GB/T 3922 is a critical national standard in China used to evaluate the colorfastness of textiles to perspiration. This test method simulates the effect of human sweat on dyed fabrics, ensuring that garments do not fade or stain during wear. This article provides a comprehensive technical overview of the GB/T 3922 testing procedure, sample requirements, and evaluation criteria.
Technical Overview
GB/T 3922 specifies a method for determining the resistance of the color of textiles of all kinds and in all forms to the action of human perspiration. This standard is technically equivalent to the international standard ISO 105-E04. The test aims to assess whether a textile material will change color or stain adjacent fabrics when exposed to the chemical environment of sweat. Human sweat is complex, containing salts, fatty acids, and urea, and can be either acidic or alkaline depending on physiological conditions. Consequently, the standard requires testing under both acidic and alkaline conditions to provide a comprehensive assessment of colorfastness.
- Standard Number: GB/T 3922
- International Equivalent: ISO 105-E04
- Test Principle: Contact with artificial perspiration solution under pressure and heat
Testing Samples
Sample Preparation
The testing sample must be prepared as a composite specimen. A piece of the textile to be tested is placed in direct contact with specified adjacent fabrics. The composite specimen typically measures 100 mm by 40 mm. It is crucial that the sample represents the complete construction of the textile, including all colors and fibers if the fabric is multi-colored or a blend.
Adjacent Fabrics
The choice of adjacent fabric is vital for assessing staining. The standard typically requires the use of two types of adjacent fabrics: one made of the same fiber as the test sample and the other made of a different fiber specified by the standard, often utilizing multifiber adjacent fabric (DW type). For certain specific fiber types, single-fiber adjacent fabrics are stipulated to ensure accurate staining results.
Testing Items
The evaluation of the GB/T 3922 test focuses on two primary parameters: color change and staining.
- Color Change (Fading): This assesses the degree to which the original color of the test specimen has changed after exposure to the perspiration solution. It measures the stability of the dye within the fiber itself.
- Staining: This evaluates the degree to which the dye has migrated from the test specimen to the adjacent fabric. It measures the propensity of the dye to transfer to other materials under moist conditions.
Testing Methods
Solution Preparation
Two distinct artificial perspiration solutions are prepared to simulate different physiological conditions. The alkaline solution contains histidine monohydrochloride monohydrate, sodium chloride, and disodium hydrogen phosphate dihydrate. The acidic solution contains histidine monohydrochloride monohydrate, sodium chloride, and sodium dihydrogen phosphate dihydrate. Both solutions are adjusted to specific pH levels (alkaline at pH 8.0 and acidic at pH 5.5) using sodium hydroxide.
Testing Procedure
The composite specimen is thoroughly wetted in the artificial perspiration solution at a specific liquor ratio, typically 50:1. After being allowed to soak, the specimen is removed and excess solution is drained off to a specific moisture content. The specimen is then placed between two glass plates or acrylic resin plates under a pressure of 12.5 kPa. The assembly is placed in an oven at a temperature of 37 degrees Celsius plus or minus 2 degrees Celsius for 4 hours.
Drying and Assessment
After the incubation period, the specimens are separated and allowed to dry in air at a temperature not exceeding 60 degrees Celsius. The color change of the test specimen and the staining of the adjacent fabrics are evaluated using the Grey Scale for Color Change and the Grey Scale for Staining, respectively. The results are graded on a scale from 1 (severe change/staining) to 5 (no change/staining).
Applications
The GB/T 3922 standard is widely used in the textile and apparel industry for quality control and product compliance. It is applicable to various types of materials, including woven, knitted, and non-woven fabrics, as well as fibers and yarns.
- Apparel Manufacturing: Ensuring that clothing items do not stain the wearer's skin or undergarments due to sweating.
- Sportswear: Critical for high-performance fabrics exposed to significant amounts of sweat during athletic activities.
- Safety Compliance: Mandatory for products entering the Chinese market under regulations such as GB 18401, the national general safety technical code for textile products.
- Infant Textiles: Ensuring the safety of baby clothes, which require higher standards for colorfastness to protect sensitive skin.
FAQ
Why is testing both acidic and alkaline perspiration necessary?
Human sweat varies in pH depending on an individual's physiology, diet, and health. Some dyes may be stable in acidic environments but degrade in alkaline environments, or vice versa. Testing both conditions ensures the textile can withstand the diverse range of real-world perspiration scenarios.
What is the difference between GB/T 3922 and ISO 105-E04?
While GB/T 3922 is largely equivalent to ISO 105-E04, there may be minor technical differences in specific procedural details or reporting formats. Laboratories performing tests for export or import should verify if there are specific client requirements regarding which standard to apply.
How is the result interpreted?
The results are reported as numerical grades. A grade of 4-5 or 5 is generally considered excellent colorfastness. A grade of 3 is moderate, and anything below 3 is usually considered poor and may lead to consumer complaints regarding fading or staining of other garments.