**4.1 Influence of physical properties**

Alkali treatment has a substantial influence on dimensional and mechanical properties as well as on morphological, molecular and supramolecular properties of cellulose II fibres (*e.g.* lyocell type) causing changes in their structure and performance. These physical changes were observed and examined by dimensional change, flexural rigidity (in dry and wet

Alkali Treatments of Woven Lyocell Fabrics 195

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). LOI reflects the ordered regions perpendicular to the chain direction, which is greatly influenced by chemical processing of cellulose. This index is calculated as the ratio of two signals, at 1418 cm-1 (CH2 scissoring at C(6) in cellulose II ) and at 894 cm-1 (C–O–C valence vibration of β-glycosidic linkage). First band decreases and second one increases as crystallinity decreases. Attenuated Total Reflectance Fourier-Transform Infrared (ATR-FTIR) spectroscopy analysis is appropriate methods for gathering spectroscopic data, IR absorbance bands are particularly sensitive to the vibrations of polar groups such as OH groups as well as quite reasonable to the non-polar skeletal bonds such as C–C and C–O, and C-H. Therefore, it was used to observe the qualitative crystallinity changes in lyocell

fabrics following continuous treatment with sodium hydroxide.

Fig. 11. Total crystallinity index (TCI; ), lateral order index (LOI; ) and hydrogen

concentration in treatment stage, under varying (49 or 147 N m-1) and temperature (25 or 40 °C) in treatment stage of continuous alkali treatment: A) 49/25; B) 49/40; C)

147/25; D) 147/40.

bonding intensity (HBI; ) of plain woven lyocell fabrics with increasing sodium hydroxide

The results and comparisons of crystallinity indices (Fig. 11), TCI and LOI, and hydrogenbond intensity (HBI) against NaOH treatment concentration shown parallel behavior over the whole range of concentrations and process conditions, although the absolute values differ. There were observed maxima for TCI and LOI, and minima for HBI for all examined lyocell fabrics at effective concentrations of 3.33 and 4.48 mol dm-3 NaOH, when treated at

state), mass per area, water retention and pick-up, abrasion resistance, tensile strength, elongation at break, and crease recovery following continuous treatment of the lyocell plain woven fabrics with aqueous sodium hydroxide solution under varying condition parameters.

The influence of process parameters in alkali treatment of lyocell fabrics by a continuous process on dimensional and mechanical properties was examined with focus on: alkali concentration, treatment temperature, and tension applied on fabric.(Široký et al., 2009) The alkali concentration and treatment temperature exerted significant influence on these fabric properties, but no significant influence of tension was observed in the results. It was proposed herein, that at the maxima of fibre swelling in alkali influencing fabric macroscopic structure and properties at certain NaOH concentrations and temperatures (observed peaks) the greatest NaOH effect occurs. Peaks of fabric shrinkage were observed in samples treated with 3.33 mol dm-3 NaOH at 25°C, and with 4.48 mol dm-3 NaOH at 40°C. The shrinkage peaks corresponded to peaks in flexural rigidity, and minima in water retention, crease recovery, and breaking force. The shrinkage in fabrics and corresponding changes in their properties are attributed to fibre swelling in alkali influencing fabric macroscopic structure and properties. In the range of concentrations examined in this particular work(Široký et al., 2009), the best combination of properties was observed in fabrics treated with 2.53 mol dm-3 NaOH. These fabrics exhibited low wet flexural rigidity, high water retention, high crease recovery, high abrasion resistance, and high breaking strength as compared to the untreated fabric as well as among alkali treated fabrics. Also, it was found that the NaOH concentrations in treatment baths decreased during the course of fabric passage through liquors while, the NaOH concentration in the stabilisation baths increased into extents that increased with rise in liquor alkali concentrations. The NaOH depletion was attributed to sorption of alkali by substrates, and the rise in the stabilisation bath was attributed to the transport of NaOH from the treatment to the stabilisation bath by the fabric.

#### **4.2 Attenuated total reflectance fourier-transform infrared spectroscopy to characterize crystallinity changes**

In the structure of cellulose, a linear 1,4-β-glucan polymer, there are three hydroxyl groups able to interact through intra- and inter-molecular hydrogen bonding, which form highly ordered structures. Alkali treatment of all allomorphs of cellulose has a substantial influence on morphological, molecular and supramolecular levels, causing changes in crystallinity as a result of the degree of swelling, the rate of fibre swelling, changes in the voids and pore networks, and further, on supramolecular level, the diffusion of alkali solution into the less ordered amorphous and quasi-crystalline phases of the cellulose II polymer. Fourier-Transform 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

state), mass per area, water retention and pick-up, abrasion resistance, tensile strength, elongation at break, and crease recovery following continuous treatment of the lyocell plain woven fabrics with aqueous sodium hydroxide solution under varying condition

The influence of process parameters in alkali treatment of lyocell fabrics by a continuous process on dimensional and mechanical properties was examined with focus on: alkali concentration, treatment temperature, and tension applied on fabric.(Široký et al., 2009) The alkali concentration and treatment temperature exerted significant influence on these fabric properties, but no significant influence of tension was observed in the results. It was proposed herein, that at the maxima of fibre swelling in alkali influencing fabric macroscopic structure and properties at certain NaOH concentrations and temperatures (observed peaks) the greatest NaOH effect occurs. Peaks of fabric shrinkage were observed in samples treated with 3.33 mol dm-3 NaOH at 25°C, and with 4.48 mol dm-3 NaOH at 40°C. The shrinkage peaks corresponded to peaks in flexural rigidity, and minima in water retention, crease recovery, and breaking force. The shrinkage in fabrics and corresponding changes in their properties are attributed to fibre swelling in alkali influencing fabric macroscopic structure and properties. In the range of concentrations examined in this particular work(Široký et al., 2009), the best combination of properties was observed in fabrics treated with 2.53 mol dm-3 NaOH. These fabrics exhibited low wet flexural rigidity, high water retention, high crease recovery, high abrasion resistance, and high breaking strength as compared to the untreated fabric as well as among alkali treated fabrics. Also, it was found that the NaOH concentrations in treatment baths decreased during the course of fabric passage through liquors while, the NaOH concentration in the stabilisation baths increased into extents that increased with rise in liquor alkali concentrations. The NaOH depletion was attributed to sorption of alkali by substrates, and the rise in the stabilisation bath was attributed to the transport of NaOH from the treatment to the stabilisation bath by

**4.2 Attenuated total reflectance fourier-transform infrared spectroscopy to** 

In the structure of cellulose, a linear 1,4-β-glucan polymer, there are three hydroxyl groups able to interact through intra- and inter-molecular hydrogen bonding, which form highly ordered structures. Alkali treatment of all allomorphs of cellulose has a substantial influence on morphological, molecular and supramolecular levels, causing changes in crystallinity as a result of the degree of swelling, the rate of fibre swelling, changes in the voids and pore networks, and further, on supramolecular level, the diffusion of alkali solution into the less ordered amorphous and quasi-crystalline phases of the cellulose II polymer. Fourier-Transform 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

parameters.

the fabric.

**characterize crystallinity changes** 

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). LOI reflects the ordered regions perpendicular to the chain direction, which is greatly influenced by chemical processing of cellulose. This index is calculated as the ratio of two signals, at 1418 cm-1 (CH2 scissoring at C(6) in cellulose II ) and at 894 cm-1 (C–O–C valence vibration of β-glycosidic linkage). First band decreases and second one increases as crystallinity decreases. Attenuated Total Reflectance Fourier-Transform Infrared (ATR-FTIR) spectroscopy analysis is appropriate methods for gathering spectroscopic data, IR absorbance bands are particularly sensitive to the vibrations of polar groups such as OH groups as well as quite reasonable to the non-polar skeletal bonds such as C–C and C–O, and C-H. Therefore, it was used to observe the qualitative crystallinity changes in lyocell fabrics following continuous treatment with sodium hydroxide.

Fig. 11. Total crystallinity index (TCI; ), lateral order index (LOI; ) and hydrogen bonding intensity (HBI; ) of plain woven lyocell fabrics with increasing sodium hydroxide concentration in treatment stage, under varying (49 or 147 N m-1) and temperature (25 or 40 °C) in treatment stage of continuous alkali treatment: A) 49/25; B) 49/40; C) 147/25; D) 147/40.

The results and comparisons of crystallinity indices (Fig. 11), TCI and LOI, and hydrogenbond intensity (HBI) against NaOH treatment concentration shown parallel behavior over the whole range of concentrations and process conditions, although the absolute values differ. There were observed maxima for TCI and LOI, and minima for HBI for all examined lyocell fabrics at effective concentrations of 3.33 and 4.48 mol dm-3 NaOH, when treated at

Alkali Treatments of Woven Lyocell Fabrics 197

*al.* (2009) using inversion size exclusion chromatography (ISEC). It was demonstrated that for pore diameters of 19 Å and below that APV increased with increasing NaOH concentration to a maximum around 2.5 mol dm-3 NaOH, which was ca. 10% higher than for untreated lyocell. Applying molecular dynamics, the geometry and electronic properties of hydrolyzed RR120 were explored, and it was found that the dimensions of employed dye are about 30 Å (length) × 14 Å (wide) × 3.5 Å (depth) in one of the minimum energy states, providing a molecular diameter of 14 Å (end-on). It is less than 19 Å and therefore, it is likely that the maximum APV at around 2.5 mol dm-3 NaOH observed by (Özturk et al., 2009) influences the accompanying maxima in the theoretical monolayer capacity (*q*0) and adsorption energy (Δ*G*0) also known as a standard free energy of dyeing or standard affinity of the dye for the substrate, which was indeed observed from the experimental results.

The measurement of *iodine sorption* has been frequently applied in order to study an accessibility of cellulosic fibers.(Nelson et al., 1970; Schwertassek K., 1956; Široká et al., 2008; Strnad et al., 2001) This method has also been employed as a measure of fiber crystallinity.(Elesini U. S. & Cuden A. P., 2002; Hessler & Power, 1954; Zemljic et al., 2008) The computation of substrate crystallinity from iodine sorption value is based on the principle that iodine sorption in substrates is limited only to amorphous regions. However, earlier studies have shown that iodine penetrates into crystalline regions when the adsorption exceeds 11-12%, and the potassium iodide, in which the iodine is dissolved, acts as a swelling agent for cellulose.(Doppert H. L., 1967) These factors will influence results of iodine sorption. Hence, the iodine sorption may be better regarded as a general measure of overall accessibility in substrates. From the iodine sorption experiments performed on alkali treated lyocell fabrics, it was observed that the results do not follow the crystallinity results obtained by ATR-FTIR method. It seems that not only crystallinity of alkali treated lyocell fabrics swelling which is generally considered to increase accessibility of substrates, but also

the construction of substrate can significantly influence the accessibility to iodine.

**4.4 Woven lyocell structure effect on sodium hydroxide release (wash-off)** 

compactness, fabric diffusion, swelling, and fabric bulk density and porosity.

Crank's equation for the flow through a membrane(Crank, 1975):

While in previous sections the discussion was oriented to the extended study of lyocell plain woven fabrics with effect of alkali concentration, treatment temperature and applied tension based on the previous work (Široký et al., 2010, 2011b; Široký et al., 2009), in this chapter, the influence of fabric structure (plain-, twill-, or sateen-woven fabrics) on NaOH release from lyocell after pad-batch pre-treatment (Široký et al., 2011a) will be explored by conductivity measurements in the system of deionized water-NaOH impregnated assemblies-the washoff bath. Weaving of the fabric is distinguished according to the manner the yarns or threads, longitudal-warp and lateral-weft, are interlaced to form fabric or cloth. Three basic weaves are used the most, plain-, twill- or sateen-weaving. Differences in fabric weaving or construction provide also differences in terms of accessibility, substrate surface and

Different fabric construction of the same fibre and yarn, herein weaving, plays a crucial role in liquid-fabric interactions. For example, wet pick-up (*WPU*) differs, which in turn effects the swelling, bulk density, or porosity of such a porous substrate as it shown in Fig. 12. Due to mathematical complexicity, only the changes on the macro-level were further investigated by measuring the conductivity in the wash bath and applying Crank's approximation, the

25°C and 40°C, respectively. Under these treatment conditions, it was proposed therein that maximum molecular reorganisation occurs in the amorphous and quasi-crystalline phases of the cellulose II polymer, which are corresponding to the changes evidenced from evaluation of physico-chemical properties (Široký et al., 2009). Moreover, it was demonstrated that even subtle changes in ATR-FTIR spectra can substantially affect crystallinity indices.
