New Waterborne Cationic Binders for Primer Applications
On the other hand, new high-molecular-weight, epoxy-based waterborne cationic primers show excellent barrier properties that can effectively prevent topcoats from staining and retarded drying.
The amount and the composition of tannin in wood are not uniform; it depends on the species of tree and on the region where it has grown. The main component is penta-meta-digalloylglucoside, a derivative of gallic acid (3,4,5-trihydroxybenzoic acid). Colorless solutions of gallic acid, especially of the alkali metal salts, turn brown in contact with air. With iron, an intensive, colored precipitate is formed. When exposed to moisture, tannins migrate through the wood and waterborne coatings, depositing on the coating surface and creating yellow or brown discolorations.