Oxygen barriers that use free radical chemistry

Oxygen barriers made of linoleic acid, ethyl cellulose and a cobalt catalyst can reduce oxygen penetration over 2,000 times compared with an ethyl cellulose barrier of the same thickness. The barrier is effective only when the product of linoleic acid concentration and barrier thickness exceeds a critical value, which is apparently necessary to effectively initiate the reaction. When this condition is met, the time that the barrier is effective can be predicted using a theory that assumes oxygen consumption is diffusion-controlled. Operating in this condition, the barrier is about 70% efficient, that is, about two-thirds for the double bonds available in linoleic acid react with oxygen. The results provide a rationale for the design of better oxygen barriers.