The Influence of Ultrasound on Virgin Paper Fibres

The research is in the area of paper recycling and concerns the effects on paper fibres during a recycling process. It is a development of the work carried out by Levandoski and Norman. The article details the effects of irradiating cellulose fibres (Skogcell 90, Kotlas and Kraft) with high intensity ultrasound. The ultrasound employed in this investigation operated at a frequency of 20kHz to allow maximum cavitation effects to be produced. The results show that exposure to ultrasound promoted fibrillation of the fibres without any fibre breakage, results confirmed from Kajaani tests. The fibrillation process was found to occur predominantly at sites on the fibre wall that had been previously damaged by the normal mechanical refining process. The conclusion reached was that commercial fibre refining could be enhanced by a combination of mechanical and ultrasonic refining. This new combination refining would give a reduction in the breaking and cutting of fibres that would reduce fibre loss during the refining process. The investigation also measured some important properties of the pulp slurries (Canadian Freeness and fibre length distributions) as well as properties of the resultant paper hand-sheets (strength and burst values). A series of photomicrographs showing the extent of the fibrillation are also included in the paper. The paper is the first to demonstrate the commercial advantages to be gained from combining ultrasonic and mechanical refining. Progress in Paper Recycling is published in the USA and has an International Advisory Board of members from industry and universities. All published papers are peer reviewed by at least two referees. It is the premier journal dedicated to issues involved with paper recycling. Virgin fibres for this investigation were supplied by UK Paper, Sittingbourne, Kent, and PIRA International both of the UK