A model system for understanding the distribution of fines in a paper structure using fluorescence microscopy

• When making paper a sheet is formed by draining a specific amount of dilute water suspension of pulp and wet end additives through a wire-cloth. The procedure is well known but the underlying mechanisms are not fully understood. The pulp stock is composed by different particles such as fines, fibers, retention aids and other additives that interact with each other during the papermaking process. These interactions are important since they influence the properties of the formed paper. Pulp fibers have different sizes and the finest particle fraction is referred to as fines. In this study fines from bleached Kraft pulp were used.The fines were oxidized to some extent as a consequence of the Kraft pulp process.A model system containing fibers and latex was used together with fluorescence microscopyand image analysis to study the Brownian motion of a probe in different electrolyte concentrations. The model system was built up of:• A water suspension of 1 % fines, negatively charged. At this concentration the fines are interacting with each other, forming a gel like structure.• Negatively charged probes with three different sizes (radii 50, 100 and 500 nm).• Two types of electrolytes (NaCl and CaCl2). The electrolytes were used for altering the electrical double layer of the charged surfaces in the system.By studying the Brownian motion of the probes with different sizes in the network of fines more can be understood about this model system. The knowledge obtained from this model system can be used for further understanding of the paper chemistry mechanisms.ReferencesCarlsson G., Warszynski P., van Stam J., J. Colloid Interface Sci., 2003, 267, 500-508Carlsson G., van Stam J., Nord. Pulp Pap. Res. J., 2005, 20, 192-199Carlsson G.,  Järnström L., van Stam J., J. Colloid Interface Sci., 2006, 298, 162-171Rådberg W., Bachelor thesis, Karlstad University, 2010

Ämnesord

NATURVETENSKAP  -- Kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences (hsv//eng)

Nyckelord

Fluorescence microscopy

diffusion coefficient

image analysis

Chemistry

Kemi

Kemiteknik

Chemical Engineering

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