Preparation And Properties Of Highly Conductive Rubber With Electro-corrosive Electronmagnetic Shilelding

High conductive rubber composites have excellent electromagnetic shielding properties and environmental sealing properties,but in some humid environments,such as sea or dense forest,the salt solution formed by moist water and gas will attach to the surface of electromagnetic shielding rubber and electronic equipment in some salt fog environment.Electrochemistry occurs due to the existence of potential difference.Corrosion leads to the failure of the electromagnetic seal and the environmental sealing performance of the conductive rubber.The factors that affect the electrochemical corrosion resistance of electromagnetic shielding high conductive rubber are usually conductive filler and rubber matrix.In this paper,silicone rubber and ethylene propylene diene monomer as the matrix,silver plated nickel powder and nickel plated aluminum powder as conductive filler,the conductive rubber composite material required by military standard SJ 20673-1998 "general specification for military electromagnetic shielding rubber liner" was prepared,and the electrochemical corrosion resistance of the material was studied.The effect of the type of coupling agent and the surface modification method on the properties of the composites was studied.The results showed that the dispersion of conductive filler in rubber could be improved and the interaction of conductive filler with rubber was improved after treating by silane coupling agent A-151,thus the mechanical properties and electrical conductivity of the composites be improved.The effects of the amount of silver plated nickel powder and nickel plated aluminum powder on the properties of silicone rubber and ethylene propylene diene monomer were studied.The results showed that with the increase of the amount of conductive filler,the shore A hardness of the conductive rubber composite was increased,the elongation at break and the volume resistivity were decreased;when different kinds of conductive fillers were added to the same type rubber matrix,the composites have different percolation threshold.The percolation threshold of the silver plated nickel powder/silicone rubber is 33.4%,and the silver plated nickel powder/ethylene propylene diene monomer is 37.5%,indicating that the silver plated nickel powder is more easily formed in the silicone rubber,and the different kinds of conductive fillers also have different percolation threshold.The percolation threshold of nickel plated aluminum(75)/three EPDM is 37.4%,and the nickel plated aluminum powder(2778)/ethylene propylene diene monomer is 32%.It shows that the more dense the surface coating is and the higher the content is,the more easily the conductive path is formed.The stability of the silicone rubber and ethylene propylene diene monomer matrix composites has been studied.The results show that the silicone rubber matrix composites have good electrical stability and processing stability,and the ethylene propylene diene monomer matrix composites have good electrical stability,but the processing stability is poor.The electromagnetic shielding effectiveness of the silicon rubber base and the ethylene propylene diene monomer matrix composites before and after the salt spray test is studied.The results show that the electromagnetic shielding effectiveness of the silicon rubber matrix composite is greater than that of the ethylene propylene rubber matrix composite before and after the salt spray test,and the electromagnetic shielding effectiveness before and after the smoke is smaller,in which silver plated nickel powder/silicone rubber,the decrease of electromagnetic shielding effectiveness is the least.The electrochemical corrosion resistance of the silicone rubber and ethylene propylene diene monomer matrix composites was studied.The results showed that the electroless corrosion resistance of the nickel plated aluminum powder filled composite material was better than that of the nickel graphite/silicon rubber composite and the silver plated nickel powder/silicone rubber composite.The results indicated it is ont only related to the surface coating material of the conductive rubber but also the content of the surface coating material and the material of the conductive rubber core;The electroless nickel aluminum powder(2778)/silicone rubber composite material with higher coating content and even more compact and uniform coating has better electrochemical corrosion resistance than the nickel aluminum powder(75)/silicon rubber composite.The electrochemical corrosion resistance of the conductive rubber is related to the content of the coating material,and the same rule is found for the ethylene propylene diene monomer composite material.When adding the same kind of conductive powder,the silicone rubber based conductive rubber composite has better electrochemical corrosion resistance than the ethylene propylene diene monomer base.