The highly reactive terminal mercaptans of liquid polysulfide polymers can be converted into high molecular weight products very easily at ambient temperatures by oxidation or by reaction with other active polymers. Polysulfides have excellent solvent resistance, predictable cure, good low-temperature performance, good weathering, and excellent adhesion to many substrates. This combination of properties has given polysulfide polymers a modest but significant position as specialty polymers since their commercialization in 1929. Polysulfide sealants have found wide acceptance in industries, e.g., construction, aircraft, automotive, marine, and insulating glass. In fact, polysulfide sealants were the first elastomeric sealants used in the construction industry and continue today, to a large extent, the standard against which other sealants are compared. Polysulfide sealants, although facing strong challenges by silicones and polyurethanes, continue to be the dominant segment of the elastomeric sealant market [1–6].