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Why Is Spandex Fabric Prone to Creases or Yellowing?
Spandex fabric, known for its exceptional elasticity, is a widely used material in textiles. However, it has some inherent challenges, including its tendency to yellowing and creasing under certain conditions. Understanding the properties of spandex and the factors contributing to these issues can help in better handling and maintaining spandex fabrics.
Characteristics of Spandex
1. Exceptional Elasticity
Spandex fibers are renowned for their superior elasticity, with an elongation capacity of 400% to 500%. The elastic recovery rate is equally impressive, ranging from 95% to 99%, making spandex an ideal choice for stretchable garments.
2. Thermoplastic Nature
Spandex is a thermoplastic fiber, meaning it softens at high temperatures. Its safe ironing temperature is below 150°C, with a heat setting range of 185–190°C. Improper heat exposure can damage the fiber and affect its performance.
3. Low Moisture Absorption
Spandex is a hydrophobic fiber, meaning it has low hygroscopicity. This property makes it resistant to moisture and quick-drying, but it can also contribute to certain maintenance challenges.
4. Lightweight Structure
With a relative density of about 1.20, spandex fibers are lightweight and loosely textured, enhancing comfort in garments.
5. High Surface Friction
The surface friction factor of spandex is significantly higher than that of other fibers, ranging from 0.7 to 1.30—much greater than synthetic fibers like polyester or nylon. This high friction requires the use of silicone oil lubricants during spinning to facilitate stretching and winding.
6. Sensitivity to UV Rays
Spandex is not UV-resistant, making it prone to yellowing when exposed to prolonged sunlight. Polyether spandex is especially vulnerable compared to polyester spandex.
7. Chemical Resistance
Spandex is resistant to dilute acids and alkalis at room temperature, as well as reducing agents, oxidants, and bleaches without chlorine. However, it can degrade when exposed to certain atmospheric pollutants and oils.
Reasons for the Yellowing of Spandex Fabrics
1. Reactive Groups in Spandex
Spandex contains reactive groups like amino groups in its molecular chain. These groups are prone to reactions during high-temperature setting or long-term storage, leading to yellowing. This issue is particularly noticeable in light-colored fabrics and those treated with fluorescent whitening agents.
2. Additives and Lubricants
During the weaving process, spandex is treated with silicone oil lubricants and other additives to improve its performance. Over time, these additives degrade, causing the fibers to yellow.
3. UV Light Sensitivity
Long-term exposure to sunlight causes spandex to yellow due to its sensitivity to UV rays. Polyether spandex is more susceptible to this than polyester spandex. Additionally, dry heat treatment at high temperatures or for extended periods can oxidize the fibers, leading to yellowing, loss of strength, and reduced elasticity.
4. Environmental Factors
Atmospheric pollutants like nitrogen oxides, sulfur oxides, aldehydes, and flue gases can react with spandex, causing yellowing and affecting the fabric’s appearance. Skin secretions containing unsaturated oils and fatty acids can also degrade stabilizers in spandex yarn, increasing its susceptibility to photo-oxidation and yellowing.
5. Chlorine Exposure
Contact with chlorine-containing chemicals can cause yellowing. To prevent this, spandex fabrics should be stored under protective coverings, such as polyethylene film, to minimize exposure.
6. Incomplete Dyeing Processes
Spandex is inherently difficult to dye using conventional dyes. If the fabric is not adequately cleaned and reduced after dyeing, residual substances can cause yellowing over time.
Causes of Indentation in Spandex Fabrics
1. Degrading Additives
Similar to yellowing, the additives used to improve spandex performance, such as silicone oil lubricants, degrade over time. This can lead to loss of elasticity and contribute to permanent creases in the fabric.
2. Cold Setting
Spandex-containing fabrics can undergo a phenomenon called cold setting during long-term storage. This results in permanent wrinkles that cannot be removed during post-processing.
3. Preventive Measures
To minimize creasing:
- Reduce the storage time of spandex-containing fabrics.
- Open the fabric width immediately after weaving to prevent the formation of creases during storage.
Final Thought
Spandex, while offering unmatched elasticity and comfort, requires careful handling to avoid issues like yellowing and creasing. At Pura Fabric, we prioritize quality and innovation in our spandex fabrics, ensuring they meet the highest standards for durability and performance. Proper care and maintenance can significantly enhance the lifespan and appearance of spandex-based garments.
