Analysis of test methods for formaldehyde content in automotive interior fabrics

Automotive interior textiles are mainly used for automotive interior seat fabrics, headrests, door interior decorative panels, carpets, roofs, and instrument panel sundries box cover fabrics. It is a technical fabric that integrates decoration and functionality. Its raw materials Selection and decoration design directly affect the comfort, beauty, safety and environmental protection of the car. In recent years, the rapid progress of China's automobile industry has promoted the localization of auto parts, and also promoted the development of domestic automobile interior textiles. Automotive interior textile fabrics include imitation leather, plain weave, velvet and other varieties, as well as pure textiles and composite materials to meet people's various needs. The toxic gases released by the interior decoration materials of automobiles are very harmful to people. These toxic substances mainly include benzene, xylene, and formaldehyde. Therefore, for people's health, safety and environmental protection, detecting toxic gases and limiting them to a certain range has become a very important task in our country. Relevant departments at home and abroad attach great importance to formaldehyde in automotive interior materials and have successively formulated detection methods, but these methods still have some problems in practical applications. This article briefly describes four domestic and foreign testing methods for formaldehyde content in automotive interior textiles, and compares them, studies various factors that affect the results of formaldehyde determination, and explains the problems that should be paid attention to in the testing. Manufacturers can better control the quality of products and provide a basis for quality control of automotive interior textile materials when automakers purchase warehousing inspections. 1 Test method 1.1 Test principle Hang a sample of a certain size and weight in a sealed 1 L polyethylene bottle containing distilled water, and keep it at a certain temperature for a certain period of time. The formaldehyde solution absorbed by the distilled water is combined with ammonium ions and acetylacetone. The reaction produces a yellow complex—diacetyldihydrolutidine (DDL), which is then measured with an ultraviolet spectrophotometer at a wavelength of 412 nm to calculate the formaldehyde content. 1.2 See Table 1 for sampling requirements and test conditions during the test. (1) Take a sample of a certain size and quality, hang it in a 1 L polyethylene bottle with a hook on the cap, add 50 ml of distilled water, tighten the cap, and place it in a thermostat at a certain temperature for a certain period of time, then Take it out and let it cool at room temperature for 1 h. (2) Open the cap of the polyethylene bottle, take out the sample, tighten the cap, shake it fully, and then use a pipette to accurately transfer 10 ml of the formaldehyde absorption solution into a 50 ml graduated test tube with a stopper, and add 10 ml of 20% mass fraction respectively. Ammonium acetate solution and 10 ml 0.4% volume fraction acetylacetone color developer, cover the stopper and shake well, put the test tube in a constant temperature water bath at a certain temperature for a certain period of time, and then take it out and place it at room temperature to avoid light and cool for 1 h . (3) Measure the absorbance of the solution in the test tube with an ultraviolet spectrophotometer at a wavelength of 412 nm, and do a blank test at the same time. 1.3 Formaldehyde standard curve The formaldehyde solution is calibrated according to the formaldehyde calibration method (iodometric method or sodium sulfite method) specified in the standard. Then, according to the concentration of the formaldehyde standard solution, prepare a series of formaldehyde standard solutions (0-15 μg/ml) with a concentration ranging from low to high, and operate according to 1.2 (2) and (3) to determine their absorbance. According to the formaldehyde standard solution concentration (C)-absorbance value (A) relationship, formulate a formaldehyde standard working curve or determine a linear regression equation Cu003dkA (k is the correction factor). 1.4 The measured moisture content of a sample with a known weight of (40 × 100) mm is placed in a constant temperature oven at (103 ± 2) ℃, kept for 2 h, then taken out, and placed in a desiccator to cool for 0.5 h before weighing. Table 2 lists the results of formaldehyde content in various automotive interior materials (used by Volkswagen and General Motors) measured by the GME60271 method. The limit value of formaldehyde concentration in automotive interior materials is ≤10 mg/kg. Most of the materials in Table 2 meet the requirements, but a small number of materials exceed the limit value standard. 2.2 Obtaining formaldehyde absorption solution In the experiment, after the polyethylene bottle of the suspended sample is kept at a certain temperature, it must be taken out and cooled to room temperature, so that the formaldehyde released by the sample in the bottle can be completely absorbed by the aqueous solution; then the sample is taken out, It is very important to tighten the cap again and shake the solution in the bottle sufficiently to make the concentration of the formaldehyde absorption solution uniform. 2.3 Storage of Acetylacetone Chromogenic Reagent As the acetylacetone solution is extremely unstable under light, the prepared acetylacetone chromogenic reagent should be stored in the dark for no more than 4 weeks. The formaldehyde standard solution used in the test must be retested once a week to check the changes in the acetylacetone solution. In addition, the yellow DDL produced by the reaction of the formaldehyde absorbing solution with ammonium ions and acetylacetone solution will change its color over time when it is cooled in the sun, which will affect the test results. Table 3 lists the absorbance and formaldehyde content of the DDL solution after cooling for different times. It can be seen from Table 3 that the formaldehyde content of DDL will change over time when placed in the sun. Therefore, the sample solution after color development should be protected from direct sunlight, and the cooling time should not exceed 1 h. 2.4 Storage of samples before the test Automotive interior textiles should be sealed and sealed before the test, otherwise the formaldehyde in the sample will be emitted into the air and affect the accuracy of the test results.

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