Improvement of dyeing and antimicrobial properties of nylon fabrics modified using chitosan-poly(propylene imine) dendreimer hybrid

Accepted Manuscript Title: Improvement of dyeing and antimicrobial properties of nylon fabrics modified using chitosan-poly (propylene imine) dendreimer hybrid Author: Mousa Sadeghi-Kiakhani Siyamak Safapour PII: DOI: Reference:

S1226-086X(15)00443-8 http://dx.doi.org/doi:10.1016/j.jiec.2015.09.034 JIEC 2667

To appear in: Received date: Revised date: Accepted date:

14-3-2015 7-9-2015 25-9-2015

Please cite this article as: M. Sadeghi-Kiakhani, S. Safapour, Improvement of dyeing and antimicrobial properties of nylon fabrics modified using chitosan-poly (propylene imine) dendreimer hybrid, Journal of Industrial and Engineering Chemistry (2015), http://dx.doi.org/10.1016/j.jiec.2015.09.034 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Highlights  The effect of CS-PPI on the dyeability of nylon fabrics was studied.

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 Two reactive dyes were applied to investigate the dyeability of nylon fabrics.  The dyeing property of CS-PPI grafted nylon fabrics was increased.

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 Fastness properties of the dyed nylon fabrics have also been discussed.

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 The antimicrobial property of CS-PPI grafted nylon fabrics was improved.

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Improvement of dyeing and antimicrobial properties of nylon fabrics modified using chitosan-poly (propylene imine) dendreimer hybrid

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Mousa Sadeghi-Kiakhani1*, Siyamak Safapour2 1. Institute for Color Science and Technology, Department of Organic Colorants, Tehran, Iran.

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2. Faculty of Carpet, Tabriz Islamic Art University, P.O. BOX 51385-4567, Tabriz, Iran.

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Corresponding author: Tel: +98 21 22969774; fax: +98 21 22969774; E-mail: [email protected]

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Abstract

Nylon fabric surface modification using chitosan-poly(propylene imine) dendreimer hybrid (CS-

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PPI) as a novel eco-friendly finishing agent has been reported. Effects of some operational

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parameters such as pH, temperature, time and CS-PPI concentration on grafting yield were examined through dye up-take using two commercial reactive dyes in terms of color strength

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(K/S). FTIR, SEM, and DSC data confirmed the grafting of CS-PPI onto nylon substrate. Optimal grafting values obtained were pH 4, temperature 60 °C, time 6 h and 2.5 g/L CS-PPI concentration. The performance of CS-PPI grafted nylon was investigated in terms of its dyeability, color fastness, and antimicrobial properties. Keywords: Chitosan; Dendreimer; Dyeing; Nylon fabrics; Reactive dyes.

1. Introduction A wide range of dyes are nowadays available in the market for dyeing of nylon (polyamide) textiles and among them acid, metal complex and reactive dyes are being extensively used [1, 2].

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All these dye are anionic which can be absorbed by cationic sites (amino groups) of nylon polymer chains. Some advantages of reactive dyes over other dye classes are their brilliancy, high wet fastness, convenient usage, wide range of hues, and high applicability. However, there

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are some challenges with the use of these dye which limit their application. Reactive dyes need almost a large amount of electrolyte as auxiliary agents in dyeing, demonstrate low dyeing

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ability, and generate high volume of discharged wastewater [3-5]. In addition, color yield of

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reactive dyes is generally low, depending on the different natures of the both dye and textile materials used. In general, 40-50% of the reactive dyes remain unexhausted in dye bath after

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dyeing [6, 7]. The discharge of such colored textile wastewater into the environment has therefore generated serious environmental and ecological problems [8].

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Considering nylon textiles as target material for dyeing, on the other hand, the number of

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terminal amine groups as dye absorbing sites on nylon is restricted, and therefore, heavy shades

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can be hardly obtained [9]. The improvement of dyeing ability of nylon textiles with reactive dyes has been investigated by some researchers [10-19]. Of the various methods examined, it is

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well accepted that surface modification may enhance some physical and chemical properties nylon such as dye-ability, antimicrobial properties, color fastness, wettability, and shrink-proof characteristics. Moreover, by surface modification the load of hazardous materials in the dyeing waste water can be appreciably decreased. Recently, chitosan and its derivatives have been extensively used in surface modification of textiles. One of promising chitosan derivative, having numerous terminal amine groups, is chitosan-polypropylene imine dendrimer (CS-PPI) which its potential has been reported as efficient compound in dye removal from wastewater [20], antimicrobial finishing agent for textiles [21], and salt-free reactive dyeing of wool and cotton [22,23].

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To the best our knowledge, thus far, the surface modification of nylon using CS-PPI hybrid has not been reported. Therefore, the aim of this study was to determine whether the surface modification with chitosan-poly(propylene imine) dendreimer hybrid (CS-PPI) could improve

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the dye-ability of the nylon 6 with reactive dyes. Hence, CS-PPI was applied on nylon fabrics according to the dip-dry-cure method. Then, the modified nylon were dyed with two commercial

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reactive dyes by conventional exhaustion method in order to explore the optimal key parameters

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of treatment such as CS-PPI concentration, pH, temperature and time. Then, color fastness and antibacterial activity against two common pathogen bacteria, namely, E. coli and S. aureus of

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dyed nylon modified at optimal conditions were investigated and deliberated.

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2. Experimental

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2.1. Materials and apparatus

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Chitosan with degree of deacetylation (DD): 98.5 % and MW = 200 kDa and poly(propylene

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imine) (PPI) dendrimer (Generation 2, MW = 770 g/mol) were obtained from Kitotak Co. (Iran) and Ciba Ltd. (Switzerland), respectively. Polyamide (Nylon 6) knitted fabric (101 g/m2) was used. Nonionic detergent (Lotensol, Hansa) was utilized for scouring of fabrics. Two commercial reactive dyes, C.I. Reactive Black 5 (RB5) and C.I. Reactive Red 198 (RR198), were provided from Dystar, and used for nylon dyeing as received without further purification. All other reagents were of analytical laboratory grade. The dyeing of treated and pristine nylon fabrics was accomplished in acidic media (pH 5) (adjusted by acetic acid) using a laboratory HT dyeing machine. UV-visible absorption spectra of samples were recorded using a Cecil 9200 double beam spectrophotometer. The reflectance characteristics of the dyed samples were measured on a Macbeth spectrophotometer Color-Eye 4 Page 4 of 35

7000 A, color eye reflection spectrophotometer (D65 illumination, 10° observer). Attenuated Total Reflectance Fourier transform Infrared Spectroscopy (ATR-FTIR) spectra of the samples were recorded in a Nicolet FTIR spectrophotometer (Madison, USA). 2 mg of samples were

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grinded with100 mg dry potassium bromide (KBr), and pressed into a mold in a uniaxial hydraulic press under a load of 0.9 MPa to obtain IR-transparent pellets. The spectra were then

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collected in transmittance mode in the region of 4000-400 cm-1 with resolution of 4 cm-1.

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Morphological analyses of nylon fabrics were carried out with a LEO 1455VP scanning electron microscope (SEM). Fabrics were coated with gold (Au) in a high-resolution sputter coater.

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Differential scanning calorimetry (DSC) was measured under constant nitrogen purge on a TA Instrument in pierced aluminum pan in the range of 0-300 °C with the scanning rate of 10

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2.2. Preparation of CS-PPI hybrid

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°C/min.

(5 g) Chitosan (1, Scheme 1) was dissolved in 80 mL water/methanol 1/1 (V/V) and 1.5 mL

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acetic acid solution, and then 0.5 mL Ethyl acrylate was added to the solution. After stirring at 50 °C for 10 days, the reaction mixture was quenched and precipitated in 80 mL acetone saturated with NaHCO3. The precipitate was separated by filtration, and then the filtrates dispersed in 20 mL water saturated with NaHCO3. The resulting mixture was dialyzed against 4L water, and lyophilized to give N-carboxyethyl chitosan ethyl ester (2, Scheme 1). For the preparation of Ncarboxyethyl chitosan (3, Scheme 1), the prepared compound (2, Scheme 1) was added to 50 mL NaOH solution; the mixture was stirred for 2 h, dialyzed, and lyophilized as above. The precipitated powders were obtained in quantitative yield of 95%.

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(100 mg) Compound (3, Scheme 1) was dispersed in 50 mL methanol, poly(propylene imine) (PPI) (G=2) was added to the prepared suspension and the mixture was stirred at room temperature. After three days, the mixture was evaporated to dryness, dispersed in NaOH

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solution (0.2 M) at room temperature for 2 h, dialyzed, and lyophilized to yield CS-PPI. The summarized preparation of CS-PPI is shown in Scheme 1, and was explained in detail in our

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previous work [20].

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Scheme 1

2.3. Preparation of nylon fabrics

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Nylon fabric was scoured with 5 g/L nonionic detergent at 60 °C for 20 min, liquor ratio (L:R) of 40:1, rinsed and air dried. A fine powder of CS-PPI was dissolved in citric acid solution (pH 4)

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method as follows:

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and the grafting of nylon fabrics with CS-PPI was carried out according to the dip-dry-cure

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The scoured fabrics were immersed in CS-PPI solutions at various conditions. The treated fabrics were then dried for 5 min at 70 °C, and cured in the curing chamber at 120 ºC for 5 min. In this study, the effects of some important operational parameters such as CS-PPI concentrations (1, 2.5, 7.5 and 12.5 g/L), treatment temperature (40, 60 and 80 °C), treatment time (2, 6 and 12 h), and pH (4, 6 and 7) were evaluated on the grafting process.

2.4. Dyeing method Pristine and treated nylon fabrics were dyed with 4% owf (on weight of fiber) reactive dye at pH 4 using a buffer solution produced from acetic acid and sodium acetate mixture, the procedure which is recommended by dye manufacturer for dyeing at 60 °C. All dyeing trials were 6 Page 6 of 35

performed using a rapid laboratory dyeing machine at L:R 20:1. The fabrics were wetted for 5 min in the dye bath at 30°C before the addition of dye. The temperature of dye bath was then gradually raised from 30 °C to 60 °C at rate of 2 °C/min. Dyeing was continued for 60 min at

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this temperature. After completion of dyeing cycle, the fabrics were rinsed with hot and then cold water, and then air dried.

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Effects of operational parameters such as CS-PPI concentration, pH, temperature, and time on

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the grafting yield were monitored by changes in dye up-take ability of substrates as expressed by color strength (K/S) values. K/S values were calculated at λmax (wavelength of maximum

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absorption) using Kubelka-Munk equation (Eq. 1) as follows:

Eq. 1

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K (1  R ) 2  S 2R

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2.5. Fastness properties

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Where, R is the reflectance, K and S are the absorbance and scattering coefficients, respectively.

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Wash fastness was measured by the standard ISO 105 C06 C2S:1994 (E) method. The washing was conducted for 30 min at 60 °C, rinsed with cold water, air dried, and analyzed with grey scale. Light fastness test ISO 105 B02:1988 (E) was evaluated with the xenon arc lamp using blue reference samples. The rub fastness test was performed according to ISO105-X12:1993 (E) standard using a crockmeter. For the wet rub test, the testing squares were thoroughly immersed in distilled water; the rest of the procedure was the same as in the dry test. The staining on the white test cloth was assessed according to the gray scale. The perspiration fastness was assessed in acidic and alkaline media according to the procedure prescribed in the ISO 105 - E04:1994 (E) standard. The samples were prepared by stitching a piece of dyed wool fabric between two pieces of adjacent fabrics, all of the same length, and then 7 Page 7 of 35

immersed in the acid and alkaline solutions for 30 min. The staining on the adjacent fabrics was evaluated according to the gray scale.

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2.6. Antimicrobial activity of the treated fabrics

Antimicrobial properties of treated fabrics were examined according to ASTM E2149-01, a

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quantitative antimicrobial test method performed under dynamic contact conditions using test

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bacteria of E. coli and S. aureus. In this method, a number of test tubes, each containing 5.0 mL of Muller-Hinton broth (MHB, Difco, England) was autoclaved for 15 min at 121 ˚C. Bacterial

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inoculums (1.0 ± 0.1 mL) were added to the circular fabric swatches (1.0 g). These inoculums were nutrient broth cultures containing 106-107 mL-1 CFU (colony-forming units) of bacteria.

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Positive control tubes contained 5.0 mL of the nutrient broth medium with tested bacterial

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concentrations of 105-106 CFU/mL while negative control tubes contained only the inoculated

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broth. Tubes were incubated at 37 ˚C for 24 h at a constant temperature of incubator. Treated nylon fabrics with CS-PPI were cut into 25 × 50 mm and used for antimicrobial tests. All fabrics

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were incubated for 24 h at 37 ˚C. Then, 100 μL of solution was taken from each incubated fabric, and distributed over an agar plate. All plates were incubated again for 24 h, and the colonies formed on them were counted.

The antimicrobial activity was expressed in terms of reduction of the organisms (%) after contacting test specimen compared to the number of bacterial cells surviving after contacting the control. The percentage reduction was calculated using (Eq. 2) as follows: Reduction (%) =

B A  100 B

Eq. 2

Where, A and B are the surviving cells (CFU/mL) for the flasks containing test samples (treated nylon) and the reference sample, respectively. 8 Page 8 of 35

To assure the accuracy of data, at least three individual measurements were preformed, averaged, and reported. The reproducibility of all reported data was acceptable, with standard deviation

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≤4%.

3. Results and discussion

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3.1. Optimization of grafting process

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3.1.1. Effect of CS-PPI concentration

The impact of CS-PPI concentration on the dye-ability of nylon fabric was explored. The nylon

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fabrics, pretreated with CS-PPI, were dyed with two selective reactive dyes. K/S values as a function of CS-PPI concentrations are shown in Figure 1a. It is observed that the treatment with

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CS-PPI was resulted in a noticeable increase in K/S values apart from the type of reactive dye

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used. Moreover, it seems that only few concentration of CS-PPI (2.5 g/L) was quite effective in

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surface alteration of nylon substrate. Indeed, K/S values increased up to around 2.5 g/L CS-PPI where reached plateau. No appreciable improvement in K/S values was obtained with further

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raise in CS-PPI concentrations higher than 2.5 g/L suggesting beyond this concentration naylon surface saturated, so that no further improvement in K/S was achieved. According to the results and depending of the dye used, K/S values of the nylon increased from 2.46 to 12.0 in the case of RR198 and from 8.07 to 22 for RB5. From the dye up-take results, it may be suggested that the number of vacant amine sites to host dye molecules is quite limited in pristine nylon polymer chains, and thus, the amount of dye adsorbed would be low in general. As the CS-PPI was applied onto nylon, the number of free amine groups on the surface of substrate increased, thereby the probability of interaction of new amine groups (-NH2) on nylon surface, protonated in acidic medium and present in amino (-NH3+), with reactive dyes increased. This phenomenon

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resulted in much better electrostatic interaction of positively charged amino groups with anionic reactive dyes and thus resulted in a noticeable improvement in dye adsorption and dye up-take (K/S) of treated nylon fabric. Additionally, terminal carboxyl and amine groups as well as amide

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linkages from nylon along with numerous hydroxyl groups from chitosan (CS-PPI), having potential to form hydrogen bond with dye molecules, may favor the dye adsorption process

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[22,23]. Thus, from the above results, the appropriate CS-PPI concentration for grafting of nylon

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Figure 1

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was found to be 2.5 g/L.

3.1.2. Effect of grafting pH

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In grafting process using chitosan and its derivatives, pH plays a key role since it appreciably

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affects the solubility, changes the characteristics of material, etc. Hence, this parameter should be

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properly selected in order to achieve optimum grafting yield. In this study, the effect of treatment pH on grafting yield, i.e., the amount of CS-PPI grafted onto nylon surface, was investigated.

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Dye up-take (K/S) data versus grafting pH are shown in Figure 1b. It is obviously seen that at pHs>6, K/S drastically demonstrated a progressive fall so that only a small difference between color strength of treated and untreated nylon fabrics could be observed. In fact, this behavior denoted a significant decrease in the amount of effective CS-PPI present on the nylon surface. Such phenomenon may be explained by an appreciable decrease or complete loss in solubility of CS-PPI in the grafting solution where at such pHs no grafting of CS-PPI onto nylon substrate took place [22]. Instead, as the pH decreased to weak acidic media, K/S values of treated fabrics markedly enhanced possibly as a consequence of increased solubility of CS-PPI in the grafting solution, and therefore, the higher grafting yield. Theoretically, progressive improvement in

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grafting yield and subsequent dye up-take were expected with further decrease in the grafting pH due to more protonation of CS-PPI. However, at pHs<4 the grafting yield was not appreciably improved possibly due of the occurrence of partial damage in macromolecular chains of either

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nylon or CS-PPI complex at strong acidic medium at high temperatures and prolonged processing times [22,23]. According to the results, in the range of pH studied, pH 4 can be

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suggested as optimum pH for grafting process of CS-PPI hybrid onto nylon substrate.

3.1.3. Effect of grafting temperature and time

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A considerable energy may be saved by optimizing the processing temperature and time as important operational parameters in the grafting process [21]. Figure 1c exhibits the impact of

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treatment temperature on color strength of dyed substrates. As it is seen, K/S values of treated

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nylon fabrics increased with rising temperature up to 60 °C possibly due to accelerated and

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enhanced interactions between nylon and CS-PPI. However, further raise in grafting temperature did not result in appreciable improvement in K/S values as it is evident from the plateau of the

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Figure 1c. Therefore, the temperature of 60 °C was chosen as optimum grafting temperature. Figure 1d demonstrates the effect of time as another important factor in grafting process. It is seen that K/S values of both dyes increased with grafting time up to around 6 h and then nearly reached plateau suggesting 6 h reaction time was suitable enough for the completion of the grafting between nylon macromolecules and CS-PPI compound. According to the results, the optimum conditions for grafting variables can be summarized as follows; pH 4, CS-PPI concentration of 2.5 g/L, Temperature of 60 ºC and time of 6 h. In order to compare the extent of the performance of grafting of nylon on its dye up-take improvement, K/S values of some textiles undergone to surface modification treatments and then

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dyed with different dyes have been presented in Table 1. An appreciable improvement in dye uptake of modified nylon can be obviously seen in comparison with the results of other modified substrates.

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Table 1

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3.2. Characterization of the grafting

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3.2.1. FTIR analysis

The primary motivation for characterization of molecular structure of a polymer using FTIR

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spectroscopy is to establish a relationship between the structure and performance properties of the polymer in end use [24]. FTIR analysis is also a helpful technique generally used for

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characterization of functional groups in polymeric materials. Formation of new functional groups

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and their interaction can be investigated through analyzing FTIR spectra. In this study, the

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chemical modifications in the CS-PPI modified nylon were investigated in the range of 4000-400 cm−1. The FTIR spectra of pristine and modified samples are shown in Figure 2. Some

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vibrational band assignment is made nylon material, thereby confirming its molecular structure [24]. Inherent bands of nylon at 3419 cm-1 can be related to N-H stretching vibrations. The peaks at 2921 and 2856 cm-1 may be attributed to the CH2 asymmetric and symmetric stretching vibrations, respectively. The absorption band at 1634 cm-1, often referred to amide I band, may be assigned to the amide carbonyl C-O stretching vibrations. Instead, the amide II band at 1537 cm-1 may be attributed to N-H bending motion [25]. The presence of the hydrogen-bonded secondary amide, as expected, is confirmed by the in-plane N-H deformation vibration of the peak shoulder at 729 cm-1. The band at 695 cm-1 is also attributed to the bending of O-C-N group [25]. Indeed, it is obviously seen in Figure 2 that after modification with CS-PPI, the treated

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nylon showed a significant increase in the intensity and broadening of the N-H stretching vibrations, C-O stretching band as well as of the bending band of the O-C-N group. This may be a sign of the alterations and amine groups addition on the fiber surface. On the other hand, the

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significant increase in the intensities for the N-H, asymmetric and symmetric C-H stretching vibration bands at 3433, 2925 and 2855 cm-1, respectively, could also be assigned to the

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formation of new etched material due to the CS-PPI treatment of the nylon [26]. Comparison of

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the FTIR spectra of nylon and CS-PPI grafted nylon clearly demonstrated indicative structural changes and effective inclusion of CS-PPI onto the nylon surface responsible for the

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improvements in properties imparted.

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Figure 2

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3.2.2. DSC analysis

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Fine structural changes of polymeric fibers when exposed to heat can be explored by DSC characterization method [27]. Thermal properties of raw and modified nylon 6, investigated by

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DSC, are shown in Figure 3. It is observed that melting peak temperature of raw nylon 6 located at 216 °C shifted towards lower temperatures of 211 °C while glass transition temperature (Tg) increased from 27 to 31 °C after treatment with CS-PPI at optimum condition. The quantity of amorphous regions was higher in modified nylon. Such changes in thermal properties could be owing to different chemical structure of CS-PPI modified nylon compared to un-treated nylon. Figure 3

3.2.3. Surface morphology analysis

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SEM has been extensively used as a main tool for characterizing the surface morphology and essential physical properties of the material surface. Different valuable information can be obtained using this characterization method such as particle shape, porosity, appropriate size

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distribution, etc [20]. SEM images of raw and CS-PPI treated nylon fabrics are exhibited in Figure 4. Fabric treated with CS-PPI clearly showed the presence of foreign materials deposited

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on their surfaces with a thin continuous coating layer formed over the filaments. The

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morphological features of raw and untreated nylon were therefore different. Based on the SEM results, it is reasonable to assume that the presence of the deposits to be responsible for the

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enhancement observed in dyeing characteristics, antimicrobial properties and color fastness properties (see sections 3.1, 3.4, and 3.5).

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3.3. Colorimetric properties

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Figure 4

CIE Lab values of raw and grafted nylon fabrics dyed with 4% owf dye are given in Table 2. It is

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apparent that treatment with CS-PPI, indeed, resulted in noticeable changes in color of fabric. In general, dyed CS-PPI treated fabrics exhibited darker shades (lower lightness values). Moreover, depending on the dyestuff used, a* and b* and accordingly chroma values (C*) varied in different manner. When RB5 dye was used, yellowness, redness, and chroma (color purity) increased as the amount of CS-PPI increased in treated fabrics. However, no remarkable changes in a*, b* or C* were observed using RR198 dye. The observed variations in colorimetric data may be attributed to different chemical interactions may be formed among nylon/CS-PPI/dye complexes. Table 2

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3.4. Fastness properties Textiles are exposed to repeated washing, rubbing and perspiration during their usage. Hence,

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durability of the finish applied on textile materials at these conditions is very important [20]. Fastness data of raw and CS-PPI modified nylon fabrics, measured according to standard

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methods, are presented in Table 3.

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Table 3

According to the results, wash fastness ratings for staining of adjacent fabrics are good and those

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for color change are also in acceptable level. It should be mentioned that no color change was observed at higher CS-PPI concentrations. According to Table 3 result, washing fastness nearly

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remained unchanged, indicating the independency of fastness properties from CS-PPI

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concentrations. Rubbing fastness of the samples measured in dry and wet conditions was in very

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good level as well. Light fastness data indicated that modification with CS-PPI, indeed, resulted in a an enhancement in light fastness presumably because of the inherent properties of

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dendrimers which is generally used to increase the optical stability of the materials [32]. Perspiration fastness properties (in acidic and alkaline conditions) in terms of ratings for staining of adjacent fabrics and change in color are also given in Table 3 for all dyed fabrics. The ratings for staining of adjacent fabrics and change in color in both acidic and alkaline media were overall good. The lower ratings for change in color at both acidic and alkaline conditions represent the sensitivity of the CS-PPI dyed samples to pH changes. This phenomenon may be ascribed to structural changes of dyes and/or their degradation at acidic or basic test conditions. In general, fastness data confirmed that CS-PPI had no adverse impacts on color fastness of dyed modified nylon fabrics.

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3.5. Antibacterial properties Numerous standard methods are being used to evaluate the antibacterial properties of textiles. In

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this study, antimicrobial properties of the fabrics were investigated according to ASTM E214901, a quantitative antimicrobial test method performed under dynamic contact conditions against

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two pathogen bacteria E. coli and S. aureus, and the results are presented in Table 4. The results

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clearly showed strong microbial reduction in cases of E. coli and S. aureus bacteria. This bactericidal activity may be attributed to the presence of the CS-PPI on the nylon fabric surface

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with huge number of active amine groups which may have come into contact with the bacterial cell surface and prevented the leakage of intracellular components [20, 26, 30]. The most

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accepted mechanism for microbial inhibition by CS-PPI may be the interaction of the positively

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charged amine (amino) groups (NH2→NH3+) with the negatively charged residues at the cell

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surface of many microorganisms, which causes extensive alteration of cell surface and cell permeability [20, 30, 33, 34]. This causes the leakage of intracellular substances such as

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electrolytes, UV-absorbing materials, proteins, amino acids, glucose, and lactate dehydrogenase. As a result, CS-PPI inhibits the normal metabolism of microorganisms and finally leads to their death. In the case of S. aureus, a gram-positive bacterium with a thicker cell wall, more reluctance and resistance to CS-PPI is observed as compared to E. coli [20, 30, 33]. Furthermore, when the contact area between the treated nylon fabric and bacteria was increased, more bacteria were inhibited. Table 4 In addition, antibacterial activity of the treated fabrics was retained to a great extent even after dyeing and subsequent washing which may be attributed to form the high durability of the finish

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applied presumably due to strong linkages formed between CS-PPI and nylon fabric. So that, antimicrobial activity of treated nylon against gram negative and gram positive microorganisms

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was overall suitable.

4. Conclusions

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Nylon 6 fabric surface was successfully modified through CS-PPI treatment. Maximum grafting

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yield was obtained at optimum treatment conditions of pH 4, CCS-PPI 2.5 g/L, time 6 h, and temperature 60 °C. After CS-PPI treatment, dye up-take of nylon was considerably improved

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independent of the dye used. On the other hand, color hue was dependent essentially on the dye employed presumably due to the different dye/CS-PPI interactions. Antibacterial activity against

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E. coli and S. aureus micro-organisms was additional property imparted to nylon fabrics through

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treatment with CS-PPI. Applied finish fastness on nylon was overall satisfactory as it was

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evident from color fastness and antibacterial tests data. Therefore, based on the results obtained, it can be deduced that CS-PPI can be used as an eco-friendly finishing agent for multifunctional

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modification of the nylon 6 fabrics.

5. Acknowledgments

Institute for Color Science and Technology, Tehran, Iran and Tabriz Islamic Art University, Tabriz, Iran are gratefully acknowledged for all the supports throughout this study.

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[2] D.M. Nunn, The Dyeing of Synthetic Polymer and Acetate Fibres, SDC: Bradford, 1979. [3] S.F. Zhang, W. Ma, B.Z. Ju, N.Y. Dang, M. Zhang, SL. Wu, Color. Technol. 121 (2005) 183186.

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Technol. 201 (2006) 4384-4388.

[13] J. Yip, K. Chan, K.M. Sin, K.S. Lau, Color. Technol. 118 (2002) 26-30. [14] C. Labay, J.M. Canal, A. Navarro, C. Canal, Appl. Surf. Sci. 316 (2014) 251-258. [15] P. Malshe, M. Mazloumpour, A. El-Shafei, P. Hauser, Plasma Chem. Plasma P. 32 (2012) 833-843.

[16] F. Puch, C. Hopmann, Polymer 55 (2014) 3015-3025. [17] L. Razafimahefa, S. Chlebicki, I. Vroman, E. Devaux, Dyes Pigm. 66 (2005) 55-60. [18] F.R. Oliveira, A. Zille, A.P. Souto Appl. Surf. Sci. 293 (2014) 177-186. [19] K. Ravikumar, Y.A. Son, Dyes Pigm. 75 (2007) 199-206

18 Page 18 of 35

[20] M. Sadeghi-Kiakhani, M. Arami, K. Gharanjig, Iranian Polym. J. 22 (2013) 931-940. [21] M. Sadeghi-Kiakhani, M. Arami, K. Gharanjig, J. Appl. Polym. Sci. 127 (2013) 2607-2019.

ip t

[22] A. Zargarkazemi, M. Sadeghi-Kiakhani, M. Arami, S.H. Bahrami, J. Text. I. 106 (2015) 8089.

cr

[23] S.M. Burkinshaw, M. Mignanelli, P.E. Froehling, M.J. Bide, Dyes Pigm. 47 (2000) 259-

us

267.

an

[24] S. Davarpanah, N.M. Mahmoodi, M. Arami, H. Bahrami, F. Mazaheri, Appl. Surf. Sci. 255 (2009) 4171-4176.

M

[25] M. Sadeghi-Kiakhani, S. Safapour, Clean Techn. Environ. Policy 17 (2015)1019-1027.

d

[26] M. Sadeghi-Kiakhani, S. Safapour, Fibers Polym. 16(5) (2015) 1078-1081.

te

[27] J. Charles, G.R. Ramkumaar, S. Azhagiri, S. Gunasekaran, E-J Chem. 6 (2009) 23-33.

Ac ce p

[28] K.H. Kale, S.S. Palaskar, J. Text. I. 103 (2012) 1088-1098. [29] M.C. Gupta, R.R. Pandey, J. Polym. Sci. Polym. Chem. 26 (1988) 491-502. [30] M. Ranjbar-Mohammadi, M. Arami, H. Bahrami, F. Mazaheri, N.M. Mahmoodi, Colloids Surf., B: Biointerfaces 76 (2010) 397. [31] B. Klaykruayat, K. Siralertmukul, K. Srikulkit, Carbohydr. Polym. 80 (2010) 197-207. [32] M. Sadeghi-Kiakhani, S. Safapour, Color. Technol. 131 (2015) 142-148. [33] H.K. Shin, M. Park, Y.S. Chung, H.Y. Kim, F.L. Jin, S.J. Park, J. Ind. Eng. Chem. 20 (2014) 1476-1480. 19 Page 19 of 35

Ac ce p

te

d

M

an

us

cr

ip t

[34] M. B. Kasiri, S. Safapour, Environm. Chem. Lett. 12 (2014) 1-13.

20 Page 20 of 35

Figure captions

ip t

Scheme 1. The chemical reaction between chitosan and PPI dendrimer G=2 Figure 1. Effect of a) CS-PPI, b) pH and c) temperature d) time on the grafting process

cr

(Expressed as K/S values)

us

Figure 2. FTIR spectra of untreated and treated nylon at optimum conditions

Figure 3. DSC analysis of fabrics: (a) nylon, (b) nylon treated at optimum conditions.

M

an

Figure 4. SEM images of fabrics: (a) nylon, (b) nylon treated at optimum conditions.

Table captions

te

d

Table 1. K/S values for treated textiles with other materials using various dyes

Ac ce p

Table 2. CIE L*a*b* values of dyed nylon fabrics (Cdye=4%) Table 3. Color fastness of dyed nylon fabrics (Cdye=4%) Table 4. Antimicrobial test results of control and CS-PPI treated nylon fabrics under optimized grafting condition before and after dyeing process.

21 Page 21 of 35

Table 1 K/S Dye

Materials

Substrate

References

Dendrimer

Cotton

2.0

Reactive Deep Blue A-GD

HBP-NH2

Cotton

3.0

HBP-NH2

Cotton

Acrylamide

Cotton

16.7

[4]

21.6

24.7

[7]

Silk

9.1

11.1

[24]

Ramie

6.1

13.2

[6]

4.7

an

M

Acid Black NB.B

us

[3]

A-4GLN

Chitosan-

[23]

8.0

Reactive Brilliant Yellow

C.I. Reactive Black 5

4.5

cr

Reactive Blue 140

ip t

Untreated Treated

HBP-NH2

Ac ce p

C.I. Reactive Blue 5

te

d

acylated silk

C.I. Reactive Orange 122

CS-PPI

Wool

7.0

22.0

[25]

C.I. Reactive Red 195

CS-PPI

Wool

9.0

25.0

[25]

C.I. Reactive Black 5

CS-PPI

Cotton

2.0

4.0

[26]

C.I. Reactive Red 198

CS-PPI

Cotton

6.0

12.0

[26]

C.I. Reactive Black 5

CS-PPI

Nylon

8.0

22.0

Present study

C.I. Reactive Red 198

CS-PPI

Nylon

2.46

12.0

Present study

22 Page 22 of 35

Table 2

RR198

a*

b*

C*

h˚

K/S

Raw nylon

55.68

33.36

-6.13

33.92

349.58

8.07

2.5

42.79

48.24

0.04

48.24

0.04

19.22

7.5

41.05

50.19

50.20

0.51

20.31

Raw nylon

33.02

1.30

-15.01

15.07

274.97

2.46

2.5

22.08

0.09

-14.93

14.93

270.34

10.70

23.49

-1.66

-14.88

14.97

263.62

11.71

cr

us 0.45

Ac ce p

te

d

7.5

ip t

L*

an

RB5

CS-PPI (g/L)

M

Dye

23 Page 23 of 35

Table 3

CS-PPI

Washing

Rubbing

Perspiration

Dye S

C

S

N

Light Ch

Acidic Dry

Wet

4

5

5

2.5

4-5

5

5

5-6

5

4-5

7.5

4-5

5

5

5-6

4-5

Raw nylon

4-5

4-5

4-5

4-5

5

2.5

4-5

4-5

5

6

7.5

4-5

4-5

5

6

CS

NS

Ch

4-5

5

4-5

5

5

4-5

4-5

5

4-5

5

5

4-5

4-5

4-5

5

4-5

5

5

4-5

5

4-5

4-5

4-5

4-5

5

5

5

5

4-5

5

4-5

4-5

5

5

4-5

4

4-5

5

4-5

4-5

5

5

an

5

Ch

M

5

d

RR198

4-5

Alkaline

te

RB5

Raw nylon

NS

us

CS

cr

(g/L)

ip t

Fastness

Ac ce p

S: Staining; Ch: Change; C: Cotton, N: Polyamide.

24 Page 24 of 35

Table 4

CS-PPI (g/L)

Reduction (%)

Reduction (%) After dyeing and washing

Surviving cells (CFU/ml)

ip t

Before dyeing

RB5

RR198

S. aureus

E. coli

S. aureus

E. coli

S. aureus

E. coli

S. aureus

0

5

1

4.2×105

4.7×105

5

1

5

1

2.5

99.99

99.99

2.1×102

2.9×102

61.90

53.19

62.11

52.60

7.5

100

100

10

13

77.38

68.08

75.28

69.74

Ac ce p

te

d

M

an

us

cr

E. coli

25 Page 25 of 35

Ac ce p

te

d

M

an

us

cr

ip t

Figure

Scheme 1

Page 26 of 35

ip t cr us an M d te

Ac ce p

Figure 1

Page 27 of 35

ip t cr us an M d

Ac ce p

te

Figure 2

Page 28 of 35

ip t cr us an M d te Ac ce p

Figure 3

Page 29 of 35

ip t cr an

us (b)

Ac ce p

te

d

M

(a)

Figure 4

Page 30 of 35

Table

Table 1 K/S Dye

Materials

Substrate

References

Dendrimer

Cotton

2.0

Reactive Deep Blue A-GD

HBP-NH2

Cotton

3.0

HBP-NH2

Cotton

Acrylamide

Cotton

16.7

[4]

21.6

24.7

[7]

ChitosanAcid Black NB.B

Silk

9.1

11.1

[24]

Ramie

6.1

13.2

[6]

us

[3]

4.7

an

M

C.I. Reactive Black 5

[23]

8.0

Reactive Brilliant Yellow A-4GLN

4.5

cr

Reactive Blue 140

ip t

Untreated Treated

HBP-NH2

Ac ce p

C.I. Reactive Blue 5

te

d

acylated silk

C.I. Reactive Orange 122

CS-PPI

Wool

7.0

22.0

[25]

C.I. Reactive Red 195

CS-PPI

Wool

9.0

25.0

[25]

C.I. Reactive Black 5

CS-PPI

Cotton

2.0

4.0

[26]

C.I. Reactive Red 198

CS-PPI

Cotton

6.0

12.0

[26]

C.I. Reactive Black 5

CS-PPI

Nylon

8.0

22.0

Present study

C.I. Reactive Red 198

CS-PPI

Nylon

2.46

12.0

Present study

Page 31 of 35

b*

C*

h˚

Raw nylon

55.68

33.36

-6.13

33.92

349.58

2.5

42.79

48.24

0.04

48.24

0.04

7.5

41.05

50.19

0.45

50.20

Raw nylon

33.02

1.30

-15.01

2.5

22.08

0.09

7.5

23.49

-1.66

K/S

8.07

us

cr

a*

19.22

0.51

20.31

15.07

274.97

2.46

-14.93

14.93

270.34

10.70

-14.88

14.97

263.62

11.71

Ac ce p

te

d

RR198

L*

an

RB5

CS-PPI (g/L)

M

Dye

ip t

Table 2

Page 32 of 35

Table 3

Washing

CS-PPI

Rubbing

Perspiration

Dye Light S

C

S

N

Ch

Acidic Dry

Wet

5

4

5

5

2.5

4-5

5

5

5-6

5

4-5

7.5

4-5

5

5

5-6

4-5

Raw nylon

4-5

4-5

4-5

4-5

5

2.5

4-5

4-5

5

6

7.5

4-5

4-5

5

CS

NS

Ch

5

4-5

5

5

4-5

4-5

5

4-5

5

5

4-5

4-5

4-5

5

4-5

5

5

4-5

5

4-5

4-5

4-5

4-5

5

5

5

5

4-5

5

4-5

4-5

5

5

4-5

4

4-5

5

4-5

4-5

5

5

M

6

Ch

4-5

an

5

d

RR198

4-5

Alkaline

te

RB5

Raw nylon

NS

us

CS

cr

(g/L)

ip t

Fastness

Ac ce p

S: Staining; Ch: Change; C: Cotton, N: Polyamide.

Page 33 of 35

Table 4

CS-PPI (g/L)

Reduction (%)

Reduction (%) After dyeing and washing

Surviving cells (CFU/ml)

ip t

Before dyeing

RB5

RR198

S. aureus

E. coli

S. aureus

E. coli

S. aureus

E. coli

S. aureus

0

5

1

4.2×105

4.7×105

5

1

5

1

2.5

99.99

99.99

2.1×102

2.9×102

61.90

53.19

62.11

52.60

7.5

100

100

10

13

68.08

75.28

69.74

an

us

cr

E. coli

Ac ce p

te

d

M

77.38

Page 34 of 35

Ac

ce

pt

ed

M

an

us

cr

i

*Graphical Abstract

Page 35 of 35