| The conductive rubber is a kind of conductive polymer materials prepared by adding conductive fillers in the rubber matrix. It retains the original properties of matrix and the conductivity of conductive fillers. In reducing the amounts of conductive fillers to improve the mechanical properties of the conductive rubber, how to maintain or even increase the conductivity of conductive rubber at the same time was the aim of this research. In this paper, using ethylene-propylene-diene monomer(EPDM) rubber and nitrile-butadiene rubber(NBR) as the matrix, the properties of rubber blends filled with different conductive fillers were studied.The effect of the blending ratio on properties of rubber blends was investigated. The blends were characterized by DSC, TG, SEM. The results show that conductive carbon blacks are selectively distributed in the NBR phase, the EPDM and NBR are incompatible. As the proportion of NBR phase increases, the oil-resistant property of EPDM/NBR vulcanizate is greatly improved. When the blending ratio of EPDM/NBR is 50/50, the blends show good synthetical properties, that is, good mechanical properties and thermal stability and the conductivity of composite are best.The silver-coated carbon fibers were obtained by electroless plating. XRD proved that the preparation of it was successful. The conductive rubber was prepared using silver-coated carbon fibers or silver powders as fillers. The silver-coated carbon fibers are disorderly distributed in matrix which made them function as bridges between the non-adjacent conductive phases, while the Ag particles are mainly located in the EPDM phase. Adding silver-coated carbon fibers can improve the mechanical properties of conductive rubber, but the addition of silver powders plays a negative role on the mechanical properties. With the same amount of conductive fillers, the effect of silver-coated carbon fibers on the thermal stability of conductive rubber is better than that of silver powders. When 80 phr silver-coated carbon fibers or 100 phr silver powders are added to the matrix, the electrical resistivity of rubber are respectively 0.0072 ?·cm and 0.0044 ?·cm.By using improved Hummers method, graphite oxide as the precursor was firstly prepared. Graphene-Ag compounding particle was prepared by chemical reduction method. Graphene oxide and ammoniacal silver ions in silver-ammonia solution were reduced at the same time. The average particle size of Ag on the graphene sheets calculated according to the Scherrer formula is 33 nm. A small amount of graphene-Ag compounding particles has reinforcement effect on the matrix, but the mechanical properties decrease when the compounding particles content is excessive. The addtion of compounding particles less than 40 phr can improve the thermal stability of the blends. Exceeding this amount, the thermal stability decreases. The electrical resistivity of conductive rubber is 0.0085 ?·cm when 60 phr graphene-Ag compounding particles are added to the matrix.The influence of the mixture of conductive fillers on the properties of rubber blends was studied. For the composites loaded with 30 phr CB, 6phr TRG(graphene prepared by the thermal expansion reduction method, 900°C) or 30 phr CB, 10 phr CF(coupling agent modification), the electrical resistivity of these blends are respectively 0.33 ?·cm and 0.28 ?·cm. For the CB/CF/Ag/EPDM/NBR composite, the hardness of composites increases while the tensile strength and elongation at break decrease as the weight fraction of silver powder increases. The addition of Ag has no effect on the compatibility of EPDM and NBR, but has a favorable influence on the thermal stability of rubber blends. When 30 phr CB, 10 phr CF together with 10 phr Ag are added to the matrix, the electrical resistivity of conductive rubber is 0.0058 ?·cm. |
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