CAN OUTDOOR DEGRADATION BE PREDICTED BY LABORATORY ACCELERATION WEATHERING

This paper describes various laboratory-accelerated weathering methods for evaluating the susceptibility of geotextiles to degradation by ultra-violet radiation. A potential correlated method is also presented, for extrapolating laboratory results to outdoor conditions. A geotextile polymer's sunlight degradation is governed mainly by the photo-degradation mechanism. Tests are described here with each of the three available types of accelerated weathering test devices: (1) carbon arc types (ASTM G 23 and ASTM G 23 open flame); (2) xenon arc (ASTM G 26); (3) ultra-violet (UV) fluorescent lamp method (ASTM G 53, D 5208). All these test devices can maintain a constant test temperature, to control the rate of the reactions. Moisture is also introduced to the test specimens in either spray or condensation form. It is very difficult to transfer artificial weathering results to life expectancy under natural conditions. Any correlation method would probably have to be qualitative, and an appropriate mathematical approach is applied, that uses the energy equivalency method. An illustrative worked example is given for each of the three test methods. Although precautions are needed, the laboratory weatherometers can still be good ranging devices for index-type tests. With enough outdoor information, the tests' errors can be quantified, to achieve better correlations.