The Preparation Of Nickel-coated Graphite Conductive Silicone Rubber Ring And Property Research

In this paper, nickel-coated graphite powder is taken as conductive filler to prepareconductive silicone rubber. Through extrusion process, vulcanization and secondarybonding, the seal ring of hollow structure is produced for electromagnetic screen.It carries out research on the influence of the nickel plating graphite with differenttypes (different particle size) on the conductivity property and mechanical property of thecomposite. It turns out that, under the condition with the same addition amount, the largerthe particle size of the nickel plating graphite is, the better conductivity property willachieve, but it will give rise to greater degradation effect on the mechanical property; thenickel plating graphite with different particle size will leads to different percolation value,and the larger the particle size is, the smaller the percolation value will get, and the averageparticle size is100um, the percolation value is between100and120shares; the averageparticle is50um, and the percolation value is between140and160shares; the averageparticle is25um, and the percolation value is between160and180shares.It studies the vulcanization effect of dicumyl peroxide (DCP), benzoyl peroxide(BPO), bis2,4-dichlorobenzoyl peroxide,2,5-dimethyl-2,5-di (tert-butylperoxy)hexane on conductive silicone rubber. It turns out that the samples with the crosslinking ofDCP and2,5-dimethyl-2,5-di (tert-butylperoxy) hexane have good mechanicalperformance, which is followed by BPO effect, while the crosslinking effect of bis2,4-dichlorobenzoyl peroxide is so weak.The influence of the coupling reagent species and silicone oil dosage on theconductivity and mechanical property of the silicone rubber. The result shows that, toconduct the nickel plating graphite throughbis-(γ-triethoxy silyl propyl)-tetrasulfide(WD-40) or methacryloxy propyl trimethoxyl silane (WD-70) will have serious impact onthe vulcanization of the silicone rubber, and reduce the mechanical property andconductivity of the composite materials; however, after applying the vinyl triethoxysilane (WD-20), the mechanic property and conductivity of the conductive silicone rubberis obviously improved, and addition of little silicone oil can remarkably reduce the hardness of the conductive silicone rubber and has small influence in the mechanicalproperty and conductivity, and the best dosage is3shares.According to the properties of the conductive silicone rubber and the propertyrequirements of the electromagnetic shielding seal ring, it studies and formulates themolding technology and vulcanization technology. To improve the property of the seal ring,increase the deformation quantity of the elasticity, and reduce the cost, it makes the sealring with hollow structure. Its production process includes rubber tubing extrusion molding,vulcanization, jointing and ring formation process. Moreover, it designs the extrusionhead, and confirms the extrusion process parameter, vulcanization ways, vulcanizationtemperature, vulcanization pressure, jointing ways, etc.The straight-through design is adopted by the self-design extrusion head to design andcalculate the draw ratio, extrusion caliber, sizing length, mandril, diverter (integrated ingeneral), etc.It studies the influence of screw revolving speed, temperature, material thickness andother extrusion process conditions on the conductive silicone rubber tube. It turns out thatthe screw speed has positive correlation with the torque and the sizing material temperature.When the revolving speed reaches70rpm, the extrusion velocity is not stable, and it givesrise to extrusion defects. When the speed reaches90rpm, it will lead to melt fracture. Thesizing material is better with2-3mm. The air cooling is required to reduce the extrusiontemperature during the extrusion. The dumping temperature is controlled under60℃.It studies the vulcanization technology of the conductive silicone rubber tube. Theresult shows that, taking DCP as the vulcanizing agent, when the hot air vulcanization isadopted, the mechanical property of the conductive silicone rubber is so weak. If it isvulcanized in the saturated vapor vulcanization can at0.45MPa, certain mechanicalproperty can be achieved, but it is weaker than that of the mould pressing vulcanization.However, through the hot liquid vulcanization, take the glycerinum as the heat-conductingmedium, and vulcanize it for20min under160℃, and finally, the conductive siliconerubber tube can be achieved with good property. It studies the jointing and ring formation process of the conductive silicone rubbertube, and compares the different jointing ways before and after the vulcanization. It turnsout that the organic silica gel with room temperature vulcanization (RTV) as the adhesiveafter vulcanization has the best effect on jointing and ring formation, and the achieved sealring can meet all property requirements.