Gas permeability (airtightness) of rubber

Gas permeability of rubber is the product of solubility and diffusivity of gases in rubber. The solubility of gases decreases as the solubility parameter of rubber increases, and the diffusion rate of gases in rubber depends on the number of side-chain groups in the rubber molecule. The gas permeability in various rubbers is very different, in the rubber gas permeability is lower than the polyether rubber and butyl rubber, butyl rubber gas permeability is only 1/20 of the natural rubber, and the gas permeability of silicone rubber is the largest. The air permeability of rubber with the increase in temperature and the rapid increase in the use of carbon black as filler products, its varieties and the amount of filler on the air permeability performance has little effect. But the amount of softener has a great influence on the air permeability of vulcanized rubber.The amount of softener should be reduced as much as possible for rubber products with high air permeability requirements.