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

Abstract

Cellulose is a linear 1,4-b-glucan polymer where the units are able to form highly ordered structures, as a result of extensive interaction through intra-and intermolecular hydrogen bonding of the three hydroxyl groups in each cellulose unit. Alkali has a substantial influence on morphological, molecular and supramolecular properties of cellulose II polymer fibres causing changes in crystallinity. These physical changes were observed herein using ATR-FTIR spectroscopy, following continuous treatment of the cellulose II fabrics with aqueous sodium hydroxide solution under varying condition parameters. Posttreatment, maxima for total crystallinity index and lateral order index, and minima for hydrogen bond intensity, were observed at concentrations of 3.3 and 4.5 mol dm -3 NaOH, when treated at 25°C and 40°C, respectively. Under these treatment conditions, it is proposed that maximum molecular reorganisation occurs in the amorphous and quasi-crystalline phases of the cellulose II polymer.

Investigation into the supramolecular properties of fibres regenerated from cotton based waste garments

“…The broad band between 3600-3000 cm -1 was assigned to hydrogen bonds between OH groups of cellulose II structure, where the 3488 cm -1 and 3447 cm -1 absorptions were due to the general OH stretching and specific O(3) H….O(5) vibration due to the intramolecular hydrogen bonds in the cellulose II unit cell, respectively. Similar FTIR peaks for the cellulose II has previously been reported (Carrillo, Colom, Sunol & Saurina, 2004;Široký, Blackburn, Bechtold, Taylor & White, 2010), however the previous studies reported the O(3)H-O(5) vibration at 3442cm -1 .…”

“…Nelson and others (Nelson & O'Connor, 1964a, b) proposed the band at 2900 cm -1 was due to the C-H stretching in Cellulose I and Cellulose II structures and they used the intensity ratio of the 1372 cm -1 and the 2900 cm -1 bands as a measure of the total crystallinity index for cellulose fibres. In this study intense bands of the same magnitude were observed at 2892 cm -1 for both Lyocell and the ReCell fibres and similar absorption intensities were reported for other lyocell fibrous materials (Široký, Blackburn, Bechtold, Taylor & White, 2010). Examination of the ATR-FTIR spectra of the Lyocell and ReCell fibres in the 2000cm -1 -800cm -1 region indicated that the fibres have similar structural features, Figure 2.…”

“…The ReCell-2 fibres exhibited weaker absorption intensity relative to the other fibres in the 1685cm -1 -1600cm -1 spectral range. The band between 1685-1655cm -1 can be assigned to the C=O stretching in the cellulose II structure (Široký, Blackburn, Bechtold, Taylor & White, 2010) and the band at 1635cm -1 was assigned to the OH water absorbed in the cellulose (Carrillo, Colom, Sunol & Saurina, 2004;Široký, Blackburn, Bechtold, Taylor & White, 2010) and is a characteristic of all cellulosic materials. The 1470cm -1 and 1420cm -1 absorption bands can be assigned to the OH in-plane bending and the CH 2 symmetrical bending of cellulose II structure, respectively, with these bands having similar intensities for all the fibres under investigation except the ReCell-2 fibres which exhibited relatively weaker absorption at 1470cm -1 .…”

Analysis of the physical properties of developing cotton fibres

“…In previous research we have demonstrated that ATR-FTIR can be successfully employed to monitor changes in crystallinity of cellulosic fibres through crystallinity indices [55,56].…”

Alkali Treatments of Woven Lyocell Fabrics

“…FourierTransform Infrared spectroscopy (FT-IR) is currently one of the best available techniques in the textile science to obtain structural information (Široká et al, 2011), which has been universal accepted for many years as a powerful tool for analytical and chemical characterisation in wide range of scientific disciplines and widely used in polymer characterisation, providing information about chemical nature, isomerisation, conformational order, state of order, and orientation. Using FT-IR, a clear relationship between interaction of hydroxyl groups and crystallinity in cellulose has been established, and numerous papers have been published in relation to infrared spectroscopy analysis of native cotton and mercerised cotton as well as regenerated fibres (Hurtubise & Krassig, 1960;Nelson & O'Connor, 1964;Široký et al, 2010) in order to establish or develop the ratio indices of absorption bands, crystallinity indices, the so-called 'total crystallinity index' (TCI) and 'lateral order index' (LOI). TCI represents the overall degree of order in cellulose given by the ratio of absorption at 1372 cm -1 (C-H deformation in cellulose II) and 2892 cm -1 (C-H stretch in cellulose II).…”