Research on emission testing of automotive interior paint coatings

The air quality problem in the car is closely related to people's physical and mental health, so it has been paid more and more attention. Air pollution in automobiles is mainly caused by volatile organic compounds (VOCs) volatilized by heating of automobile interior parts (paint, plastic, rubber, leather, carpet and other decorative materials). Therefore, it is of great significance to effectively establish a method for the determination of organic volatiles in automotive interior parts and related materials, and to control the emission of organic compounds from pollution sources. It is understood that there is no relevant national standard method for testing the volatile organic compounds in automotive interior parts or decorations. At present, the detection of volatile organic compounds in automotive interior parts and materials generally adopts thermal desorption-gas chromatography-mass spectrometry (TDS).—GC/MS), headspace-gas chromatography (HS)—GC), sampling bag-thermal desorption-gas chromatography mass spectrometry (Bag—TDS—C, C/MS) and high performance liquid chromatography (HPLC). The author of this paper aims to establish a simple and feasible method for the determination of volatile organic compounds in automotive interior materials by using the environmental test chamber developed by our institute, that is, the test chamber-thermal desorption-gas chromatography method. This method uses the total carbon content (( Using toluene as an equivalent) to characterize the amount of volatile organic compounds, replacing Bag to some extent—TDS—The quantitative method of GC/MS method can effectively evaluate the volatile properties of materials. In addition, the method was applied to determine the emission of volatile organic compounds of five kinds of automotive interior coatings. 1. Test part 1.1 Test principle The dry coating sample is placed in a closed environmental test box, and after a certain time of emission test under certain temperature and humidity conditions, the Tenax TA adsorption tube is used to quantitatively collect the emission from the sample. volatile organic compounds. After sampling, the adsorption tube was connected to the gas chromatography system for analysis and testing. The components to be tested enter the gas chromatographic column with the inert carrier gas, and are detected by FID. The retention time is used for quantification, and the peak area is used for quantification. Use n-eicosane (C20) as the marker and toluene as the equivalent to calculate all the boiling points lower than C20. The sum of substances, characterized by the total carbon content, is the volatile organic compound emission of the sample, and its emission is studied by the emission. 1.2 Test instruments and materials KFlll-02UB type environmental test box: self-developed by Guangzhou Synthetic Materials Research Institute, with a closed volume of 0.24m3, the sampling inlet and outlet of the circulating air flow can be used for sampling connection; the temperature and humidity test conditions can be controlled and adjusted by program ; Test light sources are available. QC-2 Atmospheric Sampler: Beijing Institute of Labor Protection Science. GC7890 II gas chromatograph: Shanghai Tianmei Chromatography Instrument Co., Ltd. rip-2030 thermal desorption instrument: Beijing Beifen Temple Instrument Company. Tenax—TA adsorption tube: Beijing Zhongke Huijie Analysis Technology Co., Ltd. Three sets of automotive interior paint samples (1’, 2+, 3. ): Guangdong Yatu Chemical Co., Ltd. Methanol: analytically pure. Toluene: above analytical grade. n-Eicosan: analytically pure. 1.3 Preparation of coating samples Prepare mixed samples according to the construction ratio of the product. After stirring evenly, the size is 210mm.×It is sprayed or painted on 148mm clean aluminum foil, and the dry film thickness is controlled at 501xm+5 1xm. Then, the coated sample was dried according to the drying conditions provided by the product supplier. After drying, it was ventilated at room temperature for 24 hours, and then wrapped in aluminum foil and placed in a polyethylene bag to be sealed for testing. 1.4 Test condition p. J1.4.1 Gas chromatography conditions Column: polydimethylsiloxane capillary column, 50m×0.32mm×1. O bucket m; the column temperature adopts a programmed temperature increase: the initial temperature is kept at 50 °C for 5 min, and then the rate is 8. C/min was raised to 260cc and held for 10min; inlet temperature: 280°C; detector temperature: 280°C; carrier gas flow rate: 2.0ml/min; split ratio: 15:1. 1.4.2 Thermal desorption conditions Desorption temperature: 280°C; desorption time: 5 rain; injection time: 50s; desorption gas flow: 50ml/min. 1.5 Test steps 1.5.1 Determination of response coefficient of toluene Take 2 buckets of L of this solution and quickly inject the sample into the adsorption tube, and pass nitrogen flow to make the standard sample fully absorbed. Then, connect to a gas chromatograph for thermal desorption analysis, record the chromatogram and peak area, and calculate the response coefficient of toluene. 1.5.2 Coating emission test According to the specified load rate, weigh a coating sample of a certain quality, and place it in an environmental test chamber with set test conditions for a certain period of emission test. 1.5.3 Sampling and analysis Sampling conditions: flow 200—500mL/min, time 20-50min, general sampling volume is 10L. According to the test period of 6h, 24h, 48h, 72h, gas sampling and analysis were carried out. Set the instrument parameters according to the optimal conditions when measuring the calibration factor, connect the adsorption tube of the collected gas sample to the gas chromatograph for thermal desorption analysis, record the chromatogram, and calculate the peak area of ​​all substances whose boiling point is lower than that of the marker. The response coefficient of the equivalent toluene was used to calculate the total carbon content of the volatile organic compounds in the sample. 2. Results and discussion 2.1 Selection of load rate The environmental test chamber used in the emission test has an effective volume of about 0.24m3.
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