Chemistry of Denim Manufacturing

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Ashraful Islam

Denim, the world’s most iconic fabric nowadays, comes from French “serge de Nimes” which refers to a particular type of fabric that was produced in Nimes, a town of France. Alongside accessories like belt, shoes, purses the majority of denim fabric is used in making apparel like jeans, skirts, shirts, jackets etc. Bangladesh is one of the largest denim exporters of the world. According to otexa, 585 million dollar denim goods were exported from Bangladesh to USA in 2019 and in Europe it was more than 1 billion dollar. This article will be described chemical uses in the denim production and their function.

In Pre-treatment stage following chemicals are used-

Chemical Name Function
 

Peroxide Stabilizer

o    Prevents degredation of pinholes and strength by suppressing decpmpositon of peroxide

o    Plays an important role to obtain high quality bleach product

Scouring Agent o    Eleminating hydrophobic impurities without deteriorating fabric itself
Desizing Agent o    It helps in the removal of added impurities in the form of starch and other synthetic sizes without having any adverse effect on the fiber.
Caustic Soda o    It is used to open up fabric for absorbtion of dye.

o    It is major chemical that fixes the dye and hydrosulphite in fabric.

 

In Dyeing stage following chemicals are used-

Chemical Name Function
 

Dispersing Agent

o    Assist the process of particle size reduction of dye.

o    Maintain a dispersion in a fine form through dyeing process.

 

 

Acrylic Polymer

o    Acrylic polymer containing hydroxyl groups are utilized in base coats as binders, which bind the pigments together usually a catalyzed cross linking mechanism with a polyisocyanate hardener providing a cheap resistant coating.
 

Polyvinyl Alcohol

o    It gives greater strength to yarn

o    It is used to make fabric more resistance to oil & greases

Dye Fixative o    Uses to prevent dye bleeding into the white areas
Scouring Agent o    Eleminating hydrophobic impurities without deteriorating fabric itself
NaOH o    Uses to maintain the pH level
Synthetic Dye o    It provides long lasting color effect
Sodium Bisulphite o    Use as a disinfectant or bleaching agent
Ethylene Diamine (EDTA) o    Prevents metal ion impurities from modifying colors of dyed product.
Silicon Defoamer o    Using to remove existing foam from fabric.
Ammonia o    Use to increase pH level
Potassium Persulphate o    Used as disinfectant and fabric bleach

 

In Sizing for weaving stage following chemicals are used-

Chemical Name Function
Lubricating Agent o    Use to remove crease mark, wrinkle mark
Polyvinyl Alcohol o    Use to make fabric resistant to oil & grease
Polyacrylates o    Used as a thickening agent because of its unique ability to absorb & hold onto water molecule
Modified Polyester o    Used to control shrinkage, wrinkle
Anti-Back Staining Agent o    It is an effective washing off agent to remove back stain from processed denim

 

In Rinse wash and desinzing following chemicals are used-

Chemical Name Function
Amylase Enzyme o    It gives denim a softer & worn in look
Silicon Softener o    Use to improve the strength of fiber & reduce abrasion
Resins o    It makes the fabric more stiffer, harsh & abrasive & increase durability
Acetic Acid o    Control pH value
Detergent o    Help fabric hold onto dyes & deactive chlorine in the water that can fade colors
Sodium Hypochlorite o    It is used when the indigo’s color needs to be lightened as required by fashion
HCL o    It is used to remove stubborn stains & debris
Acrylic Resins o    It is used to increase abrasion resistance & anti pilling effect

 

In wet fades and finishing stage following chemicals are used-

Chemical Name Function
Silica o    Creates a precise breached look
Sodium Hypochlorite o    Clean up the pocket linen & inner face of the jeans
Potassium Permanganate o    Used to increase bright effect in sandblast area
NaOH o    Remove impurities
Polyurethanic Resins o    Increase dimentional stability & anti-creasing effect
Acrylic Resins o    It is used to increase abrasion resistance & anti pilling effect

 

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