Characterization of thin water layers in pulp by tritium exchange. Part 1: Methods development

Abstract

A new technique for measuring the monolayer water content of fiber is presented. Tritiated water is added to a pulp/water suspension, whereupon the tritium partitions between the bulk water and the pulp. In the pulp phase the tritium can exchange with free water, bound water, and with hydroxyl and other protons present in the pulp matrix. The free water in the pulp is then removed by displacement with acetone. The tritium remaining in the pulp is mostly associated with tightly bound water, with a small fraction being tied up with the exchangeable hydrogen in pulp. The procedure provides a value of 10% for the tightly bound water content of hardwood or softwood fiber, either bleached or unbleached. If this water is assumed to cover the fiber surface as a monolayer, then an estimate of the wet surface area of the fiber can be obtained. This estimate compares well with independent measurements of surface area.

Mechanism of foaming on polymer‐paperboard composites

“…Figures 3c and d illustrate a uniformly foamed board and a poorly foamed board, respectively. The water in the fiber is present at 6% by weight, which means that it covers the fiber surface as a monolayer 9, 10. At these low concentrations, nucleation of water vapor to form a vapor bubble is improbable.…”

Effect of Recycling on the Properties of Paper Surfaces

“…K p/w is the (dimensionless) partition coefficient of tritiated water between fiber and water and is a measure of the tightly bound water content of pulp. 11 It is obtained by adding tritiated water to a pulp/water suspension whereupon the tritium partitions between the bulk water and the pulp. The free water associated with the pulp is removed with a dry, water-miscible, aprotic solvent such as acetone, which physically displaces the free water without exchanging with the tritium.…”

“…Let us now consider the effect of recycling on the surface of a fiber. K p/w is the (dimensionless) partition coefficient of tritiated water between fiber and water and is a measure of the tightly bound water content of pulp . It is obtained by adding tritiated water to a pulp/water suspension whereupon the tritium partitions between the bulk water and the pulp.…”

“…Tritium pulp: water partition coefficients (K p/w ) were measured as described by Walsh and Banerjee. 11 Four determinations were made for each sample.…”

“…An OpTest Laboratory Fiber Quality Analyzer (FQA) was used to determine the average fiber length for each level of refining and recycling of the bleached kraft pulp. Tritium pulp:water partition coefficients ( K p/w ) were measured as described by Walsh and Banerjee . Four determinations were made for each sample.…”