Polysulfide Liquid Polymers

Abstract Polysulfide liquid polymers are a comparatively recent development conceived at the Thiokol Laboratories in 1943. The development was initiated by the problem of finding methods to reduce the molecular weight of a polysulfide rubber which was too tough to process on conventional rubber milling equipment. The problem was solved by reduction of a few of the disulfide links present in the polymer chain. It was soon found that the method was applicable to the preparation of polymers low enough in molecular weight to be liquids. The method produces dithiols of high purity which are extremely active in a wide variety of chemical reactions. Some formulations have been developed which depend on conversion from the liquid to rubber state at temperatures as low as 50° F in about 30 minutes. Most of the converting agents function through oxidation with hydrogen removal from the thiol and a linkage of sulfurs to reform the disulfide group. The converted polymers have the general properties of polysulfide polymers: good solvent resistance to a wide range of solvents, low diffusion rate of gases, good resistance to oxidation, ozone, and weathering, and a service temperature range from −65° to +250° F. (Some compounds can withstand intermittent temperatures as high as +350° F.) The low temperature properties are inherent in the polymer and do not depend on special compounding techniques.