Properties of Sorghum Red Pigment and its Application to Rayon Fabric

Dyeing

LIU Zhimeia, SONG Mingshub and LU Yanhua*c

Department of Light Chemical Engineering, Eastern Liaoning University, 325 Wenhua Road, Dandong, Liaoning, 118000, China

aemail:liuzhimei2@126.com,

bemail: songmingshu@163.com,

cemail: yanhualu@aliyun.com

Keywords: sorghum red; natural dye; wool dyeing; orthogonal experiment

Abstract. Natural dye sorghum red pigment is a kind of natural product from sorghum shell. In this

paper, the sorghum red pigment was extracted from a black sorghum shell produced. The spectrum

property of and photostability were analysized. The results showed that the maximum

absorption wavelength of the sorghum red pigment changed with pH values. The light stability

changed with pH values under light and no light conditions. Then rayon fabrics were dyed with direct

dyeing method by orthogonal experiments. The result indicated that the sorghum red pigment has

good property for rayon fabric dyeing, the rubbing and washing color fastness of rayon fabric samples

are reach to the requirement of textile dyeing.

Introduction

In recent years, some dye research and application organizations in many countries pay more attention

to vegetable dyes for its environmental compatibility. Natural vegetable dyes can be used to develop

ecological textile. It doesn’t pollute our environment and is safe for our body[1, 2]. Sorghum red

pigment is a kind of vegetable dye extracted from sorghum shell. As a natural pigment, sorghum red

pigment exhibits better biodegradability and generally have a higher compatibility with the

environment in comparison with synthetic dyes. In addition, many kinds of vegetable dyes have the

function of health protection [3, 4]. China is one of the countries produce mass sorghum, and there

are about 2 billion kilograms every year [5, 6]. However, large amount of sorghum shell is usually

burnt as fuel. Beside a few kinds, pigment content in sorghum shell is higher than other vegetable

dyes. There is no pollution in the production process, and the extraction method is simple. Sorghum

red pigment is stable to light, heat, oxidizing agents and reduction agents[7]. It has good dyeing force,

improved telangiectasia, anti-inflammatory function, reduced plasma glucose concentrations and

blood pressure, and so on[8].

Sorghum red natural pigment belongs to flavonic compounds, and it mainly contains two

components: One is 5,4'-dihydroxyl-isoflavone-7-O-galactoside, the other is

5,4'-dihydroxyl-6,8-dimethoxyisoflavone -7-O-galactoside[9]. The molecular structure is as follows.

O

OH

O

O

OH

Galactose

O¡¡ O

OOH

CH3O OH

OCH3

Galactose

5,4'-dihydroxyl-isoflavone-7-O-galactoside 5,4'-dihydroxyl-6,8-dimethoxyisoflavone-7-O-galactoside

From the view of domestic and overseas, research on the sorghum red pigment is mainly about the

development of extraction technology of its edible pigment, and it is used only on the aspect of food

dyeing, but it is not widely used on the fabric dyeing. In our previous work, the sorghum red pigment

was applied to silk, wool and cotton fabric dyeing process. In this paper, the properties of sorghum red

pigment were studied, and then rayon fabrics are dyed by direct dyeing with orthogonal experiment,

the dyeing properties including K/S value, color fastness were analysis.

Advanced Materials Research Vols. 821-822 (2013) pp 638-641Online available since 2013/Sep/18 at www.scientific.net© (2013) Trans Tech Publications, Switzerlanddoi:10.4028/www.scientific.net/AMR.821-822.638

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Experimental

Reagents and Materials. Black sorghum shell was from the waste of sorghum byproduce in Dandong,

China. Wool fabrics was from commercial product. Sodium hydroxide, hydrochloric acid

and absolute alcohol are all chemical pure agents.

Extraction of sorghum red pigment. The extraction process of sorghum red pigment was according to

our previous work [10]. The extraction condition is as follows:

80g/L crashed sorghum shell and Sodium hydroxide 20g/L were put into 500mL 1:1

deionized water and alcohol mixed solvent at 100°C for 2 hours, the extraction process was repeat 2

times, the solution was then filtered and volumed to 1000 mL to be used the following dyeing process.

The concerntration was defined as X which was a relative concerntration defined in the experiment.

Spectrum property and photostability test. Dyeing process of rayon fabric with sorghum red pigment.

The maximum absorption wavelength and the absorbance used to characterize photostability of the

sorghum red pigment were tested with UV-VIS spectrophotometer 751MC (Shanghai Instrument

Factory, China) spectrophotometer.

Dyeing of rayon fabric with sorghum red pigment. Rayon babric dyed with sorghum red pigment

by direct dyeing method. The dyeing process was carried out at a ratio of 1:50 MLR for 30 min at

80 °C at neutral pH. Dyed samples were further treated with the non-ionic detergent Lissapol N (0.5

g/L) at 60°C for 20 min, and rinsed in hot and then cold water.

Dyeing properties of sorghum red dyed rayon fabric measurement. Color values including

K/Svalue and ∆E were charecterized with measured by a spectrophotometer (Color-Eye 7000A U.S.).

Rubbing fastness tests were performed according to AATCC8-2004 with Y571B rubbing fastness

tester (Ningbo Textile Instrument Factory, China), and washing fastness tests were performed

according to AATCC61-2003（3A）with the SW-12A washing fastness tester (Wuxi Textile

Instrument Factory, China). Colorfastness was evaluated with ∆E by a Color-Eye 7000A

spectrophotometer.

Results and discussion

Spectrum property and photostability of sorghum red pigment. 1 mL of extraction sorghum red

pigment was used to dilute to 100 mL, the optical path was selected 1cm, maximum

absorption wavelength (λmax) at different pH values was tested as Fig.1.

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

380 400 420 440 460 480 500 520 540 560 580 600 620 640 660 680 700 720 740 760

Wavelength λ(nm)

Ab

sorb

ance

pH=3pH=4pH=5pH=6pH=7pH=8pH=9

Fig.1. Maximum absorption wavelength of sorghum red pigment at different pH values

Fig.1 showed that λmax was 490 nm when pH were 3 and 4, while λmax was 500 nm when pH was 5,

6 and 7. There was noλmax to be found when pH were 8 and 9, theλmax may be at ultraviolet region.

4 copies 1mL extracted sorghum red pigment were volumed 100 mL, then the pH values were

adjusted to 3, 5, 7, 9 respectively. The volumed solution were then divided to 2 parts, the 2 parts were

put under natural light and no light condition, the absorbance were then tested as Fig.5.

Advanced Materials Research Vols. 821-822 639

0.2

0.3

0.4

0.5

400 420 440 460 480 500 520 540 560 580 600

Wavelength(nm)

Ab

sorb

ance

Light 7 daysNo light 7 dayspH=3

0.2

0.3

0.4

0.5

400 420 440 460 480 500 520 540 560 580 600

Wavelength(nm)

Ab

sorb

an

ce

Light 7 daysNo light 7 dayspH=5

0.2

0.3

0.4

0.5

0.6

400 420 440 460 480 500 520 540 560 580 600

Wavelength(nm)

Ab

sorb

an

ce

pH=7No light 7 daysLight 7 days

0.20.30.40.50.60.7400 420 440 460 480 500 520 540 560 580 600

Wavelength(nm)

Abso

rban

ce

pH=9No light 7 daysLight 7 days

Fig.2 Anti-light stability of sorghum red pigment at different pH values

It was found from Fig.2 that the absorbance increased and the maximum absorption wavelength of

sorghum red pigment did not changed when pH were 3 and 5 under natural light and no light

condition, while the absorbance decreased. It meant that the unti-light stability is poor under nutural

and basic condition. The maximum absorption wavelength changed little when pH were 3, 5 and 7.

Dyeing process of rayon fabric with sorghum red pigment. The orthogonal experiment and result

analysis are shown in Table 1.

Table1 Quadrature experiments of direct dyeing L934

data

Factors

Levels

Temperature(°C) Concerntration pH value NaC1(g/L) Results

1 70 X 3 4 7.51

2 70 X/2 4 5 5.23

3 70 X/3 5 6 4.63

4 80 X 4 6 6.56

5 80 X/2 5 4 5.34

6 80 X/3 3 5 5.21

7 90 X 5 5 6.87

8 90 X/2 3 6 5.94

9 90 X/3 4 4 5.28

K/S

k1 5.790 6.980 6.220 6.043

k2 5.703 5.503 5.690 5.770

k3 6.030 5.040 5.613 5.710

R 0.327 0.940 0.607 0.333

640 Advances in Textile Engineering and Materials III

Table 1 showed that the effect order of each factor on K/S values of the sorghum red dyed rayon

fabric was Concerntration＞pH value＞Dyeing temperature＞Concerntration of NaC1. The dyeing

process condition could be determined as follows: the concerntration was X, pH value was 3, dyeing

temperature was 90°C, concerntration of NaC1 was 4 g/L.

Color fastness of crocking and washing. The color fastness of rayon fabrics dyed with sorghum

red pigment is shown in Table 2.

Table 2 Fastness results of sorghum red dyed rayon fabric

Fastness Rubbing fastness Washing fastness

Dry Wet Fading Staining

Direct dyeing 4 4 3～4 Cotton Wool

4 4

Table 2 indicated that the rubbing fastness of dry or wet of dyed rayon sample was 4, the fading

fastness of washing was 3～4, the staining fastness of washing is more than or equal to 4. The color

fastness results indicated that the results reached the require of dyeing process.

Conclusion

The sorghum red pigment can be extracted from natural waste of black sorghum shell. The maximum

absorption wavelength changed with pH value, λmax was 490 nm when pH were 3 and 4, while λmax

was 500 nm when pH was 5, 6 and 7. There was noλmax was found when pH were 8 and 9 in the visual

light region, and the light stability change with pH values under light and no light conditions.

The dyeing process condition was determined by means of orthogonal experiments. i.e. the

concerntration was X, pH value was 3, dyeing temperature was 90°C and the concerntration of NaC1

was 4 g/L.

The sorghum red pigment has good property for rayon fabric dyeing, the rubbing and washing color

fastness of rayon fabric samples are reach to the requirement of textile dyeing.

Acknowledgements

This work was financially supported by Natural Science Foundation of Liaoning Province

(No.201202081), and the Foundation of Key Discipline Project of Liaoning Province Universities

(No. 2012310).

References

[1] M. Ben Ticha, N. Meksia, N. Driraa, M. Kechidac and M.F. Mhennia. Ind. Crop. Prod. Vol. 46

(2013), p.350

[2] S. P. Vankar, S. Rakhi and V. Avani: J. Clean. Prod. Vol. 15 (2007), p. 1441

[3] F. A. Nagia and R.S.R. EL-Mohamedy: Dyes. Pigments. Vol. 75 (2007), p. 550.

[4] P. Roshan, S. Conxita and E. Pilar: Colloid. Surface. A Vol. 253 (2005), p. 175

[5] X. S. Li and S. Q. Tian. West. South. Ethnic. Univ. Vol. 17 (1991), p. 77

[6] L. Y. Wu and L. F. Jiang. Fine. Che m. Vol. 10 (1993), p. 7752.

[7] Yanhua Lu, Wanli Cheng, Jie Lin, J. China Text Lead. Vol. 5, (2005) p.109

[8] Xi Rao, Boling Yu, J. Text. Dye. Finish. J. Vol.2(2002), p. 49

[9] Wanli Cheng, Textile Auxil. J. Vol.1(2002), p. 31

[10] Y. H. Lu, W. L. Cheng, Y. Y. Chen and Z. M. Liu. Wool. Text. J. Vol. 2, (2007) p.22

Advanced Materials Research Vols. 821-822 641

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DOI References

[2] S. P. Vankar, S. Rakhi and V. Avani: J. Clean. Prod. Vol. 15 (2007), p.1441.

http://dx.doi.org/10.1016/j.jclepro.2006.05.004 [3] F. A. Nagia and R.S.R. EL-Mohamedy: Dyes. Pigments. Vol. 75 (2007), p.550.

http://dx.doi.org/10.1016/j.dyepig.2006.07.002 [4] P. Roshan, S. Conxita and E. Pilar: Colloid. Surface. A Vol. 253 (2005), p.175.

http://dx.doi.org/10.1016/j.colsurfa.2004.11.003