The first step in defining the suitability of lignin as a polyol replacement is to measure its reactivity toward isocyanate. In this study, the properties of more than ten different lignin samples were measured using phosphorus nuclear magnetic resonance spectroscopy (<sup>31 </sup>PNMR) to determine hydroxyl content and gel permeation chromatography (GPC) for molar mass distribution analysis. Additionally, C, H, N, S, Na and K content of lignins were measured using elemental analyzer and inductively coupled plasma atomic emission spectroscopy (ICP-AES). Subsequently, the degree of reactivity of these lignin samples was measured with four different isocyanates: methylene diphenyl diisocyanate (MDI), toluene diisocyanate (TDI), phenyl isocyanate (mono NCO), and polymeric methylene diphenyl diisocyanate (pMDI). In each case, lignin was mixed with an isocyanate(NCO) based on 1:1 equivalent weight and the percentage of unreacted NCO were analyzed using titration (ASTM D5155), quantitative Fourier transform infrared spectroscopy (FTIR). Also, the reaction kinetics between lignin and NCO was studied using differential scanning calorimetric (DSC). The FTIR and DSC data were analyzed using MATLAB software. Finally, the correlation between lignin properties and their reactivity toward isocyanates were modeled using partial least square regression (PLSR) modeling with Umetric software. Our preliminary results indicate lignins display a higher reactivity toward MDI and pMDI than TDI, and the aliphatic hydroxyl content of the lignin has the most significant effect on the reactivity of lignins toward isocyanate.

Lignin as a polyol replacement in polyurethane applications

2019 Fall National Meeting

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