ISO 62:2008 pdf download – Plastics — Determination of water absorption
1 Scope 1.1 This International Standard describes a procedure for determining the moisture absorption properties in the “through-the-thickness” direction of flat or curved-form solid plastics. This International Standard 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 that all test specimens be of identical dimensions and, as nearly as possible, have the same physical attributes, e.g. surface smoothness, internal stresses, etc. However, moisture equilibrium is not reached under these conditions. Therefore, results from this type of test cannot be used to compare the water absorption properties of different types of plastics. For more reliable results,
5.2 Square-shaped test specimens for homogeneous plastics 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.