Effect of Amine Type on Lignin Modification to Evaluate Its Reactivity in Polyol Construction for Non-Isocyanate Polyurethanes (NIPU)

Abstract

Polyols are groups of organic compounds which contain carbon and are randomly linked to other atoms, espe-cially carbon-carbon and carbon-hydrogen. These compounds are mainly used as reactants to make other poly-mers. Among biopolymers, lignin is regarded as the base of a new polymer in polyol construction. The present study aimed to investigate the effects of amine type (diethylenetriamine and ethylenediamine) on the modification of lignin-based polyols, so as to provide an alternative to petroleum polyols and, in turn, increase functional groups and reduce their harm to humans’ health and the environment. To this aim, first, lignin was extracted from raw liquor. Next, the extracted lignin was reacted with diethylenetriamine (DETA) and ethylenediamine (EDA). Finally, the Mannich method was used for the reaction between amine lignin and propylene carbonate. The results of the Fourier Transform Infrared (FTIR) spectroscopy analysis showed that modification with DETA led to more structural change in lignin and peak 1100 indicates the presence of C–O bond related to urethane bonds in modified lignin. Moreover, adding propylene carbonate to aminated lignin did not result in much change in the results of the FTIR analysis. Additionally, urethane bonds can be seen in the results of GPC at 400°C–500°C. Furthermore, a slight decrease in thermal stability was observed in lignin modified with amine and propylene carbonate, compared to the raw lignin sample.