Bio-based Polyurethane Derived from Carbon Dioxide and Epoxidized Soybean Oil

The synthesis of polyurethane relies on a toxic and petroleum-based isocyanate reactant. The aim of this research was to synthesize Polyurethane using environment-benign and renewable starting materials such as carbon dioxide and soybean oil. The carbonated soybean oil was first prepared from carbon dioxide (CO2) and epoxidized soybean oil (ESBO) using zinc glutarate (ZnGA) as a catalyst but the result of FTIR indicated the absence of the peak of cyclic carbonate around 1800 cm-1. Therefore, in this work, the synthesis of Polyurethane was modified from A. Lee (Lee & Deng, 2015) using tetramethylammonium bromide (TBAB) as a catalyst. The as-synthesized carbonated soybean oil (CSBO) was allowed to react with two types of substances, 3-aminopropyltriethoxysilane or diethylenetriamine with the molar ratios of cyclic carbonate:NH2 of 1:1 with THF or DMF as solvents to obtain Polyurethanes (U1THF, U1DMF, U2THF, U2DMF). After 3 hours lignin solution was added to form a film. Raman spectra confirmed the catalyst removal from CSBO. FTIR spectra showed the peak around 1800 cm-1 assigned to cyclic carbonate of CSBO, and a new peak of urethane linkage around 1700 cm-1 (C=O stretching) of Polyurethanes. The conversion of epoxide to cyclic carbonate was also confirmed by 1H-NMR. Upon adding lignin into the Polyurethanes, the lignin-urethane U1THF, and U1DMF formed films whereas U2THF, and U2DMF formed viscous liquids. In terms of applications, all four formulations can be potentially applied as bioadhesives.