Soil Release Finish | Mechanism of Soil Release Finish | Factor Affecting the Soil Release Finish

What is Soil Release Finish?

The finish that allow stains to leave the fabric faster & makes fabric cleanable without significant loss of soil release properties.

Soil release is the term used to describe the clean ability of the fabric by the laundring process.

What is Soiling?
Soiling can be defined as smearing large surface of the fabric with dust or dirt or oil or grease or both.

What is Release Finish?
Release finish allows stains to be removed more easily during laundering compare to most common untreated fabrics.

Mechanism of Soiling:
A fabric gets soiled mainly by three types of mechanism

1. By mechanical adhesion:
  • The soil is adhere to the cloth by direct contact with a soiled surface or by rubbing of the garments against the skin or picking up dirt from liquors or from air.
  • The fabric construction facilitates such adhesion as the soil gets entrapped in inter fiber and inter yarn spaces or even into the capillary spaces of the fiber where it gets firmly deposited. Also soil which is oily in nature can diffuse into the fiber.
2. By adhesion by electrical forces
  • The soil is adhere to the fabric due to attraction of dust particles from air by electrically charged fiber surface.  
  • This phenomenon occurs mainly with synthetic fibers because of their low moisture regain. Positively charged fabric surface is soiled more than negatively charged surface.
3. By Redeposition of soil during washing
Which occurs particularly with nylon and polyester fabrics,the redeposition on these
  • Fibers takes place because of their oleophilic nature.
  • Another aspect of soiling is the effect of time lag between soiling and washing. When a soiled fabric is allowed to lie unwashed for many days, the soil diffuses inside the fiber and it becomes difficult to remove it.
Factors Influencing Soiling :

1. Moisture Regain:
  • Moisture regain of the fiber is the most important factor that influences soiling. Natural fibers and regenerated cellulose rayons have high moisture regain and have little tendency to accumulate static electricity. Even if static electricity is generated, it is quickly dissipated to the atmosphere.
  • Therefore, the problem of soiling and soil removal is not very acute in the case of fibers having high moisture regain.
  • Synthetic fibers have low moisture regain, therefore they accumulate static electricity which attracts dirt and dust from atmosphere.
  • Lower the moisture regain, higher is the attraction of soil. When the moisture regain of the fibers drops below 4%, soiling increases rapidly.
  • Polyester has the lowest moisture regain (0.4%) among synthetic fibers; therefore it attracts maximum soil. Since these fibers are hydrophobic, they do not swell in water and the removal of soil from the fiber becomes difficult.
  • In the case of blends with cellulosic fibers, whatever soil is removed from the cellulosic component during washing, gets redeposited on the synthetic fiber because the synthetic fiber being oleophilic, attracts oily matter from the dirty wash waters.
2. Electrostatic Charge:
  • Synthetic fibers accumulate static charge during manufacture and during wear. Charged fibers attract soil from the atmosphere, positively charged fabric attracting more soil than the negatively charged one.
Fabric Construction:
  1. Fabric construction, yarn count, twist and the cross section of the fiber influence soiling. Smaller the denier, greater is the tendency to soil because circular cross sectional fiber retains less soil than one with an irregular cross section
  2. Higher the twist in the yarn, greater the soil retention. Because Fabric with protruding fibers assists soiling.
  3. Loosely woven and open knitted fabrics are more prone to soiling than closely woven fabrics but removal of soil from loosely woven fabrics is easy. Because Fabrics made from filament yarn do not get soiled as fast as those made from spun yarns.
Particle Size of Soil:
The smaller the size of the soil particles, grater is the soil retention by the fabric.

Mechanical Work Lead in Soil Release Finish:
  1. Hydrodynamic flow of washing washing carrying away the removed soil
  2. Fiber flexing to force soil from between fibers during washing
  3. Surface abrasion to remove soil physically during washing
  4. Swelling of finish to reduce inter-fiber spacing.
Factor Affecting the Soil Release Finish: 

FACTORS
EXPLANATION
Nature of the soil
Oily soil or particulate soil, hydrophobic or
hydrophilic, liquid or solil
Kind of fibres
Type of fibre, hydrophilic or hydrophobic, smooth or porous fibre surface
Nature of textile
Textile construction; yarn (staple or filament), fabric (knit, woven or nonwoven
Effects of dyeing and printing
Difference in binder films, residual hydrophobic dyeing auxiliaries
Effects of other finishes
Compatible with antistatic finishes, easy-care finishes and other finishes not harmed by a hydrophilic surface.
Not compatible with conventional repellent finishes and other finishes where hydrophilicity is detrimental to finish performance
Washing conditions
Detergents, hydrodynamic flow in the washing machine

Mechanism of Soil Release Finish (DUALACTION):
  1. The flouro carbon polymers have the unusual property of being hydrophobic and oleophobic in air and hydrophilic and oil-releasing during the laundering process
  2. This is called as ‘dual action’ mechanism .
  3. The hydrophilic blocks are shielded by the fluorocarbon segments when dry, presenting a repellent surface
  4. After immersion in the wash bath, the hydrophilic blocks can swell and actually reverse the interfacial characteristics of the surface, yielding the hydrophilic surface necessary for easy oily soil release during washing.
  5. So the detergent used during washing can easily penetrate inside the fabric and enhance the soil release.
  6. Typically, these modified fluoro polymers are pad applied to fabrics followed by drying & curing 
Soil Release Finish
Development in Soil Release Finishes:
  1. Stain-repellency performance has been achieved by the fluorocarbon resins based upon C8 perfluoroacrylates.
  2. C8 fluorocarbon finishes produced via electrochemical fluorination, it is discontinued because PFOS (perfluorooctane sulfonate) can result as a breakdown product during the manufacturing process.
  3. At present only C6 fluorocarbon products are manufactured using this route because they do not involve PFOS, which is a does not causes pollution that is also bioaccumulative.
Troubleshooting for Soil-release Finishes:
  1. The performance of a soil-release finish depends upon its ability to provide a hydrophilic surface during the laundering process.
  2. Therefore any material deposited on the fibre surface that would reduce this necessary hydrophilicity should be avoided.
  3. Softeners, lubricants and other products that modify surface properties should be carefully investigated in laboratory trials before being used with fabrics treated with soil-release finishes.
Properties Achieved by Soil Release:
  1. Add care to garments
  2. Permits better wearability for improved soil release.
  3. Provides greater comfort in hot weather.
  4. Resists redepositing of soil when laundering. 
 
Author of This Article:
Manoj Kumar
B.Tech in textile Chemistry
SSM COLLEGE OF ENGINEERING
Salem, Tamilnadu, India
Email: manossm.kumar@gmail.com
 
 

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