Poly sulfide performance

The formation of dialkyl sulfones in the oxidation of sulfides proceeds most likely through the corresponding sulfoxides [34, 40], which may be isolated. Sulfoxides are major products in the indirect oxidation of sulfides performed by a reagent electrochemically generated from crosslinked poly(4-vinylpyridine)hydrobromide [75]. 

When reduced ferredoxin is used as the electron donor for polysulfide reduction, the reaction is monitored by the production of sulfide. The assays are performed in 8-ml serum-stoppered vials under Ar that are shaken at 150 rpm at 80°. The reaction mixture (2 ml) contains 100 vaM EPPS buffer, pH 8.0, 10 mM pyruvate, 2 toM coenzyme A, 150 p,g POR from P. furiosus, 25 lM ferredoxin, 40 p.g FNOR, and a source of elemental sulfur. This is polysulfide (1.5 mA/), sublimed elemental sulfur (0.5%, w/v J. T. Baker, Marietta, GA), or colloidal sulfur (0.05%, w/v Fluka, Ronkonkoma, NY). Note that sublimed elemental sulfur has a very low solubility, whereas colloidal sulfur generates a fine suspension. At 20 min intervals over 2 hr, aliquots of the reaction are removed with a syringe and the amount of sulfide produced is measured by methylene blue formation." One unit of activity is defined as 1 p.mol sulfide produced per min. When reactions are monitored by sulfide production, it is important that control assays be carried out without the addition of enzyme. This is particularly important when poly sulfide is used as the source of elemental sulfur. 

IV. Performance Testing of Two-Part Poly sulfide Sealants, J. Paint TechnoL, 45(580), 49 (May... 

The principal classes of high performance fibers are derived from rigid-rod polymers, gel spun fibers, modified carbon fibers, synthetic vitreous fibers, and poly(phenyiene sulfide) fibers. 

Because the chemical stmcture of poly(phenylene sulfide) [9016-75-5] (PPS) does not fall into any of the standard polymer classes, the Federal Trade Commission granted the fiber the new generic name of Sulfar. The fiber has excellent chemical and high temperature performance properties (see... 

Acrylic ESTER POLYMERS Acrylonitrile POLYMERS Cellulose esters). Engineering plastics (qv) such as acetal resins (qv), polyamides (qv), polycarbonate (qv), polyesters (qv), and poly(phenylene sulfide), and advanced materials such as Hquid crystal polymers, polysulfone, and polyetheretherketone are used in high performance appHcations they are processed at higher temperatures than their commodity counterparts (see Polymers containing sulfur). 

In automotive and aerospace end uses, the apphcations ate also often electrical. Polysulfones do not have as good solvent resistance as poly(phenylene sulfide). They perform well in hydrocarbons like gasoline and oil, or in antifreeze, but ate attacked by the alcohol-blend fuel mixtures. This may limit their under-the-hood apphcations. 

Ethers, esters, amides and imidazolidines containing an epithio group are said to be effective in enhancing the antiwear and extreme pressure performance of lubricants. Other uses of thiiranes are as follows fuel gas odorant (2-methylthiirane), improvement of antistatic and wetting properties of fibers and films [poly(ethyleneglycol) ethers of 2-hydroxymethyl thiirane], inhibition of alkene metathesis (2-methylthiirane), stabilizers for poly(thiirane) (halogen adducts of thiiranes), enhancement of respiration of tobacco leaves (thiirane), tobacco additives to reduce nicotine and to reduce phenol levels in smoke [2-(methoxymethyl)thiirane], stabilizers for trichloroethylene and 1,1,1-trichloroethane (2-methylthiirane, 2-hydroxymethylthiirane) and stabilizers for organic compounds (0,0-dialkyldithiophosphate esters of 2-mercaptomethylthiirane). The product of the reaction of aniline with thiirane is reported to be useful in the flotation of zinc sulfide. 

Grades of fiberglass that are resistant to methanol have been developed, primarily for use in bulk storage tanks. Fiberglass not designed for methanol will quickly soften and delaminate. Ford has reported that onboard fuel lines made of poly phenylene sulfide resin give good performance [3.6]. 

Polyiphenylene Sulfide) Blends Poly(phenylene sulfide), PPS, is an expensive, high-performance, but brittle specialty resin. Blending can offer a good alternative both in... 

As shown in Scheme 29, aromatic and vinylic dithioester groups can be converted to trifluoromethyl groups directly by treating them with (Bu4N)H2p3-DBH (l,3-dibromo-5,5-dimethylhydantoin) (Path a) [17]. The use of NBS or NCS (Path b) in place of DBH yields a,a-difluoro sulfides 130 [17]. This fluorination can also be performed with poly(hydrogen fluoride) pyridinium (Path c) [32]. 

In the same way, poly(phenylene sulfide-phenyleneamine-phenylene-amine) (PPSAA) has been synthesized via a soluble precursor polymer through an acid-induced polycondensation reaction of A-(4-methylsulfin-yl)phenylene-A -phenyl-hd-phenylenediamine." The polymerization is performed by treating the monomer with methanesulfonic acid for 24 h at room temperature. The demethylation is performed in refluxing pyridine. Precipitation in methanol yields the PPSAA as a light purple solid in 91% yield. 

---