Analysis and Study of Effect of Natural Dye From Bombax malabarica on Silk Fabric

Abstract

The current study deals with the extraction of natural dye from Bombax malabarica flowers, readily available by-product. Dye was extracted under different operating conditions such as time (60–90 min), temperature (90–95 °C), and pH 9. The dyed samples were subjected to CIELAB system using Gretag Macbeth Color Eye 7000A Spectrophotometer for the evaluation of color strength and L*a*b* C and H values. To improve the dye uptake and color fastness, pre and postmordanting was carried out using alum, tannic, and tartaric acid mordants. Dyed silk fabrics were tested for its color fastness when subjected to light, washing, and rubbing. Fastness properties of dyed silk fabric samples were found considerably good. Mordanted silk fabric samples showed increase in dye uptake resulting in high color strength and better fastness properties. The dyed silk samples displayed good antimicrobial activity (reduction rate: 48%) against the bacteria Escherichia coli and (reduction rate: 55%) against Staphylococcus aureus.

Keywords

color dye process natural dyes

With increasing public awareness of eco-safety and health concerns, environmentally friendly and nontoxic bioresource products are gaining popularity in different aspects of our lives (Ebrahimi & Gashti, 2016; Kiumarsi, Gashti, Salehi, & Dayeni, 2017). Natural dyes obtained from insects and plants are renewable and sustainable bioresource products (Gong et al., 2019; Narayanaswamy, Ninge Gowda, & Sudhakar, 2013; Sudhakar & Ninge Gowda, 2011; Willemen, van den Meijdenberg, van Beek, & Derksen, 2018). Bombax malabarica, a member of family Malvaceae, is a lofty, deciduous tree found throughout India and in other parts of tropical and subtropical Asia. It is popularly known as the red silk cotton tree or the Indian kapok tree and is well distributed in temperate and tropical Asia. It is an important multipurpose tree, providing food, fodder, fuel, and fiber. In various ethnobotanical studies, researchers have shown that almost all parts of the plant (i.e., root, stem bark, leaf, flower fruit, seed, gum, thorns, and silk cotton) possess medicinal potential. However, its roots, stem bark, and flowers are the most commonly used to treat various ailments (Gupta, Khare, & Laha, 2004; Jain & Verma, 2012). B. malabarica is used for the treatment of gastrointestinal and skin diseases, gynecological and urinogenital disorders, general debility, diabetes, and impotence (Chadha, 1972). Flavonoids present in the flowers are kaempferol (Figure 1) and quercetin (Figure 2; Gopal & Gupta, 1972). In the present study, I explored the possibility of using the flower extract of B. malabarica as a source of natural colorant for silk. The plant material chosen for the study is abundantly available throughout India and is usually treated as waste. No report of these flowers being used as a source of dye is available; we report the performance attributes of the flower extract on silk for the first time.

Figure 1.

Kaempferol.

Figure 2.

Quercetin.

Materials and Methods

Materials

I collected the plant material, such as the fallen flowers, from B. malabarica. The collected plant material (2,000 g) was washed under flowing water to remove dust particles and then shade-dried at room temperature (25 ± 2 °C). The processed plant material was ground to powder form in an electrically operated grinder. Plain woven degummed mulberry silk fabric, weighing 52 g/m² with a yarn density of 122 ends/in. and 106 picks/in., was used for dyeing.

Chemicals Used

Chemicals such as alum [K₂SO₄Al₂(SO₄)₃·24H₂O], tannic acid [C₇₆H₅₂O₄₆], tartaric acid [C₄H₆O₆], acetic acid [CH₃COOH], sodium carbonate [Na₂CO₃], and sodium sulfate [Na₂SO₄] were procured from Vasa Scientific Pvt. Ltd, Bangalore, India.

Extraction of Color Component

For optimizing the extraction method, the aqueous extraction of dye was carried out under varying conditions of pH, duration, and temperature. In each case, the absorbance at maximum wavelength (λ_max) was measured using a Hitachi U-2000 UV–Vis absorbance spectrophotometer.

Mordanting Process

The dyeing experiments were carried out using silk fabric by adopting pre and postmordanting techniques. The samples were treated with different mordant solutions before and after dyeing. The material was dipped in 30 ml of prepared 5% mordant solution at a 1:30 material: liquor ratio (MLR) at 50–60 °C for 30 min. Then, the mordanted yarn was air-dried for 15 min. The dye solution was prepared at a 1:30 MLR with 10% dye, and the mordanted sample was then dipped in the dye solution for 60 min at 90 °C. The dyed material was washed with cold water, followed by a soap solution, then washed thoroughly again with water. The wet samples were dried at room temperature. Mordanting was carried out after dyeing for postmordanted samples (Gashti, Katozian, Shaver, & Kiumarsi, 2014; Narayanaswamy, Ninge Gowda, & Sudhakar, 2014).

Absorbance Measurements

The absorbance of the 10% dye solution was recorded before and after treatment of material on optical density at an average of three measurements. The amount of dye absorbed was calculated by using the relation:

% Dye absorbance = \frac{Absorbance before treatment - Absorbance after treatment}{Absorbance before treatment} \times 100

Optimization of Dyeing Conditions

Optimization of pH

Silk fabrics were dyed with equal concentration of the extract at 90 °C for 60 min to examine the effect of pH. The samples were dyed at various pH conditions (4–10), and the K/S values of dyed samples were determined. The maximum dye uptake expressed in terms of K/S values was observed at pH 4; hence, this was considered the optimum pH for dyeing silk (Gashti, 2009; Narayanaswamy, Ninge Gowda, & Sudhakar, 2016).

Optimization of temperature

Silk fabric samples were dyed with equal concentration of the extract at varying temperatures ranging from 50 to 90 °C and then the K/S values of the dyed samples were determined. The samples dyed at 90 °C showed maximum K/S values; hence, this was considered the optimum temperature for dyeing. Similarly, samples were dyed with equal concentrations, maintaining a dye bath at pH 4 and 90 °C for varying durations (30–120 min) to optimize the duration of extraction.

Dyeing

The dyeing of silk fabric samples was carried out at 90 °C in a dye bath maintained at pH 4 and containing 10% shade (On weight material) at an MLR 1:50 in a beaker dyeing machine for 60 min. After dyeing, samples were rinsed and soaped at 40 °C for 10 min using nonionic soap and then rinsed.

Determination of K/S Value

Color strength value was measured using a reflectance measurement. Color values were evaluated by means of K/S and CIELAB color difference values with an illuminant D₆₅/10° observer on Gretag Macbeth Color Eye 7000A Reference Spectrophotometer. Four measurements were made for each sample, and the variation in percentage reflectance values over a range of 350–750 nm was recorded. The K/S values were assessed using the Kubelka–Munk equation:

K / S = \frac{{(1 - R)}^{2}}{2 R},

where K is the coefficient of absorption, S is the coefficient of scattering, and R is the surface reflectance value of the sample at a particular wavelength.

Measurement of Fastness Properties

Washing fastness was assessed according to ISO 105 C02 (International Organization for Standardization, 1989) using a launderometer. Rubbing fastness was performed according to ISO 105-X12 (International Organization for Standardization, 2016) using a crockmeter. Light fastness was assessed according to ISO 105 B02 (International Organization for Standardization, 2013a) using a Xenotest light fastness apparatus. Color fastness to perspiration was measured according to ISO 105 E04 (International Organization for Standardization, 2013b).

Antimicrobial Activity

Escherichia coli, a gram-negative bacterium, was selected due to its popularity as a test organism and its resistance to common antimicrobial agents. Staphylococcus aureus, a pathogenic gram-positive bacterium, was used as it causes major cross-infection in hospitals and is the most frequently evaluated species (Chen & Chang, 2007; Gupta et al., 2004; Singh, Jain, Panwar, Gupta, & Khare, 2005).

Quantitative Assessment by Percentage Reduction Test

Specimens of the test material were shaken in a known concentration of bacterial suspension, and the reduction in bacterial activity was measured in standard time according to AATCC 100-2004 (American Association of Textile Chemists and Colorists, 2004). The efficiency of the antimicrobial treatment was determined by comparing the reduction in bacterial concentration of the treated sample with that of the control sample, expressed as a percentage reduction in standard time (Djipa, Delmée, & Quetin-Leclercq, 2000; Narayanaswamy et al., 2014):

% Reduction = [(A - B) / B] \times 100,

where A and B are the surviving cells (CFU/ml) for the flasks containing the control (blank cotton fabric) and test samples (natural dye–treated cotton fabric), respectively, after 18 hr of contact time.

Wash Durability Test

The wash durability of antimicrobial activity of the dyed sample was evaluated after different wash cycles. The samples were washed with 5% neutral soap solution for 20 min. The washed samples were tested for the retention of antimicrobial activity after 0, 1, 5, 10, and 15 launderings by the AATCC test method.

Results and Discussion

Optimization of Dye Extraction

The optical absorbance spectrum of extracts shows a maximum absorption peak in the visible region at the 354 nm wavelength, as shown in Figure 3. Figure 4 shows that the absorbance of the dye extracts increases with the increase in pH, which may be the result of high solubility of the dye component in alkaline conditions. The temperature for the extraction process varied from 60 °C to boiling, and the yields were found to be maximum at boiling (Figure 5).

Figure 3.

UV–Vis spectra of dye extract.

Figure 4.

Effect of pH on dye yield.

Figure 5.

Effect of temperature on dye yield.

The yield of dye was found to increase with duration, but the rate of extraction gradually decreased after 90 min (Figure 6). Therefore, the optimum condition for extraction was pH 9 at boiling temperature, with a duration of 90 min. The dye yield (crude) was found to be 38.5%. Increase in dyeing time increased the color strength (Figure 7). Unevenness of dyeing was observed when dyeing was obtained at 90 min. This is because the dye aggregates continuously accumulate on the surface of the fabric. Therefore, 60 min of dyeing duration with uniform dyeing was selected as the optimum dyeing time. Figure 8 shows that dye uptake increases gradually with increasing dye concentration. The quantity of dye uptake increased until the concentration of the dye bath reached 15% (w/v).

Figure 6.

Effect of duration on dye yield.

Figure 7.

Effect of dyeing time on color strength.

Figure 8.

Concentration of dye bath.

Absorption, Color Strength, and Color Coordinates of Dyed Samples

Maximum absorption was 93.5% using the tannic acid–treated sample, followed by alum- and tartaric acid-treated samples. The K/S values and color coordinates of the dyed silk samples pre and postmordant with different mordants are presented in Table 1. The K/S values of the mordanted dyed samples were found to be higher than the unmordanted sample. It was observed that all the color coordinates were positive with respect to red-green a* and yellow-blue b*; therefore, all of them lie in the yellow-red quadrant of the color space diagram. The maximum L value (90.85) was found in the case of the control sample, indicating a lighter shade compared to other samples. Minimum value (44.18) was recorded for the tartaric acid postmordanted sample. The coordinate a* ranged from 10.69 (postmordanted tartaric acid) to 13.22 (premordanted tannic acid), while the control sample showed 2.31. The coordinate b* ranged from 8.86 (premordanted tannic acid) to 11.65 (premordanted alum). Chroma of the dyed sample ranged from 41.27 (postmordanted tartaric acid) to 49.35 (postmordanted alum). The hue angle of the dyed samples ranged from 60.65 (premordanted alum) to 75.54 (premordanted tannic acid), while the control sample showed 46.74.

Table 1.

Colorimetric Data of Silk Samples Dyed With Bombax malabarica Flower Extract.

Mordant	Method	Absorption %	K/S	L*	a*	b*	C	H
Undyed	—	—	—	90.85	02.31	00.25	02.25	365.15
Control	—	63.3	1.34	52.28	13.22	09.63	43.18	46.74
Alum	Pre	87.6	4.69	48.81	11.81	11.65	45.36	60.65
Alum	Post	65.3	5.38	44.88	11.15	11.27	49.35	70.85
Tannic	Pre	93.5	5.22	46.74	12.67	8.33	44.24	75.54
Tannic	Post	65.3	5.45	44.75	11.35	10.68	44.28	68.68
Tartaric	Pre	86.6	4.74	45.42	11.80	10.14	43.41	67.35
Tartaric	Post	65.3	5.79	44.18	10.69	8.86	41.27	65.68

Note. Pre = premordanting; post = postmordanting; control = silk dyed without mordant; undyed = fabric without mordant and dye.

Table 2 shows data for color fastness to washing, light, and rubbing for silk samples dyed with the flower extract of B. malabarica in the presence and absence of mordants. In all cases, there was an overall improvement in the fastness properties of dyed samples over that of the control. The probable reason attributed is the tannin component of the dye, which might have helped in bonding with the fiber, thereby enabling the proper fixation on the fibrous material. Hence, mordanting alters the light absorption of tannins and makes them insoluble in water—ultimately improving washing fastness properties. It was observed that with the increase in K/S values, the fastness attributes of the silk samples also improved. This can be attributed to the bigger crystals formed due to the complex formation involving coumarin of the B. malabarica extract with various mordants.

Table 2.

Fastness Properties for Silk Fabric Dyed With Bombax malabarica Flower Extract.

Mordant	Method	Light	Washing Fastness		Rubbing Fastness
Mordant	Method	Light	CC	CS	Dry	Wet
Control	—	2	3	4	5	4
Alum	Pre	4	4	5	5	4–5
Alum	Post	4	4–5	5	5	4–5
Tannic	Pre	3–4	4	5	5	4–5
Tannic	Post	4	4	5	5	4–5
Tartaric	Pre	3	4	5	5	4–5
Tartaric	Post	4	4–5	5	5	4–5

Note. CC = color change; CS = color staining; Control = silk dyed without mordants.

Quantitative Assessment by Percentage Reduction Test

In the test against E. coli and S. aureus in the AATCC bacteriostasis broth, inoculated control and inoculated test fabrics were evaluated for percentage bacterial reduction by cell counting. The results of the percentage reduction test are shown in Table 3. The reduction percentages for E. coli and S. aureus correspond to the bacterial numbers on the respective control test of 9.3 × 10⁶/ml. The reduction percentage was found to be 55% for S. aureus and 48% for E. coli. It was surmised that bacterial inhibition may be due to the slow release of active substances from the fabric surface (Han & Yang, 2005).

Table 3.

Antibacterial Activity of the Dyed Fabric by Percentage Reduction Test.

Fabric Sample	Test Organism	Survival Cells (CFU/ml)		%Bacteria Reduction
Fabric Sample	Test Organism	Control Fabric	Treated Fabric	%Bacteria Reduction
Silk fabric treated with S.macrophylla extract	Staphylococcus aureus	9.3 × 10⁶	0.8 × 10⁶	55
Silk fabric treated with S.macrophylla extract	Escherichia coli	9.3 × 10⁶	1.3 × 10⁶	48

Wash Durability Test for Antimicrobial Activity

A wash durability test carried out with the test fabrics showed that significant antimicrobial activity was retained in the fabrics dyed with the extract for up to five washes (Figure. 9). After five wash cycles, the percentage of bacterial reduction was very low, and much less activity was found in the fabrics after 10 washes.

Figure 9.

Number of wash cycles.

Conclusion

In the current study, major emphasis has been given to extraction of dye, colorimetric assessment, and the study of antimicrobial properties of dye with extracts from waste flowers of B. malabarica. Dye extract can effectively dye silk fabric, imparting a brilliant brown color. The color varied with the change of mordanting agents under the same dyeing conditions. Postmordanting is a better procedure than premordanting, as the color depth of all the dyed fabrics had good color fastness to washing and rubbing and acceptable color fastness to light. The antimicrobial tests demonstrate an exciting opportunity for the dyed textile as a potential method in developing protective clothing against common infections in hospitals and hotels. In my current findings, I clearly demonstrate that extraction of natural colorants from abundantly available waste flowers of the plant B. malabarica is a sustainable technique for waste utilization and a potential alternative to harmful synthetic dyes.

Footnotes

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

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