Textile Yellowing Causes, Tests and Solutions

Textile yellowing is a common problem that affects various fabrics. It causes them to lose their original color and appear discolored or yellowed. This phenomenon can occur in both natural and synthetic fibers, and it can be caused by several factors.

Understanding the causes behind this, conducting appropriate tests, and implementing effective solutions are crucial to maintaining the aesthetic appeal and quality of textile products.

It can affect both natural and synthetic fibers. The underlying mechanisms differ between the two, but the end result is a similar visual change in color. Let’s explore the causes of each type of fiber.

Causes of Textile Yellowing

Understanding the underlying causes of textile yellowing is crucial for implementing effective preventive measures and solutions. There can be the following Conditions of Yellowing Fabrics, and all of them have different causes, read on:

Light Yellowing

It is a discoloration that occurs as a result of exposure to light, especially ultraviolet radiation. When textiles are exposed to sunlight or artificial light sources containing UV rays, the fabric’s color can gradually change. Hence, it becomes light yellow. This is a common cause in both natural and synthetic fibers.

The UV rays present in light can initiate chemical reactions within the fibers of the textile. These reactions can cause the molecules responsible for the fabric’s original color to break down or rearrange, resulting in a yellowing effect. This process is often more pronounced in natural fibers, such as cotton or linen, but synthetic fibers can also be affected.

Factors that contribute to light yellowing include the intensity and duration of exposure to light. Fabrics exposed to prolonged periods of direct sunlight or intense artificial light sources are more susceptible to yellowing. Additionally, the presence of certain dyes or chemicals in the fabric can influence the degree of yellowing.

Phenol Yellowing

It is a type of yellowing that can affect textiles. It occurs when fabrics are exposed to phenolic compounds, such as:

• Certain Cleaning Agents
• Cosmetics
• Pollutants present in the environment

Phenols can react with the fabric’s fibers and cause discoloration, resulting in a yellow hue.

The exact mechanism of this is not fully understood, but it is believed to involve the formation of chromophores, which are responsible for the yellow color. Phenolic compounds can react with the fibers of the fabric, causing alterations in their molecular structure and resulting in discoloration.

This can affect both natural and synthetic fibers, although it is often more noticeable in lighter-colored fabrics. Certain dyes or finishes applied to textiles can also interact with phenols, intensifying the yellowing effect.

Oxidative Yellowing

It is a process in which textiles undergo chemical reactions with atmospheric oxygen. This type of yellowing is particularly common in natural fibers, such as cotton or linen. Over time, exposure to oxygen can cause the fabric to yellow, especially in conditions of high humidity or elevated temperatures.

When textiles are exposed to oxygen over time, the molecular structure of the fibers can undergo changes. This process is accelerated under high humidity or elevated temperatures. Oxidative yellowing can also be influenced by other factors such as the presence of impurities or residual chemicals in the fabric.

Brightener Yellowing

It occurs when optical brighteners, also known as fluorescent whitening agents, are used in the manufacturing or laundering of textiles. Optical brighteners are additives that are often employed to enhance the brightness and whiteness of fabrics.

The exact mechanisms behind this are complex and can vary depending on the specific brightening agent and the fabric composition. It is believed that the breakdown or alteration of the brightener molecules can result in the appearance of yellow hues.

Preventing brightener yellowing involves careful selection and application of optical brighteners. It is essential to choose brighteners that are stable and compatible with the fabric type. Following appropriate laundering instructions, such as using mild detergents and avoiding excessive heat during washing or drying, can help a lot.

Softener and Other Finishing Agents Yellowing

It can contribute to yellowing in textiles under certain circumstances. While these agents are commonly used to improve the softness, texture, and overall feel of fabrics, they can sometimes interact with the fibers and cause discoloration.

The effect can occur due to various reasons:

Residue Accumulation: If softeners or other finishing agents are not properly rinsed out during the manufacturing or laundering process, residual amounts can remain in the fabric. Over time, these residues can accumulate and result in yellowing.

Chemical Reactions: Some finishing agents, when exposed to external factors like light, heat, or atmospheric pollutants, can undergo chemical reactions that lead to yellowing. These reactions may involve the breakdown or alteration of the molecules in the finishing agents, resulting in a yellow hue.

Incompatibility with Fibers: Certain types of fabrics or fiber compositions may be more susceptible to yellowing when in contact with specific finishing agents. The interaction between the agents and the fibers can cause color changes, including yellowing.

Its prevention techniques include:

• Using the appropriate amount of softener or finishing agent as recommended by the manufacturer.
• Ensuring thorough rinsing during the laundering process to remove any residual product.
• Choosing finishing agents that are compatible with the fabric type and composition.
• Avoiding excessive exposure to light or heat, as these factors can contribute to the development.

Judgment methods of textile yellowing

There are several judgment methods commonly used to assess and evaluate textile yellowing. Some of the main judgment methods include:

Visual Assessment

Trained professionals compare the fabric’s color to reference standards and evaluate the degree of yellowing. This method relies on subjective judgment based on the observer’s perception of the color change.

Colorimetry

It involves using a spectrophotometer to analyze the fabric’s reflectance or transmittance of light across different wavelengths. By comparing the color values obtained with reference values, the degree of color change can be determined.

Whiteness Index

It quantifies the deviation of the fabric’s color from an ideal white. A higher whiteness index indicates a greater level of yellowing. This method provides an objective measure of the fabric’s color change.

Grey Scale Assessment

The observer matches the fabric’s color to the closest gray scale value, which corresponds to the degree of yellowing. This method provides a visual and comparative assessment of the color change.

Delta E Measurement

Delta E (ΔE) is a color difference measurement that compares the color of the yellowed fabric to its original or reference color. It quantifies the magnitude of color change by calculating the Euclidean distance between the two colors in a color space. A higher ΔE value indicates a greater level of yellowing.

Artificial Aging Tests

It involves subjecting the fabric to accelerated aging conditions to simulate long-term exposure to environmental factors. These tests may include exposing the fabric to UV light, heat, humidity, or chemical agents. The yellowing of the fabric is then evaluated based on visual or instrumental methods.

Chemical Analysis

Analytical techniques such as gas chromatography-mass spectrometry (GC-MS) and Fourier transform infrared spectroscopy (FTIR) can identify specific substances responsible. Chemical analysis provides valuable insights into the underlying causes of yellowing.

Moisture Aging

Fabrics are exposed to controlled humidity levels, and changes in color are monitored over time. Moisture aging tests help assess the fabric’s susceptibility to yellowing under humid conditions. It makes them particularly relevant for products used in high-humidity environments.

Textile yellowing test standards

These standards ensure that testing procedures are consistent and enable reliable comparisons across different fabrics and manufacturers.

• AATCC Test Method 124: Determining the Colorfastness of Dyed or Printed Textiles to Washing
• ISO 105 C06: Colour Fastness to Domestic and Commercial Laundering
• ASTM D1925: Standard Test Method for Yellowness Index of Plastics
• ISO 105 B10: Colour Fastness to Artificial Weathering like Xenon Arc
• ASTM E313: Standard Practice for Calculating Yellowness and Whiteness Indices from Instrumentally Measured Color Coordinates
• AATCC Test Method 133: Colorfastness to Heat, like sunlight or Hot Pressing
• ISO 105 X18: Colour Fastness to Dry Cleaning
• AATCC Test Method 135: Colorfastness to Crocking i.e. Rubbing
• ISO 105 D01: Colour Fastness to Water

Textile Yellowing Test Instrument: UV Accelerated Weathering Tester

These instruments simulate the effects of sunlight and other environmental factors on textiles. It allows manufacturers and researchers to assess color fading and resistance to yellowing.

Working Principle of UV Accelerated Weathering Tester

This device utilizes a combination of UV lamps and environmental chambers to recreate sunlight and other environmental conditions. The fabric samples are placed in the tester, and they are exposed to controlled cycles of UV radiation, moisture, and temperature. The duration and intensity of exposure can be adjusted to simulate various real-world scenarios.

Features and Specifications of UV Accelerated Weathering Testers

UV accelerated weathering testers come with several features and specifications to ensure accurate and reliable testing. Some common features include:

UV Lamp Array: These testers are equipped with an array of UV lamps that emit a spectrum of UV radiation similar to sunlight.

Environmental Chambers: The testers have environmental chambers that can control temperature, humidity, and moisture levels during testing.

Sample Holder: A sample holder or specimen tray is provided to securely hold the fabric samples during exposure.

Programmable Controls: The testers offer programmable controls to set the desired test parameters, including exposure time, temperature, and humidity.

Monitoring and Data Logging: It often comes with monitoring and data logging capabilities to track and record the test conditions and results.

Benefits of UV Accelerated Weathering Testing

The device offers several benefits for evaluating textile yellowing:

Time Efficiency: These tests accelerate the aging process. It allows manufacturers to assess the long-term effects of UV radiation in a shorter time frame.

Realistic Simulation: Testers can replicate the effects of sunlight and other environmental factors, providing a realistic assessment of fabric performance.

Comparative Analysis: By testing multiple fabric samples simultaneously, manufacturers can compare the performance of different materials and finishes.

Quality Control: It helps ensure that textile products meet quality standards by identifying potential yellowing issues early in the development process.

Considerations for UV Accelerated Weathering Testing

While UV accelerated weathering testing is a valuable tool, there are a few considerations to keep in mind:

Limitations: It cannot perfectly replicate the complex aging process that occurs over extended periods in real-world conditions. It serves as an approximation.

Complementary Tests: Testing should be complemented with other tests, such as visual assessment and colorimetric analysis..

Standard Compliance: It is important to follow established test standards, such as ASTM or ISO standards, to ensure consistency and comparability of results.

How to prevent textile yellowing?

By following preventive measures, it is possible to minimize or prevent yellowing and ensure the longevity of textile products.

Control Storage Conditions

Proper storage conditions play a crucial role in preventing textile yellowing. Here are some key considerations:

• Avoid Humidity: High humidity can accelerate yellowing. Store textiles in a dry environment with controlled humidity levels.
• Temperature Control: Extreme temperatures can contribute. Maintain a moderate and stable temperature to preserve fabric quality.
• Air Circulation: Ensure adequate air circulation to prevent moisture buildup and the growth of mold or mildew.
• Clean Storage Area: Keep the storage area clean and free from dust, dirt, and contaminants.

Avoid Direct Sunlight

Here’s how to minimize its impact:

• Store Away from Windows: Avoid storing textiles near windows or areas with direct sunlight exposure.
• Use Window Coverings: If textiles must be near windows, use window coverings such as blinds or curtains to reduce exposure to sunlight.
• Rotate Textiles: Periodically rotate textiles to minimize consistent exposure to sunlight, distributing any fading more evenly.

Select Suitable Dyes and Finishes

The choice of dyes and finishes can significantly impact the resistance of textiles to yellowing. Consider the following:

• Lightfast Dyes: Select dyes that are known for their lightfastness properties, which means they are resistant to fading when exposed to light.
• Non-Yellowing Finishes: Choose finishes that have been specifically formulated to resist yellowing and discoloration over time.

Use UV Absorbers and Stabilizers

UV absorbers and stabilizers can help protect textiles from the harmful effects of UV radiation. Consider the following options:

• UV Absorbers: These additives absorb and dissipate UV radiation, minimizing its impact on the textile’s color.
• UV Stabilizers: These additives protect the textile by stabilizing the molecular structure, enhancing its resistance to UV-induced degradation.

Consider Environmental Factors

Environmental factors such as air pollution and chemicals can contribute to textile yellowing. Here are some preventive measures:

• Avoid Exposure to Pollutants: Keep textiles away from areas with high levels of air pollution or chemical fumes.
• Proper Laundering: Follow appropriate laundering techniques and use mild detergents to minimize the accumulation of chemicals that can cause the effects.

Regular Cleaning and Maintenance

Regular cleaning and maintenance practices can help prevent color change and maintain the appearance of textiles:

• Follow Care Instructions: Adhere to the care instructions provided by the textile manufacturer to ensure proper cleaning and maintenance.
• Prompt Stain Removal: Treat stains promptly using appropriate methods and stain-removal products to prevent long-term discoloration.
• Gentle Handling: Handle textiles with care to avoid unnecessary wear and tear that can contribute to color changes.

Conclusion

Textile yellowing is a common issue that affects the aesthetic appeal and quality of fabrics. By understanding:

• The causes of textile yellowing
• Implementing appropriate testing methods
• Utilizing preventive measures and solutions

It is possible to minimize the occurrence of yellowing and preserve the fabric’s original color. Taking proactive steps to address, this ensures that textile products retain their visual appeal and durability.

Got Any Questions?

How does light contribute to textile yellowing?

Exposure to light, especially UV radiation, can initiate chemical reactions within textile fibers. This can cause the molecules responsible for the fabric’s color to break down or rearrange, resulting in a yellowing effect.

What are phenolic compounds and how do they cause yellowing?

Phenolic compounds are substances found in certain cleaning agents, cosmetics, and environmental pollutants. When fabrics are exposed to these compounds, they can react with the fibers and cause discoloration, resulting in a yellow hue.

Why does oxidative yellowing occur more commonly in natural fibers?

It occurs when textiles undergo chemical reactions with atmospheric oxygen. Natural fibers, such as cotton or linen, are more susceptible because their molecular structure can undergo changes when exposed to oxygen over time.

How do optical brighteners contribute to yellowing?

Optical brighteners, or fluorescent whitening agents, can cause yellowing in textiles when used in manufacturing or laundering. The breakdown or alteration of brightener molecules can result in the appearance of yellow hues in the fabric.

What are the key considerations for UV accelerated weathering testing?

While UV accelerated weathering testing is valuable, it has limitations and should be complemented with other tests for a comprehensive evaluation. Following established test standards, such as ASTM or ISO, is important for consistent and comparable results.