PERFORMANCE OF 1,4-CYCLOHEXANEDICARBOXYLIC ACID IN POLYESTER POLYOLS FOR TWO-COMPONENT POLYURETHANE COATINGS USED IN WEATHERING APPLICATIONS

摘要

Polyurethane coatings are known for their durability and overall good balance of mechanical properties. Both acrylics and polyesters are used as polyols in two-component, solvent-borne polyurethane coatings. In exterior applications, polyester polyols containing isophthalic acid (PIA) weather extremely well, but they have poor flexibility. Usually, a combination of a flexible diacid, such as adipic acid (AD), and PIA are used to achieve a balance of flexibility and hardness in the coating. While improving flexibility, AD may have an adverse effect on the beneficial properties of PIA, especially outdoor durability. As a modifying diacid component, 1,4-cyclohexanedicarboxylic acid (CHDA) offers a unique balance of aromatic and aliphatic diacid character in one molecule.rnThe objective of this experiment was to evaluate the performance, particularly outdoor durability, of high-solids, two-component, pigmented polyurethane coatings containing CHDA. Experimental variables included the CHDA/PIA molar ratio in a model polyester polyol, coating crosslink density, and effect of a commonly used ultraviolet absorber (UVA) and hindered amine light stabilizer (HALS) package. Comparisons were made to control polyester polyols containing AD/PIA and commercially available acrylic polyols marketed for exterior applications. Responses included coating viscosity, cured film glass transition temperature, gloss, hardness, flexibility, acid resistance, and Florida weathering over a three and a half year period.