Acousto-optical characterization of fibers: New results

Results of pulp fiber analysis with a new acousto-optical technique are presented. Fibers in a very dilute water suspension submitted to a stationary ultrasonic field reorient sensibly in the direction of the wavefronts and regroup in layers coinciding with nodal planes of acoustic pressure. Reorientation velocity is higher for short fibers, while regrouping is faster for fibers with a large diameter. The measurement of light scattered at small angles in orthogonal directions by the suspension is related to its characteristics. These phenomena should allow characterization of fiber sizes in less than 2 min. Mathematical correlations are established between the signals given by the apparatus and the weighted average fiber length obtained from a Bauer-McNett classification for stoneground softwood pulps. These signals are described by 4th-degree polynomials which coefficients vary according to these lengths.