Title
Kinetic analysis of the effect of bleaching and temperature increase on the ageing of a chemical-mechanical pulp derived from poplar wood
Authors
RUMYANA BOEVA and GRETA RADEVA

Received November 5, 2013
Published Volume 48 Issue 7-8 July-August
Keywords high-yield fiber materials, chemical-mechanical pulp, kinetics, bleaching, correlations

Abstract
A comparative kinetic analysis of the effect of bleaching pretreatment and temperature increase on the thermal ageing of high-yield fiber material derived from poplar wood is presented. Comparative investigations have been carried out with pulp chips not subjected to preliminary bleaching. The temperature values studied were the following: 90 °C, 105 °C and 120 °C. Brightness reversion was observed within the interval from 6 to 36 hours. It has been found that the ageing process is best described by an exponential kinetic equation valid for processes taking place on uniformly inhomogeneous surfaces. The values of the activation energy and the preexponential factor in the Arrhenius equation applied increased simultaneously in the course of the process for the bleached and the unbleached samples. The correlation between them indicating a compensation effect leads to the conclusion that the mechanism of the thermal ageing process is identical. It is not affected by the temperature, the treatment duration and the bleaching applied.