5.1 This test method evaluates, under carefully controlled conditions, the changes in the mass of a test specimen on exposure under vacuum to a temperature of 125°C and the mass of those products that leave the specimen and condense on a collector at a temperature of 25°C.
5.2 The 24 h test time does not represent actual outgassing from years of operation, so a higher test temperature shorter time was selected to allow material comparisons with no intent to predict actual outgassing in service. The test temperature of 125°C was assumed to be significantly above the expected operating temperature in service. If expected operating temperatures exceed 65 to 70°C the test temperature should be increased. It is suggested that test temperature be at least 30°C higher than expected maximum service temperature in order to provide material comparisons for TML and CVCM.
5.3 Comparisons of material outgassing properties are valid at 125°C sample temperature and 25°C collector temperature only. Samples tested at other temperatures may be compared only with other materials which were tested at that same temperature.
5.4 The measurements of the collected volatile condensable material are also comparable and valid only for similar collector geometry and surfaces at 25°C. Samples have been tested at sample temperatures from 50 to 400°C and at collector temperatures from 1 to 30°C by this test technique. Data taken at nonstandard conditions must be clearly identified and should not be compared with samples tested at 125°C sample temperature and 25°C collector temperature.
5.5 The simulation of the vacuum of space in this test method does not require that the pressure be as low as that encountered in interplanetary flight (for example, 10−12 Pa (10−14 torr)). It is sufficient that the pressure be low enough that the mean free path of gas molecules be long in comparison to chamber dimensions.
5.6 This method of screening materials is considered a conservative one because maximum operating temperatures in service are assumed not to exceed 50 to 60°C for most applications. It is possible that a few materials will have acceptable properties at the intended use temperature but will be eliminated because their properties are not satisfactory at the test temperature of 125°C. Also, materials that condense only below 25°C are not detected. The user may designate additional tests to qualify materials for a specific application.
5.7 The determinations of TML and WVR are affected by the capacity of the material to gain or lose water vapor. Therefore, the weighings must be accomplished under controlled conditions of 23°C and 508201;% relative humidity.
5.8 Alternatively, all specimens may be put into open glass vials during the 24-h temperature and humidity conditioning. The vials must be capped before removal from the conditioning chamber. Each specimen must be weighed within 2 min after opening the vial to minimize the loss or absorption of water vapor while exposed to an uncontrolled humid......