Novel Method of Ecofriendly Single Bath Dyeing and Functional

Jul 26, 2017 - The present work mainly deals with the study of the efficacy of coconut shell extract (CSE), an eco-friendly natural waste product, as ...
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Research Article pubs.acs.org/journal/ascecg

Novel Method of Ecofriendly Single Bath Dyeing and Functional Finishing of Wool Protein with Coconut Shell Extract Biomolecules M. D. Teli* and Pintu Pandit* Department of Fibers & Textile Processing Technology, Institute of Chemical Technology, University under Section -3 of UGC Act, 1956, Matunga, Mumbai−400019, India ABSTRACT: The present work mainly deals with the study of the efficacy of coconut shell extract (CSE), an eco-friendly natural waste product, as a dye and also as an acid dyeing medium, for coloration and multifunctional finishing of wool fabric for fire retardancy and UV-protective effects. The wool fabric was dyed with coconut shell extract “as-it-is” and in concentrated form at pH 4.5. A UV−visible spectrometry determination was used for color measurement whereas gas chromatography mass spectrometry identified some of the components of CSE. The limiting oxygen index (LOI), vertical flammability, and fire retardancy were determined, while thermal degradation was studied using thermogravimetric analysis. Scanning electron microscopy energy dispersive X-ray spectroscopy analysis was used to examine the surface depositions for elements present in the CSE treated fabric. The chemical modification and the structural conformation of the wool fabric were studied using attenuated total reflection Fourier transform infrared spectroscopy and X-ray diffraction analysis. Fabric dyed with CSE at pH 4.5, and with synthetic acid dye in CSE, showed more exhaustion of color and color strength as well as thermal stability as compared to that of the fabric dyed in water medium with synthetic acid dye. KEYWORDS: Coconut shell extract, Wool, Dyeing, Flame retardant

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positively charged wool fiber.2 Researchers have also used SiO2−Al2O3 sol which produces Si−Al oxide offering increased thermal stability by restricting combustible, flammable gas formation and by enhanced char formation.3 A large number of halogen based fire retardants though reported in the literature are toxic or potentially toxic to organisms, and themselves affect our environment. Hence, there is a need for their replacement by ecofriendly agents having good fire retardant properties. In order to make textile materials fire retardant some researchers have studied the application of biomolecules such as chitosan, phytic acid, casein, whey, banana pseudostem sap, coconut shell extract, spinach leaves, hydrophobins, or DNA from herring sperm and Salmon fish as they contain proteinous nitrogen, phosphate, phosphite, chloride, and other metallic salts.4−9 However, devising an easy, eco-friendly, economical fire retardant process for wool maintaining proper fabric quality is still a major concern for the researchers. Apart from this, an increasing awareness about human health and hygiene is also driving the demand for textiles finished with natural products for coloration using natural dyes and antimicrobial finishing using neem and aloe vera extract.10,11 The literature also indicates to the best of our knowledge that no researcher has reported on the application of natural biomolecule waste resource such as green coconut shell extract

INTRODUCTION To make operations sustainable, industries must control the necessary inputs right from the raw material to the finished products and follow the 4R principle, i.e., reduce (chemical quantity), recycle (dyes/chemicals/fabrics), replace (harmful quantity), and reject (banned items). Green chemistry using biosourced macromolecules has acquired incredible importance in the fibers and processing industry. Among the different natural textile fibers, wool fibers are one of the most popular natural proteinous biopolymers widely used as apparel and interior textiles for their comfort and aesthetic qualities, as well as inherent characteristics of heat retention, good moisture regains, and water repellency.1 However, the existence of scales on the surface of the wool fibers causes difficulty in the diffusion of dye molecules and felting propensity, thus hindering the dyeing and finishing processes and limiting the application of wool products. Wool fiber has cross-linked polypeptides in its helical structure, and it contains a high amount of nitrogen and moisture as well as sulfur which makes it naturally fire resistant. Its limiting oxygen index (LOI) is 25 which is much higher than that of many other natural textile fibers with LOI values less than 21. However, this level of flame retardance is not sufficient for safety, some treatment imparting fire retardance to wool fiber is still needed so that it can meet the standard flammability norms. Researchers had developed a successful Zirpro process which was based on the application of 2% negatively charged hexafluoro zirconate and titanate salts at acidic pH on the © 2017 American Chemical Society

Received: June 26, 2017 Revised: July 21, 2017 Published: July 26, 2017 8323

DOI: 10.1021/acssuschemeng.7b02078 ACS Sustainable Chem. Eng. 2017, 5, 8323−8333

Research Article

ACS Sustainable Chemistry & Engineering

oxygen and nitrogen flow meter (cm3/min) was set as per LOI value with a 38 mm length of the flame. For an LOI of 25, the oxygen flow meter was set as 77 (4275 cm3/min), and the nitrogen flow meter was set as 108 (12825 cm3/min). The results are expressed as

(CSE) for imparting fire retardancy to the protein wool fiber. In this paper thus the use of widely available biowaste CSE as a potential fire retardant agent for wool fabric has been reported. Also, coloration properties of CSE on wool have been studied. The dyed wool fabric is also tested for ultraviolet protection properties.

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LOI (%) =

Material. A woven 120 g/m2 wool fabric having a plain weave with 73 ends per inch and 66 picks per inch was procured from Raymond, India. The acid dye used for dyeing was Telon Blue RR 01 (C. I. Acid Blue 62), having M.W. 422, supplied by DyStar, India. Coconut Shell Extract Application on Wool Fabric. Wool was scoured with 2 g/L soda ash in the laboratory and used for the singlebath dyeing and functional finishing. Green coconut shell waste was collected from the local market at Mumbai, India. The mesocarp of green coconut was cut into pieces, and then sap was extracted out using a grinder. Original fresh coconut shell extract was yellowish brown in color and showed a pH of 4.5. Scoured wool fabrics were then subjected to dyeing (treatment) with this coconut shell extract (CSE) solution at pH 4.5 by maintaining a material to liquor ratio of 1:15. The dyeing was carried out at 90 °C for 60 min. Similarly, the CSE solution in the second set of the experiment was doubly concentrated by evaporating water in it to 50% of volume by boiling it. This CSE is called CSE-B, and the original CSE is referred to as CSEA. Also, to research the possibility of CSE replacing water in the normal acid dyeing of wool three more experiments were carried out in which synthetic acid dye, i.e., C.I. Acid Blue 62, was used for 2% shade and CSE-A and CSE-B were used in place of water while dyeing. Dyed and washed wool fabric samples were then dried in air at room temperature and then conditioned for 48 h at 65% relative humidity (R.H.) before testing. Particle Size Analysis of CSE. The average particle size of the coconut shell extract particles was measured by nanoparticle size analyzer, Shimadzu SALD-7500 (Wings SALD II: Version 3.1.1). Gas Chromatographic Mass Spectrometric (GCMS) Analysis. The GCMS analysis was carried out on Agilent 7890 model, with a head space injector and combi Pal autosampler, with the following specification: mass spectrometer JEOL, auto TOF GCV, mass range 10−2000 amu, mass resolution 6000 gas chromatography with capillary HP5MS GC/MS column of 30 m × 0.25 mm i.d., 0.25 μm. The temperature programming was from 60 to 200 °C: hold at 60 °C for 1 min, increase at a rate of 3 °C/min, and hold at 200 °C for a run time of 82 min. The carrier gas was high purity helium (99.99%) at a flow rate of 1.0 mL/min. The temperatures of the injector, transfer line, and ion source were set at 230, 250, and 200 °C, separately. The mass spectrum was also equipped with a computer fed mass spectra NIST data bank. A 2 mL portion of freshly prepared CSE was mixed with an equal volume of 2-propanol and filtered through anhydrous sodium sulfate for water removal. The filtrate was taken for analysis. Reagents and solvents like isopropanol were of analytical grade procured from Merck, Germany. CSE components were identified by matching the peaks with NIST MS library and confirmed by comparing mass spectra of the peaks with those from literature.12,13 Determination of Add-on Percentage. The add-on percentage of the CSE treated fabrics was determined gravimetrically using the following formula:

M 2 − M1 × 100 M1

(2)

In vertical flammability, the different parameters were measured as per ASTM D 6413-09 standard test method for flame resistance of textiles.15 Specimen size was 30 × 7.6 cm2 and flame height 38 mm. The cut edge of the fabric on the bottom was exposed to a controlled flame for 12 s. After exposure to the flame, after flame, afterglow, and char length were measured. Five tests for each sample were performed, and the averaged results are reported. Evaluation of Coloration on Wool Fabric. The color depth of the samples was evaluated measuring the reflectance values on a computer color matching system using spectra scan 5100 + spectrophotometer. The Kubelka−Munk function, K/S, which is proportional to the color strength, was determined using the following equation:

MATERIALS AND METHODS

add‐on (%) =

O2 × 100 O2 + N2

(1 − R )2 K = S 2R

(3)

where K is the absorption coefficient, S is the scattering coefficient, and R is the reflectance of the dyed fabric at λmax (maximum wavelength). Here K/S was determined at 420 nm λmax for CSE treatment and 600 nm λmax for acid dye treated wool fabric. Other color parameters such as L* (lightness−darkness), a* (red−green), and b* (blue−yellow component) were also measured. Ultraviolet (UV) Visible Spectrophotometric Analysis. UV− visible spectrophotometric analysis of CSE-A, the acid dye in a distilled water medium, and acid dye in CSE-A and CSE-B media was carried out by scanning from 200 to 800 nm wavelength using a UV-1800 spectrophotometer from Shimadzu, Japan. Thermogravimetric Analysis (TGA). The untreated and the treated wool fabrics were cut into small pieces, and TGA was carried out. The thermograms were recorded on Shimadzu 60H DTG apparatus in the temperature range of 30−700 °C with a heating rate of 10 °C/min under an inert atmosphere of nitrogen and also in the air at a flow rate of 50 mL/min. The temperature accuracy of the instrument was ±0.3 °C, with a reproducibility of ±0.1 °C; the weighing precision was 1 μg, with a sensitivity of 0.1 μg, and a dynamic range of ±500 mg, having a measurement accuracy of ±1%. Ultraviolet Protection Factor (UPF) Analysis. The UPF values of the untreated wool fabric and dyed fabric with CSE-A and CSE-B were measured using a Shimadzu UV-2600 spectrophotometer in the range of 280−400 nm. The UPF value of each fabric was determined from the total spectral transmittance based on AS/NZS 4399:1996 method. Attenuated Total Reflection (ATR) Fourier Transform Infrared (FTIR) Analysis. The IR spectra of untreated and treated wool samples were recorded using pike miracle ATR module with diamond/ ZnSe crystal on FTIR spectrometer (Shimadzu 8400S, Japan) by recording 45 scans in percent transmittance mode in the range of 4000−800 cm−1 Scanning Electron Microscopic (SEM) Analysis. The surface morphology of the untreated and CSE-A and CSE-B treated wool fabric was analyzed using field emission gun-scanning electron microscope (FEG-SEM, JEOL, JSM-7600F). Specimens of size 5 mm × 5 mm were taken, and the conductive agent used was of platinum sputter coated for the 600 s duration. The beam voltage of 10 kV, 2000× magnification, and 6 mm working distance for examining the sample were used. Char analysis of untreated and CSE treated fabric was also done using FEG-SEM of TESCAN having specimen size of 5 mm × 5 mm. The conductive agent used was of platinum sputter coated for 600 s, and it was examined with a beam voltage of 10 kV. Energy Dispersive Spectrometric (EDS) Analysis. EDS analysis was carried out using a field emission gun scanning electron

(1)

where M1 and M2 are the dry oven weight of the untreated and treated fabric samples, respectively. The reported results are an average of five tests in each case. Flammability Assessment. Standard methods evaluated the burning behavior of both untreated and treated samples. For the determination of flammability of limiting oxygen index (LOI) analysis, IS 13501:1992 for textiles test procedure was used.14 As per standard, flame contact time was kept as the 30 s; specimen size was 6 × 4 cm2; 8324

DOI: 10.1021/acssuschemeng.7b02078 ACS Sustainable Chem. Eng. 2017, 5, 8323−8333

Research Article

ACS Sustainable Chemistry & Engineering microscope, (FEG-SEM, JEOL, JSM-7600F) on pure coconut shell extract (CSE), untreated wool, and CSE treated wool samples to determine elements present and their respective weight percentage. Specimens of size 5 mm × 5 mm were used. The conductive agent used was of platinum sputter coated for 600 s. A beam voltage of 15 kV and a working distance of 15 mm for examining the sample were maintained. X-ray Diffraction (XRD) Analysis. XRD analysis of the untreated and CSE-B treated wool samples was carried out on Shimadzu 6100 model equipped with Cu Kα radiation (λ = 1.54 Å) in the 2θ angle ranging from 5 to 35°. The generator voltage was kept at 40 kV, and generator current was 30 mA, in step of 0.02°. The sample in the form of chopped fibers was prepared and placed on the stub. Assessment of Fastness Properties. Washing fastness of CSE-A and CSE-B treated dyed samples at different pH values was carried out according to ISO 105 C-10:2006 method A. Similarly, light fastness and rubbing fastness of the same samples were also assessed according to ISO 105-B02:2013 and ISO 105-X 12:2002 methods, respectively. Wash Durability of the Finish. The flame-retardant activity of the finished samples was evaluated after washing them in a launderometer using a standard detergent of 5 g/L at 40 °C for 40 min. The fabric was then rinsed in freshwater for 5 min, followed by drying at 100 °C for another 5 min. The samples were then conditioned in a desiccator before conducting LOI and flammability tests for 24 h.

contrasting the NIST standard spectra on the computer and combined with open, published information. The main components were furfural (6.18%), 2-butanol,2nitroso-acetate (ester) (1.67%), 4-hydroxydihydrofuran-2-one (1.07%), 4H-pyran-4-one,2,3-dihydro-3,5-dihydroxy-6-methyl (8.31%), 2-furancarboxaldehyde, 5-(hydroxymethyl) (24.59%), 1-guanidino succinimide (2.33%), benzeneethanamine, 2fluoro-β,5-dihydroxy-N-methyl (2.37%), 2-aminononadecane (0.44%), 3-trifluoroacetoxypentadecane (0.6%), pregnan-18oic acid (8.27%), erucic acid (28.04%), eicosane (4.49%), and ethylene brassylate (11.52%). Out of these, N- and Fcontaining compounds could be responsible for imparting flame retardance and long chain fatty acid components could be responsible for imparting an UV protective effect. Natural and Acid Dyeing of the Wool Fabric. CSE-A and CSE-B on treatment on wool fabric at 4.5 pH showed distinct coloration, and CSE-B showed 6.11% higher color strength as compared than that of CSE-A. This may be attributed to concentrated nature of coloring components present in CSE-B. The treated wool fabric turned to reddishbrown in tone after the treatment. In the next set of experiment, the synthetic acid dye was used for dyeing wool. The effect of the use of CSE-A and CSE-B in place of water as a medium of dyeing was studied here. Wool fabric was dyed with C.I. Acid Blue 62 in water as well as in CSE-A and CSE-B solution at pH 4.5. Color strength along with color coordinates L, a*, and b* values are reported in Table 3. Wool fabric dyed with acid dye in CSE-A and CSE-B mediums showed 44.7% and 74.65% increase in the K/S values over the color value obtained when water was used as a medium of dyeing. It may be due to the formation of dye−metal complexation in the presence of some inorganic salts in CSE medium, as happens in the case of the general process of mordant dyeing. Coloration effect of CSE itself is also responsible for the enhancement of K/S values. Dyed fabric with CSE-A as a medium showed bluish−green tinge. Moreover, bluish−green color observed when CSE-A was mixed with 2 mL of 2% solution of ferric chloride, which indicated the presence of tannin and phenols. Hence, it could be said that the coloration property of CSE-A may be due to its tannin richness. When wool is treated with CSE-A which is rich in tannins (polyphenols), dyeing occurs, and as seen in the FTIR spectrum (discussed further in the text), the breaking of sulfide bonds between the chains causes changes in the wool amide I band. The UV−visible spectra (as shown in Figure 3) show that acid dye in water which has maxima at 594 and 636 nm red, shifts on complexation in CSE-A medium to maxima at 599 and 640.5 nm, along with a simultaneous doubling in the intensity of the absorption. Tannin−protein complexation proceeds through the formation of highly cross-linked adducts at acidic pH. At low pH, reaction mechanism has been proposed in the literature,16 wherein quinone intermediates of the polyphenol formed adducts with the nucleophilic sites at −COO− and S− on wool protein.

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RESULTS AND DISCUSSION Particle Size Analysis of CSE Particles. It was observed that formed CSE particles have a uniform size distribution with a mean volume diameter of 30 nm for CSE-A. For CSE-B mean volume diameter changed to 178 nm (Table 1). It might be due Table 1. Particle Size Diameter of CSE-A and CSE-B

CSE-A CSE-B

median diameter (nm)

modal diameter (nm)

volume mean diameter (nm)

standard deviation

30 256

28 331

30 178

0.098 0.396

to collision and agglomeration of the CSE nanoparticles, after evaporation of water molecules enhancing its concentration. These CSE nanoparticles were applied on wool fabric to get the combined effect of dyeing and functional finishing properties. Gas Chromatographic Mass Spectrometric (GCMS) Analysis. The GCMS chromatogram (Figure 1) of the CSE showed peaks indicating the presence of 13 compounds in the CSE (Table 2 and Figure 2). The area of each peak and the relative components could be calculated. The chemical components could be identified according to the MS data,

ASO3− + +3HNWCOOH (acid dye)

→ Figure 1. GCMS analysis chromatogram of coconut shell extract. 8325

(wool)

ASO3−+3HNWCOOH ⎛ ionic interaction between anion of acid dye ⎞ ⎟⎟ ⎜⎜ ⎝ and charged sites in wool protein chain ⎠ DOI: 10.1021/acssuschemeng.7b02078 ACS Sustainable Chem. Eng. 2017, 5, 8323−8333

Research Article

ACS Sustainable Chemistry & Engineering Table 2. GCMS Analysis of the Various Peaks from Coconut Shell Extract chromatogram peak

compound name

molecular formula

molecular mass

retention time (min)

% content

96

3.44

6.18

fragment peaks and abundance

1

furfural

C5H4O2

2 3 4

C6H11NO3 C4H6O3 C6H8O4

145 102 144

6.91 9.80 14.23

1.67 1.07 8.31

C6H6O3

126

19.15

24.59

C5H7N3O2 C9H12FNO2

141 185

22.77 38.41

2.33 2.37

C19H41N C17H31F3O2 C21H34O3

283 324 334

59.93 68.46 73.64

0.44 0.6 8.27

44 (99.9%) 43 (17.7%) 57 (57%) 43 (84%) 55 (77%) 69 (66.2%) 83 (32%) 69 (99.9%) 83 (78.2%) 81 (55.0%)

11

2-butanol,2-nitroso-acetate (ester) 4-hydroxydihydrofuran-2-one 4H-pyran-4-one,2,3-dihydro-3,5dihydroxy-6-methyl 2-furancarboxaldehyde,5(hydroxymethyl) 1-guanidino succinimide benzeneethanamine,2-fluoro-β,5dihydroxy-N-methyl 2-aminononadecane 3-trifluoroacetoxypentadecane pregnan-18-oic acid,20-hydroxyl[5α]erucic acid

39 (64.4%) 42 (5.3%), 67 (11.4%), 95 (99.1%), 96 (99.9%) 43 (99.9%) 73 (14.3%) 101 (31.4%) 44 (99.9%) 43 (50%) 43 (99.9%) 55 (25.1%) 72.03 (19.7%) 101 (31.4%) 144 (36.1%) 53.04 (13.1) 69 (28.9%) 97 (99.9%) 109 (13.1%) 124 (13.61%) 126 (71%) 44 (99.9%) 43 (44.2%) 44 (99.9%) 43 (31%)

C22H42O2

338

75.05

28.40

12 13

eicosane ethylene brassylate

C20H42 C15H26O4

282.556 270

78.06 80.32

4.49 11.52

5 6 7 8 9 10

55 (99.9%) 57 (41.7%) 69 (63.5%) 83 (48.4%) 97 (36.7%) 57 (99.9%) 41 (59.6%) 85 (41.0%) 55 (99.9%) 69 (31.3%) 84 (37.1%) 98 (72.6%)

Figure 2. Structures of the compounds from GCMS analysis of coconut shell extract.

of charged sites for interaction with acid dye, leading to enhanced coloration by a higher number of acid dye molecules binding to wool and enhanced π−π* interaction between wool amino acid residues and polyphenol.19,20 Vertical and LOI Flame Retardancy Analysis. Any textile material with LOI value of >26 is considered to be fire retardant. Untreated wool fabric showed the oxygen index value of 25, which means it has some inherent fire retardant properties. However, the wool polymer cannot sustain prolonged high-temperature heating as it fails the vertical flammability test. After application of the CSE-A and CSE-B,

Noncovalent bonding between wool protein and polyphenols involves hydrogen bonds that are formed between electronegative atoms of nitrogen or oxygen, especially of hydroxyl (−OH) groups, amino (−NH2), and a positively charged hydrogen atom from neighboring hydroxyl or amino group of another polyphenol or protein molecules (wool in our specific case).17 In addition to hydrogen bonds that involve polar groups, protein and polyphenols may interact via hydrophobic, nonpolar aromatic rings of polyphenols and aromatic amino acids, (proline, phenylalanine, tyrosine, tryptophan, histidine).18,19 The tannin−wool complex has a greater number 8326

DOI: 10.1021/acssuschemeng.7b02078 ACS Sustainable Chem. Eng. 2017, 5, 8323−8333

Research Article

ACS Sustainable Chemistry & Engineering

EDS analysis), an increase in add-on percent, and the presence of the phenolic groups in CSE medium. Thermogravimetric Analysis (TGA) in a Nitrogen and Air Atmosphere. Thermogravimetric (TG) analysis of the untreated wool and CSE treated wool fabric was performed to confirm the thermal stability as shown in Figures 4 and 5. It

Table 3. Color Value Details of the Untreated and Acid Dyed Wool Fabrics at pH 4.5a treated wool fabric

L*

a*

b*

K/S

only CSE-A only CSE-B acid dye in water acid dye in CSE-A acid dye in CSE-B

80.55 81.00 44.45 48.71 49.83

1.74 2.52 4.25 0.14 0.18

11.10 11.76 −46.62 −40.01 −37.45

1.31 1.39 2.17 3.14 3.79

a L*: lightness (0 black; 100 white). a*: red−green coordinates (positive values red; negative values green). b*: yellow−blue coordinates (positive values yellow, negative values blue).

Figure 4. TG analysis of the (a) untreated, (b) the acid dye in water, (c) only CSE-B, and (d) acid dye in CSE-B treated wool fabric in air.

Figure 3. UV of coconut shell extract (CSE-A) at (a) its original concentration, (b) acid dye in water medium 75 μg/mL, and (c) acid dye in CSE-A medium 75 μg/mL.

LOI values of the treated wool samples were found to increase to 30 and 36, respectively. This increase in LOI was about 20% in CSE-A and 44% in CSE-B when compared with that of untreated wool. Wool fabric, when treated with acid dye in water medium at 4.5 pH showed LOI of 26, and during vertical flammability testing, it showed flame and char dripping. However, with wool fabric treated with acid dye in CSE-A and CSE-B media at same pH, LOI values were found to increase to 36 and 38, respectively, which were almost 38% and 46% higher than that of acid dyed wool in a water medium. It also cleared the vertical flammability test with excellent results, and the details regarding flammability data have been reported in Table 4. These results indicate that the untreated wool fabric got burnt with flame within the 90 s, whereas CSE-A and CSE-B treated wool fabrics showed no flame and no after glow giving 8 and 5 cm char lengths, respectively. Wool dyed with acid dye in CSE-A and CSE-B media also showed char length of 6 and 2 cm, respectively with no flame and no after glow. This may be attributed to the presence of some inorganic compounds (refer

Figure 5. TG analysis of the (a) untreated, (b) the acid dye in water, (c) only CSE-B, and (d) acid dye in CSE-B treated wool fabric in nitrogen.

could help in understanding the mechanism of the flame retardant on CSE treatment on the wool biopolymer. From the TG curve, under air atmosphere (Figure 4), it was observed, that the untreated (a) and acid dye treated wool fabric in a water medium (b) showed multiple stages of weight loss starting from the first stage of 35−150 °C. The first stage may be attributed to the evaporation of the moisture which is in the form of free, loosely bound, and chemically bound in the wool polymer. Here in this stage, 8−9% mass loss occurred (Table 5). The TG curve for nitrogen (Figure 5), for the same

Table 4. Flammability Test Results of Vertical Flammability sample details add-on (%) LOI after flame (s) after glow (s) char length (cm)

untreated

CSE-A

25

6.89 30

burnt with flame in 90 s (char dripping occurs) 3−4 nil

no no 8

CSE-B

acid dye in water

10.9 2.5 36 26 Vertical Flammability Test no burnt with flame in 90 s (char dripping occurs) no 2−3 5 nil

8327

acid dye in CSE-A acid dye in CSE-B 12.9 34

14.29 38

no

no

no 6

no 2

DOI: 10.1021/acssuschemeng.7b02078 ACS Sustainable Chem. Eng. 2017, 5, 8323−8333

Research Article

ACS Sustainable Chemistry & Engineering

Table 5. Weight Loss Percent for Untreated and CSE Treated Wool Fabric at Different Temperature Ranges, from TGA Curves weight loss (%) in air

weight loss (%) in nitrogen

temperature (°C)

35−150

150−350

350−470

470−650

35−150

150−350

350−470

untreated (a) acid dye in water (b) only CSE-B (c) acid dye in CSE-B (d)

8.43% 7.77% 8.93% 9.06%

34.22% 31.77% 31.04% 34.13%

20.68% 21.32% 16.21% 37.66%

42.30% 43.06% 37.66% 29.42%

7.85% 7.43% 9.53% 9.75%

37.36% 38.83% 35.17% 38.05%

34.4% 33.56% 24.91% 19.32%

Table 6. UPF Values Untreated and Treated Wool Fabric parameters

UVA (315−400 nm)

UVB (290−315 nm)

UPF (290−400 nm)

untreated wool only CSE-A only CSE-B acid dye in water acid dye in CSE-A acid dye in CSE-B

14.11 1.55 0.94 3.76 1.10 0.55

3.64 0.80 0.51 1.59 0.59 0.27

20.38 116.61 189.47 55.11 165.81 364.97

samples showed earlier decomposition, lower weight loss, and suppression of the weight loss at 470 °C in air. The amount of residual char formation observed was more in the case of CSE treated wool both in the case of only CSE-B (c) and acid dye in CSE-B medium (d) than that observed in the case of untreated (a) and acid dye in water (b) systems. This may be due to the cross-linking of CSE with the wool and the formation of black, insulating, graphite-like intumescent layer on the fabric surface [refer to Figure 9b and d for char image], having higher resistance to oxidation. The increase in thermal stability for only CSE-B treated, and acid dye in CSE-B treated wool is supported by the lower mass loss as compared to that of untreated wool, as shown in Table 5. The flame retardant acts by altering the initial stage of wool pyrolysis favorably. The mechanism of fire retardancy proceeds by a decrease in the wool polymer volatilization causing char formation as well as the formation of a protective layer against the heat of the flame and retarding diffusion of combustible volatile compounds to the flame. Ultraviolet Protection Property of CSE Treated Wool Fabric. Ultraviolet protection abilities of textile materials are influenced by the functional groups (light absorbing) present in the dye or pigment, shade intensity, and additives. Ultraviolet protection factor (UPF) of the untreated wool fabric of 20.38, showed inherently good ultraviolet protective abilities from transmission of solar radiation. There was an excellent improvement of UPF rating of wool fabric after application of CSE-A and CSE-B at 4.5 pH. From Table 6, it was observed that UPF rating increased with increase in the concentration of CSE-B. Coconut shell extract behaves as a natural dye, and it bears deeper color when applied in CSE-B form as compared to CSEA. UPF property increased with a deep coloration which might be due to the richness in tannin in the case of CSE-B. Moreover, excellent UPF property after treatment with CSE-A and CSE-B on wool may be attributable to coated layer formed on the dyed wool fabric as shown in SEM image (refer to Figure 7). EDS analysis also showed the presence of elemental peaks for sodium, potassium, magnesium, silicon, phosphorus, sulfur, calcium, etc., on the dyed wool fabric which supports the improvement in UPF properties of wool fabric. ATR−FTIR Analysis. FTIR analysis was carried out for understanding the chemical groups present in the untreated and CSE-B treated wool fabrics as shown in Figure 6.

temperature range, confirmed the greater mass loss in CSE treated (flame retardant) wool compared to the one without CSE treatment. This is so because wool produces an extra 1.0 mmol of water per gram of wool in the peak below 300 °C, which may be derived from the hydroxyl groups of serine and threonine 9.7% and 7% respectively by weight of the amino acids present, when they are protonated by the flame retardant like CSE.21 The second stage of mass loss took place in the range of 150−350 °C wherein at 230−240 °C decomposition of the protein fiber structure occurs via rupturing of the hydrogen bond peptide helical structure and the ordered regions of wool undergo a solid to liquid phase change. This is followed by the destruction of disulfide linkage, and hydrogen sulfide liberation (250−295 °C); along with general pyrolytic decomposition above 250 °C, including char-forming reactions with dehydration and loss of other volatiles like carbon dioxide, water, hydrogen cyanide, ammonia, etc. In the presence of air, the formation of sulfur dioxide occurs between 270 and 320 °C.22 Singularly, for the only CSE-B treated wool fabric (c), only 35.17% mass loss occurred at this second stage under an inert atmosphere, less than control and dyed samples. This is also repeated in the TGA in the air, wherein the CSE treated wool with 31.04% mass loss and acid dyed in CSE wool with 34.13% mass loss show lower values than that of the untreated. The decreased mass loss for CSE treatment is also due to greater char formation than volatilization compared to control. This is supported by the lower mass loss figures in heat treatment under air compared to that of nitrogen, since oxidative dehydrogenation, an important char formation mechanism, occurs only in the presence of oxygen. The third stage of mass loss occurred exothermically above 350 °C, mostly due to the acceleration of hydrolytic scissions of keratin polypeptide chains, along with volatile-favoring reactions, and slower char oxidation reaction. In a nitrogen atmosphere, the rate of mass loss decreases to a lower extent and approximately with uniform rate up to 700 °C (Figure 5) while in the air, the rate increases and a major weight loss begins at about 470 °C. In air the rate later decreases until 650 °C all the sample has been volatilized (Figure 4). In an air atmosphere, beyond 470 °C, char cross-linking reactions become favored, thereby restoring the char versus volatile balance and form more complex cross-linked and probably aromatic structures, explaining its higher-than-expected resistance to oxidation.22 The flame retardant CSE coated wool 8328

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At 1400−1440 cm−1, a peak pair is observed when CSE-B (c, d) is present in dye mixture, attributed to CH2 and CH3 bending modes. The peak observed at 1232 (a), 1238 (b), 1242 (c), and 1252 cm−1 (d) for amide III which were almost same for all the curves. The regularity of molecular chains within a fiber can be estimated by the peak intensity at 1240 cm−1 of the amide III band, relative to the band which is around 1440 cm−1.26 The greater the value of I1240/I1450, the more disordered the molecular chains become.27 This suggests a greater degree of order in a molecular arrangement in the CSE treated wool compared to untreated and acid dye in water medium treated wool. The peak observed at 1044 cm−1 may be due to cysteic acid (−SO3−). The intensity of this peak is more for CSE-B treated wool without (c) and with acid dye (d) due to the more cysteic acid formation by acidic oxidation of (−S−S−) disulfide linkages. Significant is the binding of keratin with the dye SO3−2 groups in the 1050 cm−1 area. This is more in the case presence of CSE-B than in the case of acid dye in water. Also at 800−840 cm−1, doublet peaks appear in the presence of CSE-B, due to tyrosine residues which are due to permeation of CSE-B in disordered areas of wool keratin. The ATR-FTIR spectra also allow changes in the secondary structure of protein during fiber dyeing to be assessed, wherein protein modifications are limited to hydrogen, hydrophobic and van der Waals bonds, with the protein binding at positively charged fragments of the amino-acid chain. The main problem in identifying the real reaction areas in wool concerns the bonds between the dye and amino-acid reactive chain that participates in the reaction. SEM Analysis. SEM analysis showed (Figure 7) the waxy, smooth, untreated wool fiber with the presence of distinct, prominent scale edges, whereas CSE-A and CSE-B treated wool fiber forms a uniform thick layer coating on the surface of the wool fabric. CSE-A and CSE-B treated wool surfaces look much rough and without distinct scaly edges, more visible in the case of CSE-B treatment. Deposition of CSE-A and CSE-B on treated wool polymer is responsible for fire retardant and ultraviolet protection properties of the wool fabric. EDS Analysis. The energy dispersive X-ray spectroscopy (EDS) analysis of the pure dried CSE, untreated, and treated wool are represented in Figure 8. As far as the elemental analysis is concerned, pure CSE contains metallic elements like sodium, potassium, magnesium, phosphorus, sulfur, and

Figure 6. FTIR analysis of the (a) untreated, (b) the acid dye in a water medium, (c) only CSE-B, and (d) acid dye in CSE-B medium treated wool.

Untreated wool fiber showed a peak at 3286 cm−1 (a), only CSE-B treated wool at 3299 cm−1 (b), the acid dye in water medium at 3305 cm−1 (c), and acid dye in the CSE-B medium at 3284 cm−1 (d) due to −N−H stretching vibration of secondary amide (−CONH−). This mode of vibration of −N− H is stretching in the amide A band is very sensitive to the strength of a hydrogen bond.23 Hence, the increasing intensity of this peak in the presence of CSE is due to stronger and more numerous hydrogen bonds between wool −N−H··· (−O−) CSE dye (where ··· indicates a hydrogen bond). Another important peak was observed at 1615−1630 cm−1 responsible for the elastic vibration of CO bond (amide I). In the presence of CSE-B, the peak broadens up to 1680 cm−1, reducing sharp, symmetrical appearance. This indicates changes in the keratin conformation, increasing α-helix content and increasing disordered form, and reduced β-sheet forms (α helix 1648−1652 cm−1; β sheet 1628−1651 cm−1; disordered 1685−1692 cm−1). Increasing α-helix content is supported by the skeletal −C−C− at 938 cm−1, assigned to the α-helical backbone.24,25 Also, peaks observed at 1530 cm−1 (amide II band, for the bending deformation of C−N−H) in the case of untreated (a) and acid dye in water medium treated wool (b) decreased in intensity when CSE binds in wool, confirming reduced N−H bending due to increased hydrogen bonding.

Figure 7. SEM analysis of the (a) untreated wool, (b) only CSE-A treated, and (c) only CSE-B treated wool fabric. 8329

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Figure 8. EDS images showing the peak for (a) coconut shell extract, (b) untreated wool, and (c) only CSE-B treated wool fabric.

more blackish carbonaceous char mass. However, treated wool fabric in CSE-B medium showed also more shrinkage, and it formed residual char which was comparatively lighter grayish than that of acid dye in CSE-B medium treated fabric. As far as the char morphology is concerned, wool fabric (b and d) showed less damage (structural integrity and scales have been maintained partially) by burner flame. Also here, structural degradation along the axis also comes into play with distortion of the scales. However, the deformation is far less than the char morphology of the untreated wool (a) and acid dye in water medium treated wool (c), which had shown complete structural destruction. The char morphology of b and d showed melting, swelling, axial failure, and a distorted scale layer. X-ray Diffraction (XRD) Analysis. XRD patterns of wool fabric specimens, both untreated and dyed with acid dye in water or CSE-B medium as shown in Figure 10, show reducing intensity after treatment. The peak at about 9° corresponds to contribution from both α-helix and β-sheet crystalline structures. The broad peak at about 2θ = 21° is probably due to overlapping of the α-helix peak at about 17.8°, d = 5.1 Å, and the characteristic β-sheet structure peak at about 19°, which has d = 4.65 Å.29 The α-form crystal modification is the lattice structure that accommodates polypeptide chains with α-helical configuration, visible in the 17.8° peak while in the β-form crystal modification, the chains are parallel to the fiber axis. The CSE-B treated wool as seen from Table 8 shows the appearance of the distinct α-helix portion, while the β-conformation contribution shows a decrease in intensity of the peak at 19°, with increased interplanar distance by 0.06−0.08 Å. The CSE-B treated wool shows peak at 9° with reduced interplanar distance, by 0.07−0.16 Å, and the peak at 21° shows increased interplanar distance by 0.09−0.1 Å, both peaks of reduced intensity, compared to untreated and acid dye in water medium treated wool. The CSE-B treatment reduces crystallinity more than that observed in the case of acid dye treatment in water (Table 8). The least crystallinity occurs in the wool treated with acid dye/ CSE-B, with the distinct broadening of peaks. Crystallinity determination by X-ray diffraction analysis relies on a meaningful decomposition of the crystalline diffraction component and amorphous scattering component from the total intensity profile. In this analysis, it is achieved by a curve fitting technique, in which the crystalline and amorphous components are assumed to be a Lorentzian function. Percent crystallinity as obtained by X-ray measurements is defined as the ratio of areas under the crystalline peaks to the sum of the crystalline and amorphous peak areas:

calcium in addition to carbon, oxygen, nitrogen, and chlorine, which might be present in the form of natural inorganic biosalt molecules in the pure liquid CSE. The presence of these metals may also be responsible for the observed thermal stability of the treated wool. Untreated wool showed the presence of carbon, oxygen, sulfur, nitrogen and the very trace amount of sodium. As far as the EDS analysis for CSE-B treated wool fabric is concerned, unlike untreated wool fabric, it contains sodium, potassium, magnesium, chlorine, phosphorus predominantly. Data regarding the EDS analysis is represented in Table 7. Table 7. EDS Analysis of the Pure CSE, Untreated, and CSE Treated Wool Fabrics coconut shell extract (CSE) (a)

untreated wool (b)

only CSE-B treated wool (c)

elements

weight (%)

error (%)

weight (%)

error (%)

weight (%)

error (%)

C N O S Na Mg P Cl K Ca

44.29 0.00 44.88 0.47 1.22 0.43 0.45 4.17 3.89 0.19

±0.50 0.00 ±0.45 ±0.04 ±0.06 ±0.04 ±0.07 ±0.07 ±0.08 ±0.04

47.59 16.54 32.23 3.65 0.00 0.00 0.00 0.00 0.00 0.00

±0.56 ±0.80 ±0.46 ±0.07 0.00 0.00 0.00 0.00 0.00 0.00

44.39 8.99 37.21 4.16 0.87 0.13 0.40 2.24 1.61 0.00

±0.63 ±0.78 ±0.57 ±0.08 ±0.05 ±0.03 ±0.07 ±0.06 ±0.06 0.00

In the literature it is reported that coconut water also showed the presence of similar types of inorganic elements such as Ca, Fe, Mg, P, K, Na, Cu, Cl, S, Al, etc., and thus it supports the EDS results found in coconut shell extract.28 These elements which may be present as salt molecules on the treated wool fabric must be responsible for fire retardant property due to the richness of sulfur, phosphorus, and chlorine as primary constituents. Char Characteristics of Untreated and CSE Treated Wool Fabric. Figure 9 showed the char structure of the untreated and CSE-B treated wool fabric obtained from the vertical flammability test. The char picture of the untreated wool fabric (a) and wool fabric treated with acid dye in water medium at pH 4.5 (c) showed completely deformed structure. During burning untreated and acid dye in water, medium treated wool fabric showed rapid shrinkage and formed a lightweight, fragile, ashy black color char mass, broken into small pieces with a lot of water release. On the contrary, only the CSE-B treated (b) and acid dye in CSE-B medium (d) treated wool fabric showed less shrinkage and gave hard and 8330

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Figure 9. Char mass and morphology of (a) untreated wool, (b) only CSE-B, (c) the acid dye in water, and (d) acid dye in CSE-B treated wool fabric.

But in the presence of CSE-B, new α-helix regions are viewed, (also supported by FTIR data), though the overall crystallinity is reduced (refer Table 8). The primary structural units in the natural wool fiber are successive turns of the α-helix. The intrinsic stability of the α-helix, and thus the fiber results from intramolecular hydrogen bonds. Hence, CSE-B treatment gives greater thermal stability. Assessment of Fastness Properties of the Dyed Wool Fabric. The fastness ratings of CSE-A and CSE-B treated wool fabric in the presence of acid dye and absence of it are presented in Table 9. Wash fastness ratings of the wool fabrics dyed with only CSE-A and CSE-B were found to be good to very good. Also for acid dye in water and both CSEs showed

percent crystallinity = Acrystalline /(Acrystalline + KA amorphous) (4)

where K is a constant related to the different scattering factors of crystalline and amorphous phase and set to 1 for relative measures, computed by the X-ray crystallinity calculation module of the software (XRD-6100/7000 ver 7.01, with 6100 LabX Shimadzu X-ray diffractometer). The values of crystallinity, so obtained, compare well with reported crystallinity values of wool: 23.80%30 and 27.1%.31 The α helix to β-sheet transition (α−β transition) is a universal deformation mechanism in α-helix abundant protein materials such as wool, and it is seen in acid dyeing in water. 8331

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be “good” for acid dye in water and acid dye in CSE-A and CSE-B treated wool fabric. Wash Durability of the Fire Retardant Finishes on the Wool Fabric. Wash durability of CSE treated wool fabric was tested, and it was found that after ISO 1 wash, the acid dye in CSE-A and CSE-B treated wool fabric showed LOI of 29 and 33 respectively with hard blackish char mass formation occurred, whereas the untreated wool fabric showed dripping off the lightweight ashy char mass. It can be seen that the LOI value of the washed fabric decreased from 38 for CSE-B unwashed fabric to 33 in the washed fabric sample. However, it is significantly 27% higher than that of the wool treated with acid dye in a water medium (LOI 26). Vertical flammability of the washed acid dye in CSE-treated wool fabric showed flame for 3−4 s (CSE-A) and 1−2 s (CSE-B) and then extinguished whereas untreated wool fabric was burnt completely by flame. Therefore, we can say that the fastness property of flame retardant is still more promising in the case of CSE treated wool fabric which might be due to the formation of more crosslinkages with acid dye as compared to only CSE treated wool fabric. In the case of only CSE treated wool fabric after washing its LOI decreased from 30 to 27 for CSE-A and 36 to 29 for CSE-B. The decrease in the flame-retardant properties in the CSE treated sample after washing may be attributed to the partial removal of the active component of CSE molecules such as metal salts, phosphate and sulfates, and silicates as observed from EDS analysis.

Figure 10. X-ray diffraction analysis plots of (a) untreated wool, (b) the acid dye in a water medium, (c) only CSE-B treated, and (d) acid dye in CSE-B treated wool.

Table 8. Comparison of XRD Parameter Analysis for Untreated and Treated Woola parameters 2θ (deg) d* (Å) intensity (I/I1) 2θ d* intensity 2θ d* intensity 2θ d* intensity 2θ d* intensity 2θ d* intensity crystallinity (%) (lorentzian correction)

untreated wool (a)

acid dye in water treated wool (b)

only CSE-B treated wool (c)

acid dye in CSE-B treated wool (d)

8.96 9.8 44

8.88 9.95 44

9.16 9.64 33 17.59 5.03 23 19.00 4.66 35 20.02 4.43 100 20.22 4.39 100 21.28 4.17 63 22.54

9.08 9.73 65 17.71 5.00 44 19.08 4.647 44 20.06 4.42 100 20.48 4.33 87 21.189 4.189 63 21.96

19.40 4.557 43 20.0 4.43 100 20.24 4.38 91 21.7 4.09 89 26.47

19.36 4.58 47 20.02 4.43 97 20.26 4.38 100 21.42 4.14 85 25.91

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CONCLUSIONS The present study indicates that biowaste coconut shell extract (CSE) can impart coloration, flame retardancy, and ultraviolet protection properties to the proteinous wool fabric. The test results indicate that after application of CSE, the flame retardance measured in terms of LOI increased significantly. The thermal stability of the wool fabric was also increased, and in the vertical flammability test, treated samples showed selfextinguishment property and specific char length. Also, when CSE was used, instead of water, during acid dyeing, there was increased extent of coloration as well as thermal stability as compared to the fabric dyed from the water medium. Flame retardancy properties in the case of the CSE treated wool fabric may be attributed to the presence of phosphate, sulfate, silicates, metal salts, especially sodium and potassium chloride, etc. CSE treated wool fabric also showed excellent ultraviolet protection on the wool fabric which is possibly due to the formation of CSE-acid dye coating on the fabric. Thus, CSE being a waste biomaterial, and showing enhancement in acid dyeing as well as fire retardance and ultraviolet protection, is not only economically preferable but also is nontoxic, biodegradable and ecofriendly. Hence, the results clearly indicate the promising potential for application of CSE in multifunctional dyeing and finishing of wool.

a

d*: interplanar distance. 2θ: diffraction angle. CSE: coconut shell extract.

Table 9. Fastness Properties of CSE Treated Wool Fabric without and with Acid Dye fastness property

only CSE-A

only CSE-B

acid dye in water

acid dye in CSE-A

acid dye in CSE-B

washing fastness light fastness rubbing dry fastness wet

3−4 5 5 4−5

3−4 5 4−5 4

4−5 6−7 5 5

4 6 5 4−5

4 6 4−5 4

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AUTHOR INFORMATION

Corresponding Authors

a

*E-mail: [email protected] (M.D.T.). *E-mail: [email protected]. Tel. No.: +912233612811. Fax: +91-22-3361-1020 (P.P.).

Wash/rubbing fastness ratings: 5 excellent, 4 very good, 3 good, 2 fair, 1 poor. Light fastness ratings: 8 excellent, 7 very good, 6 better, 5 good, 4 fair, 3 moderate, 2 poor, 1 very poor.

ORCID

very good to excellent wash fastness ratings. The rubbing fastness for all the samples was also found to be very good to excellent. Light fastness was found to be “better” for only CSEA, and CSE-B treated wool samples was improved and found to

M. D. Teli: 0000-0003-0674-1128 Notes

The authors declare no competing financial interest. 8332

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ACKNOWLEDGMENTS One of the authors P.P. is indebted to University Grants Commission-Basic Scientific Research (UGC-BSR) having award letter number F.25-1/2014-15 (BSR)/No. F.5-65/ 2007(BSR), for the scholarship support from the Govt. of India during the study period.

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