CHAPTER 10 IMPROVING LIGHT FASTNESS OF ...shodhganga.inflibnet.ac.in/bitstream/10603/33163/15/15...166 CHAPTER 10 IMPROVING LIGHT FASTNESS OF REACTIVE DYED COTTON FABRIC WITH COMBINED

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CHAPTER 10

IMPROVING LIGHT FASTNESS OF REACTIVE DYED

COTTON FABRIC WITH COMBINED APPLICATION OF

ULTRAVIOLET ABSORBERS AND ANTIOXIDANTS

10.1 INTRODUCTION

In the light fastness of dyes the impact of testing atmosphere, effect

of covalent bond and admixture of dyes were studied by the researchers. The

mechanisms by which dyes undergo photo degradation are thought to be

complex process (Oakes 2001). However, most of the research papers on this

subject suggest that UV light induced decomposition and visible light-induced

photo-oxidation are the two most important pathways of fading, as shown in

Equations (2.6) and (2.7).

Many authors studied the chemistry and reactive species involved

in photofading. Notably, Egerton & Morgan (1971b) in a series of papers

showed that reactive oxygen species (ROS) were produced by irradiation of

dyed fabrics which were capable of destroying dyes. Antioxidants are organic

compounds that are added to oxidisable organic materials to retard auto

oxidation (Cristea & Vilarem 2006). Antioxidants have been used only on

fabric dyed with natural dyes for light fastness improvement.

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UV photofading does not require oxygen (Batchelor et al 2003).

Rich & Crews (1993) studied the ability of UV absorber to reduce fading of

nylon coloured with acid dyes and concluded that UV absorbers were more

effective at reducing colour change on lighter shades. Yang & Naarani (2007)

studied improvement of the light fastness of reactive inkjet printed cotton and

found that the water soluble UV absorber had better light fastness improvement

than the water insoluble UV absorber. In the previous chapter, it has been

established that UV absorber and antioxidant application shows improvement

in light fastness. The light fading happened with ultraviolet light and visible

light in the presence of oxygen. This chapter analyses the effect of combined

application of antioxidants and ultraviolet absorbers on light fastness of

reactive dyed fabrics.

Nickel arylcarboxylates provide a greater improvement in the light

fastness in sunlight of acid colours than did conventional stabilizers (Oda et al

1981). Nickel sulphonate or carboxylate group was therefore of interest to

study the effectiveness of UV absorbers. Antioxidants containing these

groupings improve the light fastness of dyes.

The individual application of ultraviolet absorbers is not giving

significant improvement on yellow dyed samples, so this dye is expected to

fade by the visible light. Red dyed sample treated with vitamin C shows very

less fading as compared to phenyl salicylate, benzophenone, cafeic acid and

gallic acid treated samples. On blue dyed sample, both the antioxidant and

ultraviolet absorber treatment show improvement in light fastness and vitamin

C treatment shows good improvement on light fastness as narrated in the

Chapter 9.

In this Chapter, combined applications of antioxidants and

ultraviolet absorbers were tried on reactive dyed materials by exhaust and

pad-dry-cure application methods for improving light fastness properties. The

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durability of the both after treatments is analyzed by subjecting the treated

material to ten wash cycles and testing for light fastness.

10.2 MATERIALS AND METHODS

10.2.1 Materials

The materials used in this study and treatments to which they were

subjected to are described in sections 3.1.2.3 (single jersey fabric), 3.1.3

(chemicals used for pretreatment), 3.1.5 (dyes) and 3.1.4 (chemicals used for

dyeing). Antioxidants and ultraviolet absorbers used were listed in section

3.1.7 and fastness chemicals in section 3.1.10 of Chapter 3.

10.2.2 Methods

The single jersey fabrics made using 30 Ne cotton yarn were

pretreated by semi bleaching method (3.2.1.3) and dyeing carried out by

exhaust (3.2.2.1) method. Antioxidants and UV absorber application methods

were described in section 3.2.3. Fastness to wash, rubbing and light were

tested as per international standards explained in section 3.3. Colour strengths

and colour differences were measured by colour matching system as

described in 3.2.4.4 and 3.2.4.5 respectively.

10.3 RESULTS AND DISCUSSION

10.3.1 Effect of Antioxidants on Light Fastness Improvement

Visible light requires oxygen to degrade the dyes. Antioxidants like

gallic acid, vitamin C and cafeic acid absorb the oxygen radicals available for

photo degradation. Oxygen Radical absorbance capacity of ascorbic acid is

found to be more than Gallic acid and cafeic acid. This is the reason for good

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results of vitamin C (ORAC value 12.5) than cafeic acid (ORAC value 9.5)

and gallic acid (ORAC value 11.7).

10.3.2 Effect of UV Absorbers on Light Fastness Improvement

The ultraviolet light is an important cause in the fading of all dyes,

in the weakening of fibres and fabrics and in the photodegradation of many

other substances. The mechanism was explained in the previous Chapter

9.3.3.

10.3.3 Light Fastness Results of Chemical Treated Samples

Table 10.1 shows the colour difference (dE) measured by keeping

chemical treated sample as standard and 40 AFU light faded samples as batch.

In dyeing industry, the tolerance for passing shade between standard and batch is

dE 0.50. The grey scale or blue wool reading has wider denomination, so even

the smallest variation in fading can be measured by colour difference dE value.

The statistical analysis is also possible with dE value.

Table 10.1 Effect of application methods on light fading in terms of (dE)

Treatment C.I. Reactive Yellow 84 C.I. Reactive Red 22 C.I. Reactive Blue 198

Exhaust Pad-dry- cure Exhaust Pad- dry- cure Exhaust Pad- dry- cure

Without Treatment 2.76 2.76 6.35 6.35 5.32 5.32

Phenyl salicylate + Vitamin C 1.23 1.25 4.14 3.81 2.43 2.45

Benzophenone + Vitamin C 1.41 1.38 3.16 2.73 2.21 2.09

Phenyl salicylate + Gallic acid 1.61 1.72 4.54 4.34 2.97 2.87

Benzophenone + Gallic acid 1.38 1.26 4.12 3.98 3.45 3.23

Phenyl salicylate + Cafeic acid 1.55 1.61 4.65 4.43 3.12 3.19

Benzophenone + Cafeic acid 1.67 1.73 4.49 4.35 2.87 3.24

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The ANOVA test for the chemical treatments for each three

samples done and found that exhaust and pad-dry-cure shows (p-value 0.07 <

0.05) not significant. The chemical treatments with antioxidant and ultraviolet

absorbers are (p-value 1.46 E -06 > 0.05) significantly different with 95%

confidence level.

Figure 10.1 Light fastness (40 AFU) of C.I. Reactive Yellow 84 with chemical treatment

Figure 10.1 shows that light fastness results of C.I. Reactive Yellow

84 without treatment and after chemical treatment with exhaust and pad-dry-

cure methods. The light fastness after 40 AFU light exposure is measured as

dE with computer colour matching.

The colour difference (dE) is measured by keeping dyed sample as

standard and light faded samples as batch. Colour difference of dyed sample

after 40 AFU light fading is found to be dE 2.76, for phenyl salicylate +

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vitamin C treated sample dE is 1.23, for benzophenone + vitamin C treated

sample dE is 1.41, for phenyl salicylate + gallic acid treated sample dE is

1.61, for benzophenone + galic acid treated sample dE is 1.38, for phenyl

salicylate + cafeic acid treated sample dE is 1.55 and for benzophenone +

cafeic treated sample dE is 1.67.

The least colour difference dE was observed in phenyl salicylate +

vitamin C combination as the visible light induced photofading reduced by

antioxidant. Oxygen radical observance capacity of the vitamin C is higher

than the other antioxidants. Auto antioxidant by ultraviolet radiation is

inhibited by the presence of phenyl salicylate (UV absorbers). Combination of

the phenyl salicylate and vitamin C reduced the light fading from dE 2.76 to

1.23. Other combinations also give reduction in light fading.

The nickel complexes of phenylester ultraviolet absorbers and

phenolic antioxidants on light fastness in a polymer substrate are investigated

and found to be showing improvement. The most positive protection was

achieved in Acid dye by the presence of nickel carboxylate grouping,

particularly in the case of nickel salt of salicylic acid salicylate (Oda 2004).

The usage of ultraviolet absorbers or radical scavengers bearing a singlet

oxygen quencher has not been investigated for improving light fastness of

dyes by Oda (2004). These results correlate with our results.

The ANOVA test for the yellow dyed sample helps to confirm the

chemical treatments by exhaust and pad-dry-cure shows (p-value 0.63 > 0.05)

that the difference are not significant. The chemical treatments with

antioxidant and ultraviolet absorbers are (p-value 1.46 E -06 < 0.05)

significantly different with 95% confidence level.

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Figure 10.2 Light fastness (40 AFU) of C.I. Reactive Red 22 with chemical treatment

Figure 10.2 shows that light fastness of C.I. Reactive Red 22 after

chemical treatment. The light fastness after 40 AFU light fading is measured

as dE with computer colour matching. The colour difference is measured by

keeping dyed sample as standard and light faded samples as batch. Colour

difference of dyed sample after 40 AFU light fading is found to be dE 6.35,

for phenyl salicylate + vitamin C treated sample dE is 4.14, for benzophenone

+ vitamin C treated sample dE is 3.16, for phenyl salicylate + gallic acid

treated sample dE is 4.54, for benzophenone + gallic acid treated sample dE is

4.12, for phenyl salicylate + cafeic acid treated sample dE is 4.65 and for

benzophenone + cafeic treated sample dE is 4.49.

The lower colour difference was observed in benzophenone +

vitamin C combination dE is 3.16 achieved. It is comparable against the fabric

tested without treatment dE is 6.35. As the visible light induced photofading

reduced by antioxidant oxygen radical absorbance capacity of the vitamin C is

higher than the other antioxidants, auto antioxidant by ultraviolet radiation is

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inhibited by the presence of benzophenone (ultraviolet absorbers). Other

combinations also give reduction in light fading.

The ANOVA test for the Red dyed sample helps to confirm the


that the difference due to dyeing method are not significant. The chemical

treatments with antioxidant and ultraviolet absorbers are (p-value 1 E -06 <

0.05) significantly different from the sample tested without chemical with

95% confidence level. Figure 10.3 shows that light fastness of C.I. Reactive

Blue 198 after chemical treatment. The light fading after 40 AFU is measured

as dE with computer colour matching. The colour difference is measured by

keeping dyed sample as standard and light faded sample as batch. Colour

difference of dyed sample after 40 AFU light fading is found to be dE 5.32,

for phenyl salicylate + vitamin C treated sample dE is 2.43, for benzophenone

+ vitamin C treated sample dE is 2.21, for phenyl salicylate + gallic acid

treated sample dE is 2.97, for benzophenone + gallic acid treated sample dE

is 3.45, for phenyl salicylate + cafeic acid treated sample dE is 3.12, and for

benzophenone + cafeic treated sample dE is 2.87.

Figure 10.3 Light fastness (40 AFU) of C.I. Reactive Blue 198 with chemical treatment

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The lower colour difference was observed in benzophenone +

vitamin C combination dE from 5.32 to 2.21. The visible light induced

photofading got reduced by antioxidant. oxygen radical absorbance capacity

of the vitamin C is higher than the other antioxidants. Further auto antioxidant

by ultraviolet radiation is inhibited by the presence of benzophenone (UV

absorbers). All other chemical treatments also reduced the fading.

The ANOVA test for the Blue dyed sample helps to confirm the


not significant effect on light fastness. The light fastness results of the

chemical treated fabrics with antioxidant and ultraviolet absorbers are (p-

value 5.9 E -06 < 0.05) significantly different against without chemical treated

fabric with 95% confidence level.

The effect of application method of antioxidant and ultraviolet

absorber on light fastness can be derived from Table 10.1. All combined

chemical treatments show reduction in fading than the untreated sample.

Combined application of antioxidants and ultraviolet absorber gives better

light fastness than the individual application results. The above improvement

is due to the reduction in fading by both ultraviolet and visible light. Both

exhaust and pad-dry-cure application methods do not give significant change

in light fastness result. Lower fading was observed in yellow dyed samples

which are treated with phenyl salicylate and vitamin C in combination.

Improvement in light fastness of Red and Blue are found with Benzophenone

and vitamin C treatment compared with other treatments. As vitamin C has

higher ORAC value, that combination gives good results on light fastness.

Figure 10.4 shows the effect of exhaust method of chemical

application on light fading. It is found that the benzophenone and Vitamin C

combination shows the reduction in fading Yellow, Red and Blue dyed fabric.

Figure 10.5 shows the effect of pad-dry-cure method of chemical application

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on light fading. It is found that the benzophenone and Vitamin C combination

shows the reduction in fading of Yellow, Red and Blue dyed fabric.

Figure 10.4 Effect of exhaust method of chemical application on light fading (40AFU)

Figure 10.5 Effect of pad-dry-cure chemical application on light fading(40AFU)

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10.3.4 Durability of Chemical Treatment for Ten Wash Cycles

The durability of chemical treatment application method after ten

washing cycles is analysed. Table 10.2 and Figure 10.6 show the dE of the

faded sample before and after ten washing cycles. It is found that the

durability is good in pad-dry-cure method and not up to the expected level in

exhaust method. In exhaust method, there is no bond formed between cotton

and applied chemicals. Chemicals are applied only on the surface which is the

reason for poor stability. The durability of pad-dry-cure application method is

much better than the exhaust application. In this method, acrylic based binder

helps to retain the applied chemicals on the surface of fabric.

Table 10.2(a) Stability of chemical treatment after ten washing cycles in terms of light fastness (dE) for Yellow 84

Treatment on Reactive Yellow 84 dyed sample

Exhaust Pad-Dry-Cure Before wash

After wash

Before wash

After wash

without treatment 2.76 3.12 2.76 3.12Phenyl salicylate +Vitamin C 1.23 2.21 1.25 1.78Benzophenone+ Vitamin C 1.41 1.93 1.38 1.61Phenyl salicylate +Gallic acid 1.61 2.32 1.72 1.89Benzophenone+Gallic acid 1.38 2.35 1.26 1.92Phenyl salicylate+Cafeic acid 1.55 2.35 1.61 1.75Benzophenone +Cafeic acid 1.67 2.15 1.73 2.07

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Table 10.2(b) Stability of chemical treatment after ten washing cycles in terms of light fastness (dE) for Red 22

Treatment on Reactive Red 22 dyed sample


After wash

Before wash

After wash

without treatment 6.35 7.45 6.35 7.45Phenyl salicylate +Vitamin C 4.34 5.28 4.41 4.87Benzophenone+ Vitamin C 3.96 4.99 3.73 4.37Phenyl salicylate +Gallic acid 4.54 5.42 4.34 4.86Benzophenone+Gallic acid 4.12 5.37 3.98 4.64Phenyl salicylate+Cafeic acid 4.65 5.12 4.43 4.78Benzophenone +Cafeic acid 4.49 4.81 4.35 4.98

Table 10.2(c) Stability of chemical treatment after ten washing cycle in terms of light fastness (dE) for Blue 198

Treatment on Reactive Blue 198 dyed sample


After wash

Before wash

After wash

without treatment 5.32 6.43 5.32 6.43Phenyl salicylate +Vitamin C 2.43 4.12 2.45 2.98Benzophenone+Vitamin C 2.21 3.98 2.09 2.72Phenyl salicylate +Gallic acid 2.97 4.42 2.87 3.34Benzophenone+Gallic acid 3.45 4.34 3.23 3.91Phenyl salicylate+Cafeic acid 3.12 4.22 3.19 3.82Benzophenone +Cafeic acid 2.87 4.08 2.65 3.42

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(a) C.I. Reactive Yellow 84

(b)C.I. Reactive Red 22

Figure 10.6 Stability of application method of chemical treatment after ten washing cycles in terms of light fastness

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(c) C.I. Reactive Blue 198 Figure 10.6 (Continued)

10.3.5 Effect of Chemical Treatment on Wash Fastness

The effect of chemical treatment of staining on cotton fabrics

during wash fastness is shown in Table 10.3. The wash fastness of Yellow,

Red, Blue dyed samples are tested. The staining on adjacent fabrics is

measured by grey scale. The colour change during wash fastness is also

measured and no significant difference is observed. The result shows that the

chemical treatment does not affect the wash fastness.

Table 10.3(a) Effect of chemical treatment on wash fastness of Yellow 84

Without treatment wash fastness is 4.0

Treatment C.I. Reactive Yellow 84

Exhaust Pad-Dry- Cure Phenyl salicylate + Vitamin C 4.0 4.0Benzophenone+ Vitamin C 4.0 4.0Phenyl salicylate + Gallic acid 4.0 4.0Benzophenone+Gallic acid 4.0 4.0Phenyl salicylate+ Cafeic acid 4.0 4.0Benzophenone + Cafeic acid 4.0 4.0

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Table 10.3(b) Effect of chemical treatment on wash fastness of Red 22


Treatment C.I. Reactive Red 22

Exhaust Pad-Dry- Cure

Phenyl salicylate + Vitamin C 4.0 4.0

Benzophenone+ Vitamin C 4.0 4.0

Phenyl salicylate + Gallic acid 4.0 4.0

Benzophenone+Gallic acid 4.0 4.0

Phenyl salicylate+ Cafeic acid 4.0 4.0

Benzophenone + Cafeic acid 4.0 4.0

Table 10.3(c) Effect of chemical treatment on wash fastness of Blue 198


Treatment C.I. Reactive Blue 198

Exhaust Pad-Dry- Cure







10.3.6 Effect of Chemical Treatment on Rubbing Fastness

Figure 10.7 and Table 10.4 show the effect of chemical treatment

on dry rubbing fastness. The chemical treatment does not give any significant

influence on dry rubbing fastness. The dry rubbing fastness is slightly

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decreased in the phenyl salicylate + gallic acid combination treatment. There

is no change in the dry rubbing fastness by the application technique of

chemicals.

Figure 10.7 Effect of chemical treatment on dry rubbing fastness

Table 10.4(a) Change of dry rubbing fastness by chemical treatment of Yellow 84

Without treatment dry rubbing fastness is 4.5


Exhaust Pad-Dry-Cure







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Table 10.4(b) Change of dry rubbing fastness by chemical treatment of Red 22










Table 10.4(c) Change of dry rubbing fastness by chemical treatment of Blue 198










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Figure 10.8 Effect of chemical treatment on wet rubbing fastness

Figure 10.8 and Table 10.5 show the effect of wet rubbing fastness

by chemical treatment. The Exhaust method of chemical treatment does not

improve the wet rubbing. But, the pad-dry-cure method with acrylic binder

gives 0.5 rating improvement in wet rubbing fastness. It is due to the bonding

of surface dyes by binding chemicals.

Table 10.5(a) Effect of wet rubbing fastness by chemical treatment of Yellow 84

Without treatment wet rubbing fastness is 4.0)


Exhaust Pad- Dry- Cure Phenyl salicylate + Vitamin C 4.0 4.0Benzophenone+ Vitamin C 4.0 4.0Phenyl salicylate + Gallic acid 4.0 4.0Benzophenone+Gallic acid 4.0 4.0Phenyl salicylate+ Cafeic acid 4.0 4.0Benzophenone + Cafeic acid 4.0 4.0

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Table 10.5(b) Effect of wet rubbing fastness by chemical treatment (without treatment wet rubbing fastness is 3.5)


Exhaust Pad- Dry- Cure







Table 10.5(c) Effect of wet rubbing fastness by chemical treatment (without treatment wet rubbing fastness is 4.0)









10.3.7 Effect of Chemical Treatment on Light Fastness of Combination Shades

The Figure 10.9 shows the effect of chemical treatment on light

fastness of trichromatic shades. The light fastness for 20 AFU is tested and

compared in computer colour matching system against unexposed sample. It

was found that the chemical treatments reduce the colour fading. The trend of

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the colour fading is found similar for grey, brown and olive colour dyed

fabric. The best light fastness improvement in individual chemical application

was observed with Vitamin C treatment.

Figure 10.9 Effect of chemical treatment on light fastness of combination shades

In the combination treatment with ultraviolet absorbers and

antioxidants, the light fading is reducedcompared with the individual

treatment of dyed samples. The best result was found in phenyl salicylate +

vitamin C combination and benzophenone + vitamin C combination. The

reasons for the improvement are

1. Reduction in ultraviolet induced unimolecular colour

decomposition by ultraviolet absorber.

2. Reducion in visible light induced photo oxidation of colour by

removal of oxygen with antioxidants.

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The Table 10.6 shows the effect of chemical treatment on light

fastness of combination shades. The above treatments are statistically checked

by two way ANOVA with 95% confidence level and found that the

treatments are (p value 3.21E-11) significantly different from each other. The

best treatment to improve the light fastness is found to be the phenyl

salicylate and vitamin C combination.

Table 10.6 Effect of chemical treatment on light fastness of combination shades in terms of dE

Colour change in dE Light Grey Light Brown Light OliveWithout Treatment 3.23 2.87 2.67Phenyl salicylate 2.54 2.32 1.95Benzophenone 2.44 2.31 1.94Vitamin C 1.93 1.81 1.76Cafeic acid 2.21 2.42 2.07Gallic acid 2.15 2.21 2.01Phenyl salicylate + Vitamin C 1.59 1.31 1.18Benzophenone+ Vitamin C 1.63 1.38 1.32Phenyl salicylate + Gallic acid 1.91 2.12 1.62Benzophenone+Gallic acid 1.96 1.8 1.71Phenyl salicylate+ Cafeic acid 1.87 1.52 1.21Benzophenone + Cafeic acid 1.91 1.62 1.42

10.3.8 Effect of Chemical Treatment on Light Fastness of Combination Shades by AATCC 16E 20 AFU Method

Table 10.7 shows the effect of chemical treatment on combination

shades by AATCC 16E method. For the dyed sample and phenyl salicylate +

vitamin C treated samples, light fastness was tested as per AATCC 16E 20

AFU method. The result shows a reduction in fading up to one rating. This

will help to save the processor from any claim from the buyer for lower light

fastness.

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Table 10.7 Effect of chemical treatment on combination shades by AATCC 16E 20 AFU method

Treatment Sample Rating

Grey shade without treatment

2-3

Grey shade with Phenyl salicylate + vitamin C

3-4

Brown shade without treatment

2-3

Brown shade with Phenyl salicylate + vitamin C

3-4

Olive shade without treatment

3.0

Olive shade with Phenyl salicylate + vitamin C

4.0

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10.4 CONCLUSION

Visible light requires the oxygen to degrade the dyes. Usage of

antioxidants like gallic acid, vitamin C and cafeic acid absorb the oxygen

radicals available for photo degradation. The ultraviolet light is an important

cause for fading of dyes and this reaction does not require oxygen. The

combined application of antioxidants and ultraviolet absorbers improves the

light fastness of reactive dyed fabric. The combination treatment with

ultraviolet absorber and antioxidant reduces the light fading better than the

individual treatment of dyed samples. The best result was found in phenyl

salicylate + vitamin C combination and benzophenone + vitamin C

combination. The reduction in light fading up to one rating is achieved. This

research will help to save the processor to avoid claim from the buyer for

lower light fastness.

The chemical treatment does not change the staining on adjacent

fabric during wash fastness. The chemical treatment does not give significant

change in dry rubbing fastness. The dry rubbing fastness is slightly

decreased on treatment with the phenyl salicylate + gallic acid in

combination. There is no change in the dry rubbing fastness by the

application technique of chemicals.

Treating with chemicals gives 0.5 rating decrease in some of the

chemical treatments. The lower wet rubbing fastness was observed only in

blue shade. The red shade is treated with phenyl salicylate and vitamin C

combination gives 0.5 rating improvement whereas other treatments do not

alter the wet rubbing fastness. The pad-dry-cure with acrylic binder also gives

0.5 rating improvement in wet rubbing fastness due to the bonding of surfacr

dyes by binding chemicals.

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It is observed that the durability of the chemical treatment is better

in pad, dry and cure method than the exhaust method of application. The

reason is that the acrylic binder helps to bind the ultraviolet absorber and

antioxidants better on to the fabric surface.

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CHAPTER 10 IMPROVING LIGHT FASTNESS OF ...shodhganga.inflibnet.ac.in/bitstream/10603/33163/15/15...166 CHAPTER 10 IMPROVING LIGHT FASTNESS OF REACTIVE DYED COTTON FABRIC WITH COMBINED