Spandex (Polyurethane Fiber)

Spandex, also known as polyurethane fiber (Polyurethane, abbreviated as PU), is a highly elastic fiber that people commonly use in knitted garments, especially in underwear, swimwear, and bikinis. DuPont first successfully developed it in 1958 and registered it under the trademark LYCRA (commonly referred to as “Lycra” in Chinese). As a result, many people also refer to it as Lycra.

People translate Spandex as “Spandex,” and it is an elastic fiber with the scientific name polyurethane fiber. In mainland China, people call it (Spandex). It exhibits high elasticity, capable of stretching 6 to 7 times its original length, and can quickly return to its initial state once the tension is released. Its molecular structure consists of a chain-like, soft, and stretchable polyurethane, which people enhance by connecting it with hard segments. Spandex offers superior elasticity, with a strength 2 to 3 times higher than latex silk, finer linear density, and better resistance to chemical degradation. It also demonstrates excellent resistance to acids, alkalis, sweat, seawater, dry cleaning, and abrasion.

Spandex is a synthetic fiber with high elongation at break (over 400%), low modulus, and high elastic recovery. In China, people commercially know it as (Spandex) or elastic fiber. It features high extensibility (500%–700%), low elastic modulus (0.04–0.12 g/denier at 200% elongation), and high elastic recovery (95%–99% at 200% elongation). Apart from its higher strength, its physical and mechanical properties are very similar to natural latex silk. It is more resistant to chemical degradation than latex silk and has moderate thermal stability, with a softening temperature above 200°C. People can use most dyes and finishing agents for synthetic and natural fibers on spandex as well. It resists sweat, seawater, dry cleaning agents, and most sunscreens. However, prolonged exposure to sunlight or chlorine bleach can cause fading, with the degree of fading varying significantly depending on the type of spandex.

The high elasticity of spandex fibers comes from their macromolecular structure, which consists of low-melting-point, amorphous “soft” segments as the matrix and high-melting-point, crystalline “hard” segments embedded within. The flexible segments form a network structure through cross-linking, allowing free extension due to weak intermolecular forces, resulting in high elongation. The rigid segments, with stronger intermolecular forces, prevent unlimited stretching, ensuring high elasticity.

Most spandex filaments have a dog-bone-shaped cross-section, while some have smooth or serrated surfaces. Spandex has the lowest breaking strength among all textile fibers, ranging from 0.44 to 0.88 CN/dtex (polyether types are stronger than polyester types). Its moisture absorption is relatively low, typically between 0.3% and 1.2% (multifilament absorbs slightly more than monofilament). Heat resistance varies by type, but most fibers can withstand short-term exposure to temperatures between 90°C and 150°C without damage. People can safely iron it at temperatures below 150°C, and they can wash it in warm water. Spandex dyes well, with strong dye affinity, and people can use most dye types on it. It also has good chemical resistance, withstanding most acids, alkalis, chemicals, organic solvents, dry cleaning agents, and bleach, as well as sunlight and weather conditions. However, it does not resist oxidants, which can cause yellowing and reduced strength.

People rarely use spandex alone but typically blend it in small amounts into fabrics. This fiber combines the properties of rubber and fiber, often serving as the core in core-spun yarns, which people call elastic core-spun yarns. These yarns offer several advantages:

1. They provide a good feel and appearance, with the outer natural fibers offering excellent moisture absorption.
2. People only need 1%–10% spandex filaments to produce high-quality elastic yarns.
3. They can control elasticity within a range of 10% to 20%, allowing customization based on the product’s intended use.

People can easily spin spandex into yarns of varying thicknesses (25–2500 denier), making it widely used in elastic woven fabrics such as socks, furniture covers, ski suits, sportswear, medical fabrics, belts, military equipment, and the elastic parts of space suits. As consumer demand for lightweight, comfortable, and soft fabrics grows, low-denier spandex fabrics are increasingly dominating the synthetic fiber market. People also use spandex in bare yarns and twisted yarns, which they primarily use in warp knitting, weft knitting, woven fabrics, and elastic textiles.

Spandex (Lycra): The Revolutionary Elastic Fiber

People commonly know spandex as Lycra, a highly elastic fiber that DuPont invented in the United States in 1958. It boasts remarkable elasticity, capable of stretching up to 600% and returning to its original shape. Compared to rubber, spandex is stronger, more breathable, and more wear-resistant. Its introduction revolutionized the clothing industry, transforming the way people design and wear garments.

Characteristics of Spandex

• Softness and Dyeability: Spandex is soft and easy to dye, with a density ranging from 1.0 to 1.3 g/cm³.
• Elasticity and Durability: While its rebound force is slightly less than rubber, spandex is more durable, with an elasticity of about 5–12 cN/tex.
• Moisture Absorption: Spandex has low hygroscopicity, absorbing only 1% of its weight in moisture.
• Static Resistance: It does not pill or accumulate static electricity, making it easy to care for.
• Care Instructions: For daily maintenance, manufacturers recommend washing spandex fabrics at a water temperature of 40°C or below, though people can raise temperatures to 60°C if necessary.
• Chlorine Resistance: Exposure to ionized chlorine, such as in swimming pool water, can reduce spandex’s elasticity and elongation. To address this, manufacturers often add zinc oxide, magnesium oxide, magnesium hydroxide, or phenolic compounds to enhance chlorine resistance, making it ideal for swimwear.

Uses of Spandex

Thanks to its excellent elasticity, strength, wrinkle resistance, and quick-drying properties, people widely use spandex in various types of clothing, particularly in:

• Underwear and Intimate Apparel: Spandex provides a snug fit and comfort.
• Sportswear: People commonly find it in professional swimsuits, tights, volleyball shorts, cycling shorts, triathlon clothing, gymnastics suits, and tennis apparel.
• Accessories: People use spandex in belts, bras, stockings, leggings, and dance belts for ballet and other dancers.
• Medical Applications: People use it as padding to protect the skeletal system, compression clothing for therapeutic purposes, and surgical hoses.
• Furniture: Some items, such as microbead pillows, also incorporate spandex for its stretch and durability.

Blending and Market Trends

When people use spandex in clothing, manufacturers typically blend it with cotton or polyester to minimize sheen and maintain the look and feel of the primary fabric. Spandex usually makes up only a small portion of the final fabric.

• North America: In 2010, approximately 80% of clothing sold in North America contained spandex.
• China: Spandex consumption in China doubled from around 250,000 tons in 2010 to 501,000 tons in 2016, with a compound annual growth rate of 12.4%.

Conclusion

Spandex, with its unparalleled elasticity and versatility, has become a cornerstone of modern textiles. People use it in applications ranging from everyday clothing to specialized sportswear and medical uses, making it an indispensable material in the fashion and apparel industries. As consumer demand for comfortable, durable, and form-fitting garments continues to grow, spandex will remain a key player in the global textile market.

Expanded Information

Historical Development of Spandex

The invention of spandex marked a significant milestone in the textile industry. Before its development, natural rubber was the primary material used for elastic fabrics. However, rubber had limitations, such as poor breathability, lower durability, and susceptibility to degradation from oils and UV exposure. DuPont’s breakthrough in 1958 addressed these issues by creating a synthetic fiber that combined the elasticity of rubber with the strength and versatility of synthetic polymers.

The introduction of spandex revolutionized the fashion industry, enabling the creation of form-fitting garments that were both comfortable and durable. Over the decades, advancements in polymer science and textile engineering have further improved spandex’s performance, making it a staple in modern apparel.

Environmental Impact and Sustainability

As the demand for spandex grows, so does the need for sustainable production practices. Traditional spandex manufacturing relies on petrochemicals, which have a significant environmental footprint. However, researchers and manufacturers are exploring eco-friendly alternatives, such as bio-based polyurethane derived from renewable resources like corn or sugarcane.

Recycling spandex is another area of focus. While spandex itself is recyclable, its blending with other fibers complicates the recycling process. Innovations in textile recycling technologies aim to separate spandex from blended fabrics, enabling its reuse in new products.

Future Trends in Spandex Applications

The versatility of spandex continues to drive its adoption in emerging markets and applications. Some future trends include:

• Smart Textiles: Integrating spandex with conductive fibers and sensors to create smart garments that monitor health metrics or adjust to environmental conditions.
• 3D Knitting: Using spandex in 3D knitting technologies to produce seamless, custom-fit garments with enhanced comfort and performance.
• Sustainable Fashion: Developing spandex blends with recycled or biodegradable fibers to meet the growing demand for eco-conscious apparel.

Challenges and Limitations

Despite its many advantages, spandex faces some challenges:

• Cost: Spandex is more expensive than many other synthetic fibers, which can increase the cost of finished products.
• Durability in Chlorine: While advancements have improved spandex’s chlorine resistance, prolonged exposure to chlorinated water can still degrade its elasticity over time.
• Environmental Concerns: The reliance on petrochemicals and the challenges of recycling spandex blends highlight the need for more sustainable production methods.

Conclusion

Spandex has transformed the textile industry with its unique combination of elasticity, durability, and versatility. From everyday clothing to high-performance sportswear and medical applications, spandex continues to play a vital role in modern textiles. As technology advances and sustainability becomes a priority, spandex is poised to evolve further, meeting the demands of both consumers and the environment. Its future lies in innovation, ensuring that it remains a cornerstone of the global textile market for years to come.

• alibaba