TEMPERATURE AND HUMIDITY EFFECTS ON THE INTERCOAT ADHESION OF ALIPHATIC AMINE-CURED EPOXY COATINGS (REPRINTED FROM FEDERATION J, VOL 60, PG760, 1988)

Intercoat adhesion failure of bisphenol A-epichlorohydrin epoxides cro ss-linked with polyaliphatic amine cross-linking agents has been obser ved to be a function of both percent relative humidity (RH) and temper ature. According to our results, coatings cured at temperatures above 21-degrees-C (70-degrees-F) exhibit intercoat adhesion failure at rela tive humidity levels in excess of 80%. However, at lower temperatures such as 13-degrees-C (55-degrees-F), intercoat adhesion failure can be observed at RH levels as low as 40%. The addition of thinner appears to aggravate, but not initiate, intercoat adhesion failure. Infrared s tudies and pH and hardness measurements indicate that the conversion o f the amine cross-linker to the amine carbamate salt at or near the su rface, resulting in incomplete cross-linking at the interface, may be involved in intercoat adhesion failure.