Recycling potential of unbleached and bleached chemical pulps from juvenile and mature wood of Populus deltoides

The recycling potential of unbleached and bleached pulps of juvenile and mature wood of poplar (namely "eastern cottonwood", Populus deltoides) has been investigated. First, chemical and morphological characteristics of juvenile wood (JW), transition wood, and mature wood (MW) of the trunk were determined. Then, high yield and low yield pulps were produced separately from JW and MW by kraft pulping (KP), followed by bleaching of the low-yield pulp with a DED sequence. The obtained handsheet papers were subjected to five successive drying and rewetting cycles (as recycling simulation), and the properties of the corresponding pulps were characterized. The results show that JW is inferior with respect to chemical and morphological properties and resulted in low-yield KP. The bleached pulp obtained from JW required more bleaching chemical to achieve the brightness targets. The strength losses of pulps resulting from recycling were more significant in the first recycling cycle, and then the loss rate decreased with further cycles. The comparison between different pulps showed that the JW pulps were more susceptible to the effects of recycling than MW pulps.