Urethane coatings formulated with blends of polyisophorone diisocyanate and polyhexamethylene diisocyanate

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Urethane coatings formulated with blends of polyisophorone diisocyanate and polyhexamethylene diisocyanate

Wojcik, R.T. / Blackwell, R.S. / Reisch, J.W. / O'Connor, J.M.

Automotive two-component urethane coatings are formulated with blends of polyisophorone diisocyanate (IPDI trimer) and polyhexamethylene diisocyanate (HDI trimer), and acrylic polyols. Formulators for these endmarkets blend polyisocyanates in the hardener package to optimize and balance coating's performance. Coatings made with polyisocyanate blends have faster tack free times, greater hardness, and superior acid etch resistance compared to urethane acrylic coatings made entirely from polyhexamethylene diisocyanate. Similar formulations made from polyisophorone diisocyanate only, are extremely brittle and show higher spray-out VOC. Polyisocyanate blends offer many advantages to the coating's formulator but have received little attention outside the automotive industry. The purpose of this paper is to investigate the use of polyisocyanate blends in formulating urethane acrylic coatings. These coatings were prepared from IPDI trimer, HDI trimer, and commercially available acrylic polyols. The coatings were air cured and the following experimental data was obtained; application VOC, tack free time, dry time, coating appearance (gloss and DOI), mechanical performance (hardness, flexibility, and impact), environmental durability (gloss retension and yellowing), and chemical/moisture resistance.