GB/T 20671.3-2020Classification system and test methods for nonmetallic gasket materials—Part 3: Standard test method for fluid resistance of gasket materials (English PDF)

1 Scope

This Part of GB/T 20671 specifies the principle, instruments and apparatuses, test samples, test procedures, test reports and precision of the method for determining the degree of influence on the physical properties of nonmetallic gasket materials after immersion in the test liquid.

This Part applies to the determination of the liquid resistance of Type 1, Type 2, Type 3 and Type 7 materials which are described in GB/T 20671.1-2020.

2 Normative references

The following documents are indispensable for the application of this document.

For dated references, only the dated version applies to this document. For undated references, the latest edition (including all amendments) applies to this document.

GB/T 20671.1-2020, Classification system and test methods for nonmetallic gasket materials - Part 1: Standard classification system for nonmetallic gasket materials

GB/T 20671.2, Classification system and test methods for nonmetallic gasket materials - Part 2: Standard test method for compressibility and recovery of gasket materials

GB/T 20671.7-2006, Classification system and test methods for nonmetallic gasket materials - Part 7: Standard test methods for tension testing of nonmetallic gasket materials

GB/T 20671.8, Classification system and test methods for nonmetallic gasket materials - Part 8: Standard test method for flexibility of non-metallic gasket materials

4 Instruments and apparatuses

4.6 Conditioning box or conditioning room: maintain the temperature at 21 °C ~ 30 °C and the relative humidity at 50% ~ 55%.

4.7 Test tube: the outer diameter is 38 mm; the total length is 305 mm; it is equipped with a compressible plug that is wrapped in aluminum film.

4.8 Immersion container: it is equipped according to the sample size requirements.

4.9 Flask with condensing reflux device: it is equipped according to the sample size requirements.

4.10 Light metal wire mesh: its size can be put into the immersion container.

4.11 Watch glass or weighing bottle.

4.12 ASTM No. 1 oil (IRM 901), IRM 903 oil, ASTM fuel oil B, distilled water, ethylene glycol, propylene glycol and other required test liquids (see Appendix A).

4.13 Absorbent material: fast filter paper of oil absorption characteristics or similar absorbent material.

5 Test sample

5.1 The test sample shall be die-cut to keep the sample flat, clean and free of protruding fibers, fillers and particles.

5.2 The sample size shall meet the following requirements:

-- The sample that is used to test the thickness, mass and volume change rate after immersion is a single layer; its size shall be a rectangle whose diameter is 25.4 mm × 50.8 mm or a circle whose diameter is 28.6 mm;

-- The sample that is used to test the reduction rate of tensile strength after immersion shall meet the requirements of GB/T 20671.7-2006;

-- The sample that is used to test the compression ratio after immersion shall be a circle whose diameter is 28.6 mm; the number of layers shall meet the requirements of GB/T 20671.2;

-- The sample that is used to test the flexibility after immersion shall be a single-layer rectangle of 12.7 mm × 152.4 mm.

5.3 The test sample shall be adjusted according to GB/T 20671.1-2020 before the test.

6 Test procedure

6.2.1 Put the to-be-tested sample into a test tube or flask; each test tube is filled with only one material. Pour a sufficient amount of fresh liquid into the test tube to completely immerse the sample. Plug the stopper that is wrapped in aluminum film; place it on the bracket of an oven at the temperature that is specified in Table 2.

6.2.2 After reaching the specified test time, take out the sample and immediately immerse it in a cool (21 °C ~ 30 °C) and unused test liquid of the same kind; place it for 30 min ~ 60 min. Then, remove the sample from the cooled test liquid; immediately use the absorbent material to absorb the excess liquid on the surface of the sample. Be careful when absorbing excess liquid; do not squeeze the sample. When the thickness of the sample exceeds 0.79 mm, the excess liquid on the edge shall also be absorbed.

6.2.3 Perform the compressibility test according to GB/T 20671.2.

6.2.4 Take the arithmetic average of five parallel test results as the report value; round to two decimal places according to GB/T 8170.