In Situ Characterization of Coating Dry, Cure, and Resultant Residual Stress, and Stiffness as a Function of its Composition

摘要

Understanding dry and cure of coatings is critically important for successful coating application and performance in a given application. The dry and cure of a coating is dependent upon its solvent composition, binder technology, cure chemistry, and pigmentation. Not only do these variables impact coating dry and cure, but also greatly impact the degree of residual stress in the resultant film as well as its stiffness, flexibility, and toughness. For instance, many times in order to improve early hardness of a crosslinking system, the degree of crosslinking may be increased. This can lead to a stiff and brittle coating that is subject to fracture or adhesive failure. Coating chemists utilize a variety of methodologies to characterize drying, curing, and durability performance of coatings. For instance, chemists and technologists may utilize manual methods such as touching and/or scratching the coating with a finger or fingernail at given timeframes to monitor early coating dry properties such as flash, wet edge, and early hardness development. Hardness of the cured coating may be monitored by pencil hardness and/or Koenig hardness measurements, while flexibility may be monitored by impact resistance and/or mandrel testing. For wood coatings, stiffness and flexibility is often assessed by cold check resistance. In this paper, we discuss methodologies that lead to improved characterization of coating dry and cure as well as in situ characterization of residual stress and stiffness/flexibility of the final film.