Light-induced yellowing of mechanical and chemimechanical pulp sheets : influence of wood raw material, process and ageing method

The light-induced brightness reversion of different types of unbleached and bleached high-yield pulps was studied under both accelerated and long-term ambient light-induced ageing conditions. It was found that accelerated ageing conditions that mimic indoor daylight exposures overestimate the yellowing tendencies of hardwood high-yield pulps (especially aspen pulps) compared to long-term ambient aging with no indirect sunlight present. It was, however, possible to predict the yellowing characteristics of softwood high-yield pulps. The lignin content of the pulps was found to be strongly correlated with the degree of photo-yellowing in the case of long-term ambient light-induced ageing. The presence of small amounts of birch chemithermomechanical pulp (CTMP) in a fine paper furnish resulted in extensive light-induced discoloration. The extent of photo-yellowing was found to be nearly linearly related to the amount of birch CTMP in the paper.Erratum: Light-induced yellowing of mecanical and chemimecanical pulp sheets - Influence of wood raw material, process and aging method (Nordic Pulp and Paper Research Journal (2007) 22:1 (122)) Page 275ScopusID: 2-s2.0-34547245485