Cold vulcanization

The Hquid polymer is then compounded with metal oxides or peroxides, as weU as fillers (carbon black) and can undergo cold vulcanization, ie, chain extension and cross-linking iato a soHd matrix. It is largely used as a sealant and gasket material for wiadows, automobile wiadshields, etc. 

Used industrially as a chemical intermediate in the production of rayon, carbon tetrachloride, xanthogenates, flotation agents, and pesticides used in the cold vulcanization of vulcanized rubber, in adhesive compositions for food packaging as a solvent for phosphorus, sulfur, selenium, bromine, iodine, fats, resins, rubbers, waxes, lacquers, camphor, resins and in the production of optical glass, paints, enamels, varnishes, paint removers, tallow, putty preservatives, rubber cement, soil disinfectants, explosives, rocket fuel, and electronic vacuum tubes. 

An important application of P.Gr.8 is in the coloration of rubber. The pigment, however, is not suitable for use in blends which contain large amounts of basic fillers. It is somewhat sensitive to cold vulcanization. The colored articles usually perform well in general application but are not entirely fast to aromatic hydrocarbons and to some fats, and they are sensitive to acid and sulfur dioxide. P.Gr.8 also colors some plastics, especially LDPE and polystyrene. Heat stable up to 220°C, P.Gr.8 grades equal step 2-3 on the Blue Scale for lightfastness. Other areas of application include wallpaper and artists colors. 

USE Intermediate and chlorinating agent in the manuf of organic chemicals, sulfur dyes, insecticides, synthetic rubbers in cold vulcanization of rubber as polymerization catalyst for vegetable oils for hardening soft woods. 

Carbon disulfide is a volatile organic solvent, used mainly as a starting material in rayon manufacture in the viscose process. It was important historically in the cold vulcanization of rubber. Although no longer used in this form, carbon disulfide is still a major industrial precursor in rubber industry chemical synthesis and has a number of other industrial applications. Carbon disulfide is also widely used as a solvent in a variety of laboratory settings. Carbon disulfide is a metabolite of the drug disulfiram (see pp 186) and is a spontaneous breakdown by-product of the pesticide metam sodium. 

The cross-linking produced by heating natural rubber with sulfur has been discovered empirically. Since the process works with heat and sulfur and these are two of the attributed of the god Vulcan, cross-linking or rubber has been called vulcanization. Today, a distinction is made between what is called hot vulcanization, carried out with sulfur at 120-160 C, and what is known as cold vulcanization, which is carried out with disulfur dichloride or magnesium oxide. 

Cold vulcanization occurs at room temperature. It leads to monosulfide cross-link bridges when disulfur dichloride is used ... 

Since this reaction is not affected by peroxide, an ionic mechanism is suggested. In production, the vulcanization is accelerated by compounds such as 2-mercaptobenzthiazole or tetramethylthiuram disulfide, whose effect is not fully understood. The cold vulcanization is carried out at room temperature. Use of S2CI2 results in monosulfide bridges ... 

Organofunctional polysiloxanes with silanol groups can be cross-linked at low temperatures with tetrabutyl titanium, methyl triacetoxy-silane, and similar compounds and are thus used as cold vulcanization materials. In contrast, hot vulcanizable silicones possess one vinyl group in about 500-1000 monomeric units and can be cross-linked with peroxides. All silicon rubbers are filled with highly dispersed silica since the unfilled rubber is practically a useless elastomer. 

In the cold vulcanization of rubber, disulfiir dichloride (S2CI2) is used as a source of sulfur atoms, and those sulfur atoms form bridges, or cross-links, between polymer chains. S2CI2 can be produced by reacting molten sulfur (Ss(f)) with chlorine (Cl2(g)). What is the maximum mass of S2CI2 that can be produced by reacting 32.0 g of sulfur with 71.0 g of chlorine ... 

Natural and synthetic rubber High-temperature stability abrasion resistance cold vulcanization elimination of vulcanizing agents ... 

When raw caoutchouc is mixed with sulfur and the temperature raised sufficiently a remarkable change of chemical and physical properties takes place. The mass loses its adhesiveness, called tackiness in practice the elasticity may vary between great extremes differences of temperature over a comparatively wide range have little effect it is rendered insoluble in any liquid that does not permanently destroy it and finally it is much more resistant to oxidation, and therefore less liable to perish. The process is known as the hot cure or hot vulcanization. Similar alterations in properties, differing only in degree, may be brought about by what is termed the cold cure, or cold vulcanization. The hot cure is much more widely applied in practice. 

Cold Vulcanization. — The material in thin strips, or sheets, is passed through, or dipped into a solution of sulfur chloride (S2CI2) in carbon disulfide, or carbon tetrachloride. Some of the sulfur chloride remains united, physically or chemically, with the caoutchouc, and the excess is neutralized with ammonia. By this process the goods acquire a soft velvet feel, but unfortunately are liable to perish rather easily. A variation of the method, technically known as the vapor cure, consists of treating the goods with the vapors of sulfur chloride. Subsequent neutralization with ammonia is, of course, necessary. 

During cold vulcanization with S2CI2 a amilar series is formed. The highest member of this series would therefore have the formula (CioHit)io(S2Cl2)io, and the lowest (CioHie)ioS2Cl2. 

C. O. Weber and later D. Spence and J. Young claim to have found 32 per cent to be the maximum amount of sulfur that can become fixed. This would correspond to the formula CioHieS. Moreover Hinrichsen and Kindscher obtained a body by cold vulcanization that from analysis should have the formula (CioHi6)2S Cl2. From this body they formed another substance by the breaking off of hydrochloric acid. The results of the analysis would suggest the formula (CioHis)iSi. 

V. bei Raumtemperatur cold vulcanizing (cold cure), room temperature vulcanizing (RTV)... 

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