Psyllium as a thickening agent in printing of cotton with reactive dyes

Excerpt: The optimum concentration used for psyllium as a thickener for the flat bed screen printing is 3.5% and provide good results in terms of colour strength, sharpness.

Psyllium as a thickening agent in printing of cotton with reactive dyes


Parambir Singh Malhi, Aditi Saini, Manmeet Kaur, Rohit Mittal
Department of Chemistry, Guru Nanak Dev University, Amritsar, Punjab- 143005



ABSTRACT

An attempt was carried out to study psyllium as a natural thickener in printing of cotton fabric with reactive dyes. The process parameters like concentration of psyllium and its effect on the viscosity of printing paste were studied. Printed samples were compared in terms of colour yield, fastness properties and bending length i.e. stiffness of fabric with other conventional natural thickeners like sodium alginate and carboxymethyl cellulose (CMC). Samples printed with psyllium as a thickening agent provide better colour yield, comparable fastness properties and softer hand feel at low application concentration as compared to sodium alginate and CMC.

Keywords: Psyllium, Sodium alginate, Carboxyl methyl cellulose, Reactive dyes, Colour yield, Fastness, Bending length


Introduction

DIFFERENT processes have been developed for textile printing, depending on the kind of the fabric used (cellulosic, polyester, acrylic, protein), on the nature of the dyestuff applied (reactive dye, vat dye) and on the expected quality of the final product. The printing paste undergoes high deformation rates and stresses and consequently, marked changes in the rheological parameters occur such as viscosity drop and increased elasticity, which all together give the printing paste the capability to penetrate into the fabric[1, 2].

Cellulose fabrics are the most commonly printed substrate, and reactive dyes are the most commonly used dyes in textile printing. Sodium alginate, as a salt of alginic acid (carbohydrate component of brown sea weeds), possesses a unique position among all thickeners producing soft and brilliant prints especially when reactive dyes are used. Sodium alginates are readily soluble and the extent of interaction with the reactive dyes is found to be negligible[1, 3, 4] . But with excessive use of reactive dyes in textile printing, sodium alginate has now become scarce and expensive. CMC, modified cellulose, is a cellulose derivative with carboxymethyl groups (-CH2 -COOH) bound to some of the hydroxyl groups of the glucopyranose monomers that make up the cellulose backbone. It has great economical and environmental advantages and is characterized by high viscosity and good film forming properties, finds its application in textile industry as printing pastes, sizes, Queries and Responses: author.colourage@gmail.com finishing and lubricants[5, 6] . Alternative thickeners are either synthetic or etherified natural thickeners that satisfy the printing quality requirements[2].

Psyllium, the seed from Plantago, is widely distributed throughout the temperate region of the world and has high economic value. The Psyllium seed yields colloidal mucilage consisting mainly of xylose, arabinose, galacturonic, 4-O- methylglucuronic acid, tannins, fatty oils[7] . Psyllium has been widely recognized for its safe and cholesterol-lowering effects, effective laxative activity, and insulin sensitivity improvement capacity[8, 9] . Hence, it has no negative impact on the environment. Recently, its use as a flocculant for treating textile effluent has been reported[10, 11] . The rheology study of the psyllium at different concentrations, temperature and pH has been studied indicating its elastic properties and being an anionic polysaccharide, bears a negative charge due to ionized carboxyl groups[12] . This leads to negligible interaction between reactive dye and psyllium, makes its suitable application as a thickener on cotton fabric and as a substitute to the sodium alginate and CMC.

In the present study, we report the use of psyllium as a natural thickener for the very first time for the printing of cotton with reactive dyes.

Experimental

Materials

Commercially bleached, mercerized and unfinished plain

weave cotton fabric with following specifications was used for printing: count- warp 20s , weft 20s ; ends per inch, 66; picks per inch, 68; fabric weight, 242 g/m2.

Remazol Red RGB, Levafix Red CA-N and Procion Red PX-8B as commercial reactive dyes were supplied by Dystar, India.

Urea, sodium carbonate and sodium bicarbonate were of laboratory grade (provided by Merck Specialties Pvt. Ltd.). Sera Con M-LU (as a mild oxidizing agent) and Sera Sperse CSN (as a soaping agent) as commercial grade auxiliaries were supplied by Dystar India.

Sodium alginate and CMC as powder form were of laboratory grade whereas psyllium was of commercial food grade supplied by Sidhpur isabgol processing company, India as a husk which was ground in a powder form.

Printing with reactive dyes

Preparation of printing paste

Cotton printing with reactive dyes was carried out using the following printing components as shown in table 1.

A thickener stock paste was prepared by adding a thickener powder in a small amount of warm de-mineralised water and continuously stirred with a mechanical stirrer until a smooth paste was not obtained. The prepared paste was stored for overnight. Another paste was prepared by mixing urea in warm water and cooled to room temperature. To this, required amount of dye and other auxiliaries except alkali (added and mixed just before printing) were added and stirred until a smooth paste was obtained. Calculated amount of prepared thickener stock paste was added to this dye paste.

Printing of fabric

Printing pastes were applied to the sample using flat screen technique. Printed samples were then dried at 90°C for 5 minutes and steamed at 102°C for 15 minutes. The printed fabrics were then washed with 2 g/l Sera Sperse CSN at 60°C for 15 minutes followed by warm and cold rinse. The fabric was dried at 90°C for 5 minutes.

Viscosity of the print paste

The rheological properties of the thickening agent's solutions were measured at shear rate of 12 (s)-1 and 25°C using a using Brookfield Viscometer, Model RVF. The apparent viscosity (η) was calculated using the following formula: η = τ/D Pa s, where D and τ are the rate of shear (s)-1 and shear stress (dyne/cm), respectively.

Evaluation of samples

  • Colour yield and colour differences were determined by measurement of K/S values and dE (on Datacolor SF 600) at the λmax under D65 illuminant. 65
  • Bending length of the treated samples was tested as per ASTM (E290-09).
  • Rubbing fastness of the treated samples was evaluated as per AATCC 116
  • Washing fastness of the treated samples was evaluated as per AATCC 61
  • Washing fastness of the treated samples were evaluated as per AATCC 107

Results and discussions

In this study, an attempt has been carried out to evaluate psyllium as an alternative to sodium alginate and CMC as a printing thickener.

Viscosity of the print paste

Fig. 1 shows the results for the viscosity of the psyllium at different concentrations varying from 0.5 to 5%.


Fig. 1: Viscosity of psyllium at different concentrations

From the above results, it was observed that viscosity at concentration below 2% was very low and might not provide the proper rheology to the printing paste for sharp prints. At concentration of 3% and 3.5%, the viscosity was found adequate i.e. 5750 and 7400 cps (centipoises) respectively. Viscosity at concentration higher than 3.5% was found quite high i.e. 10550 cps at 4% and 11300 cps at 5%.

Colour Yield

For the optimization of the psyllium's concentration as a thickener, remazol red RGB (based on vinyl sulphone) was used as a reactive dye. Fig. 2 shows results of the colour yield in the terms of K/S at λmax 530 nm for samples printed with varying concentration of psyllium from 2% to 5%.

The result indicates that with the increase in the psyllium concentration, K/S increased up to the concentration of 3.5% i.e. K/S values of 17.89 at 2g/l, 18.45 at 2.5%, 19.52 at 3% and 20.12 at 3.5%. With further increase in thickener concentration, K/S values decreased i.e. 18.21 at 4% and 17.5 at 5%. This may be attributed to the higher paste viscosity leads to poor transfer of the colour yield on the fabric.

The samples printed with conventional printing thickeners like sodium alginate and CMC provide colour yield in terms of K/S as 14.29 and 13.59 at 8% each respectively which were found lower than the samples printed with Psyllium at all concentrations.


Fig. 2: K/S values of printed samples at different concentration of psyllium

Bending Length

Fig. 3 shows the results for bending length of the samples printed with varying concentration of psyllium from 2% to 5%.


Fig. 3: Bending length at different concentration of psyllium

The bending length of the samples increased with the increase in the concentration of thickener having a least value of 1.8 cm at 2% and highest value of 2.5 cm at 5%. It may be attributed due to increase in the concentration of the Psyllium husk on printed fabric leads to decrease in the softness of the fabric.

Bending length of the samples printed with conventional thickener like sodium alginate and CMC was found to be 3.7 cm and 3.4 cm respectively and found comparatively higher than the sample printed with psyllium which concludes that new thickener provides softer hand feel to printed fabric than conventional thickeners. This may be attributed to the low concentration usage of psyllium on the fabric for printing.

From the results of viscosity, colour yield and bending length, it was found that printing with psyllium concentration of 3.5% provides better results and can be used as a substitution to the conventional thickeners like sodium alginate and CMC.

Fastness Properties

The rubbing, washing and water fastness of the samples printed with psyllium concentration at 3.5% and others with conventional thickeners were evaluated and shown in table 2.

The fastness properties in terms of rubbing, washing and water were found to be comparable for the samples printed with all thickeners.

Printing with other reactive dyes

For the confirmation of the above results and effect on the reactive dye class, samples were printed with 2 other commercial classes of reactive dyes i.e. Levafix Red CA-N (based on Vinyl sulphone and difluoropyrimidine) and Procion Red PX-8B (based on dichlorotriazine). Table 3 shows results of K/S, bending length, rubbing, washing and water fastness of the samples printed with reactive dyes at the optimized concentration i.e. 3.5% of psyllium and conventional concentration of sodium alginate and CMC.

It was observed that the colour yield and bending length of the sample printed with psyllium was found higher than the sample printed with sodium alginate and CMC for both dye classes. The fastness properties in terms of rubbing, washing and water fastness were found comparable for all 3 thickeners w.r.t both dyes leads to conclude that psyllium as a thickener can be used on the all reactive dye classes without any problem.

Conclusion

The optimum concentration used for psyllium as a thickener for the flat bed screen printing is 3.5% and provide good results in terms of colour strength, sharpness, bending rigidity as compared to sample printed with 8% of either sodium alginate or CMC. Fastness properties in terms of rubbing, washing and water were found comparable for the sample printed with all 3 thickeners. Psyllium as a thickener can be used for all the dye classes of reactive dyes as it doesn't interact due to the anionic nature and can easily substitute the sodium alginate.

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