Introduction
White garments, known for their pristine and crisp appearance, often fall victim to a common issue: yellowing. This phenomenon can be frustrating for individuals who strive to maintain the bright whiteness of their clothing. However, understanding the underlying causes behind the yellowing process can provide valuable insights into preventing and remedying it.
Reason behind the yellowing of white/denim garments
The primary reason behind the yellowing of white/denim garments is a combination of various factors including exposure to light, aging, and chemical reactions. Let's delve deeper into each factor:
1. Light Exposure
Exposure to sunlight or artificial light sources plays a significant role in causing garments to turn yellow over time. Ultraviolet (UV) radiation from sunlight triggers photochemical reactions within fabrics. These reactions lead to the degradation and alteration of textile fibers at a molecular level.
Specifically, UV radiation breaks down certain chemical bonds present in fabric dyes or optical brighteners used during garment production. As these compounds degrade or change color under UV exposure, they contribute to the overall yellowing effect on clothes.
a. Yellowing by ozone
Ozone is a tri-atomic molecule of oxygen. It is a strong oxidizing agent.
Ozone formation
Ozone is one of the primary pollutants found naturally in the atmosphere. In addition to this, ozone is produced by the combined action of sunlight, oxides of nitrogen, and oxygen.
Under the sun's ultraviolet radiation of a shorter wavelength (<420nm), nitrogen dioxide undergoes a photolysis process to form nitrogen oxide and atomic oxygen. This atomic oxygen combines with molecular oxygen to form ozone molecules. Again this ozone reacts with nitric oxide to form molecular oxygen and nitrogen dioxide and this cycle continues.
Ozone molecules present on Earth's surface interact with denim garments. Ozone oxidizes the Indigo dye into Isatin and Anthranilic acid and the complex of the two products. Isatin is yellow, so indigo clothes turn yellow.
2. Aging Process
The natural aging process also contributes significantly to the yellowing of white garments. Many textiles undergo inherent changes over time due to prolonged use and contact with environmental elements such as air pollution or dust particles.
As fabrics age, they may accumulate microscopic particles like dirt or oils from human skin which can settle onto clothing fibers over time. These particles can cause discoloration by trapping light differently than when originally woven into the fabric structure.
Moreover, as textiles age further through multiple washes and wear, tiny cracks may form on their surfaces called microfibril fractures. These fractures disrupt how light interacts with individual fibers resulting in alterations in perceived color – leading to a more noticeable yellowness.
3. Chemical Reactions
Certain chemicals found in everyday household products have the potential to interact with white garments and contribute to their yellowing. One common example is bleach, which many people use as a stain remover or whitening agent.
While bleach effectively removes stains and brightens whites temporarily, it can also cause yellowing over time. Chlorine-based bleaches contain chlorine molecules which, if not completely rinsed out during laundering, can react with residual proteins or minerals in fabric fibers. These chemical reactions may lead to the formation of yellow-colored compounds on the surface of the clothing.
Additionally, some laundry detergents or fabric softeners contain optical brighteners – chemicals designed to enhance whiteness by absorbing invisible ultraviolet light and re-emitting it as visible blue light. However, prolonged exposure to sunlight or multiple washes can break down these optical brighteners, resulting in a loss of their effectiveness and potentially contributing to overall yellowing.
Preventive Measures
Although preventing yellowing altogether might be difficult due to various factors involved, there are certain preventive measures one can take:
i. Proper Storage: Store white garments in cool and dark places such as closets away from direct sunlight.
ii. Gentle Washing: Use gentle cycles while laundering white clothes along with appropriate detergent quantities.
iii. Avoid Overusing Bleach: Limit the use of chlorine-based bleach only when necessary and ensure thorough rinsing during laundering.
iv. Optical Brightener Awareness: Be mindful of excessive washing cycles since they can degrade optical brighteners quickly.
By implementing these preventative strategies combined with regular maintenance routines like proper cleaning and storage practices, individuals increase their chances of preserving the original whiteness of their garments for longer periods.
How to reduce the yellowing of garments
Use anti-ozone softener: The main steps involved are-
i. Film formation- The anti-ozone softener forms a film over the fabric surface thus preventing the Indigo dye from reacting with atmospheric ozone.
ii. Self-degradation- The anti-ozone film will react with atmospheric pollutants undergo a self-degradation process and break down into its colorless compounds. Thus the anti-ozone softener undergoes a scarification process in preventing indigo dyes from oxidation.
Conclusion
The phenomenon of white/denim garments turning yellow is influenced by several interconnected factors including light exposure, aging processes within fabrics themselves, and chemical reactions caused by household products used during laundry routines. By understanding these mechanisms at play behind yellowness formation on clothes and adopting preventive measures, individuals can strive to maintain the pristine appearance of their white garments for extended periods.
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