Benzothiazole-accelerated vulcanization

The decreased specific rate of crosslink formation, and the increased extent of crosslinking due to the presence of Zn++ in benzothiazole-accelerated vulcanization, have been explained by the following scheme (Coran, 1965) ... 

The Role of Zinc in Benzothiazole Accelerated Vulcanization. An increase in the... 

Damen, R. Nieuwenhuizen, P.J. Haasnoot, J.G. Reedijk, J. Homogenous zinc (II) catalyst in accelerated vulcanization V. The prevailing mechanism of crosslink formation in mercapto-benzothiazole systems. Rubber Chem. Technol. 2003, 76, 82. 

Bhatnagar S.K. and S. Baneijee. 1968. Kinetics of accelerated vulcanization. El. V-cyclohexyl-benzothiazole-2-sulfenamide accelerated sulphur vulcanization of rubbers. J. Inst. Rubber Ind. 2 177-193. 

The process that makes the chemistry, properties, and applications of elastomers so different from other polymers is cross-linking with sulfur, commonly called vulcanization. The modem method of cross-linking elastomers involves using a mixture of sulfur and some vulcanization accelerator. Those derived from benzothiazole account for a large part of the market today. Temperatures of 100-160°C are typical. 

Several derivatives of thiazole have commercial uses. One of these is 2-aminothiazole, which has shown a high toxicity to experimental animals. Benzothiazole is another related compound used in organic synthesis. Thiazoles are used as rubber vulcanization accelerators. Benzothiazole,... 

The vulcanization accelerators include the thiazole 2-mercaptobenzothiazole (MBT) (169), and its derivative benzothiazole disulfide (dibenzoythiazyl disulfide, 2,2 -dithiobis (benzothiazole), MBTS) (170). Organic accelerators enable reduction in time of vulcanization, more effective use of sulfur in formation of cross-links and use of low processing temperatures. MBTS delays vulcanization, when compared with MBT alone. They are used in production of conveyor belts, footware, etc. The 2-mercaptobenzothiazole zinc salt (MBTZ) (171) is also important, and is used in latex products. Other sulfur donors include 2-morpholinodithiobenzothiazole, 2-(4-morpholinyldithio)benzothiazole (MBSS, MORFAX) (172). 

Sulfenamides, made from 170, by reactions involving primary and secondary amines under oxidizing conditions, include A-cyclohexyl-2-benzothiazole sulfenamide (173) and N-oxydiethylene-2-bcnzolhiazolc sulfenamide (2-(morpholinothio)benzothiazole) (174). Sulfenamides release 2-mercapto accelerators and amine during vulcanization. The amine is a secondary accelerator that brings about fast vulcanization after a slow start. Applications include in tyres and conveyor belts. They are not applicable to hot-air vulcanization processes95. 

Benzothiazole derivatives as vulcanization accelerators 78YGK395. Chlorinated thiazoles, synthesis of 85S586. 

It is well-known that benzothiazoles are used as accelerators in the vulcanization process <84CHEC-l(6)330>. Because of the toxicity of the benzothiazole-containing by-products produced in rubber manufacture, it is of interest in the isolation of bacteria which degrade those by-products <93MI 306-12>. The one mainly responsible for the toxicity of rubber chemical waste water is 2-thiob-enzothiazole <93MI 306-l3>. 

If MET could be taken out of the system as fast as it forms, substantial increases in processing safety would result. Such is the case when the premature vulcanization inhibitor, N-(cyclohexylthio)phthalimide (CTP), is present. This compound (Coran and Kerwood, 1970) and others Uke it react rapidly with MET to form 2-(alkyldithio)benzothiazoles, R-S-S-ET, which are active accelerators but which do not interact rapidly with the sulfenamide accelerator ... 

Because of the low level of C=C imsatiu-ation in the polsrmer compared to, eg, natural rubber (NR) and SBR, EPDM needs significant amoimts of highly active accelerators for sulfur vulcanization. Usually, combinations of benzothiazole derivatives or sulfenamides with so-called ultra-accelerators like thiuram compoimds or dithiocarbamates are used. Because of the limited soluhihty of these various accelerators in EPDM versus the large quantities needed to obtain a sufficient level of vulcanization, an EPDM compoimd often contains four or more... 

Vulcanization by sulfur alone is of little help as it is too slow. The vulcanizing systems currently used contain accelerators like thiuram sulfides (R2N-CS-S-S-CS-NR2), zinc dithiocarbamates [(R2N-CS-S)2Zn], thiourea (H2N-CS-NH2), or zinc benzothiazoles,... 

The third mode of decomposition is only important in A-type monosulfides (and D-type from the diene model 5) and then only in the presence of catalysts. This is a simple elimination reaction, but its course is often obscured by secondary reactions of the primary products (equation Many accelerators and accelerator transformation products are catalysts for this decomposition. They include zinc benzothiazole-2-thiolate (ZMBT) and zinc dithiocarbamates and their amine complexes, as well as CBS, MBT and MBTS (which would normally not be present in quantity when monosulfide crosslinks are formed during the course of vulcanization). 

The accelerated sulfur vulcanization of m-polyisoprene and natural rubber [66] has also been studied. Three different accelerators were used tetramethylthiruam disulfide (TMTD), A/ -oxydiethylene-2-benzothiazole sulfenamide (MOR), and N-cy-clohexyl-benzothiazole-2-sulfenamide (CBS). The NMR peaks that appeared with the 3 different accelerators were found to give similar peaks as in unaccelerated sulfur cured samples. The differences in network structure were reflected in differences in the relative peak intensities between the sulfur and accelerated sulfur cures as well as differences between the 3 accelerator cured samples. Varying the accelerator-sulfur ratio also produced changes in peak intensities. Examination of vulcanizations with and... 

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