Liquid curing medium

Any method of vulcanising rubber products which proceeds without interruption from start to finish as compared to the method of vulcanising separate batches of products or sections of a product. Continuous vulcanisation processes include the cold curing of proofed cloth, the vulcanisation of belting and flooring, of cables and certain extruded products by either the Liquid Curing Medium, Fluid Bed, Microwave, or Hot Air techniques. 

Extrusion with the aid of a vacuum applied to the screw. The process is applied particularly in the preparation of extrudates to be vulcanised by either the liquid curing medium or fluid bed techniques. It assists in removing the volatiles from the compound and thus improves the quality of the extrudate. 

Steel belts are used to transport rubber profiles through the liquid salt medium in the LCM (liquid cure medium) baths. These belts, either used singly or in multiples are often used in conjunction with chain driven roller systems. Steel belts, in the high temperatures of a LCM medium expand considerably, and the multiple belt system helps to overcome this problem to some degree, by allowing easy adjustment for overall length. The belts used in these systems are customised to the particular equipment and normally can only be sourced from the original equipment manufacturer. 

Liquid Cure Medium (LCM) uses a eutectic mixture of salts to heat the extrudate. The molten salt bath usually has a metal conveyor to keep the rubber eompound submersed. This method has good heat transfer to the rubber. However, cleaning salt off the extrudate can be difficult and satisfactory disposal of dilute salt rinse is beeoming increasingly difficult. This method is advantageous for articles with the low compression set obtained by using peroxides. Sulfur can be used as a coagent to minimize surface tack. Deformation problems versus other atmospheric methods are sometimes minimized. 

Liquid curing medium (LCM) is a practical method provided that a rapid cure rate system and a high viscosity CSM are selected. A peroxide system may leave a tacky surface unless complete submersion or rain of the LCM on the part is provided. 

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 precuring of the specimens were accomplished by using the RMS environmental chamber as the curing oven. Compressed air or vaporized liquid nitrogen was used as the convection medium. 

Cutback asphalts are mixtures in which hard asphalt has been diluted with a lighter oil to permit application as a liquid without drastic heating. They are classified as rapid, medium, and slow curing, depending on the volatility of the diluent, which governs the rate of evaporation and consequent hardening. 

The monomer in radiation-curable coatings is the analog of the solvent in a conventional paint. Although it performs like a solvent by being a medium for all of the other ingredients and by providing the necessary liquid physical properties and rheology, it differs in that it enters into the copolymerization and is not lost on cure. 

Polycondensations can be carried out in an aqueous or a solvent medium, or they can be performed while the reactions are in a liquid or in a molten state. In industry, reactions of polyfunctional monomers leading ultimately to the tridimenaonal-network molecules of thermosetting resins are usually interrupted at a stage where the polymers still are soluble and fusible. They then are shipped to the fabricators, who convert them by heat curing processes into the final thermosetting product. 

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