Wrinkle Resistant Finishing Process of Cotton Fabric

Wrinkle Resistant Finishing: Mechanism, Advantages and Disadvantages

Pallavi Sunil Gudulkar
Department of Textiles (Textile Chemistry)
DKTE’S Textile & Engineering Institute, Ichalkaranji, India
Intern at Textile Learner
Email: pallavigudulkar@gmail.com

 

Introduction:
Wrinkle resistant finishing is a method of coating fabrics with a chemical resin that acts as a crosslinker between hydrogen bonds, enhancing stability and preventing wrinkling. The ability of a fabric to recover to a specific degree is referred to as crease recovery. Fabrics consisting of cellulose, regenerated cellulose, and blends containing synthetic fibers have a higher tendency to wrinkle after washing, tumble drying, and wearing. Today, everyone desires that his or her outfit would keep its ironed shape. Wrinkle-free coatings give the fabric a silky, wrinkle-free appearance. Wrinkle-free treatments are widely used in the textile industry to give wrinkle-resistance to cellulosic materials such as cotton fabric.

Why Cotton Creases More?
Bending is the main reason behind the crease formation. Bending tends to the formation of compression zone and an extension zone in the fabric. So, the outer side gets extended and inner portion of the bend gets compressed. And therefore, there must be strain and stresses getting developed in this region.

Cotton contain cellobiose unit. It has a primary hydroxyl group and secondary hydroxyl groups. Primary hydroxyl groups have high reactivity than secondary hydroxyl groups. The secondary bonds are hydrogen bonds. So many intermolecular and intramolecular hydrogen bonds can form due to a greater number of hydroxyl group and these are weak bonds. Due to weak bonds during the process of crease formation these bonds may break also as less energy is required to break them.

Mechanism of Wrinkle Recovery
Resiliency is the term used for wrinkle recovery. It has two components one is resistance to deformation and other is recovery from deformation. Creases are form due to strong mechanical forces. If covalent crosslinking is not available then wrinkle recovery will be less. Strain energy stored during bending should be release to get recovery. If covalent bonds are available then strain energy get stored the bonds gets stretched but they do not get break. So, if then the forces are released, they would like to recover by releasing that energy which has been stored during bending process. If naturally intermolecular crosslinks are not available then we have to create them. A crosslinking agent is needed for creating covalent links. Mainly bifunctional crosslinking agents are used. Polyfunctional crosslinking agents are generally not used as they can create a three-dimensional network which can make the fabric stiffer.

Evaluation of Crease Recovery
Crease recovery refers to a fabric’s capacity to return to its original state. This recovery is a quantitative measure of crease resistance expressed in terms of the crease recovery angle (CRA). The Shirley crease recovery tester is used to determine this. Fabric is given a crease by simply placing it between two glass plates and a 500gm weight for one minute. The creased fabric is clamped on the instrument.

Crease Recovery Tester
Figure 1: Crease Recovery Tester

The instrument is made up of a circular dial with a clamp to hold the specimen in place. The specimen hangs freely from the edge of a knife just beneath the dial’s center, and the angle at which the specimen recovers from creasing is determined by the index line or circle scale fitted along the circular dial. The recovery of a crease is determined by this recovery angle. When the angle is 0 degrees, recovery is zero, and when the angle is 180 degrees, recovery is full. The overall CRA of the fabric increases from around 150 degrees (untreated) to about 300 degrees when the CRAs of the warp and fill directions are added together (resin finishes). Crease recovery is dependent on the construction, yarn twist, pressure, time, and other factors. In most cases, wrinkle recovery occurs more in the warp than in the weft. This is due to the excellent quality and strength of warp yarns, as well as the fact that they are treated with size and held at higher tension during weaving, etc.

Wrinkle Resistant Finishing
Wrinkle resistant finishing mainly falls into two groups:

A. Deposition type of resin
As the name implies, this finish involves the application of resin to the cloth as a surface coating. There will be no reaction between the fiber and the resin in this case. Padding mangles with acid catalyst are used to apply them in soluble form to the surface of the cotton fabric. These resins provide a lower level of crease resistance than cross linking resins while still providing stiffness to the fabric. They include following resins:

  • Phenol formaldehyde resin
  • Urea formaldehyde resin
  • Alkyd resin
  • Ketone resin
  • Vinyl resin
Urea Formaldehyde resin
Figure 2: Urea Formaldehyde resin
Phenol Formaldehyde resin
Figure 3: Phenol Formaldehyde Resin

B. Crosslinking type of resin
It is necessary to create intermolecular crosslinking because these crosslinks are covalent. As they are covalent, they will stretch by during bending but will not break. As result recovery can take place. The crosslinking agents may be classified as

  1. Nitrogenous crosslinking agent
  2. Non-nitrogenous crosslinking agent

These type resins chemically react with the fiber and crosslink the fiber molecules. The type of finish obtain is durable and much better than deposition type. They are also known as N-Methylol compounds as the Methylol groups (-CH2OH) are attached to the nitrogen. The crosslinking compounds are commonly called resins, but the term pre-condensate is correct. Following are some example of crosslinking agents:

  • DMU (Dimethylol Urea)
  • DMEU (Dimethylol Ethylene Urea)
  • DMDHEU (Dimethylol Di hydroxy Ethylene Urea)
  • DMPU (Dimethylol Propylene Urea)
  • TMM (Trimethylol melamine/ melamine formaldehyde
Crosslinking of cellulose with DMDHEU
Figure 4: Crosslinking of cellulose with DMDHEU
Ionic crosslinking between the molecules
Figure 5: Ionic crosslinking between the molecules

Advantages of Wrinkle Resistant Finishing

  1. It improves the crease resistance and crease recovery property.
  2. It reduces the shrinkage of the fabric during laundering.
  3. It imparts a smooth and quick drying property.
  4. It improves resilience, handle and draping qualities.
  5. It improves the weight and dimensional stability.
  6. It increases the strength of rayon in both wet and dry state.
  7. It gives resistance to degradation by light and laundering.
  8. It improves the fastness to light and washing of many dyestuffs.
  9. It prevents the inter molecular slippage in the fiber core.
  10. It becomes partially water proof and Rot-proof.

Disadvantages of Wrinkle Resistant Finishing

  1. Environmental effect-release of free formaldehyde.
  2. It decreases the tensile strength and tear strength.
  3. It decreases the abrasion resistance.
  4. It gives unpleasant odor.
  5. It gives harsh and stiff feel.

Other Eco-Friendly Methods of Wrinkle Resistant Finish
To make wrinkle-resistant textiles, manufacturers often use a chemical technique called cross-linking. However, these approaches frequently use chemicals that contain high levels of the dangerous chemical formaldehyde. This material can leach from clothing during the manufacturing, wearing, or washing process, posing environmental and health risks. Other methods have been developed, however they either include formaldehyde or are prohibitively expensive. Yiqi Yang and colleagues set out to design a cross-linking process that would allow them to make wrinkle-resistant cotton clothes that would overcome these problems.

The researchers looked into a number of compounds that have been shown to exhibit wrinkle-resistance without the use of formaldehyde. They then experimented with other chemical combinations. Cross-linking citric acid with xylitol produced the best outcomes. Citric acid is a mediocre anti-wrinkling agent that causes clothes to yellow. However, when xylitol is cross-linked, the discoloration is reduced and the anti-wrinkling action is enhanced. This citric acid/xylitol combination is environmentally beneficial because it is created entirely of renewable raw resources. The researchers also established a cost-effective scale-up strategy that is comparable with formaldehyde-based approaches now employed by textile manufacturers and is more cost-effective than alternative “green” choices.

Conclusion
The advantages of wrinkle resistant finish are tremendous. Cotton is commonly used in garments because of its durability, capacity to tolerate harsh laundry processes, particularly in alkaline environments, and ability to absorb a wide range of dyestuffs. Cotton clothes, on the other hand, receive a negative grade during real wear due to their tendency for creases under slight squeezing and the retention of the crease for a long time. As a result, the ideal remedy for this issue is wrinkle resistant finishing.

References:

  1. https://www.slideshare.net/88azmir/wrinkle-resistance-finishing-wrinkle-free
  2. “Creating ‘greener’ wrinkle-resistant cotton fabric” (Press release). American Chemical Society. January 27, 2016. Retrieved July 23, 2020.
  3. https://www.slideshare.net/prateekNigamNift/2-resin-finish
  4. Textile finishing by Prof. Kushal Sen from IIT DELHI.

You may also like:

  1. Textile Finishing Process | Mechanical and Chemical Finishes in Textiles
  2. Determination of Fabric Crease Recovery by Shirley Crease Recovery Tester
  3. Classification of Textile Testing: Fiber Testing, Yarn Testing, Fabric Testing
  4. Determination of Fabric Abrasion Resistance by Abrasion Resistance Tester
  5. How to Determine Carpet Thickness by Shirley Thickness Tester
  6. Determination of Crimp Percentage of Woven Fabric
  7. Different Types of Textile Testing Methods

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