Estimation of Emission Characteristics of Sulfur Gas from Rubber
Rintaro MINAMITANI
Abstract:Silver, a typical material used in electronic devices, corrodes in sulfur gas emitted from rubber. To evaluate this corrosion damage of silver, we have established a new method for estimating the two emission characteristics of sulfur gas from rubber: initial sulfur-emission concentration and decrease rate of emission. Firstly, we used a long-term silver-corrosion test with rubber at 70-30ºC to investigate the emission mechanism and emission characteristics of sulfur gas from free sulfur, I.e., non-linked sulfur, in rubber. This investigation showed that the free sulfur in rubber is consumed by crosslink reaction between rubber chains and by sulfur-gas emission. The sulfur-consumption rate is controlled by the crosslink reaction at 70-50ºC, while it is controlled by sulfur-gas emission at 30ºC. The emission characteristics at the temperature that the sulfur-consumption rate is controlled by sulfur-gas emission (I.e., 30ºC) can be estimated by corrosion analysis considering sulfur-gas diffusion and the corrosion reaction of sulfur gas on silver. Secondly, we investigated the relationship between the amount of free sulfur and the emission characteristics. This investigation found that the amount of free sulfur can be calculated by integrating concentration of sulfur-gas emission. Given that result, we were able to establish a new method for estimating emission characteristics from the amount of free sulfur by chemical analysis and the initial concentration of sulfur-gas emission by a short-term silver-corrosion test with rubber. Key Words:Silver, Corrosion, Rubber, Emission gas, Sulfur gas, Free sulfur