Chemical characterization of different mechanical pulp fines

Different mechanical pulp fines were characterized chemically and the role of chemical composition in determining their papermaking properties was evaluated. The chemical composition (surface and bulk lignin, carbohydrates and extractives) of the fines varied widely. There were indications that variations, at least to some extent, were connected to the differences in the physical properties of fines. Correlations between the chemical components of the fines from different processes and sheet properties were not found; conversely in the refining of a TMP pulp, the chemical and physical properties of the fines produced developed simultaneosly, contributing e.g, to sheet strength. It was shown that sheet properties were not determined by any single physical or chemical property of fines alone, but that sheet characteristics are formed by a combination of several factors. It was concluded that the surface content of extractives and hemicelluloses as well as the proportion of the fibrillar material were the most important characteristics contributing to the tensile strength of a fines sheet