Lignin Effect to Synthesis of the Hybrid Polyurethane

Abstract

Lignin which is hydrophobic due to presence of carbonyl; carboxyl; hydroxyl and phenol functional group, can be used as compatibilizing agent through grafting a hydrophobic part such as polyurethanes. Lignin-based biopolyurethane (bioPU), was synthesized by two stages of reaction viz., polyurethane preparation through reacting 4,4′-Methylenebis (CyclohexylIsocyanate) (HMDI) and polyethylene glycol (PEG, molar mass of 4000 g/mol); bio-PU preparation through grafting lignin onto the polyurethane. The ratio of diisocyanate to polyol and lignin addition were varied in 1: 4, 1:1 and 0.25 g, 0.5 g, 1 g, respectively. Products were investigated by observing FESEM (Field Emmision Scanning Electron Microscope), 1H NMR (Nuclear Magnetic Resonance) and FTIR (Fourier Transform Infra-Red Spectroscopy). The FESEM result shows that lignin based bioPU with isocyanate/polyol ratio 1:4 and 1 g lignin addition is more homogenous than isocyanate/polyol ratio 1:1 and 0.25 g lignin. The NMR and the FTIR spectra reveal the lignin grafed onto polyurethane product. The addition of 0.25 and 1 g lignin resulted in 0.2 and 0.6 hidrophilic/hidrophobic segment ratio, respectively. Furthermore, characterizations of the products confirmed that the lignin-based bioPU can be a promising compatibilizer.