As a supplier of reactive dyes for polyamide, I often encounter questions from customers about how to measure the color change of polyamide dyed with reactive dyes. In this blog, I will share some professional methods and considerations to help you accurately measure and evaluate the color change of dyed polyamide. Reactive Dyes for Polyamide
Understanding the Basics of Reactive Dyes on Polyamide
Reactive dyes are a popular choice for dyeing polyamide due to their excellent color fastness and vivid coloration. These dyes form a covalent bond with the polyamide fibers, resulting in a durable and long – lasting color. However, various factors can cause color changes in the dyed polyamide, such as washing, exposure to light, and chemical treatments.
Factors Affecting Color Change
- Washing: Repeated washing can lead to color fading. The mechanical action of washing machines, along with the use of detergents, can gradually remove some of the dye molecules from the polyamide fibers.
- Light Exposure: Ultraviolet (UV) light can cause photodegradation of the dye molecules, leading to color fading and changes in hue. Different reactive dyes have different levels of light fastness, which need to be considered when using the dyed polyamide in outdoor or sun – exposed environments.
- Chemical Treatments: Exposure to chemicals such as bleach, acids, or alkalis can also cause color changes. For example, strong acids or alkalis can break the covalent bonds between the dye and the polyamide fibers, resulting in color loss or discoloration.
Methods for Measuring Color Change
Visual Assessment
Visual assessment is the simplest and most intuitive method for measuring color change. It involves comparing the dyed polyamide sample before and after the treatment (e.g., washing, light exposure) with a standard color sample.
- Sample Preparation: Cut a small piece of the dyed polyamide fabric and keep it as a reference sample. After subjecting the remaining fabric to the treatment, compare it with the reference sample under standard lighting conditions.
- Lighting Conditions: Use a standard light source, such as a D65 light source, which simulates natural daylight. This ensures consistent and accurate visual assessment.
- Color Difference Scales: There are color difference scales available, such as the Gray Scale for Color Change. This scale ranges from 1 (severe color change) to 5 (negligible color change). By comparing the dyed sample with the scale, you can assign a numerical value to the color change.
Spectrophotometric Measurement
Spectrophotometry is a more accurate and objective method for measuring color change. It measures the reflectance or transmittance of light at different wavelengths by the dyed polyamide sample.
- Instrument Setup: Use a spectrophotometer, which can be either a benchtop or a portable device. Calibrate the instrument according to the manufacturer’s instructions before use.
- Measurement Procedure: Place the dyed polyamide sample in the spectrophotometer. The instrument will measure the reflectance or transmittance of light at various wavelengths and generate a spectral curve.
- Color Calculation: Based on the spectral data, color parameters such as L* (lightness), a* (red – green axis), and b* (yellow – blue axis) in the CIELAB color space can be calculated. The color difference (ΔE*) between the original and treated samples can then be determined using the following formula:
[ \Delta E^{}=\sqrt{(\Delta L^{})^{2}+(\Delta a^{})^{2}+(\Delta b^{})^{2}} ]
where (\Delta L^{}), (\Delta a^{}), and (\Delta b^{*}) are the differences in lightness, red – green, and yellow – blue values between the two samples respectively.
Color Fastness Testing
Color fastness testing is a comprehensive approach to evaluate the resistance of the dyed polyamide to various factors such as washing, light, and rubbing.
- Washing Fastness: Follow international standards such as ISO 105 – C06 or AATCC 61. The dyed polyamide sample is washed under specific conditions (e.g., temperature, detergent concentration, number of washes), and then the color change is measured using visual assessment or spectrophotometry.
- Light Fastness: Use a xenon arc lamp to simulate sunlight exposure. The dyed sample is exposed to the light source for a specified period, and the color change is evaluated. Standards such as ISO 105 – B02 or AATCC 16 can be followed.
- Rubbing Fastness: Rub the dyed polyamide sample with a specified rubbing cloth under a certain pressure. The amount of dye transferred to the rubbing cloth is then evaluated using a gray scale.
Considerations for Accurate Measurement
- Sample Selection: Ensure that the samples are representative of the dyed polyamide. Take samples from different parts of the fabric to account for any color variations.
- Measurement Environment: Keep the measurement environment stable, including temperature, humidity, and lighting conditions. These factors can affect the measurement results.
- Calibration: Regularly calibrate the measuring instruments, such as the spectrophotometer, to ensure accurate and consistent results.
- Data Recording: Record all the measurement data, including the sample information, treatment conditions, and measurement results. This will help in analyzing the color change trends and making informed decisions.
Conclusion
Measuring the color change of polyamide dyed with reactive dyes is crucial for ensuring the quality and performance of the dyed products. By using a combination of visual assessment, spectrophotometric measurement, and color fastness testing, you can accurately evaluate the color change and take appropriate measures to improve the color fastness of the dyed polyamide.
Megaset® Dyes If you are interested in our reactive dyes for polyamide or have any questions about color measurement and dyeing processes, please feel free to contact us for further discussion and potential procurement. We are committed to providing high – quality dyes and professional technical support to meet your specific needs.
References
- ISO 105 – C06: Textiles – Tests for colour fastness – Part C06: Colour fastness to domestic and commercial laundering.
- ISO 105 – B02: Textiles – Tests for colour fastness – Part B02: Colour fastness to artificial light: Xenon arc fading lamp test.
- AATCC 61: Colorfastness to Laundering: Accelerated.
- AATCC 16: Colorfastness to Light.
Hangzhou Xiasa Hengsheng Chemical Co., Ltd.
As one of the leading reactive dyes for polyamide manufacturers and suppliers in China, we warmly welcome you to wholesale bulk cheap reactive dyes for polyamide from our factory. Good service and quality products are available.
Address: NO.169, JING 4 SUB ROAD, BAIYANG STREET, QIANTANG DISTRICT, HANGZHOU, 310018, ZHEJIANG, CHINA
E-mail: AUSTIN_LI@HSDYE.COM
WebSite: https://www.chsdye.com/
