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 ha logenated with chlorine or bromine and then remixed with the long fibr e fraction for handsheet preparation. Embedded handsheets are then exa mined by scanning electron imaging. The average atomic weight of the h alogenated fines differs sufficiently from the untreated fibre fractio n and the embedding polymer to produce high-contrast backscattered ele ctron images. The halogenation has little effect on the strength prope rties of the handsheets. Depending on their size and type, fines can f ulfill several structural functions. They act as small fibres; they fi ll interstices and bridge gaps in the long fibre structure; when of la minar shape they deposit uniformly on the outside of fibres, adn on oc casion they may directly assist in forming a bond between two fibres.