LX-5060 A Choice of Filters for Q-SUN Xenon Test Chambers

There are three general categories of filters which can be used in the Q-SUN ® xenon test chamber. The choice of filter depends upon the material tested and its end-use application. Within each general category, there may be several different types of filters. Each filter is a flat piece of specialty glass spe - cifically designed to have a particular transmission. 

Because the radiation from an unfiltered xenon arc contains too much short-wave UV to allow useful correlation to natural exposures on the earth’s surface, Q-SUN testers employ various types of optical filters to reduce unwanted radiation and achieve an appropriate spectrum. For most of the filter types used, the greatest effect is on the short wavelength portion of the spectrum. Because the damaging effects of UV are inversely proportional to wavelength (i.e., shorter wavelengths = more damaging), it is critical that the cut-on wavelength match the service environment. Nominal cut-on wavelengths are shown below for each filter type.

Daylight Filters 

Q-SUN daylight filters pro - duce spectra approximately equivalent to direct sunlight and conform to the spectral requirements of ISO 4892, ISO 11341, ASTM G155, SAE J1960, and SAE J2527. They are recommended for testing materials that are intended for outdoor use. 

Daylight - Q. With a nominal cut-on of 295 nm, Daylight - Q provides an accurate spectral match with direct sunlight. This filter is often recommended for the best correlation between Q-SUN xenon and natural outdoor exposures. 

Daylight - B/B . With a nomi - nal cut-on at 290 nm, Daylight - B/B is recommend - ed when correlation to certain rotating-drum style xenon testers is desired. 

Daylight - F. With a nominal cut-on of 295 nm, Daylight - F also provides an accurate spectral match with direct sunlight, particularly in the short-wave UV region. Devel - oped within the automotive industry, this specialty filter has become adopted in some automotive and test standards (e.g. ASTM D7869).

Extended UV Filters 

Q-SUN extended UV filters allow significant excess UV below the cut-on of natural sunlight at the earth’s surface. Extended UV filters are often used to produce faster degradation than daylight filters. They may also be used to reproduce extraterrestrial spectra for aerospace applications. 

Extended UV - Q/B. This filter has a nominal cut-on at 275 nm. For many materials it will produce faster degradation than daylight filters. This filter may be required for certain automotive test methods including SAE J1960, SAE J1885, SAE J2412 and SAE J2527. It is described in ASTM G155. 

Extended UV - Quartz. Certain special applications require a spectrum with aggressive, very short-wave UV to produce an extraterrestrial exposure condition. The quartz filter has a nominal cut-on at 250 nm. Becuase of its extreme short wave UV cuton, this filter does not meet the definitional requirements for an “extended UV filter” as defined in SAE or ASTM.

Window Glass Filters 

Intended for testing materials that are used indoors, window glass filters produce spectra equivalent to sunlight coming through the window. However, there is no single “standard window glass.” Because transmission varies due to thickness, chemical composition, etc., several window glass filters have been developed. 

The spectrum produced by the Q-SUN window glass filter also covers most of the wavelengths that would be found from the many artificial light sources used indoors (cool white fluorescent, etc.), so it is appropriate for most indoor applications. For more information on how the spectrum of window glass filtered xenon compares to indoor light sources, see Q-Lab Technical Bulletin LX-5026. 

Window - Q. This filter is equivalent to direct sunlight coming through a piece of single-strength, singlepane glass of the type most widely used in North America. This filter meets the requirements for window glass filters in ASTM and most ISO test methods. Window - Q has a nominal cut-on of 310 nm. 

Window - B/SL. This filter is slightly more transmissive and produces a spectrum with slightly more short-wave UV. Window - B/SL has a nominal cut-on of 300 nm. This filter meets the requirements for window glass filters in ASTM, ISO and AATCC test methods, including AATCC TM 16-3.

Window - IR. Infrared (IR) filters produce a similar short wavelength cut-on as other window glass filters, but also reduce the amount of long wavelength visible and IR energy that reaches the test specimen. This filter meets certain test specifications that call for “heat reducing filters" (ISO 105 B02). The IR filter has a nominal cut-on of 320 nm. 

Window - SF5. This filter is specified for certain automotive interior tests (such as Ford) that require a so-called "335 nm long pass filter." Despite this OEM-designated description, the nominal cuton for this filter is 325 nm. It is designed to simulate automotive interior conditions.