Synthesis of polyurea nanocomposite from industrial waste lignin: Classical curing of isocyanate by lignin-polyamine

Abstract

Polyurea is an important class of polymer obtained through curing of the isocyanate and polyamine. Here lignin amine processed successive three-step reactions for the synthesis of nanostructure polyurea composite. Further the competence nature is found out by combining different lignin-polyamine with various di-isocyanate. In the first step, lignin was reacted with tosyl-chloride which modified the hydroxy function of lignin as a good leaving group. This reaction for tosylated lignin (Lignin-OTs) has 80% yield. Further lignin-OTs was reacted with four different polyamines replaced tosyl functional group by amine gives aminated lignin. Eventually, a classical reaction of aminated lignin and three different di-isocyanate yield a polyurea composite. A series of changes from lignin to its tosylation eventually to polyurea composite was pursued by the change in the functional group of lignin. The tosylated lignin was confirmed by IR absorption of the C-O peak at 1190 and 1365 cm−1 and invisible peak absorption at 3500 cm−1. The aminated lignin was confirmed by IR absorption at 3120 and 3430 cm−1 for –NH. Thermal gravimetric analysis (TGA) and differential scanning colorimetry (DSC) were used to determine the product's thermal characteristics. Complete structural morphology of nanostructure lignin-polyurea composite was investigated by X-ray diffraction, FE-SEM and EDX.