Long-term Colour Stability of Navigation Buoys

Transcription

1 1 / 12 Long-term Colour Stabilit of Navigation Buos Customer: Meritaito O FI-181 Helsinki Finland Target: 7 pcs of plastic material samples of navigation buos in four different colours. The sample pieces were taken from finished products. Table 1. List of samples under test. Diameter [mm] Colour Tpe 4 RAL 917 Black Multi-laer 4 RAL 328 Red Multi-laer 4 RAL 637 Green Multi-laer 4 RAL 123 Yellow Multi-laer 8 RAL 917 Black Through-coloured 8 RAL 328 Red Through-coloured 8 RAL 637 Green Through-coloured D4 D8 Fig. 1. Plastic material samples of navigation buos. Testing Time: The start of the test: 31 st March, 216 The end of the test: 7 th November, 216

2 2 / 12 Purpose of the Test: To test the long-term colour stabilit of the navigation buos when eposed to solar radiation. The solar radiation consists of UV, visible and thermal IR radiation. To verif how the colours match to the allowed chromaticit regions according to IALA Recommendation E-18 Surface colours used as visual signals on aids to navigation, Edition 3, 213. Test Method: The eposure in this test consists of two parts. Eposure 1 Solar radiation eposure (UV+vis+IR) Intensit: 112 W/m 2 T(Amb): ~4 Ccle: 22 h solar irradiation / 2 h water spra or high RH (salt mist spra weekl) Duration: 56 das Test conditions based on ISO and MIL-STD-81G METHOD 55.5 Eposure 2 High-intensit solar radiation eposure (UV+Vis+IR) Intensit: Continuous high-intensit radiation (35 W/m 2 with sample cooling) T(Amb): ~3 Duration: until reaching an UV-energ dose that corresponds to at least of 15 ears in natural conditions on vertical surfaces Measurements Chromaticit coordinate zone analsis Colour CIELAB1976 and DE (colour change) Feasibilit of the Test Method: Solar radiation, especiall the radiation in the UV range, is the main reason for colour changes of plastic materials. In addition to sunlight, the navigation buos are eposed to moisture and salt water in their actual use environment. The intensit of solar radiation is increased up to 35 W/m 2 and solar lamps with pronounced intensit in the UV spectral range are used in order to highl accelerate the effects of solar UV radiation. Cooling air is used to prevent ecessive heating of the samples and the resulting effects. Chromaticit coordinate zone analsis can be used to verif whether the colour of the products is within the limits set b the requirements. Measurement of CIELAB colour coordinates and the colour change takes into account the lightness of the colour in addition to the chromaticit, and thus corresponds to the actual visual appearance of the product surface. Performed Actions: Solar radiation The light from the solar simulator has effectivel similar spectrum as the natural sun. The properties of the simulated solar radiation used in this test, and those of natural sunlight, are described in Table 2. Table 2 shows the spectral distribution of the standard solar spectrum for natural sunlight (CIE AM 1.5) and the spectrum of the simulated radiation used in this test in the ranges of ultraviolet (UV), visible, and thermal radiation (IR). The main part of the test, Eposure 2, was run with a solar lamp that produces an ecess amount of UV radiation when compared to natural sunlight. In addition, the intensit of radiation during Eposure 2 was increased to 35 W/m 2. In this wa, the test could be highl accelerated.

3 3 / 12 Table 2. Spectral distribution of natural sunlight (as defined in CIE AM 1.5) and radiation from solar simulator used in this test (Eposure 1 and Eposure 2) in the ranges of ultraviolet (UV), visible (Vis), and thermal radiation (IR). Spectral region Eposure 1 Eposure 2 Sunlight [nm] [%] [%] [%] [%] [%] [%] UV Vis IR The total intensit of radiation was measured with a precision pranometer from the sample area. The measured intensit and duration of eposure for Eposure 1 and Eposure 2 are shown in Table 3. The energ doses in units of kwh/m 2 and kl are given in details in Table 4. Table 3. Total intensit of radiation and duration of the eposure. Intensit Eposure time [W/m²] [h] Eposure 1 19 ± Eposure 2 35 ± 1 17 Table 4. Solar radiation energ received b the samples during the test. Spectral Eposure 1 Eposure 2 Total region [kwh/m²] [kl] [kwh/m²] [kl] [kwh/m²] [kl] UV Vis IR Total

4 4 / 12 Test conditions Ambient air temperature during the solar radiation was in the range of 3 4. During the highintensit solar radiation, Eposure 2, cooling air was used to prevent overheating of the samples. Maimum surface temperature of the samples was 7 (black samples). The first part of the test, Eposure 1, i.e., 1232 h of solar radiation, was carried out in ccles. The 24-hour test ccle consisted of 22 h solar radiation and 2 h spraing. The spraing was done using purified water. Once a week the water spra was replaced with salt spra. Details can be found in Ref. 1. Figure 2 shows the samples under solar irradiation. Fig. 2. Test arrangement showing the samples under solar irradiation during Eposure 1. Note: A larger set of samples was involved in the first part of the test (Eposure 1). Measurements Colour measurement was performed a few times during the test. A chromaticit coordinate zone analsis was carried out in connection with the colour measurements. The samples were wiped with a soft cloth which had been soaked in tap water before each colour measurement.

5 5 / 12 Visual observations The samples were visuall investigated and photographed with non-irradiated reference samples. The photographs are shown in Fig. 3. The non-irradiated reference sample is on the right in each photograph. D4 D8 D4 D8 D4 D8 D4 Fig. 3. Samples photographed after the test. The sample eposed to solar radiation is on the left, and a non-irradiated reference sample is on the right.

6 6 / 12 Used Equipment: Solar simulator, No. 2 Solar test chamber, No. 42 / Ch3 Radiation intensit: Pranometer No. 25, calibrated 28 th April, 215. Calibration is valid. Multimeter No. 6, calibrated 12 th Ma, 216. Calibration is valid. Temperature: IR Camera No. 58, calibrated 29 th Januar, 216. Calibration is valid. No. 42 / Ch3_1, calibrated 27 th Januar, 216. Calibration is valid. Colour: Spectrophotometer No. 7, calibration is made before ever measurement session. Calibration is valid. Analsis: Optical Analsis The L*a*b* colour coordinate values of the samples were measured with a spectrophotometer. The reflected specular component from the samples is included in the L*a*b* values. Colour difference E represents the Euclidean distance between two colours according to Eq. 1. Δ E= Δ L 2 +Δ a 2 +Δ b 2 (1) L*-coordinate indicates the lightness of the sample. The bigger the value the lighter the sample. +a*-coordinate indicates the red direction and -a* indicates the green direction. +b*-coordinate indicates the ellow direction and -b* indicates the blue direction. The colour coordinates are shown schematicall in Fig. 4. Under ideal viewing conditions a E value of 1 represents a just perceptible colour difference to the human ee. However, the human ee sees differentl colour differences in different colours. The differences in darker colours are more perceptible to the ee. A colour can be characterized b two parameters: luminance and chromaticit. In the CIE sstem, a luminance parameter Y describes the brightness of the colour, and two colour coordinates and specif the point on the chromaticit diagram. The CIE 1931 chromaticit diagram is shown in Fig. 5. Fig. 4. CIE L*a*b* colour coordinate sstem.

7 7 / 12 Fig. 5. CIE 1931, chromaticit diagram. Colour change E Colour change E (SCI, specular component included) as function of UV energ is shown in Fig. 6. The shape of the curves indicates that the rate of the colour change has been either slowed down or full stopped at the end of the eposure. Each value is an average of five measurement points that cover the surface area uniforml RAL RAL RAL RAL RAL RAL RAL E 15 E UV energ [kwh/m²] UV energ [kwh/m²] Fig. 6. Colour change E as a function of UV energ.

8 8 / 12 Chromaticit zone analsis Chromaticit diagrams of the samples are shown in Figs The colour coordinates and were taken from a reflection spectrum measured from each sample with a spectrophotometer. The allowed chromaticit regions according to IALA Recommendation E-18 Surface colours used as visual signals on aids to navigation, Edition 3, 213, are shown in the diagrams. For the red colour, an etended chromaticit region for matt or semi-matt surface finishes was used Red RAL Red RAL UV energ [kwh/m²] Chromaticit region Fig. 7. Chromaticit diagrams for red samples. The chromaticit region is according to IALA Recommendation E-18; etended Red for matt or semi-matt finishes. Green RAL Green RAL UV energ [kwh/m²] Chromaticit region Fig. 8. Chromaticit diagrams for green samples. The chromaticit region is according to IALA Recommendation E-18.

9 9 / 12 Yellow RAL UV energ [kwh/m²] Chromaticit region Fig. 9. Chromaticit diagrams for the ellow sample. The chromaticit region is according to IALA Recommendation E-18. Black RAL Black RAL UV energ [kwh/m²] Chromaticit region Fig. 1. Chromaticit diagrams for black samples. The chromaticit region is according to IALA Recommendation E-18. Radiation Correspondence: The mean solar radiation energ per ear onto a horizontal surface as a function of latitude is shown schematicall in Fig. 11 and the corresponding solar energies are given in units of kwh/m 2 and kl in Table 5. The mean solar energ is an average of eisting solar radiation data, e.g. Meteonorm Global Meteorological Database. It is presented as a function of latitude. Meteonorm Global Meteorological Database utilizes long-term measurement data of global solar radiation and scientific models. An approimation of the correspondence of the solar energ load of this test to the natural solar energies in ears is given in section Conclusions in Table 5. This estimate of the correspondence of the solar energ load of this test to the natural solar energies is based on the total UV energ dose and does not take into account the differences in the spectra of the simulated and natural radiation.

10 1 / 12 Since the surface of the buos is in vertical position, the energ correspondence to vertical surface is also presented in Table 5. The maimum solar energ load to the vertical surface is received when the buo is orientated to the equator, i.e., when it faces north in the Southern Hemisphere and south in the Northern Hemisphere. However, the buos are not fied and ma change their orientation because of waves, ocean currents and tides and thus face to an direction. Therefore, a range between the worst case and random orientation is estimated and given in Table 5. Aortic Ocean Atlantic Ocean Pacific Ocean Pacific Ocean Indian Ocean Fig. 11. Mean solar radiation energ per ear onto a horizontal surface as a function of latitude. The colour scale is eplained in Table 5.

11 11 / 12 Table 5. Mean solar energ per ear as a function of latitude and an approimation of the correspondence of the solar UV energ load of this test (1586 kwh/m 2 / 136 kl) to the natural solar energies in ears. The colour scale used in Fig. 11 is shown in the left column. Solar energ per ear Correspondence in ears Horizontal Horizontal Vertical Latitude [kwh/m²] [kl] Years Years 9 N 8 N N N N N N N N S 2 S 3 S 4 S 5 S 6 S 7 S 8 S 9 S Recommendations: N/A Conclusions: The test specimens, plastic material samples of navigation buos, in colours black, red, green and ellow, were eposed to solar radiation until an UV-energ dose, which corresponds to at least 23 ears in natural conditions on vertical surfaces, was reached. The black, red, green and ellow colours of the navigation buos remained in chromaticit regions according to IALA Recommendation E-18 Surface colours used as visual signals on aids to navigation, Edition 3, 213. Green RAL 637 (sample D8) was just at the border of the green chromaticit region after the eposure. The visual appearance of the colours was however changed due to changes in gloss and/or lightness of the colour that are not taken into account in the IALA Recommendation for chromaticit regions.

12 12 / 12 Remarks: This Eecutive Summar Report is derived from a comprehensive test report MeritaitoVirtanen tr91116rp.pdf [2]. The presentation Colour Stabilit of Navigation Buos, Seahow - Youtube [3] has been created on the basis of this test report. Actions, operations and reporting are in accordance with IEC/ISO 1725 'General requirements for the competence of testing laboratories'. References [1] Test Report: MeritaitoVirtanen e29616hs.pdf [2] Test Report: MeritaitoVirtanen tr91116rp.pdf [3] Colour Stabilit of Navigation Buos, Seahow Youtube Signatures: Riitta Perälä Littoinen, 8 th December, 216 Solar Simulator Finland