Comprehensive analysis of individual pulp fiber bonds quantifies the mechanisms of fiber bonding in paper - PubMed Save Email Send to Display options Full text links Cite Display options ## Abstract The process of papermaking requires substantial amounts of energy and wood consumption, which contributes to larger environmental costs. In order to optimize the production of papermaking to suit its many applications in material science and engineering, a quantitative understanding of bonding forces between the individual pulp fibers is of importance. Here we show the first approach to quantify the bonding energies contributed by the individual bonding mechanisms. We calculated the impact of the following mechanisms necessary for paper formation: mechanical interlocking, interdiffusion, capillary bridges, hydrogen bonding, Van der Waals forces, and Coulomb forces on the bonding energy. Experimental results quantify the area in molecular contact necessary for bonding. Atomic force microscopy experiments derive the impact of mechanical interlocking. Capillary bridges also contribute to the bond. A model based on the crystal structure of cellulose leads to values for the chemical b

ogen bonds ( Fig 2C ). Fig 2. Successive steps of hydrogen bonds formation between fibres in paper. Open in a new tab A) bonding via a multimolecular water layer, B) bonding via a monomolecular layer of water, C) hydrogen bonds. The polar character of water molecules is a very important factor, enabling formation of multiple hydrogen bonds between cellulose fibres in paper structure. Although water is regarded as an easily available and inexpensive solvent, in which all papermaking operations take place, the importance of water as a crucial factor influencing mechanism and outcomes of the papermaking process is usually underestimated in scientific literature. Better understanding of the role of water in paper structure formation may have both theoretical meaning and practical importance. The energy of fibre-to-fibre bonds in paper is a factor deciding of its strength properties [ 32 ]. Literature data [ 6 , 10 ] suggest that the energy of fibre-to-fibre bonds in paper is approximately a sum of the energy of hydrogen bonds and the energy of friction forces between fibres when paper sheets are torn. The replacement of polar water molecules in papermaking pulps with solvents of lower polarity may reduce the energy of hydrogen bonds and very slightly affect these properties of fibres (surface roughness, dimensions), which decide of the energy of friction forces between them. Therefore, the replacement of water by alcohols of different polarity may enable estimation of: (i) the influence of fibre-to-fibre bonds in paper on its strength properties and (ii) contribution of the energies of hydrogen bonds and friction to the total energy of interactions occurring between fibres in paper. Materials and Methods To determine the role of water in formation of hydrogen bonds and their influence on paper strength properties, water was replaced by four solvents with increasing molecular weight and decreasing polarity ( Table 1 ). The alcohols shown in Table 1 were selected as water