Fibrillation capability of kraft pulp for obtaining cellulose nanofibers.

Kraft pulp is the most common and economically advantageous raw material for making cellulose nanofibers (CNFs). However, it is revealed that high temperatures and pressures during kraft cooking cause the aggregation of cellulose microfibrils, which reduces the nanofibrillation capability of kraft pulp. Herein, we studied the optimum kraft cooking conditions required to obtain uniform CNFs by preventing aggregation. The fibrillation ability was compared with that of undried pulp treated with purification method only. Suspensions of undried pulps were mechanically fibrillated for various durations. The degree of fibrillation was evaluated by sedimentation, morphology, and water retention values. Kraft pulp cooking at a H-factor of approximately 650 for 140 °C, 160 °C and 170 °C resulted in less fibrillation than in the Wise-based pulp, even at low temperatures such as 140 °C. In contrast to expectations, high matrix substances with lignin contents of 30% did not prevent aggregation of the cellulose microfibrils. The production of CNFs requires a pulping technique for extracting cellulose without aggregation. [ABSTRACT FROM AUTHOR]