Effect of hydrothermal treatment of microfibrillated cellulose on rheological properties and formation of hydrolysis products

The aim of this study was to determine the effects of hydrothermal treatment of microfibrillated cellulose (MFC) on its gel stability, water retention and rheological behavior. MFC gel was prepared by fibrillating endoglucanase pre-treated, never-dried dissolving pulp. The MFC gel samples were then exposed in a static chamber for different times at different temperatures. At temperatures of 120–150 °C, the viscosity profile of the gels was not significantly changed and a characteristic series of 3 successive regimes in the course of increasing shear rate, showing different behavior was revealed. The amount of water released by the samples under pressure, on the other hand, was notably increased after hydrothermal treatment. After further exposure to prolonged treatment times (24 h) and higher temperature (180 °C), a significant decrease in viscosity and shear modulus was observed. Analysis of filtrates revealed the formation of cello-oligosaccharides, glucose and HMF and a decrease in surface tension indicating peeling and molecular degradation of the sample matrice. The microfibralled cellulose sample decomposition and gel network structure breakdown on a molecular level is discussed.