Printable, castable, nanocrystalline cellulose-epoxy composites exhibiting hierarchical nacre-like toughening
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10570_2021_4384_ReferencePDF.pdf
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Author(s)
Rao, Abhinav
Divoux, Thibaut
Owens, Crystal E.
Hart, A. John
Date Issued
February 2022
Journal
Cellulose
Publisher
Springer Science and Business Media LLC
Citation
Rao, Abhinav, Divoux, Thibaut, Owens, Crystal E. and Hart, A. J. 2022. "Printable, castable, nanocrystalline cellulose-epoxy composites exhibiting hierarchical nacre-like toughening." Cellulose, 29.
Version
Author's final manuscript
Abstract
Abstract
Due to their exceptional mechanical and chemical properties and their natural abundance, cellulose nanocrystals (CNCs) are promising building blocks of sustainable polymer composites. However, the rapid gelation of CNC dispersions has generally limited CNC-based composites to low CNC fractions, in which polymer remains the dominant phase. Here we report on the formulation and processing of crosslinked CNC-epoxy composites with a CNC fraction exceeding 50 wt%. The microstructure comprises sub-micrometer aggregates of CNCs crosslinked to polymer, which is analogous to the lamellar structure of nacre and promotes toughening mechanisms associated with bulk ductility, despite the brittle behavior of the aggregates at the nanoscale. At 63 wt% CNCs, the composites exhibit a hardness of 0.66 GPa and a fracture toughness of 5.2 MPa m
$$^{1/2}$$
1
/
2
. The hardness of this all-organic material is comparable to aluminum alloys, and the fracture toughness at the centimeter scale is comparable to that of wood cell walls. We show that 3D CNC-epoxy composite objects can be shaped from the gel precursors by direct-write printing, casting, and machining. The formulation, processing route, and insights on toughening mechanisms gained from our multiscale approach can be applied broadly to highly loaded nanocomposites.
Graphical Abstract
MIT Department
Massachusetts Institute of Technology. Department of Mechanical Engineering
MultiScale Materials Science for Energy and Environment, Joint MIT-CNRS Laboratory
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Creative Commons Attribution-Noncommercial-Share Alike
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DOI of Published Version
https://doi.org/10.1007/s10570-021-04384-7
