Cellulose nanofibrils (CNFs), as the most abundant biopolymer on the planet, are a promising candidate as reinforcements for next generation polymer composites. Their inherent renewability, strong mechanical properties, and biodegradability make them a green alternative to more traditional reinforcements such as carbon fiber or fiberglass. Unfavorable interfacial interactions between common matrices and CNFs lead to poor dispersion and load transfer though, which limits the applicability of the unmodified fibrils as defect sites and large aggregates reduce composite strength at higher loading levels. Aqueous modification of CNFs with surface bound polymers coupled via the grafting-through of a reactive methacrylate handle aimed to alleviate these interfacial challenges. A pre-grafting methacrylic anhydride modification was employed to facilitate the modification of the fibrils with a diverse set of polymeric species. Multiple functionalizations with both water-soluble and insoluble (meth)acrylate and (meth)acrylamide monomers were demonstrated and the resulting materials characterized extensively by multiscale microscopy and infrared spectroscopy. The ability to tune the degree of modification from 15 - 44% by weight via different monomer to CNF ratios was quantified and demonstrated. The morphology of the modified CNFs was assessed via multiscale microscopy to under how polymer grafting affected fibril aggregation. The effects of modified fibrils as reinforcements in PLA and PETG composites was assessed via tensile testing, with changes in mechanical properties as a function of CNF loading and modification type explored. Characterization of composites via DSC and fracture surfaces via SEM reveal how fibril incorporation affects matrix crystallinity and fibril dispersion. Finally, optimal modifications to fibril surfaces are discussed for each matrix explored.

Aqueous polymer modifications to cellulose nanofibrils to facilitate reinforcement of green composites

ACS Spring Meeting 2021

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