Ageing: accelerated tests weathering

In laboratories, coatings are artificially weathered in specially designed apparatus to simulate or measure the aging processes that occur during natural weathering. Artificial weathering involves a smaller number of parameters than natural weathering but can be controlled more uniformly and allows accelerated test conditions [9.49]-[9.51]. 

S.A.S. Akers and J.B. Studinka, Ageing Behavior of Cellulose Fibre Cement Composites in Natural Weathering and Accelerated Tests , Int. J. Cement composites and Lightweight Concrete. 11,1989, 93-97. 

The chemical durability of a composite resin can be tested by accelerated aging in a weathering chamber (6). Disks (36 mm in diameter and 1.3 mm thick were exposed to conditions of accelerated aging for a total of 900 hours in a weathering chamber at 43 C and 90 percent relative humidity. One surface of a sample was subjected continuously to the radiation of a 2500 watt Xenon light source filtered by borosilicate glass and to an intermittent water spray for 18 minutes every two hours. Changes in the exposure surface were studied by surface profile measurements and by SEM. 

Brown R P, Butler T, Hawley S W. Ageing of Rubber, Accelerated Weathering and Ozone Test Results, Rapra Technology Ltd, Shawbury, 2001. 

The results from this survey indicate that a wide variety of reactions occur in the photodegradation of polycarbonate under natural weathering conditions. Both oxidative and non-oxidative processes are involved, but the oxidative reactions probably cause greater loss in physical properties. Accelerated aging studies should take into account the variables tested here. In particular, acceleration should not be accomplished by the use of very short wavelength light. 

The 39 materials were subjected to accelerated heat ageing for a series of times and temperatures, artificial weathering and exposure to ozone. This report details the results of the accelerated heat ageing tests and their analysis for the prediction of changes after long-term natural ageing. The accelerated weathering and ozone test results have been published separately [2]. 

R.P. Brown, T. Butler and S.W. Hawley, Ageing of Rubber—Accelerated Weathering and Ozone Test Results, Rapra Technology Limited, 2001. 

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