Physical properties of cellulose fibers deteriorate significantly during paper recycling, which hinders the sustainable development of the paper industry. This work investigates the property deterioration and its internal mechanism of eucalyptus chemical pulp during paper recycling. The results showed that the deterioration was due to the reduction in fiber bonding strength, which was caused by the decrease in fiber bonding area and bonding force. The fiber bonding area was controlled by fiber structure and morphology affected by cellulose recrystallization while the fiber bonding force was controlled by fines structure and morphology affected by cellulose recrystallization. The theory of internal–external hornification was proposed to explain the deterioration of paper properties. Paper made from fibrillated cellulosic fibers is a fiber network material composed of fibers and fines. The structural and morphological changes controlled by cellulose recrystallization were defined as “internal hornification” for fibers and “external hornification” for fines, respectively. The internal–external hornification jointly control the fiber bonding strength, thus affecting the deterioration of paper physical properties. This work is expected to provide critical insights for controlling the deterioration of paper properties to achieve prolonged life cycle.
MO et al. (Thu,) studied this question.