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Carbohydrate Polymers 131 (2015) 168–176

Contents lists available at ScienceDirect

Carbohydrate Polymers

j ourna l ho me pa g e: www.elsev ier .com/ locate /carbpol

odification of cotton fabric with a dendrimer to improvenk-jet printing process

tasheh Soleimani-Gorgania,∗, Farhood Najafib, Zohreh Karamic

Department of Printing Science and Technology, Institute for Color Science and Technology, PO BOX 16765654, Tehran, IranDepartment of Resin and Additives, Institute for Color Science and Technology, PO BOX 16765654, Tehran, IranDepartment of Printing Science and Technology, Institute for Color Science and Technology, PO BOX 16765654, Tehran, Iran

r t i c l e i n f o

rticle history:eceived 25 October 2014eceived in revised form 15 April 2015ccepted 18 April 2015vailable online 2 June 2015

eywords:

a b s t r a c t

In this study, the cotton fabrics were modified with different polyamidoamine (PAMAM) dendrimerconcentrations to yield antimicrobial and efficient polymeric materials for ink-jet printing. PAMAM den-drimer has been covalently grafted on cotton fabric via the reaction of cellulosate anion with the cynuricchloride. The obtained modified cotton fabrics were characterized by FTIR and TGA. The morphology andyellowness of modified cotton fabrics were analysed by SEM and UV spectroscopy. The ink-jet printingonto modified cotton fabrics were evaluated at different pHs. The results at optimum pH indicated that by

eactive dyeotton

nk-jetrintingendrimerntimicrobial

increasing the PAMAM dendrimer concentration in modified cotton fabric not only the colour strength ofreactive ink-jet printed fabric increased but also the antimicrobial cotton fabric produced. A comparisionbetween printing modified and unmodified cottons suggest that the PAMAM dendrimer has the potentialfor using in single-phase ink-jet printing. The yielded prints demonstrate excellent colour fastness forwashing and dry/wet crocking properties.

© 2015 Elsevier Ltd. All rights reserved.

. Introduction

In the near future, it is expected that the traditional flat or rotarycreen printing and roller printing techniques were supersededy digital printing technologies, which have found an increas-

ng number of applications in printing textile (Chapman, 2002;ckman, 2004; Ervine, Siegel, & Siemensmeyer, 2000; Gupta, 2001;iemensmeryer, Siegel, Ervine, & Bullock, 1999; Stefanini, 1995;jiie, 2006).

Cotton fabric can be printed on with reactive dye based inksAston, Provost, & Masselink, 1993; Kumbasar & Bide, 2000;etrinic, Andersen, Sostar-Turk, & Le Marechal, 2007). Commer-ial ink-jet reactive inks are based on dyes with low to moderatexation properties. Therefore, maximizing the dye fixation forconomic and environmental reasons is considered to be verymportant. Generally, reactive dyes are applied to cellulosic fabricsn the presence of an alkali to promote the fixation of the dye to the

abric through covalent bond formation via the reaction of the cellu-osate anions with the reactive groups of the reactive dye molecule.n ink-jet printing, none of the conventional printing chemicals,

∗ Corresponding author. Tel.: +98 2296977; fax: +98 22947537.E-mail addresses: asoleimani@icrc.ac.ir, atashehs@yahoo.co.uk

A. Soleimani-Gorgani), fnajafi@icrc.ac.ir (F. Najafi), z.karami@ut.ac.ir (Z. Karami).

ttp://dx.doi.org/10.1016/j.carbpol.2015.04.031144-8617/© 2015 Elsevier Ltd. All rights reserved.

such as alkali, urea and thickener can be directly incorporated intothe ink formulations (Fan, Kim, Lewis, & Perruzi, 2003). If reactivedyes based ink formulations incorporate an alkali, then not onlythe ink can cause corrosion of the print head nozzle, but also wouldhave an extremely limited storage life, as the dye rapidly hydrolyzesto a non-reactive form leaving behind a precipitate that will blockthe nozzle. In order to prevent dye hydrolysis, a stable ink formulacontaining purely dye should be prepared and applied to cottonsubstrates that have been pre-treated prior to ink-jet printing witha print paste, which contains an alkali, urea and thickener (Hauser,2011; Walters, Santillo, & Johnston, 2005).

Application of the pre-treatment process is felt to be disad-vantageous in practice, because the pre-treatment process is envi-ronmentally unfriendly, energy-intensive and time-consuming. Inaddition, the print pastes have a short shelf life due to their pH.

Previous studies have detailed the increase of reactive ink fixa-tion through the modification of reactive dyes (Li & Tincher, 1999),fabrics (Eltz, Schrell, & Russ, 1994; Hutter & Matzinger, 2000;Kaimouz, Wardman, & Christie, 2010; Kanik & Hauser, 2003; Zhang,Westland, Cheung, Burkinshaw, & Blackburn, 2009) and ink for-mulation (Soleimani-Gorgani & Shakib, 2013), as well as the use of

fixation-enhancing chemicals in the pre-treatment process. (Yuen,Ku, Choi, & Kan, 2008).

Although, the modification of cotton fabric was used to improvethe printability back in last century, however, in recent years, the

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hemical modification offers a possibility to enhance ink fixationnd allowing the printing process to be carried out through theeduction of the chemical amount and energy consumed (Ahmed,005; Abo Farha, Gamal, Sallam, Mahmoud, & Ismail, 2010; Prabu

Sundrarajan, 2002).Recently, some dendrimers have been used as exhausting and

xing agent for dyeing cotton with reactive dye to improve the fix-tion of dye, which offered the potential of lowering costs throughhe reduction of the chemical amount and energy consumed.

Polyamidoamine (PAMAM) dendrimers are water-soluble, non-mmunogenic, biocompatible compounds (Cheng, Ma, & Xu, 2008;oseita & Tomalia, 2001; Winnicka, Bielawski, Rusak, & Bielawska,009) and their highly-branched nature could provide enormousurface area that generates great reactivity to cynuric chloride.

Basically, in commercial anionic reactive dye (Procion Red H-3B), the sulphonate group is anionic, which causes electrostaticepulsion with anionic cellulose groups. Therefore, modificationf cotton fabrics with amino groups of PAMAM dendrimer mayecrease the negative charge build-up on the fibre surface, therebyssisting the absorption of the dye onto the fabric. Under these con-itions, the electrostatic repulsion between dye and fibre would beinimized and the available nucleophilic groups (cellulose anions

nd amino groups) will be reactive towards electrophilic reactiveroups.

The aim of this work was to determine, whether the modifi-ation of cotton fabric with a PAMAM dendrimer could enhancehe printability of the fabric with reactive dye based ink. For thisurpose the functional groups of PAMAM dendrimer contained pri-ary amino groups were used because, as mentioned above, such

unctional groups could theoretically be able to react with reactiveroups under neutral pH conditions.

. Experimental

.1. Materials

The fabric used was 100% singed, desized, scoured and bleachedotton plain weave fabric (98 g/m2), which was supplied by theroojerd Textile Company, Iran. Sodium alginate, sodium carbon-te and cyanuric chloride at the highest purity were provided byigma-Aldrich Company, USA. The PAMAM G2 dendrimer used was

derivative of Polyamidoamine (Fig. 1); the preparation of the den-rimer is described in the literature (Esfand & Tomalia, 2001). Theye (Procion Red H-E3B) used for printing cotton was kindly pro-ided by DyStar Company, Germany (Fig. 2). A non-ionic detergent,ynperonic BD 100, Univar, UK, was used in the wash-off pro-ess. Other chemicals used were received from Merck Company,ermany.

.2. Equipment and instrumentation

A laboratory padder (Kimia Behris Company, Tehran, Iran) waspplied to the pre-treatment solutions onto the fabrics, after whichhey were then dried in an Ecocell oven (Munich, Germany).he prepared ink was filtered through 0.45 and 0.2 �m Sartoriusinisart filter (Göttingen, Germany). The modified and unmodi-

ed cotton fabrics were ink-jet printed using a HP DeskJet 5150rinter. Fixation was performed using a laboratory steamer sup-lied by Kimia Behris Company, operating in the atmosphericressure. The dye concentration in the washing baths was deter-ined by absorbance measurements at �max using UV Ikon 923

ouble Beam UV/Visible spectrometer (Saint-Quentin-Yvelines,rance). The reflectance measurements of the prints were deter-ined using a GretagMacbeth Spectrophotometer ColorEye7000A

New York, USA) with d/8 measurement geometry under the

te Polymers 131 (2015) 168–176 169

following conditions: measurement wavelength range from 400 to700 nm, measurement area of 10 mm in diameter, and the spec-ular component included (SCI) measurement mode. The CIELABvalues were computed under D65 illuminant and SCI 1964 (10)standard observer. The Fourier transformed infrared spectroscopyin attenuated total reflection mode (ATR-FTIR) spectrums of unmo-dified and modified samples were recorded on Bruker (IFS-48)(Bruker Optik GmbH, Germany), in the range 400–4000 cm−1.The pH, surface tension and viscosity of inks were characterizedusing 827 pH Metrohm meters (Herisau/ Switzerland), TensiometerK100MK2 (Hamburg, Germany) and Brookfield DVII (New Jersey,USA), respectively. The colour fastness to light and washing ofthe ink-jet printed fabrics were determined by AATCC Test Meth-ods 16-2001 and AATCC Test Method 61-2001. The yellownessindex was defined by ASTME313 method in which the multiplesamples were measured and the readings averaged were used.The antimicrobial test of modified and unmodified cotton fabricswas evaluated using a quantitative antimicrobial test accord-ing to AATCC100-2004. Thermal behaviours of the unmodifiedand modified samples were analysed by using Thermo Gravime-try/Differential Thermal Analyzer (Seiko Exstar 6000, TG/DTA 6100)in a nitrogen atmosphere at a heating rate of 10 ◦C/min. The sur-face morphology of the unmodified and modified cotton sampleswas determined through the use of a Scanning Electron Microscope(SEM).

2.3. Preparation of modified cotton fabrics

The modification was occurred by the route depicted in Fig. 3.In this procedure, the cyanuric chloride was used for the cova-

lent grafting of dendrimer on cotton fabrics. PolyamidoaminePAMAM G2 dendrimer, which was synthesized according to clas-sical methods (Esfand and Tomalia, 2001), used as a nucleophileagent to react with cyanuric chloride. A suspension of freshly cya-nuric chloride (4 mg, 1.2 equiv) in acetone (20 ml), which wascooled in an ice bath was added dropwise with stirring into a solu-tion of polyamidoamine PAMAM G2 dendrimer (5%, 10% and 15%omf), at below 5 ◦C and pH 4.5–5. After 30 min, at 0 ◦C and pH 5, themixture was stirred for 15 min at 25 ◦C, controlling by TLC to yieldPAMAM-triazine derivatives in solution. The product was essen-tially homogenous as judged by TLC. Then, cotton fabric (3.5-3.5 cm,0.27 g), previously soaked in 100 mL of 0.5 M NaOH during 24 h, wasintroduced and the temperature was raised to 30–40 ◦C with stir-ring at 5.5–6 for 2 h. When the reaction was complete, the solutionwas allowed to stand at 80 ◦C and pH 5 for 24 h under reflux andstirring. The modified cotton was collected and thoroughly washedwith acetone (100 ml), water (100 ml) and methanol (100 ml). Todetermine the optimum application of PAMAM, a series of modi-fied fabric samples 2, 3 and 4 were obtained with 5%, 10% and 15%omf, respectively.

2.4. Fabric pre-treatment

The pre-treatment paste was prepared using 150 g sodium algi-nate made from a stock sodium alginate solution, which was madeready by dissolving sodium alginate (50 g) in de-ionized water(0.95 dm3), sodium bicarbonate (8 g) and urea (10 g). Then, thepaste was made up to a weight of 200 g with de-ionized water(Ahmed, 2005; Fan et al., 2003; Yuen, Ku, Choi, & Kan, 2004a, 2004b)which was subsequently mixed thoroughly. The pre-treatmentwas padded onto the cotton fabric using a padding machine with

an even pressure of 2.6 kg/m2 and a constant padding speed of2.5 r/min until a pick-up of 80% was achieved. The pre-treated fab-rics were dried in an oven at 80 ◦C, and then conditioned beforeink-jet printing.

170 A. Soleimani-Gorgani et al. / Carbohydrate Polymers 131 (2015) 168–176

re of

2

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Fig. 1. Chemical structu

.5. Ink-jet printing

The ink-jet printing was carried out on a Hewlett Packard

HP) thermal ink-jet printer (HP DeskJet 5150) at 1200dpi as aolid square pattern, to allow easy colour measurement, using thenk formulations containing 100 g/dm3 reactive dye, 300 g/dm3

-methyl morpholine n-oxide, 20 g/dm3 2-pyrrolidone and

Fig. 2. The structure of P

G2PAMAM dendrimer.

25 g/dm3 propan-2-ol. The ink was made up to 1 dm3 with de-ionized water. Printing was carried out at four different pH values(5, 6, 7 and 8) using McIlvaine buffers, as shown in Table 1 (Vogel,

1944). The anionic reactive dyes used in this study were Pro-cion Red H-E3B. The prepared ink was filtered through a 0.45 �mfilter, and then through 0.2 �m filter to prevent clogging the noz-zles before pouring to the cartridge. In the preparation process for

rocion Red H-E3B.

A. Soleimani-Gorgani et al. / Carbohydrate Polymers 131 (2015) 168–176 171

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nk-jet printing of cotton, firstly a new cartridge was unfilled bypening and washing, and then it was loaded with ink formulation.ubsequently, the filled cartridge was placed into the printer. Theubstrate was a piece of cotton glued to paper, which was cut to aize just slightly smaller than the paper to provide a substrate withniform edges.

The viscosity values for the ink-jet inks were between 2 and 2.8ps, which are in the acceptable range for textile ink-jet printingnks (Daplyn & Lin, 2003). The surface tension values of the formu-ated inks were in the range of 28–31 m−1, which are also within thealues of typical commercial ink-jet inks for textile printing (Kang,991).

After printing, the fabrics were air-dried and put into a steamer.ll the printed fabrics were treated with superheated steam at10 ◦C for 10 min for colour fixation (Kaimouz et al., 2010; Yuent al., 2004a). The steamed fabric samples were washed with coldater and subsequently washed again in 10 g/dm3 of non-ionicetergent (Synperonic BD) at 60 ◦C for 10 min until all the un-eacted dyes and other chemicals were removed from the fabricurface (Yuen et al., 2004a).

.6. Determination of absorbed dye fixation

Evaluation of percentage of absorbed dye fixation from the ink-et printing technique used a methodology adapted from previouslystablished procedures for textile dyeing with reactive dyes (Bone,e, Philips, & Taylor, 2008; Kaimouz et al., 2010; Morris, Leuis,

Broadbent, 2008). Two equal square pattern printed fabrics of.5 cm × 3.5 cm at 1200 dpi were used to determine the percent-ge of fixation; one was printed with the reactive ink on a 100%olyester fabric and the other was printed with reactive ink on aotton fabric. To obtain the total amount of the dye printed on theabric, the printed polyester fabric with reactive ink was washed off

mmediately after printing and the wash-off solution was diluted

ith de-ionized water to 0.5 dm3. The printed cotton fabric witheactive ink was used for steaming followed by washing to obtainhe amount of the dye washed-off after the fixation process, and the

able 1omposition of McIlvaine Buffers in a total volume of 80 cm3.

pH 0.1 M citric acid (cm3) 0.2 M Na2HPO4 (cm3)

2 1.6 78.44 30.9 49.16 50.6 29.48 77.8 2.2

bric with PAMAM dendrimer.

wash-off solution was diluted with de-ionized water to 0.5 dm3.The percentage of absorbed dye fixation was determined accord-ing to Eq. (1), in which A0 is the absorbance of the printed dyesolution, A1 is the absorbance of the first wash-off solution and A2is the absorbance of the soaping liquor, which was diluted withde-ionized water to 0.5 dm3, at the wavelength of the maximumabsorption (�max).

Eq. (1).The percentage of absorbed dye fixation

%F = A0 − A1 − A2

A0

2.7. Antimicrobial activity of modified cotton

Antimicrobial effectiveness of modified cotton fabric was eval-uated using a quantitative antimicrobial test according to AATCC100-2004. The Escherichia coli (ATCC11229, Gram negative) wasused as a test microorganism which can be cultured and handledin a standard laboratory with a minimal health risk. Fabric sam-ples were contacted with 1 mL of bacterial inocula in a glass vessel.The inocula was a nutrient broth culture containing about 4 × 105

colony forming units (cfu)/mL of bacteria. The samples were con-tacted with the bacteria for 24 h and then 100 mL of distilled waterwas poured into vessel and vigorously shaken. The solution wasdiluted to one-tenth of the previous concentration and then 10 mLof each dilution stated on a nutrient agar and incubated for 24 hat 37 ◦C. To evaluate antimicrobial activities of the samples, thereduction in colony number between the modified and unmodifiedfabrics after incubation was compared. The percentage reductionof bacteria (R%) is calculated by Eq. (2), where N1 and N2 are theaverage numbers of bacteria recovered from the unmodified andmodified cotton fabrics, respectively.

Eq. (2).The percentage reduction of bacteria

%R = (N1 − N2)N1

× 100

3. Results and discussion

3.1. Synthesis of PAMAM-grafted cotton fabric

In a first step, PAMAM dendrimers were reacted with cya-nuric chloride at 0 ◦C, which allows substitution of a first triazine

172 A. Soleimani-Gorgani et al. / Carbohydrate Polymers 131 (2015) 168–176

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Fig. 4. ATR-FTIR of modi

hlorine atom with the amino function conducing to PAMAM-riazine derivatives (Fig. 3). From these intermediates, a highlyeactive and not isolated PAMAM-triazine link has been character-zed after the complete substitution of chlorine atom with the use ofAMAM dendrimer. Then, alkali treated cotton fabrics (3.5-3.5 cmurface) were introduced into the PAMAM-triazine reaction mix-ure as described in Section 2.3. Grafting reactions were followed byashing cycles in order to remove unbounded PAMAM dendrimer.fter drying at 100 ◦C, the resulting modified cotton samples wererinted with the reactive dye based ink.

.1.1. FTIR spectroscopy

To characterize the covalent link between cotton fabric and

AMAM dendrimer, modified cottons have been analysed by FTIR.PAMAMA-Cotton presented the bands at 3200–3600 cm−1 char-

cteristic to NH2 group, N H signals at 3076 cm−1, amide I at

Fig. 5. The thermograms analysis of mod

tton fabrics (2, 3 and 4).

1641 cm−1 (Fig. 4). FTIR analysis allowed us to better understandthe chemical structure and to show the existence of a covalent linkbetween the PAMAM dendrimer and cellulosic cotton surface.

The characteristic signals strength increased by increasing theamount of PAMAM dendrimer in the modified cotton fabric.

3.1.2. Thermogravimetric analysisThermogravimetric analysis (TGA) was used to investigate the

thermal properties of the modified cotton fabrics. TGA thermo-grams of the modified cotton fabrics are presented in comparisonwith unmodified cotton fabrics in Fig. 5. Initial weight loss wasattributed to loss of water of each sample (dehydration phe-

nomenon), which follows the order of 1>2>3>4. At much highertemperatures, modified cotton fabrics showed better thermal sta-bility than unmodified cotton fabric as a significant weight losswas observed at temperature 339 ◦C for unmodified cotton fabric

ified and unmodified cotton fabric.

A. Soleimani-Gorgani et al. / Carbohydrate Polymers 131 (2015) 168–176 173

F on fabrics with 5% PAMAM dendrimer (2), 10% PAMAM dendrimer (3), and 15% PAMAMd

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Table 2Yellowness Index of modified and unmodified cotton fabrics.

Yellowness index Sample

15.8 1

measured by using the quantitative method of counting micro-bial colony forming units of the used microorganism. Results arereported in Table 3. The results show that all samples have excellentantimicrobial properties.

Table 3Antimicrobial test results of the applied microorganism.

Sample R% (E. Coli)

ig. 6. SEM images (30 �m scale) of unmodified cotton fabric (1) and modified cottendrimer (4).

sample 1), and at temperatures 342.8 ◦C, 343.5 ◦C and 343.6 ◦C forodified cotton fabrics (samples 2, 3 and 4). The lower thermal sta-

ility of unmodified cotton fabrics in comparison to modified cottonabric was due to lower decomposition of modified cotton fabrics.y increasing the amount of PAMAM dendrimer in the modifiedotton fabric, the thermal stability slightly increased. TGA analy-es show that the change of thermal properties correlated with theovalently modified cotton surface.

.1.3. Scanning electron microscopyThe surface of unmodified cotton and PAMAM-grafted cot-

on was examined by scanning electron microscopy (SEM). SEMmages are presented in Fig. 6. The images did not show any de-tructuration of cotton fibres (similar diameter and structure).hese observations indicated that PAMAM grafting did not affectbre morphology; no destruction was observed. SEM results showhat cotton fibre structures are resistant to chemical treatment.

.1.4. Yellowness indexYellowness is considered to be associated with scorching, soiling

nd product degradation by exposure to light or chemical etc. Thus,ellowness index, which is defined by ASTM E313, can be used to

ndicate colour degradation after modification by making compar-son between the unmodified specimen and modified specimens.he Yellowness index results of modified and unmodified cottonabrics are shown in Table 2.

17.3 218.9 320.1 4

It is evident from the results that an increase in PAMAMdendrimer concentration faintly increased the yellowing of themodified cotton fabrics, which can be negligible.

3.1.5. Antimicrobial activity of modified cottonThe antimicrobial activity of the modified cotton fabric was

1 02 99.963 99.994 99.99

174 A. Soleimani-Gorgani et al. / Carbohydrate Polymers 131 (2015) 168–176

d cotton fabrics in the presence of water.

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Table 5Absorbed dye presentage (%F) of unmodified and modified cotton fabric at optimumpH and pre-treated cotton fabrics with reactive dye based ink.

Fabric %F

Fig. 7. The unmodified and modifie

In contrast, the unmodified cotton fabric did not show anyntimicrobial activity at all.

PAMAM dendrimers are biocompatible compounds and theirighly-branched nature could provide enormous surface area thatenerates great reactivity to microorganisms. Amino-terminatedroups in PAMAM dendrimer possess the strongest antimicrobialctivity. It is generally assumed that protonated amino groups onAMAM dendrimer promote the disruption of anionic bacterial cellembranes through electrostatic interactions and they are neces-

ary for the rupture of the lipids, although other interactions mightlso occur (Calabretta, Kumar, McDermott, & Cai, 2007; Wang et al.,010; Xue et al., 2013).

.2. Effect of pH on printing performance

According to the equilibrium shown in Fig. 7, in the presence ofater, depending on the pH within the fibre, the unmodified andodified cottons will be ionized to a lesser or greater degree.When the pH of the ink was raised, the ionization of cellu-

ose to the cellulosate anion and quaternary cation ammonium tohe amine in modified cotton fabric increased, thus increasing the

hance of reaction with cellulose over the competitive hydrolysiseaction of the reactive dye. Consequently, pH is a key parametern influencing the level of fixation of the reactive dye based inkn modified cotton fabric. It was thus necessary to determine the

able 4ercentage of absorbed dye (%F) on printing of unmodified and modified cottonabrics with the reactive dye based ink at different pH.

pH Modified cotton fabrics %F

5 1 40.836 1 46.867 1 47.338 1 49.125 2 44.016 2 49.677 2 52.898 2 54.425 3 47.856 3 54.757 3 56.668 3 59.925 4 48.296 4 56.787 4 58.608 4 60.03

Pre-treated cotton fabric 67Unmodified cotton fabric at optimum pH 49Modified cotton fabric (sample 4 at optimum pH) 60

optimum pH for each ink type in order to achieve optimum dye fix-ation. A series of prints at different pHs was evaluated to determinethe optimum application pH. The reactive dyes were hydrolysed atpH higher than 8 and might be damage to the print-head and car-tridge. Therefore, buffers of pH 5, 6, 7 and 8 were made as describedin Section 2.5 and reactive dye inks were used to print onto unmo-dified, modified and pre-treated cotton fabrics. The results depictedin Table 4, indicate an increase in percentage of absorbed dye withincreasing pH. Therefore, the reactive dye based inks fix more effi-ciently on cotton fabrics at pH 8.

The effectively of the added dendrimer in improving the dyeingprocess can be explained in terms of the pH-behaviour of the con-stituent amine groups. At low pH, the primary and tertiary aminegroups of the dendrimer are protonated (Prabu and Sundrarajan,2002). The ensuing local high positive charge density should act as aprimary point of attraction for the anionic dye molecules. When thepH is increased, the amines are deprotonated and the liberated pri-mary amine groups can serve as highly reactive nucleophilic sitesfor the dyes.

3.3. Effect of chemical modification of cotton fabrics on absorbeddye fixation

The results in Table 5 show that the degree of dye fixation on themodified cotton fabric at optimum pH is as high as those achievedwith printing ink on the pre-treated cotton fabric.

Table 6The colourimetric data for printed modified and unmodified cotton fabrics withreactive ink at optimum pH under D65 illuminant and CIE1964 (10o) standardobserver.

No L* a* b* C* h

1 36.80 42.30 −11.4 43.80 344.942 35.85 43.98 −1.21 44.98 356.723 33.24 48.38 3.40 48.52 357.044 32.91 50.28 4.62 50.49 358.25Pre-treated fabric 32.08 39.34 −8.58 43.51 334.71

A. Soleimani-Gorgani et al. / Carbohydrate Polymers 131 (2015) 168–176 175

Table 7Colour fastness (light, washing) properties of the printed cotton fabrics.

Sample Light Washing (staining on multi-fibre fabric)

Wool Cotton Acetate Nylon Acrylic Polyester Change

1 4 5 5 5 5 5 5 4–52 3–4 4–5 5 5 5 4–5 5 4–5

5

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4 1–2 4 5

Pre-treated fabric 4 5 5

To justify the fixation improvement, following theory could beuggested. At optimum pH condition (pH = 8), essentially the num-ers of cellulosate anion groups are increased; these are highlyucleophilic and reactive towards electrophilic reactive groups. Onhe other hand, at this high pH all the sulphonic acid groups in theommercial anionic reactive dye (Procion Red H-E3B) will be de-rotonated and hence anionic, which caused electrostatic repulsionith anionic cellulosate groups. Modification of cotton fabrics with

AMAM dendrimer may decrease negative charge build-up at thebre surface, thereby assisting absorption of dye onto the fabric.nder these conditions, the electrostatic repulsion between dyend fibre would be minimized and the available nucleophilic groupscellulosate anions and amino groups) will be reactive towardslectrophilic reactive groups.

The results in Table 4 show that as the concentrations of PAMAMendrimer are increased, the percentage of absorbed dye will be

ncreased, which may be due to reduction of electrostatic repul-ion between dye and fibre. Therefore, the high percentage of inkxation on printed modified cotton fabric is attaining by increas-

ng the concentration of PAMAM dendrimer parallel to raising pHn ink formulation.

.4. Effect of chemical modification of cotton fabrics onolorimetric properties

Table 6 shows the colorimetric data of unmodified cotton fab-ic, which had been printed with reactive ink at optimum pH. Therinted modified cotton samples with reactive ink at optimum pHave a darker shade (lower L* value) and higher chroma value (C*)han the others. This shows that the degree of dye fixation, in casef modified cotton fabrics is higher than unmodified cotton fab-ic. The hue values of all printed modified and unmodified cottonabrics are similar. The ranges of hue angle are 356.72–358.25.

.5. Effect of chemical modification of cotton fabrics on colourastness properties

Colour fastness properties, which are determined by the sta-ility of the dye-fibre system, present an interesting property foruality printing in terms of practicality. For the evaluation of colourastness properties of the printed samples, colour fastness to lightnd to wash at 60 ◦C was determined. As seen from the results inable 7, there were slight changes exhibited in the shade

of the printed samples and at the same time no staining on thecetate, cotton, nylon and polyester was observed in case of wash-ng at 60 ◦C. Acrylic and wool has little staining. The light fastnessf the printed modified cotton fabrics was decreased, finding exacteason may need more studies. Thus, colour fastness properties ofll printed modified samples show excellent dye-fibre stability ando decrease in the quality is observed.

. Conclusion

Cotton fabrics can be pre-treated with aqueous liquor contain-ng an alkali, urea and a thickening agent via a pad dry process

5 4–5 5 4–55 4–5 5 45 4–5 5 4–5

to yield a suitable substrate for subsequent ink-jet printing withreactive dye based inks. By grafting the biocompatible PAMAMdendrimer with the cotton fabric, the printed modified cotton fab-rics offer the higher level of reactive dye fixation than the printedunmodified cotton fabric. Thus, the modification of cotton fab-rics with the PAMAM dendrimer might remove the pre-treatment,which is environmental unfriendly process. The high percentageof ink fixation to printed modified cotton fabric is attaining byincreasing the concentration of PAMAM dendrimer parallel to rais-ing pH in ink formulation. It was readily demonstrated that highpercentages of fixation attained with the modified cotton fabric thatpossesses amino groups would support that the negative chargebuild up on the fabric surface decreased and the electrostatic repul-sion between dye and fibre would be minimized. PAMAM andthe available nucleophilic groups will be reactive toward the elec-trophilic reactive groups. By increasing the amount of PAMAMdendrimer in the modified cotton fabric, the thermal stabilityincreased and the yellowing of the modified fabric faintly increased.The yielded prints not only demonstrate excellent colour fastness towashing and dry/wet crocking properties but also produce antimi-crobial cotton fabrics. A comparasion between printing modifiedand unmodified cottons suggests that the PAMAM dendrimer hasthe potential for using in single-phase ink-jet printing.

Acknowledgement

This work was done as a research project in Institute for ColorScience and Technology, by financial support of INSF (Iran NationalScience Foundation) (91003295).

Appendix A. Supplementary data

Supplementary data associated with this article can be found, inthe online version, at http://dx.doi.org/10.1016/j.carbpol.2015.04.031

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