Influence of Recycling on Chemical Properties and Hornification of CMP and

Cellulose fibers undergo a series of irreversible changes i. e hornification when exposed to cycles of wetting and drying. In this study، the effect of recycling on physical and chemical properties of chemimechanical pulp (CMP) and neutral sulfite semi-chemical (NSSC) pulp was evaluated. The pulps were recycled three times. Hornification was measured by Water retention value. The results indicated that water retention value and carboxyl groups were decreased due to recycling، hornification also increased during cycles of wetting and drying. Changes in crystalline structure of the pulp during first cycle of recycling were investigated by ATR- FTIR. The crystallinity index increased to some extent، when compared to virgin pulp. Recycling influence on the fiber length was not significant. Hornification introduced as a main cause of poor properties of recycled paper. Also، reduction of carboxyl groups could be one of the causes for lowering water retention value and decrease in strengths.