coefficient effect at first, and then a positive temperature coefficient effect which was prepared by single component silicone rubber matrix with 10% content of carbon black filler. And conductive silicone rubber exhibited a negative temperature coefficient effect consistently which was prepared by two components silicone rubber matrix.