When a pulp, especially chemical pulp, is repeatedly disintegrated in water, dewatered and dried for several times, the mechanical properties of handsheets are considerably deteriorated. This paper mainly deals with changes in the micro-structure of fibre cell wall by recycling. Changes in recycled fibres were determined by the solute exclusion and the mercury intrusion methods as well as the electron microscopy. Moreover, loading of titanium dioxide in lumina of recycled fibres was investigated. Following results were obtained.
(1) Tensile strength of handsheets from recycled fibres could be partly restored by beating.
(2) By beating the recycled pulp, the pore volume in cell wall of the pulp fibres could be partly recovered. The mercury penetration volume into the handsheet increased with recycling and decreased by additional beating.
(3) It was observed that morphological changes such as delamination and crack formation in cell wall of the recycled fibre were enhanced by additional beating.
(4) The amount of TiO
2 loaded in pulp fibres increased with recycling upto 3rd time and decreased after 5th time. The amount of TiO
2 retained in handsheets seemed to be dependent on bulkness, flexibility and rigidity of fibres.
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