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Noki, Gloria

University of British Columbia

Peroxide brightening of thermomechanical pulp (TMP) in high alkali conditions, has been proven to develop the brightness and tensile properties of the treated pulp. Previous studies have generated a robust understanding of the effects the process has on the optical and strength properties of pulps. The rise in demand for pulps with low bulk and high tensile (better suited to board and packaging grades) has motivated this study on the contributions TMP fines (< 76 μm) make to the development of pulp properties using highly alkaline peroxide treatment (HAPT). When TMP fibres and fines are separately treated with high alkali peroxide, the peroxide reacts more rapidly with the fines, during the initial stages of the treatment. Likewise, weak acid groups are generated more rapidly in fines compared to fibres. Weak acid groups increase the surface charge, promoting fibre swelling and increasing the bonded area between adjacent fibres, which results in sheet densification. Thus, a correlation has emerged between the development of tensile strength and the generation of weak acid groups during HAPT. Due to their smaller size and larger specific surface area, fines are more accessible to the peroxide. Furthermore, fines consume peroxide more rapidly due to their higher lignin content; hence, weak acid groups form more readily on the surfaces of fines. Consequently, it is hypothesized that preferential formation of acid groups on the external surface of fines and fibres makes a significant contribution to tensile strength development. In this investigation, the effect of HAPT on pulp properties is evaluated by varying pulp compositions (fibres and fines % w/w) and treatment time. A better understanding of the correlation between acid group generation and tensile strength development during HAPT will lead to the cost-effective production of customizable pulp grades.

Text

2025-05-02

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/90958

Chemical and Biological Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/