Effect of Retorting On the Barrier Properties of Evoh

The effect of retort processing and storage conditions on the oxygen permeability of ethylene vinyl alcohol copolymer (EVOH) in multilayer packaging was studied. Immediately after retort processing, the oxygen permeability of EVOH increases due to plasticization by moisture. An irrecoverable effect of retorting on permeability is also seen though. This increase in permeability is attributed to the creation of excess free volume. Based on these experimental results, mathematical models were devel oped to predict EVOH oxygen permeability given the retort history and storage con ditions. It is also found that incorporating desiccant in the multilayer structure over comes the moisture effect and greatly reduces the retort path dependence.