Comparative study between mechanical and chemical treatments for the preparation of nanocellulose

Abstract

Nanocrystalline cellulose (NCC) is usually obtained by the acid hydrolysis of microcrystalline cellulose for its use as polymer reinforcement. An ecological alternative to this process, avoiding the use of acids, is a mechanical method. High intensity ultrasonication (HIU) in optimal conditions (time, wave amplitude, volume ratio fiber/solution, cellulose extraction source) can be applied to prepare nanofibrillated cellulose (NFC). In this work, the HIU method was used to mechanically prepare NFC. Ultrasonication time (t) and wave amplitude (A) were optimized seeking for NFC with high crystallinity, strong thermal stability, large aspect ratio (length to diameter) and large surface to volume ratio with diameter in nanometer scale. The morphology and the physical/chemical properties of the NFC prepared at optimal HIU conditions were compared with those of NCC prepared from the same cellulose source at optimal acid hydrolysis (AH) conditions. Similar purity, lower crystallinity, improved thermal stability and larger aspect ratio with diameter in nanoscale were obtained for NFC prepared by HIU. These results can be used as an initial screening for the selection of the optimal process for NCC manufacture focusing on their use as polymer reinforcement.