Date of Award


Degree Name

Master of Science


Chemical and Paper Engineering


Paper Engineering, Chemical Engineering and Imaging

First Advisor

Dr. John Cameron

Second Advisor

Dr. Raja Aravamuthan

Third Advisor

Dr. Margaret Joyce

Access Setting

Masters Thesis-Open Access


Recent advances in the pulping and bleaching of high-yield pulps, particularly bleached thermomechanical pulp, have made these pulps suitable replacements for bleached kraft pulps. Unfortunately, these high-yield pulps are not appropriate for making high-grade papers because of their tendency to yellow. Extensive efforts have been made to reduce the yellowing, but none of the methods that have been investigated have been at once both practical and economical.

This study investigated the ability of common pigments used in the paper industry to reduce the extent of yellowing of an 80/20 blend of bleached chemithermomechanical and bleached softwood kraft pulp. The effectiveness of the various pigments at reducing photoyellowing differed considerably. Titanium dioxide (TiO2) was found to be the most effective pigment in this study at reducing photoyellowing. Alumina trihydrate (ATH) was also found to be effective at reducing yellowing, though not as effective as TiO2. ATH at a concentration of 16.1% was found to reduce the amount yellowing by up to 45%. In comparison, TiO2 at 9.0% was able to reduce yellowing by up to 51%. Clay and ground calcium carbonate (GCC) were found to be non-significant at concentrations in the range of 1.2 to 5.9%.