Climatic chambers for test standard BS EN 13523-10
This part of the EN 13523 series specifies the basic principles and procedure for determining the resistance of an organic coating on a metallic substrate (coil coating) to a combination of fluorescent UV radiation, and water condensation and temperature under controlled conditions. This standard needs a climatic chamber-- UV Aging Test Chamber.
Due to varied conditions which occur during natural weathering and the extreme nature of accelerated testing, correlation between the two cannot be expected. Not all organic coatings will perform on an equal basis but a degree of correlation between the same generic type might be observed.
For the purposes of this document, the terms and definitions given in UN 13523-0 apply. The coating is exposed in a cyclic manner to UV radiation, condensation of water and temperature under controlled conditions. One of two types of florescent UV lamps, UVA-340 or UVB-313, is used. After exposure to UV radiation under controlled conditions, chalking and changes in gloss and colour are assessed.
Ordinary laboratory apparatus and glassware, together with the following. The test chamber shall be constructed of corrosion resistant material. Enclosed within the test chamber shall be eight fluorescent lamps, a heater pan, racks for test specimens, and provisions for indicating and controlling operating times and temperatures.
The lamps shall be in banks of four on either side of the cabinet. Electrical operating conditions for the lamps shall be as given by the manufacturer. Either UVA-340 or UVB-313, as specified in EN ISO 16474-3:
--UVA-340 starting at a wavelength of approximately 300nm with a peak emission at 340nm;
--UVB-313 starting at a wavelength of approximately 280nm with a peak emission at 313nm.
Water supply: deionized water
Sampling shall be according to EN 13523-0.
Test panels shall be according to EN 13523-0. The test specimens shall be flat and about 150mm×75mm in size. Deviations from the standard methods of panel shape, size, previous working, or conditioning may be agreed between the interested parties.
Place the test specimens in racks which are made of inert material. Expose the face of the test specimens parallel to the lamps. If there are empty spaces within the racks fill these with blanks to maintain the conditions within the test chamber. Repositioning of the specimens during exposure is desirable and might be necessary to ensure uniformity of all exposure stresses.
Cycle the test specimens through periods of 4h of dry UV exposure at a black panel temperature of (60±3)℃, followed by a period of 4h of water condensation exposure, without radiation, at a black panel temperature of (40±3)℃. (One cycle consists of 8h exposure. )
Arrange the test specimens to allow the condensate to freely run off the surface under gravity. Conclude the exposure at an agreed time, for example 2000h for UVA-340 or 1000h for UVB-313, or an agreed number of cycles, for example 250 cycles for UVA-340 or 125 cycles for UVB-313.
Where possible, use an agreed irradiance level, typically 0.83W/㎡ for UVA-340 or 0.71W/㎡ for UVB-313. For safety reasons (UV radiation), it is recommended to remove or re-arrange the test panels when the UV lamps are switched off (e.g. during the humidity cycle).
Calibration of the UV-lamps depends on the type of weathering apparatus, whether the irradiance level can be set or not. For apparatus without the possibility to set the irradiance, after every usage of 400 radiation hours, replace one lamp and rotate the others within the bank with the oldest lamp being taken out of service unless otherwise specified by the equipment manufacturer.
For apparatus with irradiation measurement, the apparatus indicates when the radiation sensors need to be calibrated. Carry out the calibration of the radiation sensors according to the method provided by the equipment manufacturer using the calibration equipment. When the irradiance of a lamp falls below the set point, it shall be replaced. This is usually triggered by an alarm on the equipment.
At the conclusion of the exposure, evaluate the test specimens for chalking, changes of gloss and colour. Assess the coating for chalking, change of gloss and change of colour at ambient temperature. For more accurate measurements, as required for instance in case of dispute, the temperature shall be (23±2)℃ and the relative humidity (50±5)%, in accordance with EN 23270.
The results shall be expressed as comparison between an unexposed test specimen and an exposed test specimen for properties defined in EN 13523-2, EN 13523-3, EN13523-14 and EN 13523-22, if appropriate in terms of, for example, x% gloss retention according to EN 13523-2, y=ΔE*ab according to EN 13523-3, z chalking according to EN 13523-14.
No precision data are currently available.
The test report shall contain at least the following information:
1. All details necessary to identify the product tested;
2. A reference to this part of the EN 13523 series;
3. The type of UV lamps used;
4. The duration of exposure in hours;
5. The results of the test, as indicated in Clause 9;
6. Any deviation, by agreement or otherwise, from the test method specified;
7. The date of the test;
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