A Literature Survey on Wet Adhesion Northwestern Society for Coatings Technology

摘要

Wet adhesion is the property of a coating that maintains adhesion and integrity while under an environment of high humidity or exposure to water. The term is usually applied to emulsion polymers although the term is used also with oil- or solvent-based systems. Environments of high humidity or water can occur outdoors with snow, rain, or dew; indoors with rooms of high humidity such as a kitchen or near baths or showers; or in applications such as inside food or juice containers, the inside of radiators, or on bridges. James (1) was the first in the literature to observe that a coating can lose adhesion upon exposure to water or humidity. He did a study on the effects of water on the adhesion between a finishing coat and the primer that are used on ships. He used both fresh water and seawater in his studies and noted that fresh water has a greater effect on the loss of adhesion. He noted also that if the samples that showed adhesion loss upon exposure to humidity were allowed to dry, the adhesion appeared to be regained fully. The coatings used were various oil- or solvent-based binders with numerous pigmentation combinations. There were two major observations noted by James: 1. The pigmentation of the coating has a pronounced effect with a pigmented system showing better wet adhesion than a non-pigmented system. The nature of the binder in the primer, though, appeared to have the greater effect. 2. The age of the primer before applying the finishing coat affected the wet adhesion. Finishing coats that were applied within four days of the application of the primer had good wet adhesion. The wet adhesion became worse with the age of the primer. This indicated that a change in the primer surface upon aging was causing a decrease in adhesion with the finishing coat.