Effects of hemicellulose content on TEMPO-mediated selective oxidation, and the properties of films prepared from bleached chemical pulp

In this work, chemical pulp was used to prepare hazy transparent films, and the effects of hemicellulose content on carboxyl group formation during TEMPO-(2,2,6,6-tetramethylpiperidine-1-oxyl) mediated oxidation, and the properties of the film prepared from the chemical pulp were evaluated. The hemicellulose content exhibited a negligible effect on carboxyl content formation, while prior alkaline extraction significantly enhanced the selective oxidation indicating a substantial increase of carboxyl group. The prior alkaline extraction and TEMPO-mediated oxidation initiated severe hemicellulose removal and fiber swelling, and therefore promoted the subsequent ultrasonic fibrillation. The optical transmittance of the film prepared from the chemical pulp was near-constant at ~ 89%, while the haze increased slightly from 85 to 94%, when the hemicellulose content was increased from 6.7 to 19.2%. Conversely, the presence of hemicellulose significantly impaired the film surface properties, possibly due to the large size of the cellulose fibers. Graphic abstract