Lignin Based Functional Additives for Natural Rubber

In this work, the possibility to conveniently exploit lignin as a functional additive for natural rubber was pursued following two strategies. The first was based on the fractionation of lignin: extraction with organic solvents is suitable to produce lignin fractions with better defined structural features, molecular weight distributions, and physicochemical properties. The second approach was based on the chemical modification of lignin in the attempt to overcome its poor affinity with the rubber: esterification with anhydrides was selected to modify relatively large samples of lignin at laboratory scale. The effectiveness of different modifications of lignin as a drop-in replacement for carbon black was evaluated analyzing the tensile mechanical properties of model elastomeric compounds. In addition, the behavior of the modified lignins was rationalized through Hansen solubility parameters predicted with the group-contribution method.