Polysulfides elastomers

Polysulfide elastomer Polysulfide polymers Polysulfide process Polysulfidepulping Polysulfide rubbers Polysulfides... 

Polysulfide Impression Materials. In 1953 the first nonaqueous, elastic dental impression material based on the room-temperature conversion of a Hquid polymer, a polyfunctional mercaptan (polysulfide), to a strong, tough, dimensionally accurate elastomer, was introduced. The conversion of the Hquid polymer to an elastic soHd has been achieved in most products by lead peroxide [1309-60-0]. Significant improvements in strength, toughness, and especiaHy dimensional stabiHty of the set polysulfide elastomers over the aqueous elastic impression materials made these materials popular. 

The synthesis of polysulfide elastomers involves the use of a small amount of trichloroalkane in addition to dichloroalkane and sodium sulfide in order to form a branched polymer. The prepolymer is treated with a mixture of sodium hydrosulfide and sodium sulfite followed by acidification to convert all end-groups to thiol groups. Further polymerization and crosslinking is achieved by oxidative coupling of the thiol end-groups by treatment with lead dioxide, p-quinone dioxime, or other oxidizing agent... 

Thiokol elastomers possess fairly low tensile and tear properties. However, they have excellent resistance to both aliphatic and aromatic solvents at room temperature and slightly elevated temperatures. The Thiokol division of Morton International Corporation is the supplier of polysulfide elastomers in the United States. It is estimated that 1360—1600 t are used annually in the United States. The primary use of polysulfide is in seals, gaskets, rolls, and diaphragms where solvent resistance and low permeability are useful. 

Liquid copolymers of butadiene and acrylonitrile with carboxyl end groups are used as contact adhesives in the automotive industry, Polysulfide elastomers, produced by the reaction of ethylene dichloride and sodium po-... 

Fig. 33 Effect of nanoclay content on adhesive strength of polysulfide elastomer/clay nanocomposites samples containing 0, 2, 4, and 8 phr of nanoclay are designated as PSCO, PSC2, PSC4, and PSC8, respectively...

Fig. 10. Compression stress-strain properties of various elastomeric syntactic foams129> (l)urethane elastomer binder and glass microspheres y = 640 kg/m3, void fraction 0.321 (2) polysulfide elastomer binder and phenolic microspheres y = 1500 kg/m3, void fraction 0.133 (3) silicone elastomer binder and glass microspheres y = 610 kg/m3, void fraction 0.407...

OTHER COMMENTS used as a solvent and extractant for resins, oils, fats, waxes, and chlorinated rubber used as a paint and varnish remover, and as a commercial solvent for degreasing metal parts useful in the synthesis of hexafluoropropylene has also been used in the synthesis of thiokol polysulfide elastomers if some branching of the polymer structure is required. 

Few argue that we have much to learn about the Thiokols and other polysulfide elastomers, the polysulfones, which have such interesting properties as the engineering plastics, and the episulfides. The chemistry of pyrites, carbon disulfide, sulfur dioxide, dimethyl sulfoxide, and many other compounds merit separate reviews. 

The first polysulfide elastomers were developed in 1927 by Dr. J.C. Patrick, who, in search for a means to make anti-freeze, reacted an organic dichloride with sodium polysulfide, and produced the first synthetic rubber manufactured. 

Polysulfide elastomers from the reaction of 1,5-pentanedithiol with thionyl chloride [144], gew-Dithiols [145]. 

A great many of outstanding adhesive formulations are based on epoxy resins. A broad spectrum of adhesive formulations with a wide range of available properties have resulted from the use of polymeric hardeners such as polyamides and polyamines, phenolics, isocyanates, alkyds, and combinations of amines with polysulfide elastomers, and the alloying of the epoxy with compatible polymeric film-formers, such as poly(vinyl acetate) and certain elastomers. 

Polysulfide elastomers are produced by the reaction of an aliphatic dihalide, usually bis(2-chloroethyl)formal, with sodium polysulfide under alkaline conditions ... 

Tobolsky has studied extensively the viscoelastic properties of polysulfide polymers [9]. Polysulfide polymers have the unique ability to relieve internal stress or stress between mercaptan and disulfide linkages. The stress decay of cross-linked polysulfide elastomer follows the equation... 

Synonyms Polysulfide elastomer Classification Synthetic polymer... 

Polysulfide elastomer. See Polysulfide Polytef. See Polytetrafluoroethylene Polyterpene resin. See Terpene resin... 

Properties of Polysulflde Rubbers. Vulcanizates of polysulfide elastomers are better than all other elastomers with respect to resistance to aromatic and chlorinated hydrocarbons, and to ketones. They have good weather and ozone resistance, and they are relatively inexpensive. However, they have somewhat lower level of mechanical properties and particularly poor compression set. 

Thiokol Corporation, which is the exclusive producer of polysulfide elastomers in the free world, is now a major producer of solid rocket engines and has annual sales of many millions of dollam. TTiiokol (now Morton-Thiokol) is the sole supplier of solid rocket boosters for the space shuttle mission and is listed on the New York Stock Exchange. 

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