Alkali treatments of lyocell in continuous processes. I. Effects of temperature and alkali concentration on the treatments of plain woven fabrics

Abstract

Experiments were conducted that were designed to study the influence of various process parameters on the properties of lyocell fabrics treated with NaOH solutions in a continuous process. The process parameters of interest were the fabric type (plain, twill, or sateen woven), alkali concentration, tension on the fabric, temperature, and duration of the treatment. In this article, we present the first set of results from these experiments and examine the effect of NaOH concentration, temperature, and tension in the continuous alkali treatments of plain woven lyocell fabrics. Alkali treatments caused fiber swelling in the fabrics to extents governed by the alkali concentration and temperature of the treatment liquors. Fiber swelling caused fabric shrinkage, which resulted in changes to the fabric macroscopic structure and properties. Changes were observed in the flexural rigidity, water retention, crease recovery, strength, and abrasion resistance of the fabrics to extents governed predominantly by swelling-related changes to the fabric structure.

Effects of mercerization in the chemical and morphological properties of amazon piassava

“…To study the effectiveness of chemical treatment in piassaba fibers, XRD analysis was performed whose result is shown in the diffractogramin Figure 6.The figure shows that piassava fiber (untreated and treated) there are three broad diffraction peaks at 2 θ, the most intense being the 22° corresponding to the crystalline part of the fiber, and halos at 16° and 35º referring to the amorphous part of the fiber, such as the hemicellulose and lignin present in the fibers microfibrils.The result obtained is very similar to those of other lignocellulosic fibers, and reflects the crystalline lattice of cellulose I [24][25][26][27][28] . Table 2 The increase of crystallinity index in alkaline treated piassava fibers indicated that the chemical treatment induced the crystallinity and it increase due to the removal of amorphous materials like hemicellulose, lignin, and some other [23,[29][30][31] .…”

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

“…The speed of passage of fabric through the system was set at 2 m min -1 . Further details about the conditions and adjustments of continuous alkali pre-treatments are available in our previous work (Siroky et al 2009). …”

“…0, 0.5, 0.6, 0.8, 1.0, and 1.4 mol dm -3 , respectively. Due to changes in the concentration in the first treatment stage, the ''effective'' concentration of alkali was established at 0.0, 2.5, 3.3, 4.5, 4.7 and 7.2 mol dm -3 , which is described in detail in our previous work (Siroky et al 2009). Washing was performed in water alone at 80°C; neutralisation was carried out using 2 g dm -3 acetic acid (80% v/v) at 80°C.…”

“…It is proposed herein, that at the maxima of swelling (crystalline conversion to amorphous phase) at certain concentrations and temperatures (observed peaks at 3.3 mol dm -3 NaOH at 25°C, and at 4.5 mol dm -3 NaOH at 40°C), the greatest reorganisation in the amorphous and quasi-crystalline structure is observed. In our previous work (Siroky et al 2009), it was demonstrated that the most substantial changes in lyocell properties occur under the same process conditions, depending upon treatment temperature and tension. This was evidenced by physico-chemical properties as follows: peaks of fabric shrinkage were observed in samples treated with 3.3 mol dm -3 NaOH at 25°C, and with 4.5 mol dm -3 NaOH at 40°C.…”

Steam Processing of Regenerated Cellulose Fabric in Concentrated LiCl/Urea Solutions

“…In woven fabrics restrictions for swelling of cellulose fibres fabrics exist, which are defined by the fabric structure 17. Lyocell fibres were used for this experiments as this material exhibits a greater swelling effect compared with CV, despite its higher degree of polymerisation of cellulose, which is 600–700 in CLY compared to 200–250 in CV 15, 18…”