Bio-Polishing of 100% Cotton Knitted Fabric Using Cellulase Enzyme in textile wet processing technology

Introduction

Bio-polishing, also known as enzyme-based fabric finishing, is an eco-friendly technique used primarily to enhance the quality of 100% cotton knitted fabrics. This process employs cellulase enzymes to remove surface fuzz, reduce pilling, and improve softness, giving the fabric a smooth, lustrous appearance. Unlike conventional chemical-based treatments, bio-polishing with cellulase enzyme offers a sustainable solution by reducing the need for harsh chemicals. This article explores the bio-polishing process, its benefits, mechanisms, and applications, along with key factors influencing its effectiveness on 100% cotton knitted fabrics.

 

What is Bio-Polishing?

Bio-polishing is a finishing process specifically designed for cellulose-based fabrics, like cotton, that uses cellulase enzymes to achieve a smoother texture and improved surface quality. The cellulase enzyme works by breaking down cellulose fibrils on the fabric’s surface, which are responsible for fuzziness and pilling. Bio-polishing is commonly applied to knitted fabrics, as these tend to have a higher surface area and are more prone to pilling compared to woven fabrics.

 

Why Use Cellulase Enzyme for Bio-Polishing?

The choice of cellulase enzyme is critical for bio-polishing because cellulase targets cellulose, the primary component of cotton fibers. These enzymes specifically hydrolyze the cellulose chains in the protruding microfibrils of the cotton fibers. By selectively targeting the surface, cellulase enzymes prevent damage to the core fibers, maintaining fabric strength while achieving a smooth and polished appearance. This enzyme treatment also has a minimal environmental impact compared to conventional chemical processes, as it requires milder conditions, such as lower temperatures and reduced water consumption.

 

Mechanism of Bio-Polishing with Cellulase Enzymes

Cellulase enzymes operate by hydrolyzing the β-1,4-glycosidic linkages in cellulose, leading to the breakdown of protruding fibrils on the fabric surface. This hydrolysis occurs in several stages:

1. Endo-Cellulase Action: Endo-cellulases randomly cut internal bonds in cellulose chains, reducing polymer size and creating additional reaction sites.
2. Exo-Cellulase Action: Exo-cellulases cleave the ends of the shortened cellulose chains, releasing small sugars such as cellobiose.
3. β-Glucosidase Action: β-glucosidases further break down cellobiose into glucose, aiding in the complete hydrolysis of cellulose fibrils on the fabric surface.

This enzymatic action leads to the removal of loose fibers and protruding fibrils, resulting in a fabric that feels softer and appears brighter, without altering its core structure.

 

Bio-Polishing Process for 100% Cotton Knitted Fabric

The bio-polishing process generally includes the following steps:

1. Preparation:
   The fabric is pre-washed to remove impurities and size materials that could interfere with enzyme activity. Achieving the right pH and temperature is also crucial, as cellulase enzymes are most effective at a pH between 4.5 and 5.5 and temperatures ranging from 50°C to 60°C.
2. Enzyme Application:
   A cellulase enzyme solution is prepared, typically at a concentration between 0.5% and 2% based on fabric weight. The fabric is then immersed in this enzyme solution under controlled temperature and pH conditions. The treatment duration varies based on fabric properties and desired effects but usually lasts from 30 to 60 minutes.
3. Neutralization and Washing:
   After the enzymatic treatment, the enzyme activity is stopped by neutralizing the solution with an alkaline agent or by thoroughly rinsing the fabric with water. This step prevents over-hydrolysis, which could weaken the fabric.
4. Post-Treatment and Drying:
   The fabric undergoes a final wash to remove any residues and is then dried under controlled conditions. At this stage, softeners or additional finishing agents may be applied to enhance the fabric’s hand feel and durability.

 

Benefits of Bio-Polishing with Cellulase Enzyme

1. Improved Softness and Smoothness
   Cellulase enzymes eliminate loose fibers and surface fuzz, resulting in a smoother and softer fabric surface, which is especially desirable for garments.
2. Enhanced Appearance and Lustrous Finish
   Bio-polished fabrics have a cleaner, brighter look, enhancing the appeal of cotton fabrics without the need for optical brighteners or harsh chemicals.
3. Reduction in Pilling
   By breaking down and removing surface fibers that can tangle and form pills, bio-polishing significantly reduces pilling, improving fabric longevity and appearance after repeated wear and washing.
4. Environmentally Friendly Process
   Bio-polishing uses biodegradable enzymes under mild conditions, reducing the need for chemicals, water, and energy, thus offering a more sustainable alternative to traditional finishing methods.
5. Improved Drapability
   By smoothing the fabric surface and reducing stiffness, bio-polishing can enhance the fabric’s flexibility and drape, making it more comfortable for apparel applications.

 

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Key Factors Affecting Bio-Polishing Efficiency

Several factors influence the effectiveness of bio-polishing, including:

1. Type of Cellulase Enzyme
   Acid cellulases are commonly used in bio-polishing for their ability to operate at a slightly acidic pH, which is compatible with the properties of cotton. The choice of enzyme type and its activity level are critical to achieving optimal results.
2. Concentration of Enzyme
   Higher enzyme concentrations can accelerate the polishing process but may also risk over-degrading the fabric. Typical concentrations range from 0.5% to 2% of the fabric weight.
3. Temperature and pH
   Cellulase enzymes are highly sensitive to temperature and pH. Maintaining optimal conditions (50°C to 60°C and pH 4.5 to 5.5) is essential for achieving uniform polishing without compromising fabric integrity.
4. Treatment Time
   Longer treatment times can enhance bio-polishing effects but may also weaken the fabric. Balancing treatment time, enzyme concentration, and other factors is necessary to optimize softness and durability.
5. Fabric Construction and Weight
   Knitted fabrics with higher weights or dense constructions may require longer treatment times or higher enzyme concentrations to achieve uniform results. Fine-tuning these parameters is essential for achieving consistent quality across different fabric types.
6. Mechanical Agitation
   Mechanical agitation improves enzyme penetration and ensures even treatment. However, excessive agitation can lead to fabric damage, especially in delicate knitted constructions.

 

Applications of Bio-Polished Cotton Knitted Fabrics

Bio-polished cotton fabrics are commonly used in a variety of apparel applications due to their enhanced aesthetics and comfort properties. Common applications include:

1. Casual Wear and Sportswear
   The softness, smoothness, and durability of bio-polished cotton make it ideal for casual and sportswear garments, where comfort is a priority.
2. Underwear and Loungewear
   Bio-polished fabrics provide a soft and irritation-free experience, making them well-suited for underwear, sleepwear, and loungewear.
3. Children's Clothing
   Given their delicate skin, children benefit from the softness and pilling resistance of bio-polished fabrics.
4. High-End Fashion
   Bio-polishing enhances the fabric's drape and appearance, making it desirable for premium fashion items that require a refined finish.
5. Home Textiles
   Bio-polished cotton is also used in home textiles such as bed linens, pillowcases, and towels, where a smooth finish and comfort are desirable.

 

Conclusion

Bio-polishing of 100% cotton knitted fabric with cellulase enzyme is an advanced, eco-friendly method that improves fabric quality by removing surface fuzz and enhancing smoothness. The process not only enhances the visual appeal and hand feel of cotton fabrics but also extends their longevity by reducing pilling. By optimizing factors like enzyme concentration, temperature, and treatment time, textile manufacturers can achieve consistent, high-quality bio-polished fabrics that meet consumer demands for sustainability and comfort. As the textile industry increasingly prioritizes eco-friendly solutions, bio-polishing with cellulase enzymes offers an effective and sustainable approach to fabric finishing that aligns with environmental and economic goals.