Additives in Rubber Processing

Abstract

Processing aids, as additives in rubber compounding, can play a significant role in assisting the industry's needs to improve output and quality.

There are however a very large number of such products, essentially mixtures, from which to choose and the whole area is popularly considered a ‘jungle’.

The different classes of processing aids are reviewed and a concept which rationalises their behaviour discussed. This differentiates between products acting as external and as internal lubricants. External lubricants promote slippage between the compound and the metal surfaces with which it is in contact; internal lubricants reduce the bulk viscosity of the compound and thus promote easier flow of the compound.

Capillary Rheometry can be used to demonstrate differences between these modes of action in relation to viscosity and to die swell.

Information of this type can assist the compounder in short-listing the number of formulations necessary for factory trials in relation to both processing characteristics and final performance.