Characterization of TEMPO―Oxidized and Refi ned Pulps （Part 2）

Abstract

Hardwood bleached kraft pulp was oxidized using a TEMPO/NaBr/NaClO system to prepare two TEMPO oxidized pulps (TOPs) with similar amounts of aldehyde groups but different amounts of carboxy groups. The original pulp and TOPs were refi ned using a PFI mill at various revolution numbers, and the influence of refining conditions on the fundamental properties of TOP sheets was investigated. The tensile strength of TOP sheets was higher than that of the original pulp sheet prepared using the same PFI mill revolution numbers. Refi ning of TOPs signifi cantly improved wet tensile strength of the TOP sheets, whereas the original pulp did not exhibit such eff ect by refi ning. A clear relationship existed between the wet strength and the amount of aldehyde groups in the pulps. These results can be explained by the formation of hemiacetal linkages between the hydroxy and aldehyde groups at the interfi ber bonds in the sheets, which resulted in the increase in the wet strength of the TOP sheets. These results also indicated that refi ning is benefi cial for improving wet tensile strength when TOPs are used for papermaking.