Renewable thermoplastics from lignin with exceptional properties and their composites

The pursuit of low-cost, higher performance thermoplastic and elastomeric polymers and polymer blends derived from lignin has long been elusive to those working in the world of polymer chemistry and materials science. Incorporation of lignin has been capped near 30% for most compositions, often requiring chemical modification for compatibility, solvent fractionation to access specific molecular weight ranges, or prohibitively expensive blend polymers - each of these deterring the final potential for industrial adoption. Herein we describe novel compositions with enhanced compatibility of unmodified industrial lignins with low cost additives in general-purpose acrylonitrile-butadiene rubber matrices to produce high-performance multiphase thermoplastics. A new class of thermoplastic elastomers was also produced by introducing nanoscale-dispersed lignin, a biomass-derived phenolic oligomer, into commodity-grade nitrile rubber with optimal acrylonitrile content. Temperature-induced controlled miscibility between the lignin and the rubber during high-shear, melt-phase blending allows for the tuning of the material's morphology and performance. This sustainable product has unprecedented yield stress (15-45 MPa), strain hardens at large deformation, and has outstanding recyclability. The multiphase polymers developed from an equal-mass mixture of a melt-stable lignin fraction and nitrile rubber, using the method described here, show 5-100 nm lignin lamellae with a high-modulus rubbery interphase. Molded elastomeric products prepared from the lignin-nitrile material offer an additional revenue stream to pulping mills and biorefineries. Characteristics of fiber reinforced composites of these novel compositions will also be presented.