Mechanical and thermal properties of nanofibrillated cellulose reinforced silica aerogel composites

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-P-750E20) 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 sigma(C), or fracture strain epsilon(F) 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 lambda values increased by approximate to 11% from 13.8 mW/m K to 15.3 mW/m K due to the presence of the NFC. (C) 2015 Elsevier Inc. All rights reserved.