Restoring Bonding Strength to Recycled Fibers, 1993 Recycling Symposium Proceedings

James L. Minor, C. Tim Scott, Rajai H. Atalla

Most recycled fibers have reduced conformability and interfiber bonding capability relative to that of virgin wood pulp fibers. The extent and reversibility of the reduction is dependent on the original pulp type and on the papermaking process. In this

report, we review six general methods of restoring or enhancing fiber strength. Examples are taken from a research study on improving inter-fiber bonding of dry-fiberized newsprint. The starting material was commercial newsprint from a stub roll that contained no printing. Dry-fiberized pulp was prepared by disk refining the dry newsprint to complete fiberization.

Wet-fiberized pulp for comparative studies was prepared by conventional hydropulping. Dry processing resulted in a pulp with significantly shortened fibers. The corresponding hand-sheet tensile strengths were less than one-third that of a wet-disintegrated pulp. However, the various enhancement procedures resulted in significant strength improvements, ranging from a 30% increase with adhesive addition up to a >500% increase via delignification.