“Fundamentals of Curing Elastomers with Peroxides and Coagents III: Blending Coagents to Optimize Processing and Physical Properties of Rubber Compounds”

Previous work in the series has demonstrated the addition of coagents affects both the quantity and quality of crosslinks in peroxide-cured elastomeric compounds.  Compound vulcanization kinetics and ultimate physical properties were dictated by structure-property relationships unique to the different classes of coagents.   In addition, it was shown that the relative impact of coagent addition correlates not only to coagent structure, but also the composition of the elastomer being cured.  

In the present study, the concept of coagent blending is explored.  While previous work has concentrated on establishing the effect of individual coagent structure on final properties, new data demonstrates that binary blends of coagents can act synergistically to balance multiple processing and cured physical properties.  By blending certain classes of coagents, it may be possible to optimize physical properties that would be mutually exclusive if only working with a single coagent. 

Specific examples define the blending rules in operation.  By blending Type I and Type II coagents, scorch safety can be extended without a loss in tensile properties.  Blends of metallic monomers and liquid monomers can produce adhesion while maintaining compression set.  Processing properties can be modified while independently adjusting compound hardness by blending coagents with various functionalities.  The utility of coagent blending is demonstrated in NBR, EPDM, HNBR, CM, and FKM model formulations.