Introduction
In textile performance evaluation, color fastness is a key metric to measure its color stability. The hot air aging chamber accelerates the material aging process by simulating a high-temperature environment, thereby evaluating the color change of textiles under long-term use or storage conditions. As one of the core components of the test chamber, the rotation speed of the sample rack directly affects the uniformity of hot air flow, temperature distribution and thermal consistency of the sample, which in turn has a significant impact on the color fastness test results. This article will explore the relationship between the rotational speed of the sample holder and the color fastness of textiles, and analyze it in combination with relevant technical standards.
The speed of the sample rack is used
The speed of the sample rack determines the air circulation mode in the chamber. When the rotation speed is low, the hot air flow may not be sufficient, resulting in an increase in the temperature gradient in the chamber, uneven heating of the sample at different positions, and deviation in the color fastness test results. Properly increasing the rotational speed enhances air convection, improves temperature uniformity, and exposes samples to a more consistent thermal environment. However, excessive rotational speeds can cause excessive airflow turbulence, physical disturbances in thin and light textiles, and even affect the fixed state of the sample, thereby interfering with the testing process. Therefore, the rotational speed needs to be balanced between temperature uniformity and sample stability.
Rotational speed affects color fastness
Textile color fastness tests are usually evaluated based on the degree of color change under thermal aging conditions. The speed of the sample rack affects the color fastness results by the following mechanisms: First, the speed affects the heat transfer efficiency. The uniform hot air circulation ensures that heat is adequately transferred to the sample surface, bringing the dye or pigment aging reaction closer to the actual conditions. Secondly, the rotational speed is related to the diffusion of volatile substances. Some textiles can release chemicals at high temperatures, and insufficient rotational speed can cause these substances to accumulate around the sample, accelerating color changes and deviating test results from true values. Experiments show that under standard test conditions, speed adjustment can lead to differences in color fastness ratings, which can be roughly described by the following formula:
ΔE = k₁ ⋅ (1 - e^{-k₂ ⋅ ω}) + C
where ΔE represents the color change value, ω is the speed of the sample holder, k₁ and k₂ are the coefficients related to the textile material, and C is the constant term. This formula reflects the significant effect of the initial increase in rotational speed on color change, and then tends to level off.
Criteria and parameter selection
A number of domestic and foreign standards provide guidance on hot air aging test conditions, in which the speed of the sample rack appears as an optional or specified parameter. For example, some standards recommend that the temperature in the chamber fluctuate within a certain range, usually between 1 and 5 revolutions per minute. The actual selection should consider the type of textile: heavy fabrics may require higher rotational speeds to ensure heat penetration, while thin and light fabrics may require lower rotational speeds to avoid physical interference. The following is a list of common textile types and recommended speed reference ranges:
| Textile type | Recommended speed range (rpm) |
| Cotton heavy fabric | 3-5 |
| Synthetic thin fabric | 1-3 |
| Blended medium-thickness material | 2-4 |
| Coated or laminated fabrics | 2-3 |
It should be noted that the specific rotation speed should be calibrated in combination with the volume of the test chamber, heating power and sample loading capacity to ensure compliance with relevant standard requirements.
Test practice recommendations
Before conducting textile color fastness testing, it is recommended to verify the uniformity of no-load temperature in the test chamber, and measure the multi-point temperature in the chamber at different speeds to confirm that the uniformity requirements specified in the standard are met. Sample placement should simulate actual use and be evenly distributed on the sample holder to avoid obstructing airflow. During the test, the color change trend can be observed by adjusting the rotation speed, and if the color fastness results of the same batch of samples are very different, it is necessary to check whether the speed setting is appropriate. Regularly maintain the sample holder drive system to ensure stable and accurate rotational speed, avoiding speed fluctuations due to mechanical wear and tear, which can affect test repeatability.
Conclusion
The speed of the sample holder is a non-negligible parameter in the hot air aging test, which indirectly affects the color fastness test results of textiles by affecting the temperature uniformity and heat transfer efficiency. Reasonable selection of rotation speed requires comprehensive consideration of textile characteristics, test chamber performance and relevant standards. Through scientific setup and verification, the consistency and reliability of testing can be improved, providing more accurate data support for textile quality assessment. Future research can further quantify the specific relationship between rotational speed and the color fastness of different textile materials, and improve the test methods.
References
1. Overview of Color Fastness Test Methods for Heat Aging in Textiles, Journal of Materials Testing Technology, 2020.
2. Research on Performance Parameters of Hot Air Circulating Aging Chamber, Journal of Environmental Testing Equipment, 2019.
3. Comparative analysis of aging test conditions in international textile testing standards, Textile Standards and Quality, 2021.