(255d) Structure-Property Relationships of Lignin-Thermoplastic Polyurethane Composites

With the growing interest in eco-friendly polymer composites, natural-driven materials are highly illuminated for filler of the composites. Lignin is an aromatic macromolecule that consists of up to 30% of total biomass from woody materials and can be acquired in extensive quantities as a by-product of pulping and biofuel industries. Among various lignin utilization strategies, a polymer composite application was selected for this project. Polymer composites are polymer materials reinforced by various support materials which show enhanced mechanochemical properties. However, conventional composite materials highly rely on petroleum-based chemicals. To make this material more eco-friendly and economically feasible, we investigated biocomposite materials by incorporating lignin with ether-based thermoplastic polyurethane (TPU).

Prior to the melting mixing of lignin-TPU composites, the characteristics of lignins, extracted from softwood and hardwood via kraft and hot-water processing, were comprehensively analyzed by wet chemistry, nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and Fourier transform infrared (FTIR). Different lignins and TPU ratios were tested to find the optimal composite performance. The mechanical, thermal, and morphological properties of the produced lignin-TPU composites were analyzed by TGA, DSC, FTIR, scanning electron microscopy (SEM), and universal testing machine (UTM). The correlations between lignin properties and the technical performance (e.g., mechanical strength, thermal stability) of lignin-TPU composites were also investigated.