Polysulfide rubber compounds

FA polysulfide rubber compounds display excellent resistance to ozone, weathering, and exposure to ultraviolet light. Their resistance is superior to that of ST polysulfide ribbers. If high concentrations of ozone are to be present, the use of 0.5 part of nickel dibutyldithiocarbamate (NEC) per 100 parts of FA polysulfide rubber will improve the ozone resistance. 

ST polysulfide rubber compounded with carbon black is resistant to ultraviolet light and sunlight. Its resistance to ozone is good but can be improved by the addition of NBC, however, this addition can degrade the material s compression set. ST polysulfide rubber also possesses satisfactory weather resistance. 

The Auger depth profile obtained from a plasma polymerized acetylene film that was reacted with the same model rubber compound referred to earlier for 65 min is shown in Fig. 39 [45]. The sulfur profile is especially interesting, demonstrating a peak very near the surface, another peak just below the surface, and a third peak near the interface between the primer film and the substrate. Interestingly, the peak at the surface seems to be related to a peak in the zinc concentration while the peak just below the surface seems to be related to a peak in the cobalt concentration. These observations probably indicate the formation of zinc and cobalt complexes that are responsible for the insertion of polysulfidic pendant groups into the model rubber compound and the plasma polymer. Since zinc is located on the surface while cobalt is somewhat below the surface, it is likely that the cobalt complexes were formed first and zinc complexes were mostly formed in the later stages of the reaction, after the cobalt had been consumed. 

These new synthetic rubbers were accessible from potentially low cost raw materials and generated considerable woddwide interest. For a time, it was hoped that the polysulfide rubbers could substitute for natural mbber in automobile tires. Unfortunately, these original polymers were difficult to process, evolved irritating fumes during compounding, and properties such as compression set, extension, and abrasion characteristics were not suitable for this application. 

Use Solvent for oils, fats, greases, resins, gums extractants, cleaning compounds intermediate for insecticides, pharmaceuticals, plasticizers, polysulfide rubbers, resins, and cationic surfactants. 

Use Antioxidants, fungicides, oil additives, plasticizers, insecticides, stabilizers, polymerization modifiers, stabilizer in tin-sulfur compounds, stripping agent for polysulfide rubber. 

Acetic acid, mercapto- isooctyl ester A13-26088 EINECS 246-613-9 HSDB 2704 Isooctyl mercaptoacetate Isoootyl thioglycolate Mercaptoacetic acid, isoootyl ester, NSC 9590, Antioxidants, fungicides, oil additives, plasticizers, insecticides, stabilizers, polymerization modifiers, stabilizer for tin-sulfur compounds, stripping agent for polysulfide rubber. Sock, Bruno Chemische FabrikKG. 

ORIGIN/INDUSTRY SOURCES/USES anthropogenic compound, not believed to occur in nature synthetic compound solvent intermediate for polysulfide rubber treatment of textiles manufacture of polymers and insecticides degreasing agents preparation of ion exchange resins... 

Polysulfide rubbers posses outstanding resistance to solvents. They exhibit excellent resistance to oils, gasoline, and aliphatic and aromatic hydrocarbon solvents, very good water resistance, good alkali resistance, and fair acid resistance. FA polysulfide rubbers are somewhat more resistant to solvents than ST rubbers. Compounding of FA polymers with NBR will provide high resistance to aromatic solvents and improve the physical properties of the blend. For high resistance to esters and ketones, neoprene W is compoimded with FA polysulfide rubber to produce improved physical properties. 

Large amounts of these rubbers are used to produce caulking compounds, cements, paint can gaskets, seals, and flexible mountings. Because of the impermeability of the polysulfide rubbers to air and gas, these rubbers have found application in the manufacture of inflatable items such as life jackets, life rafts, and balloons. 

Sealing compound, thread and gasket, fuel, oil and water resistant Sealing compound, electrical, high strength, accelerator required Sealing compound, polysulfide rubber, electric connectors and electric systems, chemically cured Silicone compound... 

Devulcanization in a sulfur cured rubber is defined as the cleavage of the mono-, di-, and polysulfidic cross-links formed during vulcanization (Fig. 1). The vulcanization process is irreversible and additional heating induces changes in the network with a shift toward shorter cross-links but does not devulcanize the compound. Other methods are therefore needed to induce devulcanization. 

It should be recognised that appreciable shifts in properties are sometimes made possible by special compounding variations. For instance, the heat resistance of natural rubber vulcanisates may be improved considerably by variation of the vulcanising recipe. The normal sulfur vulcanisation system is capable of many variants which will govern the chemical nature of sulfur crosslinks, i.e., whether it is essentially a mono, di or polysulfide linkage. The nature of sulfur crosslinks can have considerable influence on the heat and chemical resistance of vulcanisates. 

The chief uses of the polysulfide crude rubbers are in (1) rollers for applying ink, paint, and lacquer (2) hose to carry gasoline, solvents, and paint (3) putties for metal, glass, plastics, and wood (4) paper coatings for gadiets (5) plasticizer for sulfur cements (6) molded compounds in contact with fuels and (7) fabric coatings for diaphragms. 

In addition to the liquid polysulfides, polysulfide millable gum elastomers have been used for many years with conventional rubber processing equipment. Compounds based on solid elastomers are being used in the manufacture of paint spray hose, rollers, and printing blankets for the graphic arts industry. New applications for these versatile materials are still being developed. 

Sodium hexamethylene-l,6-bisthiosulflde dihydrate, when added to the vulcanization system, breaks down and inserts a hexamethylene-1,6-dithiyl group within a disulfide or polysulfide crosslink. This is termed a hybrid crosslink. During extended vulcanization periods or accumulated heat history due to product service, polysulfidic-hexamethylene crosslinks shorten to produce thermally stable elastic monosulfidic crosslinks. At levels up to 2.0 phr, there is little effect on compound induction or scorch times, nor on other compound mechanical properties (Rubber Chemicals, 1998). 

A simple process for reclaiming of rubber with a vegetable product that is a renewable resource material (RRM) was developed [38-40]. The major constituent of RRM is diallyl disulhde. Other constituents of RRM are different disulfides, monosulfides, polysulfides, and thiol compounds. 

The chemistry of the accelerated vulcanization of BR, SBR, and EPDM appears to have much in common with the vulcanization of natural rubber. Before the formation of cross-links, the rubber is first sulfurated by accelerator-derived polysulfldes (Ac-S -Ac) to give macromolecular, polysulfidic intermediates (rubber-Sx-Ac), which then form crosslinks (rubber-S -rubber). As in the case of natural rubber, the average length of a crosslink (its sulfidic rank, the value of x in the cross-link, rubber-Sx-rubber) increases with the ratio of sulfur concentration to accelerator concentration (S/Ac) used in the compounded rubber mix. However, in the case of BR or SBR, the cross-link sulfidic rank is not nearly as sensitive to S/Ac as it is in the case of natural rubber. Model compound studies of the vulcanization of EPDM (e.g., wherein ethylidenenorbomane was used as a model for EPDM) indicate that the polysulfidic rank of the EPDM cross-links probably responds to changes in S/Ac in a natural rubber-hke fashion. 

Elementary sulfur or compounds that can be used as a source of sulfur form together with suitable additives at higher temperatures thio-ether-, disulfide- or polysulfide-bridges in and between chains. This vulcanisation method is primarily suitable for those elastomers that have unsaturated bonds. The rubber produced by this method has good mechanical characteristics. However, a disadvantageous chemical characteristic of rubber vulcanised with sulfur is that additives can leach into the product. An example is the release of thiol compounds, which are incompatible with some mercury compounds. 

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