QC/T 709-2004Test method for compression set of automotive weatherstrips (English PDF)

1 Scope

This Standard specifies the test method of compression set for automobile weatherstrips.

This Standard applies to the test of compression set for automobile weatherstrips.

2 Normative references

The terms in the following documents become the terms of this Standard by reference to this Standard. For dated references, all subsequent amendments (not including errata content) or revisions do not apply to this Standard.

However, parties to agreements that are based on this Standard are encouraged to study whether the latest versions of these documents can be used. For undated references, the latest edition applies to this Standard.

GB/T 2941, Standard temperature, humidity and time for environmental regulation and testing of rubber samples (eqv ISO471:1983)

GB/T 9868, Rubber - General directions for achieving elevated or subnormal temperatures for test purposes (idt ISO3383:1985)

GB/T 8170, Rules of rounding off of numerical values

3 Principle

Compress a sealing strip sample of a known height to a predetermined height according to the compression rate; compress it at a predetermined temperature for a certain period of time; then, remove the compressive force at a standard temperature; and the sample is gradually recovered in a free state; measure the height after the recovery within the predetermined time. Use the ratio of the deformation value that cannot be recovered after compression of the sample TO the maximum deformation value when the sample is compressed, to indicate the deformation of the sealing strip that is caused by the change of compression after the force of compression is removed to prevent the material from returning to its original state.

4 Instruments and apparatuses

5 Sample and state adjustment

5.1 Except for special requirements, three samples of length (100 ± 2) mm shall be taken from different finished products.

5.2 The time interval between the test and vulcanization and the adjustment of the sample before the test shall be carried out in accordance with the provisions of GB/T 2941.

5.3 Before the test, the sample shall be parked for at least 3 hours in an environment where the temperature is (23 ± 2) °C and the relative humidity is (50 ± 5) %. The sample shall not be pressurized during the parking period. Fastener Upper plate Limit sleeve Bottom plate Benchmark

6 Test steps

6.1 Mount the sample on the corresponding test fixture.

6.2 It is recommended to use the upper surface of the bottom plate as the base level to set the zero point of the height measuring instrument.

6.3 Measure the height h0 before the compression of the sample and the height h1 of the limit sleeve. Install the upper plate and tighten the hold-down nut.

6.4 Place the clamps with the installed samples into the environment that meets the test requirements and store them as required. Unless otherwise specified, the test ambient temperature is (70 ± 2) °C, and the storage time is 96 h.

6.5 Immediately after storage, loosen the fasteners; remove the upper plate and place it in the standard environment of (23±2) °C. Adjust for (30±3) min in the free state; then, measure the height h2 after the sample is restored.

7 Test result expression

7.1 Compression set c is calculated according to Formula (1):

Where: c -- compression set, in %; h0 -- the height of the sample before compression, mm; h1 -- the height of the sample during compression (i.e. the height of the limit sleeve), mm; h2 -- the height of the sample after recovery within the specified time after compression, mm.

7.2 The calculation result is rounded to 1% according to GB/T 8170.

7.3 Take the arithmetic mean of all test data as the test result; the difference between each test data and the arithmetic mean is not more than ±10%; otherwise, three samples shall be taken and the number of samples shall be indicated in the report.

8 Test report

The test report shall contain the following contents:

a) test name, number:

b) number of this Standard;

c) sample name;

d) sample length;

e) device name and number, limit sleeve height:

f) test conditions: test temperature, time, compression ratio and other relevant parameters;

g) indicator value;

h) test result;

i) tester and date. […]