Biobased polyisocyanates from plant oil triglycerides: Synthesis, polymerization, and characterization

Abstract

In this study, an easy and efficient synthesis of unsaturated plant oil triglycerides having isocyanate groups is reported. In the first step of the synthesis, the triglyceride was brominated at the allylic positions by a reaction with N-bromosuccinimide, and in the second step, these brominated species were reacted with AgNCO to convert them to isocyanate-containing trilycerides. At the end 9 of the reaction, approximately 60-70% of the bromine was replaced by NCO groups, and the double bonds of the triglyceride were not consumed. When the amount of AgNCO was increased, the yield also increased. The final products were characterized with IR and H-1-NMR, and polyurethanes and polyureas were obtained from these fatty isocyanates with alcohols and amines, respectively. The polymers were characterized by differential scanning calorimetry and thermogravimetric analysis. Differential scanning calorimetry curves showed that glycerin polyurethane showed a glass-transition temperature at 19 degrees C, castor oil polyurethane showed two glass-transition temperatures at -43 and 36 degrees C, and triethylene tetraamine polyurea showed a glass-transition temperature at 31 degrees C. Some properties of the polymers, such as the tensile strength and swelling ratios, were also determined. The swelling rate of glycerin polyurethane was higher than that of castor oil polyurethane in dichloromethane. The equilibrium swelling ratio was highest for the castor oil polyurethane. The polyurethanes synthesized in this study had a Young's modulus around 50 kPa and a tensile strength around 0.01 N/mm(2) (100 kPa). The tensile strength of glycerin polyurethane was higher than that of castor oil polyurethane. (c) 2008 Wiley Periodicals, Inc.