CHEMICHALS THAT DAMAGES COTTON FABRIC PERMANENTLY

Cellulosic fibers are fibers made from cellulose, a natural polymer derived from the cell walls of plants. These fibers can be natural or manufactured, and they are known for their versatility, comfort, and biodegradability. Here are the main types of cellulosic fibers:

Natural Cellulosic Fibers

1. Cotton

• Derived from the seed hairs of the cotton plant (Gossypium species).
• Widely used in textiles due to its softness, breathability, and absorbency.

2. Linen:

• Made from the flax plant (Linum usitatissimum).
• Known for its strength, durability, and coolness in hot weather.

3. Jute:

• Extracted from the jute plant (Corchorus species).
• Used for making burlap, hessian, and other coarse fabrics.

4. Hemp:

• Comes from the hemp plant (Cannabis sativa).
• Valued for its strength, durability, and resistance to mold and UV light.

5. Ramie:

• Produced from the stems of the Chinese nettle plant (Boehmeria nivea).
• Known for its luster, strength, and resistance to bacteria and mildew.

Manufactured Cellulosic Fibers

1. Rayon:

• Made by chemically treating cellulose from wood pulp or cotton linters.
• Includes subtypes like viscose, modal, and lyocell, each with unique properties but generally known for their silk-like feel and drape.

2. Lyocell:

• A type of rayon made using a more environmentally friendly solvent spinning process.
• Known for its strength, softness, and biodegradability.

3. Cellulose Acetate:

• Produced by acetylating cellulose fibers.
• Used in textiles and plastics, known for its glossy finish and flexibility.

Properties of Cellulosic Fibers

• Absorbency: Highly absorbent, making them comfortable to wear in warm climates and good for use in towels and bedding.
• Biodegradability: Natural cellulosic fibers are biodegradable and environmentally friendly.
• Comfort: Soft and comfortable against the skin, with good breathability.
• Dyeability: Easily dyed, allowing for a wide range of colors and patterns.
• Strength: Generally strong, especially in the case of linen and hemp, but some (like cotton) may weaken when wet.

Applications

• Textiles: Clothing, household linens, upholstery, and industrial textiles.
• Paper: Various grades of paper and cardboard.
• Medical: Absorbent surgical dressings, bandages, and other medical products.
• Industrial: Filters, ropes, and packaging materials.

Environmental Impact

Natural cellulosic fibers are generally considered environmentally friendly due to their renewable sources and biodegradability. However, the cultivation of some plants (e.g., cotton) can be resource-intensive, requiring significant water, pesticides, and fertilizers. Manufactured cellulosic fibers like rayon and lyocell can also be sustainable if produced using environmentally responsible processes.

CHEMICHEL THAT COULD A DAMAGE THE CELLULOSIC FIBER, RESULTS FABRIC WILL WORN UP, WEIGHT LOSS, FIBERS DROPS REASONLESS IN BRUSH FABRIC, NO WAY OUT TO SAVE THE FABRIC.

Mechanism of Acid Damage to Cotton Fiber

Protonation of Glycosidic Oxygen:

• In acidic environments, the glycosidic oxygen atoms in the cellulose polymer can become protonated by the hydrogen ions (H?) from the acid.
• Protonation makes the glycosidic bond more susceptible to cleavage.

Hydrolysis of Glycosidic Bonds:

• Once protonated, the glycosidic bonds can undergo hydrolysis, where a water molecule breaks the bond between the glucose units.
• This reaction leads to the breakdown of the long cellulose chains into shorter segments and eventually into individual glucose units.

Reduction in Degree of Polymerization:

• The hydrolysis of glycosidic bonds results in a decrease in the degree of polymerization, which refers to the number of glucose units in a cellulose chain.
• As the degree of polymerization decreases, the cotton fiber loses its structural integrity.

Formation of Weak Points:

• The breaking of glycosidic bonds creates weak points along the cellulose chains.
• These weak points lead to a loss of tensile strength, making the fibers more prone to breakage and damage.

Physical and Chemical Degradation:

• As hydrolysis continues, the cotton fibers become weaker, more brittle, and less flexible.
• The fibers may also show signs of discoloration and degradation at a microscopic level.

Factors Influencing Acid Damage

Concentration of Acid:

• Strong acids, like sulfuric acid or hydrochloric acid, can cause rapid and extensive hydrolysis of cellulose.
• Even weak acids, if present over long periods or in sufficient concentration, can cause significant damage.

Temperature:

• Higher temperatures accelerate the hydrolysis reaction, increasing the rate at which glycosidic bonds are cleaved.

Duration of Exposure:

• The longer the cotton fibers are exposed to acidic conditions, the more extensive the damage will be.

Moisture Content:

• Water is necessary for the hydrolysis reaction, so the presence of moisture can enhance the damaging effects of acids on cotton fibers.

Practical Examples of Acid Damage

Textile Industry:

• Improper handling of acidic dyes or chemicals can lead to the degradation of cotton fabrics.
• Acidic perspiration can also weaken cotton garments over time.

Paper Products:

• Acidic environments can damage paper products made from cotton fibers, leading to brittleness and yellowing of the paper.

Storage Conditions:

• Cotton textiles stored in acidic conditions (e.g., in contact with acidic materials) can deteriorate faster.

Acids damage cotton fibers by hydrolyzing the glycosidic bonds in cellulose, leading to a reduction in the degree of polymerization and mechanical strength of the fibers. The extent of damage depends on the concentration of the acid, temperature, duration of exposure, and presence of moisture. This process results in weakened, brittle, and potentially discolored cotton fibers.

Mechanism of Alkalis Damage to Cotton Fiber

Alkalis can damage cotton fibers, which are primarily composed of cellulose, through several mechanisms. While cellulose is generally more resistant to alkali than to acid, strong alkalis can still cause significant damage under certain conditions. Here’s a detailed explanation of how alkalis can damage cotton fibers:

Structure of Cotton Fiber

Cotton fibers are made of nearly pure cellulose, a polymer composed of β-D-glucose units linked by β-1,4-glycosidic bonds. These long chains form microfibrils that provide strength and flexibility to the fibers.

Mechanism of Alkali Damage to Cotton Fiber

Saponification of Impurities:

• Cotton fibers often contain impurities such as waxes, pectins, and oils.
• Strong alkalis, like sodium hydroxide (NaOH), can saponify these impurities, converting them into soaps and glycerol.
• This cleaning process can sometimes weaken the fiber structure if not controlled properly.

Swelling and Distortion:

• In the presence of strong alkalis, cotton fibers absorb water and swell.
• This swelling can lead to physical distortion and weakening of the fiber structure.
• The swelling disrupts the hydrogen bonds between the cellulose molecules, leading to a temporary loss of mechanical strength.

Mercerization:

• Mercerization is a controlled process where cotton fibers are treated with strong alkalis (usually NaOH) to improve luster, strength, and dye uptake.
• However, if not done correctly, this process can damage the fibers.
• Excessive or prolonged exposure to alkali can cause irreversible weakening and loss of tensile strength.

Alkaline Hydrolysis:

• Under severe conditions, strong alkalis can break the β-1,4-glycosidic bonds in cellulose through alkaline hydrolysis.
• This reaction leads to a reduction in the degree of polymerization, breaking down cellulose chains into shorter fragments.
• Alkaline hydrolysis results in the weakening and eventual disintegration of the cotton fibers.

Factors Influencing Alkali Damage

Concentration of Alkali:

• Higher concentrations of alkali lead to more significant swelling and greater potential for damage.
• Dilute alkali solutions are less likely to cause severe damage but can still weaken fibers over time.

Temperature:

• Higher temperatures accelerate the reactions between alkali and cellulose, increasing the rate of damage.
• Elevated temperatures combined with alkali treatment can lead to more severe weakening of the fibers.

Duration of Exposure:

• Longer exposure to alkali increases the extent of swelling, distortion, and potential for hydrolysis.
• Prolonged contact with strong alkali can lead to substantial damage to the cotton fibers.

Mechanical Stress:

• Cotton fibers under mechanical stress during alkali treatment are more prone to damage.
• Stretching or pulling fibers while they are swollen can cause them to break or weaken more easily.

Practical Examples of Alkali Damage

Improper Washing:

• Washing cotton fabrics with strong alkaline detergents or bleach can lead to fiber damage, especially at high temperatures.
• Repeated washing in strong alkaline solutions can cause cumulative weakening of the fabric.

Textile Processing:

• Incorrect mercerization or other alkaline treatments during textile manufacturing can weaken cotton fibers.
• Excessive alkali use in processing can result in reduced durability of the finished product.

Environmental Exposure:

• Cotton fibers exposed to alkaline industrial pollutants or agricultural chemicals may suffer damage over time.
• Such exposure can lead to gradual weakening and loss of fiber integrity.

Strong alkalis can damage cotton fibers by causing swelling, saponification of impurities, and in severe cases, alkaline hydrolysis of cellulose. The extent of damage depends on the concentration of the alkali, temperature, duration of exposure, and mechanical stress applied to the fibers. While cotton is more resistant to alkali than acid, improper handling or prolonged exposure to strong alkalis can lead to significant weakening and degradation of the fibers.

Mechanism of Oxidative Damage to Cotton Fiber

Oxidative Cleavage of Cellulose Chains:

• Oxidizing agents such as chlorine, hydrogen peroxide, and sodium hypochlorite (bleach) can break the glycosidic bonds in cellulose.
• This process, known as oxidative cleavage, leads to the formation of shorter cellulose chains.
• The breaking of these chains reduces the degree of polymerization, weakening the fiber structure.

Formation of Carbonyl and Carboxyl Groups:

• Oxidation introduces functional groups such as carbonyl (–C=O) and carboxyl (–COOH) groups into the cellulose structure.
• These groups can lead to further degradation through chemical reactions with other components of the fiber or environmental factors.

Reduction in Mechanical Strength:

• The oxidative cleavage of cellulose chains and the introduction of new functional groups reduce the tensile strength and elasticity of cotton fibers.
• Weakened fibers are more prone to breakage and wear.

Discoloration:

• Oxidation can cause discoloration of cotton fibers, resulting in yellowing or other color changes.
• This is often due to the formation of chromophoric groups within the cellulose structure.

Specific Oxidizing Agents and Their Effects

Chlorine and Hypochlorites:

• Commonly used in bleaching processes to whiten cotton fibers.
• Excessive exposure or improper rinsing can lead to significant fiber damage, including weakening and brittleness.

Hydrogen Peroxide:

• Used as a bleaching agent that is considered more environmentally friendly than chlorine.
• While less aggressive, prolonged or improper use can still cause fiber damage and weaken the cotton.

Ozone:

• Used for bleaching and disinfecting textiles.
• Can cause oxidative damage if not carefully controlled, leading to fiber degradation.

Factors Influencing Oxidative Damage

Concentration of Oxidizing Agent:

• Higher concentrations result in more aggressive oxidation and greater fiber damage.
• Proper dilution and controlled use are essential to minimize damage.

Temperature:

• Elevated temperatures can accelerate oxidative reactions, increasing the rate of damage to cellulose fibers.
• Most bleaching and oxidizing processes are conducted at controlled temperatures to prevent excessive damage.

pH Level:

• The pH level of the oxidizing solution can affect the rate and extent of oxidation.
• For example, chlorine-based oxidizing agents are more aggressive in acidic conditions.

Duration of Exposure:

• Longer exposure times lead to more extensive oxidative damage.
• Short, controlled exposure minimizes fiber weakening while achieving the desired bleaching effect.

Practical Examples of Oxidative Damage

Textile Processing:

• Improper bleaching or use of oxidizing agents during textile processing can weaken cotton fibers, making fabrics more prone to tearing and wear.
• Controlled use of hydrogen peroxide and other milder oxidants is preferred to reduce damage.

Laundry Practices:

• Using bleach in home laundry can lead to oxidative damage if used excessively or improperly.
• Repeated exposure to strong oxidizing agents in laundry can cause cumulative weakening and discoloration of cotton garments.

Environmental Exposure:

• Cotton fibers can be exposed to environmental oxidants such as ozone and pollutants, leading to gradual degradation over time.
• Proper storage and care are important to minimize environmental oxidative damage.

Oxidizing agents damage cotton fibers by breaking the glycosidic bonds in cellulose, introducing carbonyl and carboxyl groups, and reducing the mechanical strength and elasticity of the fibers. The extent of damage depends on the concentration of the oxidizing agent, temperature, pH level, and duration of exposure. While controlled use of oxidizing agents like hydrogen peroxide can effectively bleach cotton with minimal damage, improper or excessive use of stronger oxidants like chlorine can lead to significant fiber degradation and discoloration.

Enzymes That Affect Cotton Fiber

The main type of enzyme that damages cotton fibers is cellulase. Cellulases are a group of enzymes that catalyze the hydrolysis of cellulose into smaller sugar units.

Mechanism of Enzymatic Damage to Cotton Fiber

Hydrolysis of Glycosidic Bonds:

• Cellulases break the β-1,4-glycosidic bonds in cellulose molecules through hydrolysis.
• This reaction converts long cellulose chains into shorter oligosaccharides and glucose units.

Reduction in Degree of Polymerization:

• The enzymatic hydrolysis of glycosidic bonds decreases the degree of polymerization, which refers to the number of glucose units in a cellulose chain.
• Shorter chains result in a reduction of the fiber's mechanical strength and integrity.

Surface Erosion:

• Cellulases initially act on the surface of cotton fibers, causing surface erosion.
• This leads to a reduction in fiber diameter and can create a rough, weakened surface.

Loss of Tensile Strength:

• As the cellulose chains are broken down, the overall tensile strength of the cotton fiber decreases.
• Weakened fibers become more prone to breakage and wear.

Factors Influencing Enzymatic Damage

Type of Cellulase:

• Different cellulases target specific regions of the cellulose molecule, such as endoglucanases (which cut within the cellulose chain) and exoglucanases (which remove units from the chain ends).
• The specific activity of the enzyme influences the extent and pattern of damage.

Enzyme Concentration:

• Higher concentrations of cellulase lead to more extensive hydrolysis and greater fiber damage.
• Controlled, lower concentrations are often used to achieve desired effects without excessive damage.

Temperature:

• Enzymes are most active within a specific temperature range, typically around 30-60°C for cellulases.
• Higher temperatures can increase enzymatic activity, leading to faster and more severe damage.

pH Level:

• Enzymes have an optimal pH range for their activity. For cellulases, this is usually slightly acidic to neutral (pH 4.5-7).
• The effectiveness and rate of fiber hydrolysis depend on maintaining the optimal pH.

Duration of Exposure:

• Longer exposure times to cellulase result in more extensive hydrolysis of cellulose fibers.
• Short, controlled exposure minimizes damage while achieving specific effects like biopolishing.

Practical Examples of Enzymatic Damage

Biopolishing in Textile Processing:

• Biopolishing uses cellulases to remove fuzz and improve fabric appearance and softness.
• While beneficial for aesthetics, excessive biopolishing can weaken cotton fibers and reduce fabric strength.

Stone Washing of Denim:

• Cellulases are used in the stone-washing process to give denim a worn look.
• This process can weaken the cotton fibers in denim, potentially reducing the lifespan of the garment.

Environmental Exposure:

• Cotton fibers exposed to cellulase-producing microorganisms in soil or water can undergo biodegradation.
• This natural enzymatic action can lead to fiber decay over time.

Enzymes, particularly cellulases, damage cotton fibers by hydrolyzing the β-1,4-glycosidic bonds in cellulose, leading to a reduction in the degree of polymerization and mechanical strength. The extent of damage depends on the type and concentration of cellulase, temperature, pH level, and duration of exposure. While controlled use of cellulases in processes like biopolishing and stone washing can enhance fabric properties, excessive or improper use can significantly weaken and degrade cotton fibers.

Mechanism of Heat Damage to Cotton Fiber

Thermal Degradation of Cellulose:

• At high temperatures, the cellulose chains in cotton fibers undergo thermal degradation.
• This involves breaking the glycosidic bonds and the oxidation of glucose units, leading to the formation of smaller, volatile compounds.
• The degradation process starts at around 150-200°C (302-392°F) and accelerates significantly above 250°C (482°F).

Loss of Mechanical Strength:

• Thermal degradation leads to a reduction in the degree of polymerization, weakening the fiber structure.
• As the cellulose chains break down, the tensile strength and elasticity of the cotton fibers decrease.

Dehydration and Decomposition:

• Heat can cause the dehydration of cellulose, leading to the loss of water molecules from the glucose units.
• Dehydration and subsequent decomposition result in the formation of charred and brittle residues, which compromise the fiber's integrity.

Color Changes:

• Exposure to high temperatures can cause discoloration of cotton fibers, turning them yellow or brown.
• This is due to the formation of colored degradation products and the oxidation of cellulose.

Chemical Changes:

• Heat can cause the oxidation of cellulose, leading to the formation of carbonyl and carboxyl groups.
• These chemical changes can further weaken the fibers and make them more susceptible to damage from other environmental factors.

Factors Influencing Heat Damage

Temperature:

• Higher temperatures cause more severe and rapid thermal degradation of cotton fibers.
• The critical temperature for significant damage is typically above 150°C (302°F).

Duration of Exposure:

• Prolonged exposure to heat increases the extent of thermal degradation.
• Even moderate temperatures can cause damage over extended periods.

Presence of Moisture:

• Moisture can accelerate thermal degradation by facilitating hydrolysis reactions.
• High humidity combined with heat can lead to more significant fiber damage.

Mechanical Stress:

• Cotton fibers under mechanical stress (e.g., tension or compression) during heating are more prone to damage.
• Heat can cause fibers to become brittle, making them more likely to break under stress.

Practical Examples of Heat Damage

Ironing:

• Ironing at excessively high temperatures or for prolonged periods can scorch cotton fabrics, causing discoloration and weakening of the fibers.
• Using a high setting without adequate moisture (steam) can exacerbate damage.

Drying:

• Over-drying cotton fabrics in a tumble dryer at high heat can lead to shrinkage, loss of elasticity, and weakening of the fibers.
• Prolonged drying at high temperatures can cause thermal degradation.

Manufacturing Processes:

• Improper handling during manufacturing processes such as heat setting or calendaring can result in heat damage.
• Excessive heat during these processes can degrade the fiber quality.

Environmental Exposure:

• Prolonged exposure to high ambient temperatures, especially in combination with direct sunlight, can lead to thermal degradation of cotton fibers.
• This is particularly relevant in outdoor applications or storage in hot climates.

Heat damages cotton fibers by causing thermal degradation of cellulose, leading to the breakdown of glycosidic bonds, dehydration, oxidation, and formation of volatile compounds. This results in a loss of mechanical strength, discoloration, and overall weakening of the fibers. The extent of damage depends on the temperature, duration of exposure, presence of moisture, and mechanical stress. Proper handling, controlled processing conditions, and avoiding excessive heat can help minimize thermal damage to cotton fibers.