Influence of alkali treatment on the structure of newcell fibers

Abstract

Alkali treatment can change the structures and properties of cellulosic fibers. The aim of this work was to study the mechanism of structural changes of Newcell fibers treated with different alkali concentrations and two treatment methods. Raman spectra showed that the molecular conformation of Newcell fibers remained unchanged. X-ray diffraction indicated that the crystal structure of Newcell cellulose II, treated with different alkali concentrations and different methods, did not change. With the increase of alkali concentration the crystallinty and crystallinity orientation index of Newcell fibers in their original length decreased slightly, whereas those of fibers in relaxed condition substantially decreased, and the crystallite size of 101 and 002 increased in both methods. The quasi-crystallite disassociation and recrystallization in the quasi-crystalline phase, during the process of alkali treatment, led to changes of crystallinity and orientation index of Newcell fibers.

Interpretation of relaxation and swelling phenomena in lyocell regenerated cellulosic fibres and textiles associated with the uptake of solutions of sodium hydroxide

“…Interpretation of X-ray diffraction Previous X-ray diffraction studies using lyocell fibre have revealed a critical concentration for conversion to Na-cellulose, sometimes referred to as the transition region (Zhu et al 2004). From the current work, the diffractograms in Fig.…”

“…The annealing action of the alkali has been shown to encourage recrystallisation within the cellulose II domains but may also lead to relaxation of fibre orientation if treatment is performed without physical constraint (Colom and Carillo 2002;Zhu et al 2004). Fibre swelling may cause drastic changes in fabric geometry and in gross dimensions, which may become set after washing and drying (Hearles and Miles 1971).…”

Attenuated total reflectance Fourier-transform Infrared spectroscopy analysis of crystallinity changes in lyocell following continuous treatment with sodium hydroxide

“…This quasi-crystalline phase is attributed to the presence of imperfect microcrystals and co-exists with the amorphous phases (Langan et al 1999). Based on this three-phase structure of lyocell fibres, it has been proposed (Zhu et al 2004) that alkali can only permeate into the quasi-crystalline and amorphous phases, leading to disassociation of the quasi-crystallites. However, based on the work of Okano and Sarko (1984;1985), at higher concentrations the fully crystalline phases must convert to phases of lower crystallinity; it is unclear as to whether crystalline regions have a transitional phase through a quasi-crystalline phase, but this is certainly worthy of further investigation.…”

Effect of alkaline treatment on cellulose supramolecular structure studied with combined confocal Raman spectroscopy and atomic force microscopy

“…Raman spectroscopy has recently gained rather widespread use in studying crystallinity and the effect of mercerization on crystallinity and structure of cellulose Schenzel et al 2005;Kong and Eichhorn 2005;Jähn et al 2002), partly due to relatively fast and simple sample preparation. In mercerization studies of fibres from various sources Raman spectroscopy has been combined with for example X-ray diffraction (Zhu et al 2004;Schenzel and Fischer 2001) and environmental scanning electron microscopy (ESEM) (Jähn et al 2002). ESEM images illustrated morphological changes in fibre bundles due to alkali treatment, but not on a very small scale.…”