Boeva R.Radeva G.2024-07-162024-07-162024-07-162024-07-162014-01-011314-79781314-7471SCOPUS_ID:84920693905https://rlib.uctm.edu/handle/123456789/1076The effect of thermal ageing of neutral sulfite semi-chemical pulp derived from poplar wood is followed on the ground of the comparative investigation of bleached and unbleached samples. The brightness reversion observed in the course of the process is studied at 90°C, 105°C and 120°C. The degree of brightness is determined at the 6-th, 12-th, 24-th and the 36-th hour of the process duration. The kinetic analysis carried out shows that the exponential kinetic equation valid for processes taking place on uniformly inhomogeneous surfaces describes the kinetics of the process investigated. The linear relation between the apparent pre-exponential factor and the apparent activation energy, as obtained from an Arrhenius analysis, indicates the existence of a compensation effect.enArticle