Effect of the NCO/OH ratio on the properties of Mesua Ferrea L. seed oil-modified polyurethane resins

A series of polyurethane resins with varying NCO/OH ratios (0.8-2.0) has been synthesized from the monoglyceride of Mesua Ferrea L. seed oil, poly(ethylene glycol) (M-n, 200 g mol(-1)) and 2,4-toluene diisocyanate in the presence of dibutyl tin dilaurate as the catalyst. The effects of the NCO/OH ratios of the synthesized resins on the physical properties, such as hydroxy values, acid values, saponification values, iodine values, specific gravities and isocyanate values have been studied. The formation of the polyurethane resins was confirmed by viscosity measurements, and FTIR, UV and H-1 NMR spectroscopic studies. Performance characteristics, such as impact resistance, flexibility, gloss, hardness, adhesive strength and chemical resistance, of the cured resins were investigated as a function of the varying NCO/OH ratios, with an influence of these ratios being observed for most of the above properties. Thermogravimetric analysis (TGA) demonstrated that the thermal stabilities of the cured resins increased with an increase in the NCO/OH ratios. The amounts of char residues at 550 degrees C were also found to be greater for higher NCO/OH ratios of the oil-modified polyurethane resins. (c) 2005 Society of Chemical Industry.