Abstract: The bamboo fibers were pretreated by microwave radiation and neutral 2,2,6,6-tetramethylpiperidinooxy(TEMPO) oxidation, and then the microfibrillated cellulose was prepared by ultrasonic mechanical treatment. Experimental results showed that the maximal carboxyl content was 0.729 mmol/g pulp after bamboo fibers were pretreated by 0.15 mmol/g TEMPO, 10 mmol/g NaClO₂ and 1 mmol/g NaClO at 60 ℃ for 2 h. And the yield of microfibrillated cellulose was 85.7% after the ultrasonic mechanical treatment. The FT-IR spectra indicated that carboxyl groups were introduced onto cellulose. The XRD analysis indicated that the oxidation reaction was conducted only in the amorphous region or on the crystalline surface area of the cellulose. Meanwhile, the polymerization degree results of the cellulose showed that only minor cellulose fibers were degraded when they were pretreated by microwave radiation and neutral TEMPO oxidation. Therefore, the origin length of fiber was constant through this whole pretreatment process.

Key words: microwave radiation, neutral TEMPO oxidation, carboxyl content, microfibrillated cellulose