Journal of Adhesion Science and Technology, Vol.17, No.5, 725-736, 2003
Direct adhesion of natural rubber to nickel/sulfur plating during curing
Direct adhesion between natural rubber and nickel/sulfur plating during curing was investigated. A nickel/sulfur plating was obtained by the addition of sodium thiosulfate Na2S2O3 . 5H(2)O to a nickel chloride plating bath. The sulfur content of the plating depends on the concentration of sodium thiosulfate, Na2S2O3 . 5H(2)O, the bath temperature and the plating current density. The nickel/sulfur plating is deposited in an amorphous form and the sulfur is distributed uniformly. When the nickel/sulfur plating and natural rubber are cured in a hot press, direct adhesion is formed. The sulfur content around 30% gives the best adhesion and a thinner plating is preferable. The amorphous nickel/sulfur plating is transformed to a crystalline phase [mixture of a-nickel and nickel sulfide (Ni3S2)] during curing. It is suspected that less heat stress is generated in the case of a thinner plating which causes better adhesion to rubber.