An A₂ + CB₂ approach to the synthesis of hyperbranched polyester polyol and application in PU coatings

In the present work, neopentyl glycol was used as a core for the synthesis of hyperbranched polymer by melt condensation polymerization with 2,2-Bis(hydroxymethyl) propionic acid. The A₂ + CB₂ synthetic method was used where neopentyl glycol was A₂ and 2,2-Bis(hydroxymethyl) propionic acid was CB₂. The acid value and hydroxyl values of the synthesized hyperbranched polymer were determined according to ASTM D974 and ASTM D4274, respectively. The molecular structural characterizations of hyperbranched polyol were determined by FTIR and NMR spectroscopy techniques. The hyperbranched polyurethanes were synthesized by using hyperbranched polyol and crosslinking agent isophorone diisocyanate in different mole ratios of OH:NCO (1:1.2, 1:1.4, 1:1.6). These mixtures were used as coating materials on mild steel panels and glass plates. The coating properties of polyurethanes such as gloss and cross-cut adhesion were studied. The immersion test of coatings was carried out in HCl, NaCl, NaOH and water. The electrochemical properties of the coatings were examined using an electrochemical method in electrolytes consisting of HCl, NaOH, and NaCl. Thermal stability and surface morphology were studied by TGA and SEM, respectively.