Technical Data for ReflecTech® Mirror Film (Typical Values, 11 December 2009) 
| Performance characteristics | |||
|---|---|---|---|
| Specular Reflectance 1 | 94% |
At 25 mrad, 660 nm |
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| Solar-Weighted Hemispherical Reflectance 2 | 94% |
DIN 5036-1, 3 ASTM G 173 – 03 |
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| Product/physical characteristics | Machine |
Transverse |
|
Direction |
Direction |
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| Tensile Strength (MPa) | 61 |
64 |
ASTM D882 |
| Elongation at Break (%) | 88 |
72 |
ASTM D882 |
| Yield Strength at 2% offset (MPa) | 40 |
36 |
ASTM D882 |
| Yield Elongation at 2% offset (%) | 4.7 |
4.6 |
ASTM D882 |
| Modulus (MPa) | 1430 |
1566 |
ASTM D882 |
| Nominal Thickness | 0.004 in (4 mils, 0.1 mm) |
||
| Coefficient of Thermal Expansion (cm/cm/ºC) | 5.5 x 10-5 |
ASTM E831 |
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| Application characteristics | |||
| Adhesion to aluminum 3 | Initial 11.4 Fully Cured 19.9 |
ASTM D903 |
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| 180° Peel Strength (N / 25mm) | |||
| Storage and Operation | |||
| Shelf Life 4 | 1 year |
||
| Maximum Operating Temperature | 60ºC (140ºF) |
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Notes: |
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1. At 1.4° acceptance angle measured on Devices & Services 15R Specular Reflectometer |
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2. Integrated over direct normal air mass 1.5 solar spectrum |
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| 3. Adhesion depends on the nature of the surface. The indicated values are for reference only. | |
4. Store in clean and dry environment that is not in direct sunlight in a location with an ambient temperature of 100ºF (38ºC) or less |
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Research & Development on ReflecTech® Mirror Film at the National Renewable Energy Laboratory (NREL)
To test for weatherability, reflector samples are subjected to controlled conditions more extreme than experienced in actual outdoor environments. NREL maintains a world-class testing capability for solar reflectors, and they have developed a device called a Solar Simulator (SS) that maintains high light intensities (5X the sun’s intensity between 300 and 500 nm), controlled temperatures and relative humidities (up to 70°C and 70%RH) in order to achieve highly accelerated testing of reflector samples.
Solar Simulator results are shown in the figure below for the “New Reflector” (i.e. the ReflecTech® Mirror Film) and are compared against two other reflective film constructions (ECP-305+ and ECP-300 made by 3M) that serve as useful comparisons. 3M’s ECP-300 was a silvered acrylic film that had excellent optical properties, but limited outdoor weatherability. UV-induced corrosion of the metalized silver layer in ECP-300 generally limited the film to a 3 to 5 year outdoor lifetime.
3M’s ECP-305+ was a much more corrosion-resistant silvered acrylic film that was expected to have at least a 10+ year outdoor lifetime. Unfortunately, both of the 3M reflective films suffered from “tunneling”, a problem that resulted in 3M’s discontinuance of the product line. Nevertheless, the film was deployed in many field installations and was also well characterized in the laboratory through accelerated tests. Thus, these two 3M films provide convenient references for gauging the weatherability of ReflecTech® Mirror Film.
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Download ReflecTech Film: Hemispherical Reflectance vs. Wavelength (.xml document). |
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Download ReflecTech® Mirror Film Attributes and Durability for CSP Applications (.pdf document). |
ReflecTech® Mirror Film has high reflectance in the wavelength range important for sunlight. In this graph, hemispherical reflectance of the film is plotted on the left axis while the irradiance of sunlight is plotted on the right axis, both as functions of wavelength. The solar-weighted average of hemispherical reflectance is 94%.
In the ACUVEX® testing program, which is done at AZTEST in Arizona, samples are subjected to natural sunlight concentrated 7-8 times and sprayed with de-ionized water for 8 minutes per sun-hour. ReflecTech® Mirror Film demonstrates exceptional optical durability (a near 10-year equivalent outdoor exposure test with virtually no loss in reflectance) compared to SS95 — a mirror film made for lighting applications and also used for outdoor solar concentrators.
