ISO 291:2008 pdf download.Plastics – Standard atmospheres for conditioning and testing.
This International Standard sets out specifications relating to the conditioning and testing of all plastics and all types of test specimen at constant atmospheric conditions.
Special atmospheres applicable to a particular test or material or simulating a particular climatic environment are not included in this International Standard.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 62, Plastics — Determination of water absorption
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.6
ambient temperature
environmental conditions corresponding to the usual atmospheric conditions in laboratories with uncontrolled temperature and humidity
NOTE The phrase TMat ambient temperature” refers to an environment the air temperature of which lies within a specified range, no consideration being given to relative humidity, atmospheric pressure or air-circulation velocity. In general, the air-temperature range extends from 18 °C to 28 °C and is stated as “at an ambient temperature of 18 °C to
28 °C”
4 Principle
If a test specimen is exposed to a specific conditioning atmosphere or temperature, then a reproducible state of temperature and/or of moisture equilibrium is reached between the test specimen and the conditioning atmosphere or temperature.
It is not the intent of this International Standard to define procedures specifying how to determine sensitivity to moisture.
6 Classes of standard atmosphere
Table 2 gives the different classes of standard atmosphere corresponding to different tolerance levels for the temperature and relative humidity. The tolerances given in Table 2 apply to the specimen-storage space in a test enclosure or conditioning enclosure. Class 1 cabinets will require more frequent calibration. Follow the manufacturer’s recommendations for calibration. Cabinets shall be calibrated at least once per year.
In the case of procedure b), the following rule of thumb may be useful: equilibrium can be assumed to have been reached if two weighings made at an interval of d2 weeks differ by only 0,1 % (d being the thickness, in millimetres, of the specimen).
Procedure c) is used when the moisture diffusion characteristics of the polymer are known and can be used to determine appropriate exposure periods and conditions. The specimens shall be kept in the oven or conditioning enclosure until they are, to all intents and purposes, in a state of moisture equilibrium. This may be assumed to be the case when the average moisture content of the material changes by less than 0,01 % during a conditioning period of at least 1 day, determined by loss in mass as specified in ISO 62.
If the moisture diffusion coefficient D is known, the time necessary for moisture equilibrium to effectively be reached is determined using Equation (A.2) or taken as 1 day, whichever is the longer.ISO-291-2008