Improving salt tolerance and thermal stability of cellulose nanofibrils by grafting modification.

Poor colloid stability of cellulose nanofibril (CNF) hydrogels at high temperature and high salinity can severely limit their industrial applications. This paper aims to prepare cellulose nanofibril hydrogels with improved salt tolerance and thermal stability. This was attained by simultaneous grafting of N,N-Dimethylacrylamide (DMA) and Butyl Acrylate (BA) onto the CNF surface based on the ceric ammonium nitrate-induced radical polymerization. The modified and original CNF samples were characterized by FT-IR, FBRM and rheological measurements. The FBRM results showed that the maximum salinity (NaCl) the CNF hydrogels can withstand increased from 1 wt% to 8 wt% after the simultaneous grafting of DMA (2 g/L) and BA (3 g/L). Moreover, rheological analysis results showed that the modified CNF hydrogels exhibited a much improved long-term thermal stability and a "salt-thickening" effect. As nano-cellulose based materials, the modified CNF hydrogels may have great potential as a promising petrochemical alternative for enhanced oil recovery applications.