Physical Chemistry

When making paper, fibers and additives are suspended in water to a fiber suspension. The sheet is formed by draining a specific amount of suspension through a wire-cloth. The procedure is well known, but the underlying mechanisms are not fully understood. To understand how the different particles such as fines, fibers, retention aids and other additives interact with each other, further research is needed. This knowledge is important because in the production of paper, the retention and the distribution of fines and additives within a paper structure are vital parameters for the properties and also for the profitability of the final product. In this study fluorescence microscopy was used to study fines from bleached kraft pulp which were labeled with fluorophores. When the fines exhibit fluorescence we can study their individual trajectories and understand more about the interactions between fibers, fines and additives in different chemical environments. Fines from bleached kraft pulp have no fluorescent properties and therefore it is necessary to bind a fluorophore to the material. It was difficult to find a suitable fluorophore which binds covalently to the cellulose, the dominating part of fines. The result from this study was that the labeled fines did exhibited fluorescence