Investigation of Constituent of PolysulfideSealant Used in Aerospace Industry and Effect of these Constituent in Shelf Life

Sealants based on polysulfides are one of the most used and oldest materials in aerospace industrythat properties such as suitable chemical resistance, ozone and oxygen resistance and self-repairing. The mentioned properties makes These compounds useful in various applications such as sealing of rubber fuel tank, sealing of wing and fuselage and pressurizing of an aircraft. Along With these suitable properties and various applications, shelf life of polysulfides is low so many research are doing for addition of shelf life. Any information about degradation mechanism can help for resolving this problem and for reaching this opinion. In the other hand, interpretation of degradation reaction requires sufficient knowledge of formulation. In this research, a traditional polysulfide sealant (Commercial Code of PR1440) was selected that was used widely in aerospace industry. First, different components were separated by various methods, then molecular structure of each component and their quantities in formulation were determined by various analytical methods. The result of 1HNMR, 13CNMR and GPC showed that phenolic resin was used as an adhesion enhancer. Also data given from EDX and ICP-AES revealed that CaCO3 and TiO2 were applied as filler and clay respectively. Analysis of curing agent manifested that MnO2 was the main constituent but since this inorganic oxidant have low cure rate, so in the formulation diphenyl guanidine was used as an accelerator that identified by GC-MASS .Mixing of these constituent needs a dispersing oil, such as hydrogenated terphenyl that was found with GC-MASS technique in this formulation. In addition, different method for determining thiol content was investigated too. Finally, the role of each polysulfide component in its shelf life was investigated.

کلیدواژه ها:

polysulfide ، sealant ، shelf life ، formulation