Introduction to Viscose Fiber

Viscose fiber, often labeled as "Viscose" or "Rayon" on clothing tags, is a unique and widely used man-made cellulosic fiber. Essentially, it is produced by extracting pure cellulose (mainly α-cellulose) from natural plants (such as wood, bamboo, or cotton linters). This cellulose undergoes a complex chemical dissolution process (using sodium hydroxide and carbon disulfide to form a viscous sodium cellulose xanthate solution, hence the name "viscose"). The solution is then extruded through spinnerets into an acid bath, where it coagulates and regenerates into continuous filaments. Therefore, unlike polyester or nylon, which are entirely derived from petrochemicals, viscose is a "regenerated" natural cellulose fiber. This grants it many properties similar to natural fibers but also comes with inherent limitations.

Advantages of Viscose Fiber:

People favor viscose clothing primarily for its exceptional comfort. This stems from the cellulose molecular structure rich in hydrophilic groups (-OH), giving it excellent moisture absorption (standard moisture regain around 12-15%, comparable to or slightly better than cotton). It quickly absorbs and wicks away sweat, combined with good breathability. This effectively regulates the microclimate on the skin's surface, reducing stuffiness and providing a dry, comfortable feel. It also minimizes static electricity, making it an ideal choice for summer clothing and undergarments. Secondly, the surface of viscose fiber is smooth, resulting in an extremely soft, smooth, and silky feel-often surpassing cotton and approaching silk. Visually, through process control (like adding delustering agent titanium dioxide or adjusting spinning conditions), it can display a range of lusters from soft matte to bright silky sheen. Its moderate density (approx. 1.5 g/cm³) and low stiffness give fabrics excellent drape, making garments like dresses and curtains hang with fluid, natural lines.

Disadvantages of Viscose Fiber:

However, due to its molecular structure and the regeneration process, viscose fiber has significant performance weaknesses. The core issue is the drastic reduction in mechanical properties when wet. When the fiber absorbs water and swells, water molecules penetrate the amorphous regions of the cellulose, disrupting the hydrogen bond network that provides strength. This causes its wet strength to typically be only 40%-60% of its dry strength. This makes viscose garments exceptionally fragile during washing-hand washing is strongly recommended, avoid machine washing, and absolutely prohibit vigorous rubbing or wringing, otherwise they are highly prone to deformation and damage. After washing, they should be laid flat to dry. Frequent washing also accelerates wear. Another prominent drawback is poor elasticity and dimensional stability. Cellulose molecular chains are relatively rigid and lack elastic recovery, leading to fabrics that wrinkle easily and hold creases persistently, requiring frequent ironing. Furthermore, significant shrinkage occurs due to moisture absorption/swelling and mechanical action; garments without pre-shrinking treatment are prone to deformation. Additionally, its abrasion resistance is far inferior to synthetic fibers like polyester or nylon; areas subject to repeated friction easily pill or wear through.

Production Considerations:

Although the raw materials come from renewable plants and the fiber itself is biodegradable, the traditional viscose process involves significant amounts of chemicals (NaOH, CS₂, H₂SO₄). Carbon disulfide (CS₂), in particular, is toxic and poses environmental risks. Its incomplete recovery or leakage represents a major environmental challenge. Modern industry is addressing this through closed-loop systems and promoting more environmentally friendly solvent-based processes like Lyocell (which uses the non-toxic solvent NMMO).