Influence of chemical pretreatments on plant fiber cell wall and their implications on the appearance of fiber dislocations

Abstract

The cell wall of plant fibers may contain irregular regions called dislocations. This study evaluated the effect of chemical pretreatment as a mechanochemical disloca-tion initiator in unbleached and bleached Eucalyptus sp. fibers. Accordingly, bleached and unbleached pulps of eucalyptus were subjected to chemical pretreatments with sodium hydroxide at concentrations of 5% for 2 h, 10% for 1 h and 10% for 2 h or with hydrogen peroxide. The extent of dislocations was evaluated by polarized light microscopy. Based on the observation, an index of dislocations (ID) expressing their ratio of cell wall as per two-dimensional (2D) imaging and their angle relative to the longitudinal direction of the fiber were estimated. Chemical pretreat-ments increased the ID for bleached and unbleached fib-ers as well as increased the changes in the curl of bleached and unbleached fibers for chemical pretreatments. Chemi-cal pretreatment extracted the hemicellulose of the fiber cell wall causing some fiber to curl, which in turn gener-ated new dislocations and modifications in the dislocation angles which may be useful for improving the deconstruc-tion process of the cellulose fibers.