From the macromolecular behavior of lignin components to the mechanical properties of lignin-based plastics

Besides propositions about their primary structure, there have been two alternative working hypotheses that seek to account for the most fundamental physico-chemical properties of simple lignin derivatives. As an early contributor to the discussion, D. A. I. Goring was a persuasive proponent of crosslinking in lignins, and his influence persists to the present day. When this concept, inflected by implications of polyfunctionality, was applied to linking lignin derivatives covalently into polymeric materials, incorporation limits of 25-40% (w/w) were typically encountered. Similar restrictions were observed upon introducing lignin derivatives into compatible multiphase polymer blends. On the other hand, when the importance of non-covalent interactions between the constituent molecular species had been established, plastics with lignin contents as high as 85% (w/w) materialized. Moreover, in these new formulations, strategies for optimizing plasticizer performance have depended directly on how association between lignin components is modulated by miscible low-T_g polymers.