1 Add a refrigerant (usually solid carbon dioxide or liquid nitrogen) into a cryogenic bottle filled with a heat transfer medium (usually ethanol) and stir by mechanical or manual methods to make the temperature uniform, and adjust the temperature to 4-- 5°C.
2 Immerse the compression device of the instrument into a cryogenic bottle and freeze for not less than 15 minutes.
3 Lift the compression device of the instrument from the cryogenic bottle, and then use a 10.0±0.1mm metal gauge block to quickly correct the zero of the dial indicator.
4 Adjust the temperature of the heat transfer medium to 1-2°C lower than the test temperature, then place the rubber pad sample between the indenter and the compression platform of the cooled instrument, and measure the original height ho of the rubber pad sample within 5S. Then quickly compress the rubber pad sample to 80% of the original height of the rubber pad sample and record the original height ho and compression height h1.
5 Put the compression device of the instrument together with the compressed rubber pad sample into the cryogenic bottle, freeze for 5.0±0.1 min, release the handwheel and release the compression load within 10s, so that the rubber pad sample recovers 3±0.1 min in the cryogenic bottle. 0.1min, read the recovery high h2 from the dial indicator and record it.
6 Lift the compression device from the cryo vial to remove the rubber pad sample.
7 Make another rubber pad sample according to steps 6.4-6.6.
8 During the rubber pad test, the temperature fluctuation should not be greater than 1°C, stirring should not be performed, and solid carbon dioxide should not be added.
9 During the rubber pad test, the temperature bulb of the thermometer should be in the same horizontal position as the rubber pad sample, and the penetration depth of the rubber pad sample should not be less than 75mm.
10 After the rubber pad test, the indenter and compression platform of the instrument should be wiped dry.