Page 43 - New Cloth Market November 2022 Digital Edition

Chitosan-Based Sustainable Textile Technology: Process, Mechanism, Innovation & Safety

fiber pretreatment for the resistance of effects attribute to the diffusion and fabric processing, especially for
warp breakage caused by highly deposition of the size materials in the consumer esthetic test. In this
stressed weaving process. In general, fiber thread which increase the process, dye molecules diffuse and
a sizing agent adheres to the surface brittleness and rigidity. On the other interact with functional sides of fibers
of yarn and forms a coating. It provides hand, the removal effciency of or fabrics. Therefore, various types of
the required strength and hydrophilicity hydrolyzed chitosan is found 100% fibers or fabrics made of cotton [45],
for a successful weaving process. only with water at 90°C. polyester [46], rayon [46], nylon [47],
Polyvinyl alcohols and acrylics wool [48, 49], silk [50], and composites
including all synthetic sizing agents Carboxymethylated chitosan, a [51] are processed using different
need to be washed out at the end for a modified form of chitosan, is readily functional dyes such as sulfur dye, vat
smooth finishing process, to avoid soluble in water at neutral pH and could dye [46], reactive dyes [45, 46, 52–
complications in the subsequent steps be used as sizing agent [42]. On the 54], etc. Therefore, the methodological
of fibers or fabric treatment. Chitosan other hand, in combination with wax or variations are found based on dyes and
is a better candidate in both aspects starch by an extrusion process, a form fibers/fabrics such as Jig dye, Pad
of biodegradability and effciency, while of sizing agent is obtained [43]. The dye, and Jet dye [46] for the dyeing
synthetic agents are not. Chitosan is viscosity of chitosan solution process. All methods require quite high
soluble in pH less than 6.0 since the increases with increasing chitosan energy, large amount of water and salts
pKa is 6.5 where more than 50% of concentration and limiting its until the dye molecules distribute and
chitosan molecules deprotonated and performance as sizing agent arises diffuse uniformly. In addition, these
become insoluble. from the high viscosity of chitosan at processes release a high amount of
room temperature above 2% in the complex effluents containing all
Chitosan is hydrolyzed by concentrated acidic medium. Carboxymethylated chemicals together.
hydrochloric acid 0.1 N [40], 0.2 N [41], chitosan is achieved via hydrolysis
0.5–1 N [42] at high temperature (30– using 0.5 N hydrochloric acid at a Therefore, the loss of untreated dye
90°C) to achieve soluble chitosan which minimum of 90°C for 2 h. The NaCO3 and salt and highly efficient effluent
exhibits lower apparent viscosity. The is used for the neutralization, and then, treatment all have very high equivalent
temperature is associated with the the filtration with washing is necessary cost. Moreover, the drawbacks also
activation energy, which catalyzed the for removing the sodium chloride salt. impact on aquatic environmentrelated
hydrolyzing action of HCl. Besides, the The final form is used as sizing agent health. The use of chitosan or modified
content of nitrogen reduces from 7 to [42]. chitosan has beneficial effects on
6.5% since the hydrolysis of chitosan dyeing process which reduces the
Apart from the carboxymethylated
continues around 60 min. It attributes amount of untreated dye in the bath
chitosan, the addition of wax with the
to chain scission at 1–4 glycosidic without using any salt. As a result, a
modified chitosan provides a reduction
bonds of chitosan for the regular attack simple effluent treatment would be
in surface tension which results in
of concentrated HCl resulting in the enough to process released effluent
improved wetting property including
lower molecular weight. In addition, the from dye house.
adhesion behavior of modified sizing
dissolution of short chain chitosan
agent [43]. The viscosity is reduced by
shows lower and stable apparent In the dyeing process of cotton fibers
0.5% of pure chitosan after the small
viscosity to 110 MPa s after 60 min or fabrics, reactive dyes are the mostly
proportion of wax addition. Moreover,
probably due to the retention of used due to its better wet fastness,
the sizing film also reduces the friction
crystallinity after degradation. brilliance, hue variability, easy
between metal and fibers resulting in
processability, and applicability [55]. In
the better performance in the weaving
The conformational change is attributed addition, reactive dye molecules form
process.
to the result of a transformation rod to covalent bond through reaction with
coil transition [40]. In general, the Some modified chitosans such as N- hydroxyl groups of cellulose via
sizability and desizability processes [(2-hydroxy-3-trimethyl ammonium) nucleophilic addition or substitution
are expressed as size addon and propyl] chitosan chloride (HTACC) and reaction. In general, reactive dyes and
removal percentages, respectively. The N-[(4-dimethyl aminobenzyl)imino] cotton fabrics or fibers hold anionic
add-on proportion of size mainly chitosan (DBIC) have been developed groups which affect the reaction due
depends on the apparent viscosity and for better performance of solubility and to charge repulsion in the dye bath. As
the solid content of size materials in pretreatment of polyester fabric [44]. a result, large quantities of salts are
the liquor. The tensile strength is found used for the screening of charges in
Chitosan: an auxiliary in textile
higher after drying the size coating by dyeing process. A comprehensive and
dyeing process
heat treatments, while the elongation comparative optimization process
at break decreases significantly. The The dyeing process is a major step in studies have been conducted by
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