Conveyor belts vulcanization

This system involves the use of some form of heating by air or steam in a chamber in a manner such that the vulcanization occurs immediately after the rubber is formed in an extruder or calender. This is a suitable process for extruded profiles and calendered sheets and conveyor belts. Liquid curing method (LCM) is also a continuous process which involves the use of suitable hot liquid baths in which extruded profiles can be passed through and vulcanized continuously. Items can be cured rapidly at temperatures from 200°C to 300°C however the compounds must be suitably designed to prevent porosity as this is a common problem with any extrudate. Suitable materials for curing medium includes bismuth-tin alloys, an eutectic mixture of potassium nitrate and... 

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. 

Essential steps in making conveyor belts are (1) drying the fabric (2) frictioning of the hot fabric with a rubber compound and topping to give additional rubber between plies and the outer ply and cover, using a three- or four-roll calender (3) belt building and (4) vulcanization. 

Vulcanization of conveyor belts may be carried out in sections using press cure or continuously by means of a Rotocure equipment. In press cure, vulcanization is done by heating in long presses, the belt... 

Definition Elastomer vulcanized by sulfur systems vulcanizate offers low gas permeability, good weather/ozone resist., better chem./heat resist, than butyl rubber contains 1-2% chlorine Uses Rubber for tire inner tubes/liners, tire sidewalls, pharmaceutical stoppers, conveyor belts/hoses, anti vibration mounts, food/drug seals, adhesives in closure-sealing gaskets for food containers... 

Other systems for vulcanizing polychloroprenes are in use they include the use of the metal oxides alone, and the use of thiourea derivatives. In the production of the Selby conveyor belt the sulphur system was selected in preference to thiourea because it offered greater processing safety before the vulcanizing stage. 

Chem. Descrip. Activated zinc salts of higher molecular unsat. fatty acids Uses Processing promoter, peptizing agenf and dispersant for molded and extruded rubber, conveyor belts, tire compds. vulcanization accelerator retards scorch... 

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