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Analysis of phenolic yellowing behavior on white cotton fabric using different neutralizer and softener

Over the last few years, the problem of yellowing textiles has become progressively more widespread. It would be wrong to regard yellowing as a phenomenon arising from a single cause. There are more than 20 different ways in which white or pale-colored textiles can undergo this undesirable change in appearance.

Organic polymers often develop yellowish color as they age, the result of oxidative or degradative processes. Many companies in our country cannot meet the needs of buyers due to the phenolic yellowing problem. As a result, the shipment work is always canceled, and they are victims of Huge loss.

 

The problem of yellowing textiles
Analysis of phenolic yellowing behavior on white cotton fabric (imagea source: The Spruce)

 

Afterward, this product must sell in the local market at a lower price. This project will be helpful to get rid of this problem easily as well as ever financial loss and had a good relationship with the buyers.

Resolving Phenolic Yellowing Problem is a piloting project for the commercial stage in Bangladesh. So far, no industry has started resolving phenolic yellowing with this method. This method has come with the promising advantage to replace the conventional method. This is a possible approach towards sustainability in the upcoming industry revolution.

Keywords: Phenolic yellowing, softener, neutralizer, Citric acid, Acetic acid, Complex Acid (Commercial Anti-yellowing agent), sustainability.

Introduction

End-user of white or pale shade garments has experienced this problem. White or pale shade fabric turned yellowish due to phenolic yellowing. During storage time fabric turned into yellowish in packaging material with a complex chemical mechanism that produces phenolic compound named BHT (Butyl hydroxy toluene).

The pH, antioxidant used in the packaging material, presence in the air reacts in a complex way to produce such a problem. This happens mainly when the pH of fabric is higher than 7 that means when it is available [OH-] ion.

This phenomenon hampered the normal production operation. Reprocess needed to solve which is time-consuming as well generates extra costs. The industry is facing difficulties to meet buyer requirements once this happens. When fluorescent brightening agents (FBAs) were introduced, there were.

Instances of yellowing because of light, of acid, of impurities, or even of concentration. The largest proportion of cases involve phenolic antioxidants and oxides of nitrogen. The critical factors so far identified are, hindered phenol, air and NO, pH, auxiliaries, moisture & packaging. In this study, we found that acetic acid gives the least neutralization while citric acid has better performance, but commercial complex acid gives the best effect in terms of pH & anti-phenolic yellowing behavior.

Also, the complex acid gives the best whiteness index once the finishing is completed which vital for shade matching & shipment. ISO 105 X18 test method used to evaluate the performance.

Moreover, the cationic softener has a great propensity to cause yellowing while the non-ionic softener has the least. Although the commercial complex acid adds some additional cost in terms of difficulty it is viable to use in production.

Materials and method

                Fabric:

100% cotton knit Single Jersey with gsm 160 was used. The yarn count was 26s and the stitch length was 2.9mm.

Chemicals:

The neutralizing chemicals were Citric Acid, Acetic Acid & Commercial Anti yellowing Agent(Complex acid). The softening agent was Cationic Softener, Non-ionic Softener.

Pre-treatment of fabric

                Scouring & Bleaching

                The fabric was scoured and bleached at the same time as the below recipe.

Table 1: Scouring & bleaching recipe
Chemicals name Amount  

 

 

Temperature 900c, time 60 minutes.

Sequestering agent 1g/l
Wetting agent 1g/l
Detergent 1g/l
Caustic soda (50%) 5g/l
Stabilizer 2g/l

Neutralizing and softening

  • We used 3 different neutralizers & two softeners to neutralize & softening the fabric with different dosing. We also use the Phenolic yellowing test: ISO 105-X18 method.
Table 2: Neutralizing & Softening recipe (Acetic Acid)
Neutralizer Cationic softener Grade

(phenolic yellowing test)

Non-ionic softener Grade

(phenolic yellowing test)

Acetic Acid

0.5 g/l

1g/l 2 1g/l 2.5
2g/l 2.5 2g/l 3
3g/l 2 3g/l 2
Acetic Acid

1.0g/l

1g/l 2.5 1g/l 2.5
2g/l 3 2g/l 3
3g/l 2.5 3g/l 3.5
Acetic Acid

1.5 g/l

1g/l 3 1g/l 3.5
2g/l 3.5 2g/l 3
3g/l 3 3g/l 3.5

 

Table 3: Neutralizing & Softening recipe (Citric Acid)
Neutralizer Cationic softener Grade

(phenolic yellowing test)

Non-ionic softener Grade

(phenolic yellowing test)

Citric Acid

0.5 g/l

1g/l 2 1g/l 3
2g/l 2 2g/l 3
3g/l 2 3g/l 3
Citric Acid

1.0g/l

1g/l 2.5 1g/l 3.5
2g/l 2.5 2g/l 3.5
3g/l 2.5 3g/l 3.5
Citric Acid

1.5 g/l

1g/l 3 1g/l 4
2g/l 3 2g/l 4
3g/l 3 3g/l 4

 

Table 4: Neutralizing & Softening recipe (Complex Acid)
Neutralizer Cationic softener Grade

(phenolic yellowing test)

Non-ionic softener Grade

(phenolic yellowing test)

Complex Acid

0.5 g/l

1g/l 2.5 1g/l 3.5
2g/l 2.5 2g/l 3.5
3g/l 2.5 3g/l 3.5
Complex Acid

1.0g/l

1g/l 3 1g/l 4
2g/l 3. 2g/l 4
3g/l 3 3g/l 4
Complex Acid

1.5 g/l

1g/l 3.5 1g/l 4.5
2g/l 3.5 2g/l 4.5
3g/l 3.5 3g/l 4.5

Reason for phenolic yellowing

Residual alkali on fabric

  • The insufficient neutralizing effect after bleaching or scouring (e. g. using acetic acid or volatile acids gives an alkaline pH value after drying, short and too few rinsing baths, the problem with core alkali.)
  • Alkaline processing water.
  • High concentration of hydrogen carbonate (temporary hardness).

Softeners

  • Cationic softeners can lead to Phenolic Yellowing.
  • Cationic softeners yellow more than non-ionic ones.
  • The yellowing effect becomes stronger when residual alkali is on fabric too.

 Presence of nitrogen oxides

  • During thermo-setting

Oil- and gas heated stenter frames

  • In warehouses during storage

Exhaust gases of forklifts.

  • Environmental pollution

Industrial plants, motor vehicles, etc.

Phenolic yellowing reaction on fabric

  • Yellowing of the polyamide fiber

The function of acid to protect the fabric from phenolic yellowing

Result

In this study, we found that acetic acid gives the least neutralization while citric acid has better performance, but commercial complex acid gives the best effect in terms of pH & anti-phenolic yellowing behavior. Also, the complex acid gives the best whiteness index once the finishing is completed which vital for shade matching & shipment. ISO 105 X18 test method used to evaluate the performance. Moreover, the cationic softener has a great propensity to cause yellowing while the non-ionic softener has the least. Although the commercial complex acid adds some additional cost in terms of difficulty it is viable to use in production.

Conclusion

The experimental data & testing results depict that the current conventional neutralizing process with acetic acid is not sustainable. Besides this weak organic acid is volatile which does not perform core neutralization which is another concern. The citric acid gives better neutralization but not up to the mark to avoid phenolic yellowing problems. Whereas the commercial complex acid performs good neutralization as well as phenolic yellowing rating as per buyer expectation. Besides, cationic softener prone to phenolic yellowing whereas non-ionic one gives a better result. Although this process adds some additional cost but in terms of quality & difficulty has a better advantage for the industry.

If anyone has any feedback or input regarding the published news, please contact: info@textiletoday.com.bd

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