STATISTICAL STUDY OF HYDROLYTIC STABILITY IN AMINE-NEUTRALIZED WATERBORNE POLYESTER RESINS AS A FUNCTION OF MONOMER COMPOSITION

Reversibility of the esterification reaction has limited the use of po lyester 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 hydr olytic stability in waterborne polyesters as a function of change in g lycol and diacid composition. In the glycol section of the study, BEPD and HPHP were compared. For the diacid section, adipic acid, isophtha lic acid, and 1,4-CHDA were examined. Aqueous dispersions were subject ed to storage at both ambient and elevated temperature. Response facto rs measured over time included molecular weight, pH, appearance, and c hange in properties of coatings made from the aged dispersions. Result s are discussed with reference to accepted hydrolysis rate theories. R esults show that inductively stabilized, hydrophobic, manomers such as 1,4-CHDA and BEPD produce the most stable waterborne polyesters of th e glycols and diacids studied.