What Is Viscose Yarn? and How Is it made?

Viscose yarn, a versatile and widely used material, is a manufactured fiber categorized as a "regenerated cellulosic fiber." It is primarily sourced from cellulose, typically extracted from wood pulp but also derived from various plants like bamboo. This semi-synthetic fiber undergoes a unique process where cellulose is decomposed and reconstructed into a yarn-like substance, distinct from both purely natural fibers and synthetic ones. Understanding how viscose yarn is crafted involves unraveling the intricate steps in its production, starting from cellulose extraction to the final spinning process.

What Is Viscose Yarn Made of?

Viscose stands as a manufactured fiber, categorized as a "regenerated cellulosic fiber" sourced mainly from cellulose, frequently derived from wood pulp, although various plants, including bamboo, are also viable sources. Unlike synthetic fibers derived from petroleum, viscose undergoes a process where cellulose is decomposed and subsequently reconstituted into a fiber. Notably, all types of viscose are exclusively crafted from cellulose and solely rely on this material. It's crucial to note that viscose is specifically a fiber and not categorized as yarn or fabric.

Is Viscose a Natural Fiber?

Viscose originates from cellulose, a naturally occurring material within wood. Through a chemical extraction process from sources like beech, spruce, eucalyptus, or bamboo, cellulose is obtained and subsequently compressed into fiber under significant pressure. This particular method categorizes viscose as a semi-synthetic raw material, distinct from both pure natural fibers like cotton or silk and synthetic ones such as polyester.

How Viscose Yarn Is Made?

The production process of viscose yarn involves several sequential steps, each contributing to its creation:

Steeping: Initially, the pulp undergoes treatment with NaOH at mercerizing strength. Subsequently, the pulp sheets are immersed in an 18% NaOH solution, resulting in the production of alkali cellulose as a reaction product.

Shredding: The alkali sheets are transformed into a light, fluffy mass using a high-speed machine equipped with rotating blades moving in opposite directions.

Ageing: The shredded crumbs are stored in a steel container under specific temperatures for 3 to 72 hours, a time frame that varies based on catalyst and alkali used. Air presence reduces chain length, decreasing viscosity, crucial for the spinning solution. Once the desired viscosity is achieved, these pieces are placed in a drum in an inert atmosphere at low temperatures.

Xanthation: Aged alkali cellulose crumbs are put into vats and reacted with carbon disulphide at controlled temperatures (20-30 degrees Celsius), forming cellulose xanthate.

Ripening: The viscose undergoes a designated ripening period during which two significant processes occur: redistribution and loss of xanthate groups. Viscosity initially decreases and then returns to its original value.

Preparation of Spinning Solution: The spinning solution comprises water (69%), zinc sulfate (1%), sodium sulfate (18%), glucose (2%), and sulfuric acid (10%). Sodium sulfate precipitates dissolved sodium cellulose xanthate, while sulfuric acid converts xanthate into cellulose, carbon disulphide, and sodium sulfate. Glucose imparts softness and pliability to the filaments, and zinc sulfate aids in enhancing strength.

Filtration: The viscose undergoes filtration to eliminate undissolved materials that could disrupt the spinning process or cause defects in the rayon filament.

Wet Spinning: The ripened viscose solution is pressurized through a centrifugal pump due to compressed air. This solution is then extruded through a spinneret with fine holes (0.05-0.1mm in diameter). As filaments emerge, they're guided to the surface of a spinning bath and directed toward rollers before being wound onto a spindle.

Advantages of Viscose Yarn

Viscose stands out as a soft, adaptable, and absorbent fabric renowned for its silk-like texture. Its appearance closely resembles silk, making it an excellent choice for those seeking a luxurious feel and style in their attire without a hefty price tag. This fabric offers an affordable option while exuding an opulent look.

Similar to cotton, viscose is highly breathable, ensuring comfort, ease, and relaxation when worn.

It possesses exceptional dyeing capabilities, easily acquiring beautiful shades that endure even after prolonged use and washing, maintaining color vibrancy without fading or dulling.

Resistant to mild heat, the fabric's fibers do not shrink, showcasing moisture-wicking properties.

Viscose blends seamlessly with various fibers, forming polyviscose when mixed with polyester, cotton viscose with cotton, and a fabric with good stretchability when combined with spandex.

Its drape-friendly nature enables effortless styling.

The absorbency of viscose finds applications across multiple industries, including fashion and hygienic disposables.

Notably lightweight and airy, viscose does not cling to the body, making it an excellent choice for summer clothing.

While not heat-trapping, it efficiently absorbs water and sweat, making it well-suited for workout and sportswear.

Applications of Viscose Yarn

Viscose yarn finds extensive applications due to its versatile properties, making it a practical choice for various everyday items. It is commonly utilized in the production of clothing, window drapes, cooling sheets, mattress flame retardants, protectors, and cellophane.

Clothing:
The silky texture of viscose fabric adds a touch of elegance to garments without the expense of pure silk. It's often used to create synthetic velvet, a cost-effective alternative to natural fiber velvet. This fabric's adaptable look and feel suit both formal and casual wear, offering lightweight, breathable options for blouses, t-shirts, and casual dresses. Its superb absorbency also makes it suitable for activewear while retaining color vibrancy across a wide spectrum.

Window Drapes:
Viscose's silk-like feel makes it an excellent material for curtains, draping elegantly over windows, enhancing room aesthetics. These drapes play a crucial role in creating a cool, dark sleeping environment conducive to rest and relaxation.

Cooling Sheets:
Derived from bamboo or eucalyptus cellulose treated using N-Methylmorphine N-oxide, these cooling sheets, technically known as lyocell, blur the distinction between viscose and lyocell due to eco-friendly manufacturing processes. Their lightweight, soft, smooth, and breathable properties offer a comfortable option for sleepers struggling with heat retention.

Mattress Flame Retardants:
Viscose rayon blended with silica forms flame-retardant materials used in mattresses. Although direct skin contact with silica could cause skin irritation or breathing issues, infusing silica into rayon and placing the mixture inside mattress covers mitigates these concerns. This method prevents flammability by creating bead-like structures under high temperatures, offering a safer alternative to toxic chemicals.

Mattress Protector:
Rayon, known for its water-absorbing qualities, is often blended with polyester and cotton to craft mattress protectors, enhancing their waterproofing features.

Cellophane:
Viscose, due to its low permeability to air, water, and bacteria, is a suitable material for transparent food packaging sheets made from regenerated cellulose, serving as an effective option for food packaging purposes.

Conclusion

Viscose yarn, derived from wood pulp or plant sources like bamboo, undergoes a complex process to become a "regenerated cellulosic fiber." This semi-synthetic material possesses properties akin to silk and stands out for its breathability, dyeing capabilities, and versatility. Its applications range from clothing to drapes, cooling sheets, flame retardants, protectors, and cellophane used in food packaging due to its low permeability. This versatile material's widespread use underscores its adaptability and value across multiple industries.