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Open AccessArticle

Preparation of Transparent and Thick CNF/Epoxy Composites by Controlling the Properties of Cellulose Nanofibrils

1
Department of Forest Sciences, College of Agriculture and Life Sciences, Seoul National University, Seoul 08826, Korea
2
Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 08826, Korea
*
Author to whom correspondence should be addressed.
Nanomaterials 2020, 10(4), 625; https://doi.org/10.3390/nano10040625
Received: 13 March 2020 / Revised: 26 March 2020 / Accepted: 26 March 2020 / Published: 28 March 2020
(This article belongs to the Special Issue Nanocomposites from Renewable Resources)
Cellulose nanofibrils (CNFs) have been used as reinforcing elements in optically transparent composites by combination with polymer matrices. In this study, strong, optically transparent, and thick CNF/epoxy composites were prepared by immersing two or four layers of CNF sheets in epoxy resin. The morphology of the CNF, the preparation conditions of the CNF sheet, and the grammage and layer numbers of the CNF sheets were controlled. The solvent-exchanged CNF sheets resulted in the production of a composite with high transparency and low haze. The CNF with smaller width and less aggregated fibrils, which are achieved by carboxymethylation, and a high number of grinding passes are beneficial in the production of optically transparent CNF/epoxy composites. Both the grammage and number of stacked layers of sheets in a composite affected the optical and mechanical properties of the composite. A composite with a thickness of 450–800 μm was prepared by stacking two or four layers of CNF sheets in epoxy resin. As the number of stacked sheets increased, light transmittance was reduced and the haze increased. The CNF/epoxy composites with two layers of low grammage (20 g/m2) sheets exhibited high light transmittance (>90%) and low haze (<5%). In addition, the composites with the low grammage sheet had higher tensile strength and elastic modulus compared with neat epoxy and those with high grammage sheets. View Full-Text
Keywords: carboxymethylation; cellulose nanofibrils; composite; solvent exchange; transparency carboxymethylation; cellulose nanofibrils; composite; solvent exchange; transparency
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MDPI and ACS Style

Park, S.Y.; Yook, S.; Goo, S.; Im, W.; Youn, H.J. Preparation of Transparent and Thick CNF/Epoxy Composites by Controlling the Properties of Cellulose Nanofibrils. Nanomaterials 2020, 10, 625.

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