The effect of additives on the processing behaviour of natural rubber compounds – rheology and mould sticking

This paper looks at the effect of a range of additives on the rheological and moulding behaviour of Natural Rubber compounds 

The work covers the evaluation of internal and external lubricating effects during shear flow of NR compounds and discusses the impact of this on the processing behaviour of the compound. It highlights the use of specific rheological equipment to directly measure the lubricated wallslip effects with a view to understanding how these affect the processing behaviour of NR based compounds. 

Complimentary to this the equipment also allows the evaluation of the rubber to metal interaction during cure by measuring the forces required to break the bonds formed during the cure reaction. The work also looks at the effect of the mould composition and moulding conditions on the demouldability and mould fouling.

It was found that the composition of the process aids used can control the lubrication effects and consequently the processing behaviour of the compound. It is also clear that the nature of the metal surface has a large influence on the mould fouling and consequently the need and frequency to apply mould release agents.