Ashis Kumar Samanta

Dyeing of Textiles with Natural Dyes

Textile materials (natural and synthetic) used to be coloured for value addition, look and desire of the customers. Anciently, this purpose of colouring textile was initiated using colours of natural source, untill synthetic colours/dyes were invented and commercialized. For ready availability of pure synthetic dyes of different types/classes and its cost advantages, most of textile dyers/ manufacturers shifted towards use of synthetic colourant. Almost all the synthetic colourants being synthesized from petrochemical sources through hazardous chemical processes poses threat towards its eco-friendliness. Hence, worldwide, growing consciousness about organic value of eco-friendly products has generated renewed interest of consumers towards use of textiles (preferably natural fibre product) dyed with eco-friendly natural dyes. Natural dyes are known for their use in colouring of food substrate, leather as well as natural fibres like wool, silk and cotton as major areas of application since pre-historic times. Although this ancient art of dyeing textiles with natural dyes withstood the ravages of time, but due to the wide availability of synthetic dyes at an economical price, a rapid decline in natural dyeing continued. However, even after a century, the uses of natural dyes never erode completely and they are being still used in different places of the world. Thus, natural dyeing of different textiles and leathers has been continued mainly in the decentralized sector for specialty products besides the use of synthetic dyes in the large scale sector for general textiles/apparels. Recently, most of the commercial dyers and textile export houses have started re-looking to the maximum possibilities of using natural dyes for dyeing and printing of different textiles for targeting niche market. Natural dyes produce very uncommon, soothing and soft shades as compared to synthetic dyes. On the other hand, synthetic dyes, which are widely available at an economical price and produce a wide variety of colours, sometimes causes skin allergy and other harmfulness to human body, produces toxicity/chemical hazards during its synthesis, releases undesirable/hazardous/toxic chemicals etc. For successful commercial use of natural dyes for any particular fibres, the appropriate and standardized techniques for dyeing for that particular fibre-natural dye system need to be adopted. Therefore to obtain newer shade with acceptable colour fastness behaviour and reproducible colour yield, appropriate scientific dyeing techniques/procedures are to be derived. Thus, relevant scientific studies and its output on standardization of dyeing

Application of single and mixtures of red sandalwood and other natural dyes for dyeing of jute fabric: studies on colour parameters/colour fastness and compatibility

Single and binary mixtures of aqueous extracts of red sandalwood (RSW) with aqueous extract of other natural dyes like manjistha (MJ), jackfruit wood (JFW), marigold (MG), sappan wood (SW) and babool (BL) in different proportions are applied on bleached jute fabric for its dyeing after double pre-mordanted with myrobolan and aluminium sulphate applied in sequence under optimised conditions of mordanting with effects of use of different proportions of binary mixture of selective natural dyes on colour strength and other colour. Parameters and colour fastness properties have been investigated. Compatibility of selective binary mixture of dyes was also judged by a relatively newer colour index parameter established earlier from this laboratory. Binary of mixture of RSW and MJ is found to be most compatible with rating 4 (in 0–5 scale), and mixture of RSW:MG and RSW:JFW is found to have average compatibility having rating 3. Dyed fabric samples have also been further treated with cationic dye-fixing agents namely N-cetyl-N-trimethylammonium bromide (CTAB), cetrimide and Sandofix-HCF to improve wash fastness. Treatment with 2% CTAB or Sandofix-HCF improves the wash fastness to nearly 1 unit. Treatment with 1% benztriazole improves the light fastness of natural dyed jute textiles nearly half to one unit. The possible chemistry and mechanisms for such improvement in wash fastness by CTAB and improvement of light fastness by benztriazole for jute have also been discussed to explain the observed effects.

Enzyme and silicone treatments on jute fibre. Part I: Effect on textile-related properties

Abstract The present study relates to broad-based assessment of softening of raw jute and selectively pretreated jute fibres under the action of mixed enzymes (cellulase, xylanase and pectinase) and a textile grade aminosilicone softener and to further assess how such selective treatments finally contribute in enhancing some textile-related properties. Application of 4% mixed enzyme on jute fibre at 55°C for 2 h at pH 4.8 offers much finer, softer, cleaner and brighter jute fibre with some lowering of bundle tenacity. However, pretreatment of jute fibre under combined oxidative action of 3% H2O2 and 0.75% K2S2O8 for 2 h at 30°C (pH 11) followed by subsequent treatment with 1% mixed enzyme offers a better balance of textile-related properties covering moisture regain, fineness, bundle tenacity, flexural rigidity, surface reflectance, whiteness index, yellowness index and brightness index. Treatments of jute fibre with 0.5–1% aminosilicone softener under a specified condition also make jute fibre much softer, smoother, brighter and cause noticable reduction in coefficient of friction without much change in bundle tenacity. However, keeping all textile-related properties in view, a preatment of conventional 3% H2O2 bleaching for 2 h at 85°C (pH 11) or an oxidative treatment under combined action of 3% H2O2 and 0.75% K2S2O8 for 2 h at 30°C (pH 11) prior to 1% aminosilicone treatment of jute fibre were found to be much useful for textile purpose.

Simultaneous free radical polymerization and acidic polycondensation of acrylamide—formaldehyde resin on jute fabric

Acid catalyzed grafting, polycondensation, and crosslinking of acrylamide—formaldehyde (AMF) resin and simultaneous free radical graft copolymerization of the resin moieties on jute fabric were studied using a combination of MgCl2 and K2S2O8, respectively, as the (dual) catalyst system. Resin application and finish on jute fabric were accomplished by padding at room temperature, drying at 80°C, and polymerization and curing at 150°C. Changes in chemical structure and surface morphology of jute fiber on resin treatment were examined by Fourier transform infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM), respectively. Application of 8% spectroscopy and scanning electron microscopy (SEM), respectively. Application of 8% AMF resin under the dual catalyst system in appropriate doses produced the most improved balance in the properties of jute fabric, including tenacity, modulus, breaking extension, stiffness, crease recovery angle, fiber shedding, moisture regain, and dyeability. Analysis indicated that all the major constituents of jute, namely, α-cellulose, hemicellulose, and lignin reacted with the AMF resin system and that the resin finish turned jute thermally more stable. Effects of different degrees of removal of lignin and hemicellulose from jute on its AMF resin uptake were also studied and reported.

Structural Features of Glycol and Acrylamide Treated Jute Fiber

ABSTRACT Changes in structural features of jute fiber subjected to (a) limited oxidation using K2S2O8 or NaIO4 and subsequently to (b) treatment with monomeric/oligomeric glycols or acrylamide under specified conditions have been investigated through X-ray defractometry, fourier transform infrared spectroscopy, and differential scanning calorimetry in the present study. Changes in surface morphology due to specified chemical treatments have been analyzed by scanning electron microscopic study. Observed chemical changes as revealed from FTIR-study have been explained through proposed reaction mechanism. Oxidative pretreatments by both NaIO4 and K2S2O8 causes some damage in the fiber surface structure, reduction in crystallinity percentage and show less thermal stability with generation of more -CHO groups in oxy-jute state; the treatment being relatively milder for K2S2O8 pretreatment than NaIO4 pretreatment. However, when K2S2O8 pretreated oxy-jute is further treated with either 8% dosage of acrylamide or ethylene glycol or polyethylene glycol or 1:1 mixture of acrylamide and polyethylene glycol-1500, it renders measurable improvement in surface appearance and morphology of jute fibers, somewhat increased crystallinity in fine structure, less thermal stability for polyacrylamide grafted jute, and higher thermal stability for ethylene glycol modified jute. However, the treatment of K2S2O8 pretreated oxy-jute with 1:1 mixture of 4% acrylamide and 4% PEG-1500 renders a balanced improvement in all these structural features of jute fiber.

Eco-friendly salt-free reactive dyeing of cotton (muslin) fabric after cationization with amino acid from soya

Bleached cotton fabric was chemically modified (cationized)with natural amino acids extract obtained by acid hydrolysis (6N HCL) from soya bean seed waste, adding MgCl2 as an acid donor in the pad-dry-calendaring process to investigate the changes in textile properties and its dyeability with reactive dye in both a conventional alkaline dye bath and salt-free acidic dye bath. This modified cotton incorporates new functional groups producing - NH 3 + in acid bath to obtain cationized cotton, rendering it to eco-friendly salt-free reactive dyeing at acceptable shade depth without much sacrifice of other textile-related properties. Bi-functional high exhaustion-type reactive dye shows better dye uptake than mono-functional cold brand as well as hot brand reactive dye. Moreover, the application of a specific dye fixing agent further improves surface color depth (K/S) of the soya-modified cotton fabric. The study of surface morphology of said chemically modified cotton substrate indicates a higher degree of surface deposition, that is, more anchorage of soya extracted amino acids on cotton fabric. Chemical anchorage as per the reaction scheme postulated for such modifications is verified with Fourier transform infrared spectroscopy. Finally, it is revealed that cotton treated with soya extract provides a new route of eco-friendly salt-free reactive dyeing with high exhaustion-type reactive dyes showing much higher dye uptake than the control cotton fabric.

Effects of Glycol and Acrylamide Treatments on Textile-Related Properties of Jute Fibre

ABSTRACT Changes in textile related properties of jute fibre subjected to (a) limited oxidation using K2S2O8 or NaIO4 and subsequently to (b) treatment with monomeric/oligomeric glycols or acrylamide under specified condition were studied. Comparison of observed effects indicated that presoaking of jute fibre at room temperature with 0.5% aqueous K2S2O8 followed by an exposure to U-V light for 15 min and subsequent treatment with (i) 8% ethylene glycol, (ii) 8% acrylamide and (iii) a mixture of 4% polyethylene glycol of molecular weight 1500(i.e. PEG 1500) and 4% acrylamide produced mentionworthy improvement in textile related properties in respect of weight gain, moisture absorption, linear density, tenacity retention, coefficient of friction, flexural rigidity, surface reflectance, whiteness index, yellowness index and brightness index. Treatment of oxy-jute (K2S2O8 –treated) fibre by 1:1 mixture of acrylamide and PEG under the prescribed optimal condition appears to produce the most encouraging results as far as tenacity retention, surface appeance and colour parameters including brightness and surface reflectance of jute fibre are concerned.

Studies on Color Interaction Parameters and Color Fastness Properties for Dyeing of Cotton Fabrics with Binary Mixtures of Jackfruit Wood and other Natural Dyes

Bleached cotton fabric (after sequential pre-mordanting with myrobolan and then with aluminum sulfate applied in sequence) has been dyed with a pre-fixed concentration of purified binary mixtures of jackfruit wood (JFW) and other natural dyes, like manjistha (MJ), red sandalwood (RSW), mariegold (MG), sappan wood (SW) and babool (BL) in different proportions to obtain a variety of compound shades with varying color strength (K/S values) and related color parameters. Data on color fastness ratings for such dyed cotton fabrics to washing, light, and rubbing show somewhat moderate to poor washing fastness and light fastness properties in some cases, but quite a good rubbing fastness in all cases. To improve the wash and light fastness of these dyed cotton fabrics, the dyed cotton fabrics were further treated with selected cationic dye-fixing agents and also with an UV- absorber compound, respectively. 1% CTAB and 1% Sandofix HCF post-treatment rendered these dyed fabrics one grade higher washing fastness and 1% benztriazole treatment also increased the light fastness rating by half to one unit in most cases. The chemical interaction for these improvements of washing and light fastness properties by the said after-treatments have been discussed to explain the observed effects.

Application of polyethylene glycol, cetrimide, chitosan and their mixtures on cotton muslin fabric to improve rot resistance, antimicrobial property and its salt-free reactive dyeing

In the present work, cotton muslin fabric is treated with eco-friendly antimicrobial agents in order to observe the effect of those chemicals on the rot resistance properties, physical appearance, important textile-related mechanical properties and dyeability with reactive dyes. The cotton fabric has been treated with polyethylene glycol (PEG 200), cetrimide and chitosan individually and their blends, in the presence of citric acid and sodium hydrogen phosphate as mixed catalyst to investigate the effect of such treatment on fabric properties of treated cotton mentioned above. Amongst all individual and combined applications of above said chemicals, it is observed that treatment with a mixture of chitosan and PEG is showing good result in terms of improvement in rot resistance performance and an optimum balance in other textile-related mechanical and appearance properties indicating lowest degradation against microbial attack. A series of experiments were undertaken with varying percentage of both the chemicals to arrive at the optimum ratio of mixture of PEG and chitosan and compared with such effect for treatment with conventional quaternary ammonium compound EPTAC. This treatment shows much balance results and also creates a newer provision of salt-free reactive dyeing of such treated/cationized cotton muslin fabric by unconventional reactive dyeing in acid bath after such chemical treatment/modifications.

Study on Reuse of Coconut Fiber Chemical Retting Bath. Part 1: Retting Efficiency

ABSTRACT Coconut husk is commonly retted in back water to extract coconut fiber. This retting takes about 10 months to complete and also pollutes the environment. A work on captive chemical retting of coconut fiber has carried out with NaOH, Na2S, and Na2CO3. It is found that the residual retting liquor contains unreacted alkali, which is unutilized and might cause environmental issues, if not processed before disposal. An attempt has been made to estimate the residual alkali present in the residual waste liquor in order to reuse the retting bath by suitable addition of alkali. The physical parameters of the retted fibers were evaluated against raw fiber using standard methods. It is concluded that residual retting liquor could be used for further retting process by the addition of suitable quantity of chemicals.