Humidity and Rubber-to-Metal Bonding with Silane Adhesives

Silanes are a valuable class of rubber-to-substrate bonding agents for specialty elastomers.  One drawback with silanes, however, is the sensitivity of coated inserts that have been stored under humid conditions.  The effect of exposure of silane-treated metals under low, moderate and high humidity was examined.  The impact on adhesion to AEM, EPDM and FKM elastomers was determined.  Structural changes in the silane film were monitored by FTIR microscopy.  Degradation of the bonding performance appears to be caused by advancement in the network formation of the silane under moderate to high humidity conditions.