Assessment of Biobased Polyurethane Reaction Kinetics through DSC and FTIR Analysis

The polyurethane (PU) formation reaction of liquid monomers involves a combination of physical and chemical phenomena, promoting the rapid transformation of a liquid mixture of low molecular weight components into an often solid and spongy structure. The kinetics of polymerization of polyurethanes through the reaction of the HDT isocyanate with ricinoleic acid (major fatty acid in castor oil) was analyzed. The NCO/OH ratio used in this study was 1.5 for HDT. The analyses were performed by Differential Scanning Calorimetry (DSC) with both dynamic and isothermal methods. With the dynamics methods (heat flow as a function of temperature), it was possible to determine reaction mechanism (n th order) and conversion (~100%), as well as the needed activation energy (range from 60 to 65 kJ.mol -1 ) to form an activated complex (product). Through the isothermal methods (heat flow as a function of time) it was determined that the formation reaction of PU is a reaction of n th order or an autocatalytic reaction. The synthesized PU was also evaluated by Infrared Spectroscopy (FTIR) in order to investigate the possible combinations between functional groups.