In composite solid propellants, low-molecular-weight species such as burning rate catalysts, plasticizer, etc. which migrate into liner and thermal insulation layers during curing and storage invariably result in poor mechanical and ballistic properties of the propellants. In the present study, the migration of the burning rate catalyst, acetyl ferrocene, was investigated spectrophotometrically (UV-visible) by evaluating the extent of hindrance to such migration after applying a barrier (liner) of various crosslink densities between the additive (HTPB-TDI-plasticizer-acetyl ferrocene) and nonadditive (HTPB-TDI) gumstocks replicating the propellant and insulating layer, respectively. Enhancing the crosslink densities of liner via a trifunctional aziridine crosslinking agent inhibited migration. The aging of additive gumstock was done at 60 degrees C and its mechanical properties and extent of acetyl ferrocene migration were also evaluated and analyzed. (c) 2006 Wiley Periodicals, Inc.