Optimizing lignocellulosic nanofibril dimensions and morphology by mechanical refining for enhanced adhesion

• Published in: Carbohydrate polymers 2021-12, Vol.273 (C), p.118566-118566, Article 118566
• Main Authors: Kelly, Peter V., Gardner, Douglas J., Gramlich, William M.
• Format: Article
• Language: English
• Subjects: Adhesion measurements; Fibril morphology; Lignocellulosic nanofibrils; Mechanical refinement; Multi-scale characterization; Structure-property relationships
• ISSN: 0144-8617; 1879-1344
• DOI: 10.1016/j.carbpol.2021.118566

Using lignocellulosic nanofibrils as adhesive binders in structural composites is a growing field of interest attributable to their renewability, recyclability, and strength. A fundamental understanding of their adhesion mechanisms is crucial to tailor performance and optimize production costs. These mechanisms were elucidated by studying the morphology dependent adhesion in a model system composed of cellulose nanofibrils (CNFs) at different degrees of refinement and porous paper substrates. CNFs and lignin containing cellulose nanofibrils (LCNF) were characterized at different length scales using optical, atomic force, and scanning electron microscopy, revealing a complex distribution of sizes, spanning the macroscale to the nanoscale, which are modified unequally by refinement. Strong adhesion was correlated to a decrease in fiber size on the largest length scale and with an increase in relative fibril surface area. Flocculation hampered effective LCNF adhesion, but adding suspension stabilizers improved adhesion to levels comparable to CNF. Refinement of lignocellulosic nanofibrils changes the fibril morphology on multiple length scales and was hypothesized to contribute to higher adhesion strength to porous substrates. [Display omitted] •Increased CNF surface area from refinement correlated to increased adhesion.•Large fibers in CNF suspensions primarily drove decreased adhesive strength.•Addition of carboxymethyl cellulose ameliorated poor LCNF adhesive strength.•Analyzed CNF using optical microscopy, SEM, and AFM to probe all length scales.•Refinement primarily affects the largest fibers and fibrils in suspension.