Improved anticorrosion properties of polyurethane coatings based on high-solids acrylics synthesized in a high pressure reactor

High-solids styrene-hydroxyl-acrylic copolymer resins were synthesized in different solvents above their boiling points in a high-pressure reactor and compared to the same resin synthesized at ambient pressure. High-solids acrylics, prepared in a closed high pressure reactor at temperature above solvent's boiling point, have lower molecular weight, narrower molecular weight distribution and consequently a lower viscosity compared to resins with the same chemical composition and content of solids prepared at ambient pressure. Syntheses were monitored calorimetrically and by in situ ATR-FTIR spectroscopy using an RC1e (TM) reaction calorimeter. All synthesized resins were tested in two-component polyurethane metal topcoats. Coatings based on resins synthesized in a pressure reactor cure faster according to Model Free Kinetics studies and display improved anticorrosion properties, determined by electrochemical impedance spectroscopy, when compared to the resin synthesized at ambient pressure. (C) 2014 Elsevier B.V. All rights reserved.