Permeability of silicone polymers to hydrogen

Permeability coefficients, P̄ , for H 2 in 10 different types of silicone polymer membranes were measured in the temperature range of 10.0–55.0°C and at pressures up to 100 psig (∼6.8 atm). The values of P̄ decrease slightly with increasing Δ p , the pressure difference across the membranes. The permeability of silicone polymers to H 2 increases with an increase in temperature; the values of the energy of activation for permeation are in the range of 1.4–4.3 kcal/mol. The substitution of different functional groups in the backbone and side chains of silicone polymers has similar effects on the permeability of the polymers to H 2 as observed in earlier studies with other light gases. P̄ for H 2 decreases with an increase in the bulkiness of the substituted functional groups. The substitution of SiO bonds with stiffer SiC bonds in the backbone chains also results in a considerable decrease in permeability.