Effects of recycling on papermaking properties of mechanical and high yield pulps: Part I: Hardwood pulps.

Recycling characteristics of aspen mechanical and high-yield pulps, and a spruce thermomechanical pulp have been studied using usual laboratory procedures. The results indicate that the most obvious change in fiber properties occurs during the first drying cycle. The changes are irreversible. Subsequent rewetting-drying induces relatively little effect. Losses in water retention value and fiber bonding capacity are particularly evident. Aspen TMP seems to behave differently from that made from spruce. Aspen commercial pulps have their own unique properties. Repeated drying-rewetting of lignocellulosic fibers is a complex phenomenon and needs to be further examined. Application : this study provides information that had been lacking about the effects of laboratory recycling on hardwood mechanical and high-yield pulps.