Health & Environmental Research Online (HERO)


Print Feedback Export to File
5444256 
Book/Book Chapter 
31 - Polysulfides 
Vietti, DE 
1989 
Pergamon 
Amsterdam 
Comprehensive Polymer Science and Supplements 
533-542 
Polysulfide polymers have the general structure (−R−Sx−)n (1) where x is referred to as the ‘rank’ and represents the average number of sulfur atoms in the polysulfide unit. The rank of polysulfide polymers usually ranges from slightly less than two to about four. The origin of polysulfide polymers dates back to the infancy of organic chemistry. As early as 1838, there were reports of rubbery, intractable, high sulfur, semisolid products from the reaction of potassium sulfides with a hal-ogenated product designated ‘chloraetherin’. ‘Chloraetherin’ was a mixture of products obtained from the addition of chlorine to ethylene in aqueous suspension.1–3 Subsequently, there were a number of reports of similar products obtained by various methods, 4–6 but the first useful products were developed from Patrick’s studies of the reaction of sodium polysulfide with ethylene dichloride. In 1927, the first of an extensive series of patents on the reaction of organic dihalides and inorganic polysulfides was issued to Patrick and Mnookin.7 Shortly thereafter, production of the ethylene tetrasulfide polymer under the trade name Thiokol A was started. This was the first synthetic elastomer manufactured commercially in the United States. These new synthetic rubbers, available from potentially low cost raw materials, excited considerable interest and various modifications of the polysulfide elastomers appeared all over the world. However, these original polymers were difficult to processs, evolved irritating fumes during compounding, and possessed some undesirable physical properties. Gradual improvements in the products and in methods of processing solved some of these problems but the most significant improvement came in the early 1940’s when a method for preparing thiol-terminated liquid polysulfides was developed. Cure of the liquid polysulfides could be accomplished by oxidative coupling of the terminal thiol groups. The liquid polysulfides were particularly useful because now, in effect, a rubber could be compounded without the need of heavy mixing equipment. The liquid polysulfides are the predominant form of polysulfides produced today. Polysulfide rubbers have unusually good resistance to solvents and the environment and good low temperature properties. Because of their unique properties, they have found use in a variety of applications and a number of review articles have been published on the preparation, compounding and performance of polysulfide polymers.8–16 
Bevington, John C.