Approximately 30% of softwoods remains severely unutilized. This is the amount of lignin in softwoods, which due to its heterogeneity is mainly used for the production of energy by combustion. However, interest in this material is increasing, with a variety of new applications developing, from component in thermosets and thermoplastics, to antioxidant and carbon fibres. The applications of lignin are highly dependent on its structure. Many protocols regarding analytical lignin extraction utilize ball milling, in order to make the fibres more accessible and use milder extracting conditions. At the same time, it is hypothesized that the structure of native lignin is altered, through both fragmentation and the formation of new bonds during the milling. The high energy introduced during the process, both thermal and mechanical, as well as the aromatic structure of this material, work in favour of this hypothesis. Lignin polymerization occurs via radical coupling and depending on the type of the bond, rearomatization, formation of intermediates and other mechanisms, proceed the formation of the final structure. The severe ball milling conditions may favour the formation of radicals through homolytic cleavage reactions. Subsequent re-coupling reactions could lead to an inaccurate perception of native lignin structure.<br/>This study focuses on the effect of ball milling interval duration and conduction under inert atmosphere, on the structure of lignin. Warm water and mild alkali extraction followed by enzymatic hydrolysis of the cellulose and hemicelluloses were parts of the method developed for the mild extraction of lignin. With this approach, the structural differences induced by the extraction methods will be reported. Analytical techniques include 1D and 2D NMR analyses.

Investigating structural changes in softwood lignin induced by ball milling

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.