Accelerated weathering devices

These are useful in so far as they reproduce to a fair approximation the spectral energy distribution of sunlight and provide a control of temperature and humidity. From among the several instruments that are commercially available, some of the most extensively used are briefly described here. 

The Xenotest is manufactured in two versions by Quartzlampen Gesellschaft (Hanau, Germany). The model 150 incorporates a 1500 W air-cooled xenon light source, while the model 450 uses a 4500 W air-cooled unit. Because of the ozone produced by the air cooled lamps, Xenotests should be vented directly to the outside. In the Xenotest 450, temperature is controlled by a system similar to that of the Atlas machines. Fresh air is blown through the model 150 but the temperature is not regulated. Humidity control is obtained automatically by the use of spray nozzles which atomize water into an air stream. Rainfall can be simulated by a water spray directed at the samples. 

The Degradation Accelerometer manufactured by American Ultraviolet Company (Chatham, New Jersey, USA) is a low-cost accelerated weather- 

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R M Fischer, W D Ketola and W P Murray, Inherent variability in accelerated weathering devices . Prog Org Coatings 1991 19 165-179. 

Accelerated weathering device Xenon Arc WOM (ASTM D2656-92A, G26-92) Carbon Arc WOM (ASTM D1499-92A)... 

Laboratory accelerated weathering devices have been used for more than 80 years with increasing importance concomitant with the development of more weather-able materials and the need to determine in a short time the effects of natural exposures over prolonged periods. The importance of these devices lies in their ability to accelerate the weathering processes imder controlled and reproducible conditions. They are particularly useful in research and development of new polymeric formulations. They are also used for quality control and specification testing. However, their application to prediction of service life under use conditions is still under development (see section on Laboratory Accelerated Versus Natural Weathering). 

The efficiency of photoantioxidants is tested by first subjecting the stabilized polymer to accelerated weathering and/or outdoor exposure conditions. Accelerated weathering devices have different types of light... 

Cocuzzi DA, Pilcher GR (2013) Ten-year exterior durability test results compared to various accelerated weathering devices joint study between ASTM international and national coil coaters association. Prog Org Coat 76(6) 979-984... 

The general questions addressed in the previous section ask if strict reciprocity (as defined in this paper s introduction) can be assumed for very highly accelerated weathering devices. This paper s focus returns to less accelerated rates and specifically asks if increasing UV intensity reasonably predicts degradation observed at lower UV intensity for materials when exposure temperatures are comparable. 

Sites in southern Florida (with high solar radiation coupled with high humidity, i.e. a tropical climate) and the Sonora Desert in Arizona (with high solar radiation coupled with low humidity, i.e. a desert climate) were used as sites for outdoor weathering tests. The present direct natural exposure in Miami (Florida) is regarded as real time exposure, against which the results obtained with various accelerated weathering devices may be compared. 

In summary, the utilization of accelerated weathering devices can be useful for testing painted plastic parts when data exists relating accelerated exposure data to real long-term field data. Caution should always be exercised and accelerated data should be used in conjunction with other real-time test data. 

Weatherabilities of flexible PVC sheets were compared by exposing samples in an accelerated weathering device equipped with a xenon arc lamp with quartz (inner) and borosilicate glass (outer) filters. Operating temperature (black panel temperature) was 66°C. Operating cycle was 102 minutes light exposure only, 18 minutes light and water every 2 hours. 

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