SH/T 0436-1992 Determination of compatibility between synthetic lubricating oils for aviation and rubber

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Card type: Test method

1. Method number / full title / English title / replacement relationship

• Standard number: SH/T 0436-92
• Full title: Determination of compatibility between synthetic lubricating oils for aviation and rubber
• English title: not provided in the available source
• Replacement relationship: replaces ZB E40 ?-86 (the source text reads "replaces ZB E40 a r t- 86", the standard number is incomplete, requires confirmation against the source standard (source-text extraction))
• Approval/implementation: approved by China Petrochemical Corporation 1992-05-20, implemented on 1992-05-20

2. Scope of application and non-applicability

• This standard specifies the method for determining the compatibility between synthetic lubricating oils for aviation and rubber.
• This standard is applicable to the determination of the compatibility between synthetic lubricating oils for aviation and rubber.
• Non-applicable scope: not provided in the available source.

3. Method principle

Vulcanized rubber is immersed in synthetic lubricating oil, and the compatibility between the synthetic lubricating oil and the vulcanized rubber is evaluated based on the changes in the properties of the vulcanized rubber before and after immersion (swelling—volume change, changes in tensile stress-strain properties, and hardness change). (Chapter 4 Method summary)

4. Reagents and materials (purity / preparation)

• 5.1 Qualitative filter paper or lint-free cloth.
• 5.2 Vulcanized rubber test pieces: standard test pieces such as nitrile standard rubber BD-L, BD-G, and fluorine standard rubber BF, with a thickness of 2mm±0.3mm (the standard rubber compounds used are provided by the Ministry of Aerospace Industry 621 according to the standard elastomer material standards).
• 5.3 Industrial ethanol.
• 5.4 Cleaning solution: saturated solution of potassium dichromate in sulfuric acid.
• Others: distilled water (used in 7.2.1.2.1); rubber industry solvent naphtha (7.2.1.2.4 may replace industrial ethanol); purity requirements not provided in the available source.

5. Apparatus and equipment

• 6.1 Metal constant-temperature bath (aluminum bath or steel bath): controllable at the test temperature of ±2℃ (the source text reads "1 2`C", requires confirmation against the source standard (source-text extraction)), the hole diameter matches the outer diameter of the glass oil cup (see Figure 1).
• 6.2 Glass oil cup: use an extractor with a ground-glass stopper (see Figure 2).
• 6.3 Analytical balance: sensitivity of 0.1mg.
• 6.4 Thickness gauge: used to measure the thickness of vulcanized rubber (tolerance 0.1mm, range 0—10mm).
• 6.5 Shore A type hardness tester: used to measure the hardness of vulcanized rubber.
• 6.6 Rubber tensile testing machine: see GB 528.
• 6.7 Oven: temperature control ±1℃ (the source text reads "1 1`C", requires confirmation against the source standard (source-text extraction)).
• 6.8 Beakers: two each of 100 and 500mL.
• 6.9 Measuring cup: one of 500mL.
• Figure 1 Components: 1— connecting rod; 2— nut; 3— furnace frame; 4— metal bath core body; 5— support frame; 6— refractory brick; 7— asbestos cloth; 8— annular body; 9— temperature controller; 10— temperature indicator; 11— cover plate; 12— tubular electric heating element; 13— side panel; 14— bottom plate.

6. Recommended operating conditions

• Test temperature: conduct according to the required test temperature (the specific temperature value is not provided in the available source).
• Test period: conduct according to the required test period (the specific period value is not provided in the available source).
• Constant-temperature bath temperature control: test temperature ±2℃ (requires confirmation against the source standard (source-text extraction)).
• Oven temperature control: ±1℃ (requires confirmation against the source standard (source-text extraction)).
• During the test, the rubber should be protected from light.

7. Sampling and specimen preparation

• 7.2.1.1.1 Test piece for volume change: cut a square test piece of 25mm×25mm from a vulcanized rubber sheet with a thickness of 2mm±0.3mm (any rectangular test piece may also be used, but its length or width must not be greater than 50mm, and the volume is 1—3cm³).
• 7.2.2.1.1 Test piece for tensile stress-strain: use a dumbbell-shaped test piece (for general rubber, use the 1 type cutting die in GB 528; for silicone and fluorine rubber, use the 2 type cutting die).
• 7.2.2.2.1 Cut ten test pieces from the same batch of vulcanized rubber sheet, first measure the thickness and hardness of the specimens H₀ (stack three dumbbell-shaped test pieces, and measure H₀ at the end portions according to GB 531); use five of these test pieces to measure the tensile strength and elongation before immersion according to GB 528 (T₀, E₀).
• About 370mL of test oil is used for the same batch of tests.

8. Analysis procedure

7.1 Preparation

• 7.1.1 Raise the temperature of the metal bath and keep it constant at the test temperature.
• 7.1.2 Soak the glass oil cup in cleaning solution for 2h, then rinse with tap water, finally rinse clean with distilled water, place in an oven at 80—100℃ to dry, and store in a dust-free place for later use.

7.2.1 Determination of volume change

• 7.2.1.2.1 Use three vulcanized rubber test pieces (five pieces for arbitration testing). Weigh each test piece in air to the nearest milligram (m₁), then weigh each test piece again in distilled water at laboratory temperature (m₂), taking care to completely remove all air bubbles from the surface of the test pieces.
• 7.2.1.2.2 Dry the test pieces with filter paper or lint-free cloth, then string them together with stainless steel wire and space them appropriately, suspend them freely in a glass oil cup; the volume of the test material should be at least 15 times the total volume of the test pieces to ensure the test pieces are completely immersed. Close the mouth of the oil cup with a ground-glass stopper, and place it in a constant-temperature bath, and conduct the test according to the required test temperature and period. During the test, the rubber should be protected from light.
• 7.2.1.2.3 Only test pieces of the same vulcanized rubber may be placed in the same glass oil cup. If the density of the rubber is lower than the density of the test material, use a sinker to keep the test pieces completely immersed below the liquid surface.
• 7.2.1.2.4 At the end of the immersion period, take out the glass oil cup, quickly transfer the test pieces to fresh test material at laboratory temperature to cool for not less than 30min and not more than 60min. Take out the test pieces, first rinse in industrial ethanol (or rubber industry solvent naphtha) for 20s to remove excess test material from the surface. Then dry with filter paper or lint-free cloth, then weigh the mass of the test pieces in air (m₃) to the nearest milligram, and then weigh in distilled water at laboratory temperature (m₄).
• Note: The fresh test material liquid used for cooling may be reused five times.

7.2.2 Tensile stress-strain test

• 7.2.2.2.2 String together the five test pieces for tensile strength after immersion with stainless steel wire and space them appropriately, suspend them freely in a glass oil cup. The volume of the test material should be at least 15 times the total volume of the test pieces (about 370mL) to ensure the test pieces are completely immersed. Close the mouth of the oil cup with a ground-glass stopper, and place it in a constant-temperature bath. Conduct the test according to the required temperature and period.
• 7.2.2.2.3 At the end of the immersion period, take out the glass oil cup, quickly transfer the test pieces to fresh test material at laboratory temperature (see Note 7.2.1.2.4) to cool for not less than 30min and not more than 60min. Take out the test pieces, first rinse in industrial ethanol (or rubber industry solvent naphtha) for 20s to remove excess test material from the surface, then wipe dry with filter paper or lint-free cloth. Then measure the hardness after immersion (H₁). Then mark the gauge lines, and within 30min, conduct the tensile test at laboratory temperature (record T₁, E₁).

9. Qualitative and quantitative determination and calculation formulas

Percentage volume change ΔV(%) is calculated according to formula (1):

ΔV = [(m₃ - m₄) - (m₁ - m₂)] / (m₁ - m₂) × 100 …… (1)

Where:

• m₁—initial mass of rubber in air, g;
• m₂—initial apparent mass of rubber in water, g;
• m₃—mass of rubber in air after immersion, g;
• m₄—apparent mass of rubber in water after immersion, g.

The test result is taken as the average of the results of three (or five) test pieces.

Percentage change in tensile strength ΔT(%) is calculated according to formula (2):

ΔT = (T₀ - T₁) / T₀ × 100 …… (2)

Percentage change in elongation ΔE(%) is calculated according to formula (3):

ΔE = (E₀ - E₁) / E₀ × 100 …… (3)

Hardness change ΔH is calculated according to formula (4):

ΔH = H₀ - H₁ …… (4)

Where:

• T₀—tensile strength of the unimmersed test piece, Pa;
• T₁—tensile strength of the test piece after immersion, Pa;
• E₀—elongation of the unimmersed test piece, %;
• E₁—elongation of the test piece after immersion, %;
• H₀—Shore A type hardness value of the unimmersed test piece, degrees;
• H₁—Shore A type hardness value of the test piece after immersion, degrees.

When calculating ΔH, the specimen thickness is taken as the value measured before the test; the test results of T% and E% are taken as the average of the results of five test pieces.

10. Precision

• 8.1 Repeatability: the difference between test results determined by the same operator using the same set of instruments shall not be greater than 1%.
• 8.2 Reproducibility: the error range of the difference between test results determined by different operators or using different instruments is temporarily undetermined (pending accumulation).

11. Report

The report shall include:

• a. Oil sample grade, source, and batch number.
• b. Grade of vulcanized rubber used and type of test piece.
• c. Test temperature and test period.
• d. Percentage volume change, percentage change in tensile strength, percentage change in elongation, Shore A type hardness change value.
• e. Temperature at which tensile properties and hardness were measured.
• f. Description of whether the test material has discoloration and precipitate at the end of the test (color, state).
• g. Appearance of the test pieces at the end of the test (whether there is cracking, delamination, etc.).
• h. Test personnel and date.

12. Referenced documents

• GB 528 Determination of tensile properties of vulcanized rubber (editor's note: current standard number GB/T 528, current standard title "Determination of tensile stress-strain properties of vulcanized rubber and thermoplastic rubber")
• GB 531 Rubber Shore A type hardness test method (Editor's note: current standard number GB/T 531, current standard title "Vulcanized rubber Shore A type hardness test method")

13. Source and verification

This page is an AI translation of the available Chinese method card. Human verification is pending. It is not an official translation of the standard. Check the source standard and product certificate before use.

14. Quick Reference Q&A