HIGH SOLIDS POLYURETHANE COATINGS FROM CASTOR–OIL–BASED POLYESTER–POLYOLS

Abstract

Abstract High solids polyurethane (PU) coating formulations were developed by reacting three different castor–oil–based polyester–polyols with aromatic as well as aliphatic isocyanate adducts in different NCO/OH ratios. Structure of polyurethane resins was confirmed by FTIR spectroscopy. The molecular weight between two crosslinks (Mc) and solubility parameter of the samples (polymer films) were determined by a swelling method. The polyurethane resins were coated on test panels and tested for their flexibility, scratch hardness, cross-hatch adhesion, impact, pencil hardness and solvent resistance as per standards. The effect of catalyst, structure of isocyanate and flexibility of polyols on the resulting polyurethanes was evaluated. Thermal stability of these polymers was determined by thermogravimetric analysis (TGA). Keywords: high solid coatingscastor oilpolyurethane coatingpolyester-polyol We are thankful to Prof. A. K. Rakshit, Head, Department of Chemistry, Maharaja Sayajirao University of Baroda, Vadodara, for providing departmental facilities. Notes • Hydroxyl equivalent weight = 56100/OH value @ %age N.V.M.—Non-volatile matter, determined after keeping at 120°C for 2h under vacuum ALI–Aliphatic Isocyanate adduct ARO–Aromatic Isocyanate adduct AAL1c–The composition with 0.05% Dibutyl tin di laurate (DBTDL) catalyst @75% solids in xylene: MEK, 1:1 by weight., O/N Over Night @6H > 5H > 4H > 3H > 2H > 1H > H > HB > 1HB > 2HB > 3HB > 4HB > 5HB > 6HB 0–film completely removed 1–film cracked and partially removed 2–film partially cracked 3–loss of gloss 4–slight loss of gloss 5–film practically unaffected P–pass F–fail