URETHANE COATINGS FORMULATED WITH BLENDS OF POLYISOPHORONE DIISOCYANATE AND POLYHEXAMETHYLENE DIISOCYANATE

Automotive two-component urethane coatings are formulated with blends of polyisophorone diisocyanate (IPDI trimer) and polyhexamethylene dii socyanate (HDI trimer), and acrylic polyols. Formulators for these end markets blend polyisocyanates in the hardener package to optimize and balance thecoatingis performance. Coatings made with polyisocyanate bl ends have faster tack-free times, greeter hardness, and superior acid- etch resistance compared to urethane acrylic coatings made entirely fr om polyhexamethylene diisocyanate. Similar formulations mode from poly isophorone diisocyanate only, are extremely brittle and show higher sp ray-out VOC. Polyisocyanate blends offer many advantages to the coatin gs formulator but have received little attention outside the automotiv e industry. The purpose of this paper is to investigate the use of pol yisocyanate blends in formulating urethane acrylic coatings. These coa tings were prepared from IPDI trimer, HDI trimer, HDI dimer, and comme rcially available acrylic polyols. The coatings were air cured and the following experimental data was obtained; application VOC, tack-free time, dry time, coating appearance - gross and DOI, mechanical perform ance - hardness, flexibility, and impact, environmental durability - g loss retention and yellowing, and chemical and moisture resistance.