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 eva luated. The chemical composition (surface and bulk lignin, carbohydrates an d extractives) of the fines varied widely. There were indications that vari ations, at least to some extent, were connected to the differences in the p hysical properties of fines. Correlations between the chemical components o f the fines from different processes and sheet properties were not found; c onversely in the refining of a TMP pulp, the chemical and physical properti es of the fines produced developed simultaneosly, contributing e.g, to shee t strength. It was shown that sheet properties were not determined by any s ingle physical or chemical property of fines alone, but that sheet characte ristics are formed by a combination of several factors. It was concluded th at the surface content of extractives and hemicelluloses as well as the pro portion of the fibrillar material were the most important characteristics c ontributing to the tensile strength of a fines sheet.