Techniques of Vulcanization

Numerous methods of vulcanization are available for manufacturing a rubber product. In the case of moulded goods for process 

Tyres are normally cured in a modification of the compression mould where a bladder or an inflated airbag forces and holds the green rubber stock of the tyre against the mould surface during vulcanization. This force reproduces the design of the tyre tread and the heat from the steam is introduced into the bladder to effect the vulcanization. Small size rubber expansion joints used in piping systems are moulded by compression moulding 

Transfer moulding involves the distribution of the uncured stock from one part of the mould called as pot into the actual mould cavity. This process permits the moulding of intricate shapes or the introduction of inserts like metals in many composite products. These procedures are difficult in compression moulds. Although these moulds are relatively more expensive than compression moulds, the actual process permits shorter cure times through the use of higher temperatures and better heat transfer which is obtained due to higher pressure applied to force the compound into the mould. 

This method is normally followed for plastic products. However the same with modifications of equipment is adopted for manufacture of small rubber components. By careful control of the feed stock the rubber products can be vulcanized in less than several minutes. This method can be completely controlled by proper feed, injection and demoulding cycles resulting in low rejection rates and lower finishing costs. 

Hot water cures can be used for articles that are not affected by immersion in hot water. This method is useful for thick walled articles and rubber lined equipment and especially most suitable for ebonite compositions. Direct contact with water produces better heat transfer than with hot air or steam. Consequently this system gives less deformation of products during cure. 

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Several techniques of vulcanization can be used to carry out vulcanization the oldest and still currently used in a large scale involves sulfur as a cross-linking agent in the presence of various additives. The comprehensive mechanism of such vulcanization of polyalkadienes by sulfur is still ill-known many mechanisms have been... 

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