There has been much recent interest in the use of microfibrillated and nanofibrillated cellulose as additives to improve the mechanical properties of paper. Most of the original methods used to make these materials are to costly for this purpose, but now purely mechanical processed are becoming available which have been made it a more practical possibility. The tensile strength of unfilled paper and its relation to light scattering have been the subject of extensive theoretical and experimental research a, and the effect of addition of fibrillated cellulose have been considered by several authors in the light of this work. However, much less theoretical work have been dedicated to the properties of papers with high filler contents.
In the FiberLean process, fibres are mixed with filler and found together until fibres are converted into microfibrillated cellulose, a few percent of which can be added to paper to increase its strength and allow a substantially higher filler content. We build on the work of Bown to develop a model for the effect of filler on paper tensile strength and light scattering, and use this to investigate mechanism by which mfc improves these in highly filled paper. We further demonstrate some of the advantages of its use over the conventional refining approach. There include process flexibility and some specific paper properties such as increased elasticity and higher resistance to tearing.