materials feature | Weatherability Atlas’s
LT-Emma uses ‘cool mirrors’
to concentrate UV energy without creating
temperature spikes
Heat control Some experts believe that ASTM D7869 could influence the development of similar standards around the world, notably from ISO. Allen Zielnik, senior consultant for weathering science at Atlas Material Testing Technol- ogy, believes that until ISO develops a comparable standard, global companies and test services will use the ASTM standard as a guideline for internal use. Among recent developments from Atlas are devices
that control the heat of colour samples in outdoor tests. “Outdoor tests never lie,” Zielnik says, “and they are never completely reproducible in labs.” Which is one reason why it is so important that outdoor procedures and equipment also accurately duplicate the effects on samples of the south Florida climate (and other areas including the dry, hot climate of Arizona, where Atlas also conducts outdoor tests).
One way of doing this is by managing the amount of sunlight a sample gets through the use of testing devices with special “cool mirrors” that increase solar radiation without raising temperatures to abnormal levels. The ability to increase radiation while controlling temperature, in turn, improves accelerated testing of outdoor samples, Zielnik says. Atlas has added two types of accelerated test devices
PolyOne’s Geon Bold range pro- vides durable darker colours for outdoor building materials like decking and railings
to its outdoor line-up. One type is the Ultra-Accelerated (UA) Emma (Equatorial Mount with Mirrors for Accel- eration) and its companion UA-Emmaqua (Equatorial Mount with Mirrors for Acceleration with Water). Both devices automatically track the sun, exposing samples to ultrahigh UV irradiance as well as the natural solar UV spectrum, while keeping samples at acceptable exposure temperatures. The Fresnel devices are equipped with 20 focusing
cool mirrors arranged as parabolic facets. These concentrate variable amounts of UV energy on a 15 X 91 cm2
(6 X 36 inch2 ua devices can generate 10 to 12 years of south Florida ) area. The UA-Emma and UA-Emmaq-
UV radiation exposure on samples in one year. The other type of accelerated test device, announced
in March, is the Low-Temperature (LT) Emma and the companion LT-Emmaqua, which both also use cool mirror technology. These devices have high reflectance in UV and near-visible-wavelength ranges and attenu- ate reflectance in longer visible wavelength and infrared portions of solar irradiance. The LT-Emma and LT-Emmaqua devices reportedly generate in one year the equivalent of five years of radiation exposure to samples.
The mirrors on both types of test devices selectively
reflect solar radiation onto samples, Zielnik says, which is how they manage heat. This “one sun exposure,” as he calls it, means that light and dark samples remain at essentially the same temperature during exposure, whereas with previous test devices light-coloured samples would be 5°C hotter and dark-coloured samples 10 to 15°C hotter than under non-test conditions. Efforts to improve accelerated test capabilities are a
product focus of many equipment manufacturers. Eye Applied Optix, for one, has a new weathering and degradation chamber that uses a metal halide lamp- based UV radiation technology. The company reports that the unit, the Eye SUV-W161 Super Acceleration UV Durability Test Chamber, achieves acceleration factors of up to 30 times that of sunlight and 10 times the energy of conventional accelerated UV durability test systems. The model reportedly has a range of test features, duplicates environmental conditions such as temperature, humidity and rain, and provides easy set-up and data retrieval. The company, which showed the system at the recent NPE in Orlando, Florida, states that the Eye SUV-W161 test chamber is an asset for proprietary product and colour development work, and significantly reduces the cost and time of research and development.
52 COMPOUNDING WORLD | June 2015
www.compoundingworld.com
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