EFFECT OF THERMO-OXIDATION ON PERMEATION RESISTANCE OF BROMOBUTYL COMPOUNDS

The impact of thermo-oxidation on the permeation process in a series of BIIR or bromobutyl compounds has been investigated. Methyl salicylate (MS) was used as the simulating chemical agent, and the permeation rate was measured gravimetrically using vapometers. Heat aged samples at 120 °C increased in stiffness with an accompanying decline in ultimate properties and network chain density. A reduction in permeability was found, driven primarily by the reduced solubility of MS in the thermo-oxidized BIIR matrix. The formation of a secondary oxidized chain network has been proposed to explain the decline in MS solubility. The loss of plasticizer during the heat aging process is responsible for the reduction of the MS diffusibility. Diffusion-limited oxidation during thermo-oxidation is also a likely factor in affecting the MS transport process.