GB/T 42704-2023Textile trim materials in automotive interior applications - Determination of the emissions of volatile organic compounds - Chamber method (English PDF)

Foreword

This document was issued on 23 May 2023 by the State Administration for Market Regulation; Standardization Administration of the PRC and takes effect on 1 December 2023.

It is a GB/T standard: recommended rather than compulsory, but it is the text a Chinese reviewer applies when assessing a submission.

1 Scope

GB/T 42704-2023 measures what the textiles inside a car give off. A vehicle interior is a small, sealed, sun-heated volume lined with materials that continue to release volatile organic compounds long after manufacture — from the polymers themselves, from adhesives, backings and finishes — and the occupants breathe the result. Textile trim is a large share of the exposed surface, which makes it a large share of the emission. Measuring it credibly is the difficulty: emission rates depend strongly on temperature, air exchange and the ratio of sample area to chamber volume, so a number without a specified method means nothing and two suppliers' figures cannot be compared. This document describes a chamber method for collecting and determining the emissions of volatile organic compounds from textile trim materials used in automotive interiors. It applies to all types of automotive interior textile trim materials, including woven fabrics and the other constructions used in the application. Under ICS 59.080.30 and CCS W04, it is written for textile and trim suppliers, for the vehicle manufacturers writing interior air quality requirements into their specifications, and for the testing laboratories that have to produce comparable numbers.

This document describes a test method for the collection and determination of the

emissions of volatile organic compounds from textile trim materials in automotive

interior applications using the chamber method.

This document applies to all types of textile trim materials in automotive interior

applications, including woven fabrics, knitted fabrics, non-woven fabrics and coated

fabrics, as well as composite fabrics.

2 Normative references

The following documents are referred to in the text in such a way that some or all of

their content constitutes requirements of this document. For dated references, only the

version corresponding to that date is applicable to this document; for undated references,

the latest version (including all amendments) is applicable to this document.

HJ/T 400-2007, Determination of volatile organic compounds and carbonyl

compounds in cabin of vehicles

3 Terms and definitions

For the purposes of this document, the following terms and definitions apply.

3.1

total volatile organic compounds; TVOC

Volatile organic compounds with retention time between n-hexane and n-hexadecane

when using a Tenax tube for sampling, and a non-polar chromatographic column

(polarity index less than 10) for analysis.

3.2

total hydrocarbon mass concentration

Glass or stainless-steel adsorption tube, which is filled with solid adsorption material

with a particle size of 250 um ~ 180 um (60 mesh ~ 80 mesh).

Note: In most cases, Tenax-TA tubes are used, and adsorption tubes with other fillers

can also be used.

3.10

DNPH tube

A sampling tube that is filled with 2,4-dinitrophenylhydrazine (DNPH) silica gel.

4 Principle

Put the sample into the test chamber; heat it under the specified temperature, humidity

and air change rate; monitor the sampling environment in real time through the online

hydrogen flame ionization detector (FID); use the sampling tube to collect the air in the

chamber after a certain period of time; use gas chromatography/mass spectrometry

(GC-MS) and high performance liquid chromatography (HPLC) to qualitatively and

quantitatively determine the collected benzene series and aldehydes and ketones (see

5 Instruments and materials

5.1 Test chamber

5.1.1 General

5.1.1.1 The chamber capacity of the test chamber shall be 0.05 m3 ~ 4.0 m3, and a test

chamber with a capacity of (1.00+/-0.05) m3 is recommended. The interior of the

chamber shall be composed of a gas mixing device, a temperature regulating device, a

humidity regulating device, a bracket for placing test samples, air intake and exhaust

pipes, etc.

5.1.1.2 Chamber material: The inner wall of the chamber and the bracket for placing

test samples shall be made of electropolished stainless steel. If the necessary parts or

facilities inside the chamber cannot be made of electropolished stainless steel due to

technical reasons, they shall be made of materials that have a weak adsorption of

organic matter and do not emit organic matter, and the surface area of the parts or

facilities using these materials shall not exceed 5% of the total internal surface area of

the chamber.

5.1.1.3 Tightness: In order to avoid unnecessary air exchange, the chamber shall have

good airtightness.

5.1.1.4 Gas mixing: A gas mixing device shall be equipped, so that the airflow speed in

the center of the chamber in the empty chamber state is greater than 0.1 m/s during the

test process.

5.1.1.5 Chamber cleaning: By adopting appropriate cleaning methods, such as high-

temperature thermal desorption, etc., ensure that the chamber is thoroughly cleaned

after each test is completed. Before the start of the next test, all surfaces in the test

chamber that are in contact with volatile organic compounds shall also be cleaned to

ensure that the background value of the chamber will not affect the test results.

5.1.2 Temperature regulating device

The temperature regulating device shall ensure that the temperature difference at each

point in the space of the test chamber does not exceed +/-1 °C.

5.1.3 Humidity regulating device

The humidity regulating device shall ensure that the relative humidity of the gas

entering the test chamber is 45% +/- 5% at 23 °C and 5% +/- 0.5% at 65 °C, and no steam

or spray can be generated during the humidity regulating process.

5.1.4 Test chamber tightness

In order to avoid uncontrollable gas exchange, it shall be ensured that under the

condition of positive pressure of 1 000 Pa, the gas leakage per minute is less than 0.5%

of the volume of the test chamber. In order to prevent outside gas from entering the test

chamber, especially during gas sampling, it shall be ensured that the pressure of the test

chamber is slightly higher than atmospheric pressure, that is, it is operated under the

condition of slight positive pressure.

Set the chamber temperature to 65 °C, and test the airtightness of the test chamber by

applying a positive pressure of 1 000 Pa on its surface and recording the pressure change

of the test chamber within 2 h. The pressure sensor used shall be able to detect the

pressure below 100 Pa and the deviation shall not exceed +/-5%. During the 2 h test

period, the average leakage rate shall be calculated according to Formula (1):

Where:

nL - the average leakage rate of the volume of the test space, in permillage per minute

( per mille/min);

P1 - the absolute pressure of the chamber at the beginning of the tightness test, in

Pascals (Pa);

Before each sampling, use the gas flow calibrator (5.5) to calibrate the sampling flow

of the sampling system under the sampling load conditions.

5.5 Gas flow calibrator

Used to calibrate the sampling speed of the sampling pump. The maximum allowable

error of the flowmeter does not exceed +/-1%. When calibrating the flow rate, the error

of flow rates before and after shall be less than 5%.

6 Sample preparation and sample handling

6.1 Sample preparation

6.1.1 The to-be-tested samples shall be sealed and packaged in the pollution-free

polyethylene film or aluminum foil within the specified time (negotiated and recorded

by both the supplier and the buyer) after production is off-line, and put into the packing

box. Since volatile organic compounds are greatly affected by the environment, it is

advisable to make a complete record of the history of the samples before packaging

(such as storage environment temperature and humidity conditions, storage time).

6.1.2 During the transportation of samples, it is advisable to avoid direct exposure to

strong light or high temperature environment to avoid damage to the packaging. After

receiving the samples in the laboratory, they shall be stored in an environment with a

temperature not exceeding 23 °C in a well-packaged state.

6.2 Sample handling

6.2.1 Before the test starts, the sample needs to be pre-treated for 24 hours under the

condition of 23 °C +/- 2 °C. During the pre-treatment process, it is required by the

relevant party whether to open the package. If there is no requirement, the default is

that the sample package is intact. The samples shall be placed on the shelf or grid; the

samples shall neither contact with each other nor other objects outside the grid.

Requirements for the pollution concentration value of the environment before sample

pretreatment: toluene mass concentration <=20 ug/m3, formaldehyde mass concentration

<= 20 ug/m3.

6.2.2 The test sample shall be representative; the sample size shall be according to the

procedure specified in the product standard or the agreement between the two parties;

an appropriate product loading factor shall be provided. The requirements for test

material shall be negotiated between the supplier and the buyer. If there is no special

requirement, the recommended product loading factor is 2 m2/m3, that is, in the standard

test chamber, the exposed area of the sample is 2 m2, and multiple samples can be

combined and the samples cannot be stacked. Weigh the sample mass and record,

accurate to 1 g.

7 Preparation before the test

7.1 Test chamber cleaning

7.1.1 Chamber cleaning.

First, mechanical cleaning methods (such as industrial vacuum cleaners) shall be used

to remove residual particles and impurities from the previous test, and then high-

temperature cleaning shall be used for aging of the chamber or alkaline detergent shall

be used to clean the chamber. When using heated purge air to clean the test chamber at

high temperature, it shall be ensured that the temperature of all inner surfaces in contact

with the atmosphere in the test chamber exceeds 200 °C, and the air shall be changed

and cleaned repeatedly for 10 times after reaching the heating temperature. If alkaline

detergent is used, use deionized water to rinse the entire chamber twice, followed by a

hot wash with clean air at the test temperature. Monitor the background concentration

of the chamber according to the requirements of 7.2. If the background concentration

does not meet the requirements, continue to clean the chamber until the background

concentration of the chamber reaches the requirements of 7.2.

7.1.2 Cleaning of other accessories

7.1.2.1 For the components that come into contact with the gas in the test chamber but

cannot be directly cleaned during the cleaning process in 7.1.1, technically equivalent

cleaning measures shall be taken separately.

7.1.2.2 For other components (such as sealing rings) whose temperature resistance is

lower than 180 °C in the chamber, generally use deionized water to clean, and dry at

120 °C for 2 h ~ 3 h to achieve the cleaning effect.

7.2 Chamber background concentration monitoring

Under the condition of 65 °C, collect the background gas samples, and respectively

determine the content of the target pollutants in the background gas samples. The sum

of the mass concentration of total volatile organic compounds shall be less than 50

ug/m3, and the mass concentration of each volatile organic compound shall be less than

5 ug/m3. The total hydrocarbon mass concentration monitored by online FID shall be

less than 1 600 ug/m3.

7.3 Handling of connected gas-guide tubes

Treat at (100+/-5) °C for about 12 hours.

7.4 Handling of Tenax tubes

Before use, the Tenax tube needs to undergo high-temperature aging in an aging furnace.

The aging conditions are as follows: the temperature is 300 °C, the nitrogen flow rate

is 100 mL/min, the aging time of the new Tenax tube is 18 h, and the aging time of the

the recommended sampling flow rate is 100 mL/min, and the sampling time is 30 min;

for the DNPH tube, the sampling flow rate is 400 mL/min, and the sampling time is 30

min.

Note: For Tenax tubes, it is generally recommended that the maximum sampling

volume be <=5 L.

Connect the gas-guide tube connected with the sampling tube to the outlet of the test

chamber or other sampling ports of the discharge test chamber; pay attention to and

record the time and temperature of connecting the sampling tube; record the

atmospheric pressure if necessary. At the end of sampling, disconnect the gas-guide

tube from the sampling port of the test chamber; note and record the time of

disconnection; re-determine the sampling flow; turn off the pump. Disconnect the

connection between the sampling tube and the gas-guide tube; use a screw cap fitting

with a PTFE collar to seal both ends; write the number on it; wrap it in aluminum foil;

send it to the instrument for analysis as soon as possible; analyze the samples in the

Tenax tube and DNPH tube according to Appendix B and Appendix C in HJ/T 400-

2007 respectively. If immediate analysis is not available, store it in a refrigerator at

(4+/-2) °C, for a storage period up to 7 days.

8.6 During the entire test process, the temperature and humidity of the test chamber and

the total hydrocarbon mass concentration rhox monitored by the online FID shall be

recorded.

8.7 After the test, the test chamber shall be cleaned immediately according to 7.1.