Preparation of Novel Chitosan-Starch Blends as Thickening Agent and Their Application in Textile Printing

Chitosan, a naturally available biopolymer which is now increasingly used as a functional �nish on textile substrates to impart antimicrobial characteristics and increase dye uptake of fabrics, was blended with different ratios of gelatinized starch.e chitosan was extracted and characterized by IR, H-NMR, and X-ray powder diffraction. ese blends were tested as thickeners in textile screen printing using Curcuma tinctoria as natural dye. e rheological properties and the viscosity of the printing paste were measured. e effect of chitosan on the printing properties of different fabrics (natural, blends, and synthetic fabrics) was studied by measuring the color strength value (K/S) and related color parameters of the printed fabrics. e antimicrobial properties of printed fabrics were assessed. e results proved that the printed fabrics using these new thickeners showed increase in the color strength value (K/S) giving darker color which means that chitosan increased the dye uptake on fabrics. Fastness properties of the printed fabrics to washing, rubbing, perspiration, and light have also been improved. e treated fabrics were found to be antimicrobial.


Introduction
Improving the environmental impact and unifying processes as a result of using one class of dyes in coloring fabrics made of blends of chemical and natural �bers is one of the main trends in the evolution of textile dyeing and printing technology.
Recently, there has been a revival of interest in natural dyes throughout the world as some synthetic dyes are being banned due to their toxic, carcinogenic, and polluting nature.Most natural dyes need the use of chemicals, called mordant, to help promoting dye absorption and �xing and prevent bleeding and fading of the colors.Mordants form chemical bonds between the dye molecules and the proteins of the fabrics (wool is generally the best fabric colored with natural dyes).
Treatment of textiles with chitosan which is considered as multifunctional �nish not only contributes to its antimicrobial properties but also results in enhancement of color strength thus generating much interest towards chitosan [4][5][6].It is also used as an auxiliary in printing of textiles.It has been reported that the printed samples have comparable color fastness to that of commercial printed samples, but chitosan �lm on fabric surface is not desirable since it causes the problem of fabric stiffness (poor handling) [7,8].
Blending of starch with chitosan results in formation of edible coating with a good �lm forming and mechanical properties [9]; starch must be gelatinized �rst before blending with chitosan.Hence the aim of the present study is to investigate the combined effect of chitosan and gelatinized starch as thickening agent in screen printing technique using natural dye and to explore its antimicrobial properties.(iv) Polyester: polyester-(PE-) knitted fabric of 150 g/m 2 , supplied by a private sector company which was treated with a solution containing 1 g/L nonionic detergent at 70 ∘ C for 1/2 h, thoroughly washed, and air-dried at room temperature.

Extraction of Chitosan.
Chitosan was extracted frommarine shrimp shells.e exoskeletons of the shrimps were crushed and treated in the usual way with HCl, NaOH 1-2 M then with 40% NaOH to extract the chitosan [10].Chitosan was characterized using the Fourier transform infrared (FTIR) spectroscopy, 1 H-NMR spectroscopy, and Xray powder diffraction.e degree of deacetylation (DDA%) of chitosan determined by potentiometric titration [11], and the molecular weight was calculated using the value of intrinsic viscosity [12], measured by an Ubbelohde viscometer.e value of (DDA%) and molecular weight of chitosan were 85% and 11.44 × 10 4 gm/mol, respectively.

Characterization of Prepared Chitosan. e Fourier
Transform Infrared (FTIR) Spectroscopy.e FTIR spectra were measured in KBr pellets in the transmission mode in the range 400-7000 cm −1 using Perkin-Elmer 2000 spectrophotometer. 1 H-NMR Spectra.Nuclear magnetic resonance 1 H-NMR spectra were measured using JNMAl 300; Jeol spectrometer at 300 MHz in D 2 O in which drops of DCl was added to enhance solubility.X-Ray Diffraction.Xray diffraction analysis (XRD) was applied to detect the crystallinity of the extracted samples of chitin and their corresponding chitosan.A Scintag powder diffractometer was used for this purpose between 2 angles of 5 ∘ and 40 ∘ .Ni-�ltered Cu K -radiation was used as the X-ray source.e relative crystallinity of the polymers was calculated by dividing the area of the crystalline peaks by the total area under the curve.

Gelatinization of Starch Solution in Microwave.
Starch was gelatinized �rst in microwave before blending with chitosan.Starch samples with predetermined starch concentrations, were prepared by using soluble starch and distilled water, and the samples were stirred gently just before heating them in the microwave oven in order to ensure that the starch was fully suspended in the water.e starch ratio in the prepared samples was 3, 4, 5, and 6%.en starch samples (150 mL) were heated at full power in the microwave oven WP800 for 2 minutes.

Blend Formation.
Chitosan was blended with all the prepared gelatinized starch with �xed ratio 1% of the starch samples.

Preparation of Printing
Paste.e suitability of chitosan and gelatinized starch blends as thickening agents in screen printing technique was investigated using Curcuma tinctoria as natural dye.To achieve this goal, different printing paste using the new thickeners and another one with sodium alginate as thickening agent for the sake of comparison were prepared according to the recipe givenin Table 1.
Sodium alginate was �rst soaked in small amount of water overnight at room temperature before preparing the printing paste.e natural color and urea were then added on the thickener suspension as in the recipe mention then the total weight of the whole paste was adjusted to one kilogram with the addition of the necessary amount of water.All the printed samples except the wool samples were �xed via thermo�xation at 160 ∘ C for 5 min.e wool printed samples were �xed by steaming at 100 ∘ C for 10 min a�er �xation the printed samples were washed as follows.
(i) Washing with cold running water.
(iii) Rinsing with cold water.
At this end the printed fabrics were dried and assessed for color strength value (K/S) and over all fastness properties.e color difference and relative color strength % between chitosan/starch printed samples and control samples were also obtained using the following relationships.

Determination of Fastness
Properties. e treated samples were washed as per the conditions speci�ed in the test AATCC test method [14].e color fastness to rubbing, perspiration, and light was determined according to the AATCC test methods [15][16][17].

Results and Discussion
3.1.FTIR Spectra.e FTIR spectra of chitosan represent a characteristic band at 3424 cm 1 which is attributed to -NH 2 and -OH groups stretching vibration, the band for amide at 1654 cm 1 , and the aliphatic C-H stretching between 2921 and 2876 cm  1, When starch and chitosan are mixed, physical blends versus chemical interactions are re�ected by changes in characteristic spectra peaks In the typical spectrum of chitosan/starch composite �lm, the amino peak of chitosan shied from 1578 to 1584 cm 1 with the addition of starch).is result indicated that interactions were present between the hydroxyl groups of starch and the amino groups of chitosan [19,20].

3.2.
1 H-NMR Method.e chemical shi of methyl protons in acetamide group to appear at 2.07 ppm in acidic deuterium oxide solutions while the methyl group of glacial acetic acid appears at 2.12 ppm (e Aldrich Library of NMR Spectra).erefore, the peak around 2.1 ppm can be safely assigned to the methyl protons in the acetamide group, and that around 2.2 ppm is due to the methyl group in acetic acid moiety.e chemical shi is affected by solvent type, concentration and temperature, and taking these into account, one can explain the difference between the chemical shi value reported by Shen et al. [21], and those reported here.
In the obtained spectra, the difference in chemical shis between peaks at about 2.1 and 2.2 ppm is constant (about 0.15 ppm) within the experimental errors.e setting of TMS peak to be 0 ppm is sometimes slightly affected by operational and spectral variations, and for peaks with many "spikes" as in our case, the reproducibility might be lowered.erefore, it can be safely stated that the chemical shi for amide methyl protons can be set to 2.06 ppm and that for acetic acid moiety to 2.21 ppm.

X-Ray
Diffraction.X-ray diffraction (XRD) analysis was applied to detect the crystallinity of the isolated chitin and the obtained chitosan e structure of -chitin has been determined [22] using X-ray diffraction analysis, based on the intensity data from deproteinized lobster tendon.Least-squares re�nement shows that ad�acent chains have alternating sense (i.e., are antiparallel).In addition, there is a statistical distribution of side chain orientations, such that all the hydroxyl groups form hydrogen bonds.e unit cell is orthorhombic.
e chains form hydrogen bonded sheets linked by C=O⋯H---N bonds approximately parallel to the a-axis, and each chain has an O-3′---H⋯O.5 intramolecular hydrogen bond, similar to that in cellulose.e results indicate also that a statistical mixture of CH 2 OH orientations is present, equivalent to half oxygen on each residue, each forming interand intramolecular hydrogen bonds.As a result, the structure contains two types of amide groups, which differ in their hydrogen bonding, and account for the splitting of the amide I band in the infrared spectrum.e inability of this chitin polymorph to swell on soaking in water is explained by the extensive intermolecular hydrogen bonding.

Rheological
Properties. e rheological behavior of the printing paste plays one of the most important roles in the process of textile printing because it affects the amount of printing paste applied on the textile surface and consequently on the quality of the printed substrate.Hence, pastes of the aforementioned blends were prepared and the rheological properties of the pastes were monitored before and aer storing of the pastes for 24 h.e results obtained are shown in Figures 1 and 2.
e rheograms reveal that all the pastes under investigation display non-Newtonian pseudoplastic behavior since T 2: Effect of starch concentration on the apparent viscosity at various rate of shear for freshly prepared pastes.the ascending and descending rheograms are coincident.is reveals the homogeneity of the molecular structure of the pastes which are amenable to rebuild themselves and retain their original state immediately aer removal of the acting force, thereby exhibiting pseudoplastic behavior.Figure 1 shows that, the location of the rheograms with respect to the rate of shear axis depends on the nature of the thickening agent used.As the concentration of starch increases the rheogram is located far from the rate of shear axis indicating an increase in the apparent viscosity.

Rate of shear (sec
Figure 2 represents the rheograms of the aforementioned pastes aer storing for 24 h.It is clear from the rheograms that storing has practically no effect on the rheological characteristics of these pastes where each of these pastes remains exhibiting non-Newtonian pseudoplastic behavior aer storing.
e apparent viscosity at various rate of shear of the aforementioned pastes was calculated from the values of rate of shear.e results obtained are given in Tables 2 and 3.It is clear that the storing for 24 h does not affect so much the appearing viscosity of the prepared pastes.

Color Strength and Related
Parameters.Chitosan has been proved to increase the rate of dye uptake and dye exhaustion of wool fabrics in the case of acid, reactive dyes and natural dye as henna [5,23,24].However, combination of starch with chitosan to be used as thickening agent in textile printing has not been investigated so far.erefore it has been taken up in the present study with natural dye.ickeners act as a vehicle for the dye and during the �xation the dye transferred into the fabric then the thickener is washed off completely from the fabric.K/S value is directly proportional to the amount of dye present in the material and it can be used to evaluate the efficiency of new thickeners.e K/S values and the relative color strength % of Curcuma tinctoria printed samples are given in Table 4.
It is clear from Table 4, that the K/S and the relative color strength % values of all the printed samples using starch/chitosan thickeners are higher than that of the standard samples.ese results further affirm that chitosan increases the amount of Curcuma tinctoria uptake.is holds true in all printed samples despite the nature of fabric used and the % of starch in the thickener.
It is known that all natural dye have low affinity to synthetic fabrics and this was one of its drawback especially with the increase in production of synthetic fabrics and their blends.e K/S values of the printed synthetic fabrics and their blends reveal that the presence of this ratio of chitosan in the new thickeners has overcome this problem.Cotton/polyester printed samples achieved the highest relative color % 598, where the K/S increases from 1.91 to 11.42 using 4% starch/chitosan thickener.e K/S of others synthetic printed fabrics (polyester and polyamide) increase from 0.98 to 5.12 and from 1.44 to 7.94 with relative color strength % 523 and 551, respectively, using 5% starch/chitosan thickener.For natural fabric as wool the highest K/S was achieved by using 3% starch/chitosan blend.ese results refer that the highest K/S values have been achieved at different blends although the ratio of chitosan is constant, this may be due to the nature of the fabrics and the thickener viscosity.
To evaluate the color parameter and the color difference of printed fabrics with highest K/S value, CIE Lab system is used.Where L refers to lightness-darkness values from 100 to 0 representing white to black, values run from negative (green) to positive (red) and  values run from negative (blue) to positive (yellow), and the total color difference is given by Δ.
It can be seen from Table 5 that the L values decrease in all the printed samples indicating that the sample becomes darker compared to that of the control sample.As seen from a and b values that the color hue changes to reddish yellow.e color difference (Δ) values are also given in Table 5 and it can be clearly seen that there is a signi�cant color difference between the samples and the control samples though the dye concentration is constant.e chroma is calculated as ( 2 +  2 ) 1/2 as the chromaticity increases, a color becomes more intense; as it decreases a color becomes dull and this is clear from Table 5 that the chroma of sample (C  ) increased.

Determination of Fastness Properties and Surface Roughness.
It is clear from the data of Table 6 that with this new thickeners natural dye could print all kinds of fabrics under investigation with very good to excellent color fastness to rubbing, washing or perspiration.e notice of improvement is in the light fastness.e surface properties of the antistatic-treated fabrics are very important because these fabrics are used mainly for garments in direct contact with human skin, that surface roughness has strong effect on the wearer comfort.Surface roughness results of cotton, polyester, polyamide, and blend fabrics are given in Table 6.e results showed the same or slight increase in the surface roughness of the using chitosan/starch blend compared with the standard.

Antimicrobial Activity of Treated Fabrics.
Early research describing the antimicrobial potential of chitin, chitosan, and their derivatives dated from the 1980-1990s [25].Generally, recent data in the literature has the tendency to characterize chitosan as bacteriostatic rather than bactericidal.
Table 7 shows that the printed fabrics using chitosanstarch blend exhibit antimicrobial characteristics compared with the control sample.

Conclusion
Chitosan, which is a very useful nontoxic biopolymer, can be used as an effective antimicrobial �nish and can also be used to increase the dye uptake of the fabrics.e new blends have de�nite rheological properties under varying shear stress during the entire printing process.
e addition of chitosan to gelatinous starch has twofold effects: nature dye has successfully printed all fabric with increase in the color strength and related parameters of the printed fabrics, and the other is that it produces antimicrobial fabrics.e fastness properties of these fabrics are good against washing, light and perspiration.us, a nontoxic, ecofriendly, multifunctional �nish has been developed for using natural dye in printing all fabrics.