Effect of Ultrasonic-assisted Cold Caustic Extraction on the Properties of CTMP Poplar Fibers

Abstract

Chemithermo-mechanical pulp (CTMP) has been widely utilized in papermaking industry because of its high yield. However, the poor strength properties arising from the high contents of hemicellulose and lignin have limited its applications. In this study, ultrasonicassisted cold caustic extraction (CCE) on hemicellulose removal was applied to ascertain its influence on the properties of CTMP. It was found to have a positive effect on hemicellulose removal and resultant pulp properties. At the same alkali concentration (3 wt%), hemicellulose removal and Canadian Standard Freeness (CSF) in ultrasonic-assisted CCE (360 W, 10 min) increased 53.4% and 9.6%, respectively. Ultrasonic-assisted CCE reduces alkali concentration from 5 wt% to 2 wt% to obtain similar hemicelluloses removal, whereas the pulp yield at 2 wt% NaOH was higher than that of CCE alone at 5 wt% NaOH. In addition, at the same alkali concentration (3 wt%), the tensile index, bursting index and tearing index of CTMP in ultrasonic-assisted CCE (120 W, 10 min) increased by 12.7%, 11.34% and 3.0%, respectively. Ultrasonic-assisted CCE enhanced the fibrillation of fibers at optimal conditions, as determined by SEM.