BS ISO 29664:2010 pdf free download – Plastics一Artificial weathering including acidic deposition.
6.1.3 Test duration
The lifetime of products that are susceptible to degradation by acid deposition in polluted climates shows enormous variation because the acidic precipitation occurs sporadically and shows large variations in pH. Therefore, results from tests conducted according to this International Standard cannot be used to predict service life. The results from tests conducted according to this International Standard should be useful for comparing different products for relative suitability for use in highly polluted environments where acid deposition occurs.
NOTE 1 A duration of 28 d for method A, type J, pH 2,5 corresponded to a 98 d outdoor exposure in Jacksonville (Florida) concerning the damage ranking for a specific set of 20 coatings[9] (see Annex A).
Unless otherwise specified, expose specimens according to method A for four weeks. Longer exposures may be necessary, if the differences of the measured property within the set of samples are smaller than the uncertainty of its measurement.
NOTE 2 If the exposure duration is too long, differences between materials can be less than if the materials were evaluated at a shorter time. If there are only small differences between materials and all show significant damage after the recommended 4 weeks’ exposure, a repeat of the test for a shorter duration can show larger differences between materials.
Interruptions to the test procedure are permissible; the storage of the specimens until resumption of the test shall take place under standard atmospheres 23/50 or 27/65, in accordance with ISO 291. If a break (longer than 20 mm) occurs during the first drying phase, the acid left on the specimens shall be removed by thorough rinsing with demineralized water. In such cases, the test shall be resumed by re-spraying the specimens with the acidic solution. Each interruption shall be described in detail in the test report.
At the end of the test, no acid shall remain at the surface. In addition, because water absorption can influence the results of property measurements taken after the exposure is completed, it is important the exposure be stopped during step 4.
NOTE 3 If stabilizers are damaged by exposure to weathering with acid deposition, plastics can be more susceptible to
photodegradation in subsequent weathering exposures.
6.2 Method B
6.2.1 General
Method B is intended for products made with polymers that are able to absorb or retain large amounts of moisture (e.g. textiles or geotextiles made with polymer fibres). When these products are subjected to acid rain, the acid can concentrate when the product dries, causing potential for acid-induced damage.
6.2.2 Weathering cycle
In method B, the acid deposition takes place in a 4 h-long period of spray with a pH 3,5 acid solution instead of a single daily application of a stronger acid solution, which is used in method A. Recycling of the acid rain is recommended. Method B shall also be carried out with continuous UV radiation. The procedure for method B is shown in Table 4.