Kinetic and chemorheological modeling of thermosetting polyurethanes obtained from an epoxidized soybean oil polyol crosslinked with glycerin

Abstract Thermosetting polyurethanes were obtained using an aromatic isocyanate and a hydrophobic polyol formulation obtained from epoxidized soybean oil (ESO) crosslinked with glycerin. A systematic DSC analysis of the effect of catalyst type, crosslinker concentration, isocyanate index and ESO crystallization on cure kinetics was conducted. The combination of a stannic catalyst at 0.2 wt% and glycerin at 20 wt% produced a cure kinetics governed by an autocatalytic heat flow where vitrification played a key role in the formation of chemical bonds. The evolution of T g as a function of conversion, which followed Di‐Benedetto's predictions, supported the hypothesis that vitrification was a preponderant phenomenon during cure. Dynamic Mechanical Analysis (DMA) of a post‐cured sample revealed a Tg centered at 220°C, whereas quasi‐static flexural mechanical tests shown a flexural modulus of 2.14 GPa and a flexural strength of 99.4 MPa. Rheological experiments at isothermal conditions supported the hypothesis that vitrification played a key role in the evolution of apparent viscosity. A master model using Kim‐Macosko equations was obtained for the proposed formulation. The results presented in this work will serve to further extend the use of biobased polymers applied in the polymer composite industry.