Location of fines in mechanical pulp handsheets using scanning electron microscopy

This paper describes a procedure which permits identification of fines in photomicrographs of handsheets. Fines are first separated, then halogenated with chlorine or bromine and then remixed with the long fibre fraction for handsheet preparation. Embedded handsheets are then examined by scanning electron imaging. The average atomic weight of the halogenated fines differs sufficiently from the untreated fibre fraction and the embedding polymer to produce high-contrast backscattered electron images. The halogenation has little effect on the strength properties of the handsheets. Depending on their size and type, fines can fulfill several structural functions. They act as small fibres; they fill interstices and bridge gaps in the long fibre structure; when of laminar shape they deposit uniformly on the outside of fibres, adn on occasion they may directly assist in forming a bond between two fibres.