Renewable High-Performance Polyurethane Bioplastics Derived from Lignin–Poly(ε-caprolactone)

Here, we report novel lignin-poly(ε-caprolactone)-based polyurethane bioplastics with high performance. The poly(ε-caprolactone) (PCL) was incorporated as a biodegradable soft segment to the lignin by the bridge of hexamethylene diisocyanate (HDI) with long flexible aliphatic chains and high reactivity. The effects of -NCO/-OH molar ratio, content of lignin, and molecular weight of the PCL on the properties of the resultant polyurethane plastics were thoroughly evaluated. It is important that the polyurethane film still possessed high performance in the tensile strength, breaking elongation, and tear strength, which could reach 19.35 MPa, 188.36%, and 38.94 kN/m, respectively, when the content of lignin reached as high as 37.3%; moreover, it was very stable at 340.8 °C and presented excellent solvent-resistance. The results demonstrated that the modification of the lignin based on the urethane chemistry represents an effective strategy for developing lignin-based high-performance sustainable materials.