ISO 62:2008 pdf download

ISO 62:2008 pdf download.Plastics – Determination of water absorption.
Plastics exposed to water are subject to several different effects:
a) dimensional changes (e.g. swelling) caused by absorption of water;
b) extraction of water-soluble components:
c) changes in other properties.
However, exposure to humidity, immersion and exposure to boiling water can result in distinctly different material responses. The equilibrium moisture content can be used to compare the amount of water absorbed by different types of plastics when they are exposed to moisture. Moisture content determined under nonequilibrium conditions can be used to compare different batches of the same material and to determine the diffusion constant of the material when determined under carefully controlled non-equilibrium conditions of exposure to moisture and when using plastic specimens of defined dimensions.
1.1 ISO 62 describes a procedure for determining the moisture absorption properties in the “through-the-thickness” direction of flat or curved-form solid plastics.ISO 62 also describes procedures for determining the amount of water absorbed by plastic specimens of defined dimensions, when immersed in water or when subjected to humid air under controlled conditions. The “through-the-thickness” moisture diffusion coefficient can be determined for single-phase material by assuming Fickian diffusion behaviour with constant moisture absorption properties through the thickness of the test specimen. This model is valid for homogeneous materials and for reinforced polymer-matrix composites tested below their glass transition temperature. However, some two-phase matrices such as hardened epoxies may require a multi-phase absorption model which is not covered by this International Standard.
1.2 Ideally, the best comparison of the water absorption properties and/or diffusion coefficients of materials should be carried out only using the equilibrium moisture content of plastics exposed to identical conditions. The comparison of materials using properties at moisture equilibrium does not assume, and is therefore not limited to, single-phase Fickian diffusion behaviour.
1.3 Alternatively, water absorption of plastic specimens of defined dimensions exposed to immersion or humidity under controlled conditions but for an arbitrary time period can be used to compare different batches of the same material or for quality control tests of a given material. For this type of comparison, it is essential
Test specimens are immersed in distilled water at 23 °C or in boiling distilled water, or exposed to 50 % relative humidity at given temperatures, for prescribed periods. The amount of water absorbed by each test specimen is determined by measuring its change in mass, i.e. the difference between its initial mass and that after exposure to water, the change being expressed as a percentage of the initial mass. If required, the amount of water lost after drying the test specimens can also be determined.
In some applications, 70 % to 90 % relative humidity and temperatures of 70 °C to 90 °C may be necessary. Relative humidities and temperatures higher than those recommended in ISO 62 may be used by agreement between the interested parties. When relative humidity and temperature conditions other than those recommended are used, a complete description of these conditions (with appropriate tolerances) shall be included in the test report.Unless otherwise specified or agreed by all interested parties, the dimensions and dimensional tolerances of the square-shaped specimens shall be the same as those given in ISO 294-3, with a thickness of (1,0 ± 0,1) mm. They can be prepared by moulding in accordance with ISO 294-3, using conditions given in standards applicable to the material being tested (or using conditions recommended by the material supplier). For some materials, such as polyamides, polycarbonates and some reinforced plastics, use of a 1 mm thick specimen may not give meaningful results. Furthermore, some product specifications require the use of thicker test specimens for the determination of water absorption. In these cases, test specimens of (2,05 ± 0,05) mm thickness may be used. If specimens of thickness other than 1 mm are used, the specimen thickness shall be indicated in the test report. There are no requirements for the radii of the edges and corners. However, they shall be smooth and clean to prevent material from the edges and corners from being lost during the test.
Some materials may exhibit mould shrinkage. If specimens of these materials are prepared using a mould with dimensions at the lower limits specified in ISO 294-3, the final dimensions of the specimens may be beyond the tolerances given in this International Standard, in which case they shall be noted in the test report.ISO-62-2008

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