EFFECTS OF ENVIRONMENT ON PERFORMANCE OF POLYSULFIDE SEALANTS.

Abstract

One of the most extensive aircraft repair program in recent years arose from the failure of a new integral fuel tank sealant. This material was introduced because it had been anticipated that the aerodynamic heating during flight would produce skin temperatures exceeding the thermal stability limits of the traditional polysulfide sealants. Deployment of the aircraft in hot, humid environments, however, changed the firm elastomer to a sticky paste with virtually total loss of sealing capability. The faulty sealant was shown to possess a polyester structure, which was prone to hydrolyse, particularly in tropical conditions. This extreme example of the effect of imposed conditions on performance illustrates the nexus between structure of sealants, which governs their chemical reactivity, and their resistance to environmental influences. These interrelationships are considered with reference to polysulfide aircraft sealants in the cured state, during cure and also the unmixed components of two part systems.