Mechanical and thermal properties of nanofibrillated cellulose reinforced silica aerogel composites

• Nanofibrillated cellulose (NFC) reinforced silica aerogel composites were produced.
• NFC was physically embedded but not chemically attached to silica aerogel matrix.
• NFC imparted tensile strength increases of 20–40% over neat silica aerogels.
• Minor increases in thermal conductivity λ due to NFC were measured.
• E moduli, compressive strengths, and fracture strains were not affected by NFC.

We report on the mechanical and thermal properties of monolithic nanofibrillated cellulose (NFC) reinforced silica aerogel composites. Silica aerogel composites were made by dispersing NFC into polyethoxydisiloxane (PEDS-P750E20) sols prior to gelation. Attempts to further improve the dispersibility of the NFC in ethanol were made using maleic anhydride (MA) as a surface-modifying agent. The effects of the NFC and MA-modified NFC on the properties of the aerogel composites were studied and compared to neat silica aerogel references made in the same manner. Surface-modification of the NFC using MA did not lead to any significant differences in any of the measured properties compared to the unmodified NFC. In general, the NFC reinforced silica aerogel composites did not exhibit notable improvements with regards to elastic modulus E, compressive strength σC, or fracture strain εF over neat silica aerogels of the same densities. However, improvements due to the NFC were seen in the tensile strengths of the aerogel composites which exhibited tensile strengths 25–40% higher than neat silica aerogels of the same densities. While BET analysis indicated that the mesoporous microstructure of the silica aerogel matrix was retained, thermal conductivity λ values increased by ≈11% from 13.8 mW/m K to 15.3 mW/m K due to the presence of the NFC.

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