Abstract: Nanocrystalline cellulose (NCC) prepared by the acid-extraction of bleached hardwood kraft pulp (BHKP), was oxidized by using TEMPO/NaBr/NaClO at pH 10 to prepare TEMPO-oxidized NCC (TONCC). The properties of NCC before and after oxidation were characterized by conductimetric titration, X-ray diffraction (XRD), and atomic force microscopy (AFM). The resulting product was then applied in the deinked pulp, and its improvement in pulp strength was evaluated. It was found that TONCC maintained the crystalline form of cellulose I, and showed better dispersibility, smaller dimension and higher level of carboxyl content compared with NCC. With the addition of NCC and TONCC to the deinked pulp respectively, the tearing and tensile indexes increased while they were compared with that of the control. When the addition of NCC and TONCC was 0.6%, the tensile indexes were increased by 8.7% and 14.2%, respectively. When NCC and TONCC samples were applied together with cationic polyacrylamide (CPAM), tensile indexes of the deinked pulp were increased by 19.6% and 27.7%, respectively, in comparison with that of the control.

Key words: nanocrystalline cellulose, TEMPO/NaBr/NaClO-oxidation, deinked pulp, strength improvement