Rubber Bonding: Novel Measurements for Cure Rate of Adhesives and Measurements of Reactivity of Applied Dried Adhesives

摘要

This paper characterises extremely reactive rubber bonding agents, similar to those used for rubber-to-metal application. The first half of the paper addresses the measurement of the rate of cure. Should a solid film of the dried adhesive be measured in a curemeter (such as the MDR) at normal rubber vulcanisation conditions, then an exothermic explosion can occur, with severe degradation of the sample and significant quantities of smoke. DMA machines can be utilised to obtain cure curves of such materials, but have very high variability due to the lack of constraint on the sample. A MFR (RPA) has been successfully adopted with a multi-stage test to determine the cure rate of adhesives without explosion. Cure rates of adhesives can now be compared to cure rates of the rubber for which bonding is desired. The second half of the paper addresses measurement of bonding agent reactivity once it has been applied to the substrate and dried. Peel adhesion to rubber compound tests have shown that 100% rubber tear was always observed, and that there was no measurement of the reactivity of the adhesive. In this instance, adhesive was applied as an overcoat to a rubber impregnated glass cord. The various measurements have assessed: the self-crosslinking of the adhesive with itself, the reaction between the adhesive and the rubber inside the cord (by DSC) and the reactivity of the adhesive to combine with unsaturation by using a squalene reaction test. The sensitivity and usefulness of the various tests have been assessed and compared.