Chemical poly sulfides

Superior Environmental Products, Inc. introduced a product based on liquid poly sulfide containing 40% of a surface-modified scrap tire mbber. The product, ER-IOOR, is a coating that can temporarily contain chemical, oil, and gasoline spills. Rodriguez [97] reported that an unsaturated polyester resin containing silane-treated CGR showed better mechanical properties than that containing untreated CGR. 

Addition of chemical catalysts. Compounds such as anthraquinone or poly sulfide or a mixture of the two are introduced into the Kraft cooking liquor. 

Poly sulfide compounds that are compatible with epoxy resins are liquid elastomers at room temperature. The most significant commercial resin of this type is LP-3 from Toray. The predominant product is a mercaptan-terminated liquid polymer (LP) that contains approximately 37% bound sulfur (see Fig. 7.2). It is the high concentration of sulfur linkages that provides these products with their unique chemical properties. A sulfur odor is noticeable during processing, making ventilation important. 

Chemical Operation or Reagent Mer- captans Di- sulfides Poly- sulfides Sulfides Thio- phene Elemental sulfur Hydrogen sulfide Sulfur dioxide... 

Interfacial aspects and adhesion of polysulfides have been studied extensively and reported by us [3,17]. The epoxy-modified poly sulfide has improved adhesion due to chemical reactions that increase electronic attraction forces. Water has been found to be the most potent debonding agent in cured polysulfides. Formation of thiourethane is responsible for excellent adhesion of polysulfide onto polyurethane coatings. 

Poly(thioether)s should not be confused with poly(sulfide)s, in that the term poly refers directly to the sulfide linkage, i.e., —Sn—, but at the same time to a polymer. These types of polymers are used in a completely different field of application, e.g., additives for elastomers, antioxidants for lubricating oils, intermediates for the production of organic chemicals, insecticides, germicides, and as an additive to diesel fuels to improve the octane number and ignition qualities of these fuels. These polymeric types are not dealt with in this chapter. 

When the lattice of the vulcanizate was formed by weak, especially poly-sulfide bonds, the rate of thermal decomposition of the latter exceeds the rate of oxidative destruction of the molecular chains by an order of magnitude. hi the indicated case, the rate of the chemical reaction is determined by the rate of decomposition of the transverse bonds, and all the factors that influence the oxidation of the polymer cannot essentially change the rate of chemical relaxation. Figures 181-184 illustrate the premise cited. 

However, polymer quality and cure rates were not reproducible batch to batch, and field experience showed that chemical resistance and dynamic sealant properties were inferior to those of poly sulfides. Second generation poly-mercaptans were introduced in 1974.81.82,94... 

Chemical reduction of high-order poly sulfides that diffuse to the anode ... 

More recently, in the nineteenth century, there was a great increase in the application of foreign chemicals to agriculture. Discovered or, more precisely, rediscovered was the usefulness of sulfur, lime sulfur (calcium poly sulfides), and Bordeaux mixture (basic copper sulfates). With the exception of formaldehyde, inorganic chemicals provided farmers with their major weapons. 

The resistance of these two types of polysulfide to highly aromatic solvents and ketones commonly encountered is outstanding. The resistance of Thiokol FA and ST to a few of these solvents is shown in Table 11.3. Additional chemical resistance information on poly sulfides may be found in Chemical Resistance Guide for... 

FIGURE 4.32 Chemical structure of end-functionalized poly(sulfide ketone)s with six sulfonic acid moieties at a,co-chain ends. 

Epoxy poly sulfides [10] are available as two-part liquids or pastes that cure at room temperature or higher to rubbery solids that provide bonds with excellent flexibility and chemical resistance. These adhesives bond well to a number of substrates. Shear strengths and elevated-temperature properties are low, but resistance to peel and low-temperature properties are quite high. 

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... 

The Eastman Chemical Company has pubHshed extensively in the patent Hterature (65—74) and the scientific Hterature (75—77) on processes for making poly(phenylene sulfide)- (9-(phenylene disulfide), and related copolymers. The Eastman process involves the reaction of elemental sulfur with Ndiiodobenzene to yield a phenylene sulfide polymer that also contains phenylene disulfide repeating units in the polymer. The fraction of repeating groups containing... 

The synthesis of poly(arylene sulfide)s via the thermolysis of bis(4-iodophenyl) disulfide has been reported (78). The process leads to the formation of PPS and elemental iodine. This process presumably occurs analogously to that reported by Eastman Chemical Company. 

PPS resins must compete with PEI and phenoHcs. There are two domestic manufacturers of poly(phenylene sulfide) Phillips and Fortron Industries. Worldwide there is currently large overcapacity (Table 15). Four Japanese companies, ie, Toso Susteel, a joint venture of Toso/Hodogaya Chemical Toray Toprene, a joint venture of Toto Kasei/Toren Petrochemical and Kureha Chemical have a combined capacity of 82,500 t. U.S. agents sell their materials in the U.S. markets General Electric sells for Toso Susteel Soltex Polymer, part of Solvay, Belgium, sells for Toprene Hoechst-Celanese sells for Kureha. Prices for PPS resins and compounds range from 8.80/kg for unreinforced resin to 3.30/kg for 65% filled resins. 

The PEEK resia is marketed as aeat or filled pellets for iajectioa mol ding, as powder for coatiags, or as preimpregaated fiber sheet and tapes. Apphcations iaclude parts that are exposed to high temperature, radiation, or aggressive chemical environments. Aerospace and military uses are prominent. At present, polyamideimide (PAl) resia and poly(arylene sulfides) are the main competitors for apphcations requiring service temperatures of 280°C. At lower temperatures, polyethersulfones, amorphous nylons, and polyetherimides (PEI) can be considered. 

Zinc sulfide, with its wide band gap of 3.66 eV, has been considered as an excellent electroluminescent (EL) material. The electroluminescence of ZnS has been used as a probe for unraveling the energetics at the ZnS/electrolyte interface and for possible application to display devices. Fan and Bard [127] examined the effect of temperature on EL of Al-doped self-activated ZnS single crystals in a persulfate-butyronitrile solution, as well as the time-resolved photoluminescence (PL) of the compound. Further [128], they investigated the PL and EL from single-crystal Mn-doped ZnS (ZnS Mn) centered at 580 nm. The PL was quenched by surface modification with U-treated poly(vinylferrocene). The effect of pH and temperature on the EL of ZnS Mn in aqueous and butyronitrile solutions upon reduction of per-oxydisulfate ion was also studied. EL of polycrystalline chemical vapor deposited (CVD) ZnS doped with Al, Cu-Al, and Mn was also observed with peaks at 430, 475, and 565 nm, respectively. High EL efficiency, comparable to that of singlecrystal ZnS, was found for the doped CVD polycrystalline ZnS. In all cases, the EL efficiency was about 0.2-0.3%. 

The high degree of crystallization and the thermal stability of the bond between the benzene ring and sulfur are the two properties responsible for the polymer s high melting point, thermal stability, inherent flame retardance, and good chemical resistance. There are no known solvents of poly(phenylene sulfide) that can function below 205°C. 

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