THE FIRST 85-PERCENT KRAFT LIGNIN-BASED THERMOPLASTICS

Interest in the development of lignin-containing polymeric materials h as been upheld more or less continuously for the past 20 years. Tenden cies toward high moduli and poorly defined thermal transitions have be en regarded as imposing inevitable limitations upon the use of lignin derivatives for such purposes. Incorporation of more than 25-40% (w/w) lignin had usually resulted in materials that were brittle and weak. For the first time, however, from homogeneous blends containing 85% (w /w) underivatized industrial kraft lignin with poly(vinyl acetate) and two plasticizers, a series of thermoplastics has been fabricated with promising mechanical properties. The tensile behavior of these new po lymeric materials depends directly upon the degree of association betw een the intrinsic kraft lignin components. In extending to values abou t 25 MPa and 1.5 GPa, respectively, the tensile strengths and Young's moduli vary linearly with the effective M-V(w) for the kraft lignin sp ecies, under conditions where the proportions of the individual molecu lar components, both associated and discrete, do not change. Moreover, melt-flow index measurements indicate that these polymeric materials are amenable to thermal processing by extrusion molding. Thus a signif icant step has been taken toward developing a new generation of thermo plastics that are lignin-based in a very fundamental way. (C) 1997 Joh n Wiley & Sons, Inc.