Polyurethane composite films based on modified lignin and reinforced with silica nanoparticles: Synthesis and characterization

Abstract

Novel lignin-based polyurethane (LPU) and LPU-nanosilica composite films were prepared using in situ polymerization. The effects of various nanosilica contents on the structure and properties of the LPU matrix films were investigated by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), dynamic thermomechanical analysis (DMA), tensile test, and contact angle measurements. The results showed that hydrogen bonding and cross-linking occurred between the-N-H and-C=0 functional groups in the LPU-nanosilica films. Morphological and surface energy analyses showed uniform dispersion of amine modified silica nanoparticles in the LPU matrix at low concentrations. The incorporation of silica nanoparticles considerably improved the thermal stability and mechanical properties of the LPU films because of the introduction of silicon-oxygen bond between the LPU matrix and nanosilica. Overall, the introduction of small amounts of silica nanoparticles could improve the properties of the renewable LPU films, which are useful in the development of biomaterials.