Formulating with Vinyl Gums for Addition Cure HCR

This paper will provide the formulator with a starting point for understanding and preparing addition cure HCR compounds. We will examine the differences between the more familiar peroxide catalyzed HCR and the less commonly used platinum catalyzed addition cure chemistry.

The first section will briefly explain the basic chemistry of platinum catalyzed addition cure reactions. The importance of stoichiometric calculations will be illustrated with examples.

The next section provides practical understanding of vinyl content and hydride content as this is crucial to a successful formulation. Appropriate selection of gum structure and crosslinker permits a wide range of properties to be achieved. Formulating guidelines will be presented to include the influence of additives, modifiers, fillers and surface treatments. The use of and effect of reinforcing filler and in-situ filler treatments will be reviewed. Some example starting point formulations will be presented with attendant test data.

Finally the impact of the addition cure mechanism in HCR on rubber processing and the economics of rubber molding will be illustrated. This will include the advantages and disadvantages of this particular cure chemistry.