ORIGINAL PAPER Effect of microfibrillated cellulose and fines on the drainage of kraft pulp suspension and paper strength Tero Taipale • Monika O ¨ sterberg • Antti Nyka ¨nen • Janne Ruokolainen • Janne Laine Received: 7 May 2010 / Accepted: 22 June 2010 / Published online: 8 July 2010 Ó Springer Science+Business Media B.V. 2010 Abstract Different types of microfibrillated cellu- lose (MFC) and fines suspensions were produced, characterized, and then added to a papermaking pulp suspension. High and medium molar mass cationic polyelectrolytes were used as fixatives. The drainage behavior of the pulp suspensions with additives were evaluated against the strength properties of hand sheets made thereof. The effects of salt concentration, pH, fixative type, dosage and type of fibrillar material on drainage were examined. All the MFC and fines samples produced had clearly different properties due to their dissimilar production methods, and they also introduced specific responses on the measured drain- age and paper strength. Generally, the addition of MFC decreased the drainage rate of pulp suspension and increased the strength of paper. However, it was shown that by optimum selection of materials and process conditions an enhancement of the strength properties could be achieved without simultaneously deteriorating the drainage. Keywords Drainage Á Fines Á Microfibrillated cellulose Á MFC Á Paper Á Strength Introduction The primary components of wood fiber walls are lamellas or bundles (aggregates) of microfibrils, sometimes called macrofibrils. The lateral dimension of a microfibril is estimated to be 3–20 nm, depend- ing on the source of cellulose and the method of analysis (Ale ´n 2000; Davies and Harris 2003; Pa ¨a ¨kko ¨ et al. 2007, 2008; Ahola et al. 2008b; Wa ˚gberg et al. 2008). A microfibril is formed from a cellulose elementary fibril joined or coated with other wood constituents, such as hemicelluloses, proteins, pectin and lignin (Somerville et al. 2004; Ding and Himmel 2006). It has been proposed that in higher plants the smallest cellulosic structure is an elementary fibril, consisting of 36 parallel aligned and hydrogen bonded cellulose molecules in amorphous and crys- talline regions, and having a lateral dimension of approximately 2–4 nm (Jakob et al. 1995; Davies and Harris 2003; Somerville et al. 2004; Ding and Himmel 2006). As wood fibers are disintegrated, and additionally dispersed to fibrillar level, typically in water, the suspension is called microfibrillated cellulose (MFC) (Turbak et al. 1983; Wa ˚gberg et al. 2008), or alternatively microfibrillar cellulose. Sometimes it is T. Taipale (&) Á M. O ¨ sterberg Á J. Laine Department of Forest Products Technology, Aalto University School of Science and Technology, P.O. Box 16300, 00076 Aalto, Espoo, Finland e-mail: tero.taipale@tkk.fi A. Nyka ¨nen Á J. Ruokolainen Department of Applied Physics, Aalto University School of Science and Technology, P.O. Box 15100, 00076 Aalto, Espoo, Finland 123 Cellulose (2010) 17:1005–1020 DOI 10.1007/s10570-010-9431-9