Statistical Study of Hydrolytic Stability in Amine-Neutralized Waterborne Polyester Resins as a Function of Monomer Composition

By Travis E. Jones, Julia M. McCarthy

Reversibility of the esterification reaction has limited the use of polyester resins in waterborne coating systems. As with other polyester resin properties,the rate of hydrolysis can be modified by choice of monomer. The objective of this study is to demonstrate changes in hydrolytic stability in waterborne polyesters as a function of change in glycol and diacid composition.

In the glycol section of the study,BEPD and HPHP were compared. For the diacid section, adipic acid, isophthalic acid, and 1,4-CHDA were examined.Aqueous dispersions were subjected to storage at both ambient and elevated temperature. Response factors measured over time included molecular weight, pH, appearance, and change in properties of coatings made from the aged dispersions.

Results are discussed with reference to accepted hydrolysis rate theories. Results show that inductively stabilized, hydrophobic monomers such as 1,4-CHDAand BEPD produce the most stable waterborne polyesters of the glycols and diacids studied.