Permeability of silicone polymers to ammonia and hydrogen sulfide

Permeability coefficients, P̄, for NH3 AND H2S in 11 different types of silicone membranes were measured in the temperature range from 10.0 to 55.0°C and at pressures up to 115 psig (∼ 7.8 atm). The values of P̄ for NH3 and H2S in different silicone polymers decrease considerably as the bulkiness of the functional groups in the side and backbone chains of these polymers increases. the substitution of SiO bonds with stifer SiC bonds in the backbone chains also results in a considerable decrease in gas permeability. the values of P̄ for NH3 and H2S increse exponentially with incresing δp, the pressure difference across the membrancs. The temperature dependence of NH3 and H2S varies greatly: P̄ can increase, decrease, or pass through a minimum with increasing temperature, depending on the nature of the silicone polymer. The temperature dependence of P̄ is also affected in some cases by Δp. The permeability behavior of silicone polymers to NH3 and H2S is compared with that to other penetrant gases, and the factors which might affect this behavior are discussed.