TY - CONF A1 - Trubiroha, P. A1 - Geburtig, Anja A1 - Wachtendorf, Volker T1 - Natural versus artificial weathering of polymers – main differences in climatic conditions T2 - Proceedings 8th European Weathering Symposium - Natural and Artificial Ageing of Polymers N2 - Different climatic conditions and weather variables during natural and artificial exposure of polymers may be reasons for an unsatisfying correlation between the ageing results. Here the main differences are discussed for: - Global solar radiation In weathering devices there is a constant spectral irradiance which is 5 times higher than the averaged spectral irradiance outdoors, which is strongly varying in its diurnal course. Intensified weathering using Fresnel reflectors concentrates only the direct solar radiation with a relatively low UV proportion. Problems of reciprocity may arise from the different mean of irradiance levels. - Temperatures at specimen surfaces. Because of the high irradiance levels mentioned above, artificial exposures may lead to high surface temperatures and large temperature differences between differently coloured specimen surfaces, if the artificial radiation source emits much VIS- and IR-radiation. Outdoors the surface temperature and temperature differences of exposed specimens are influenced by considerably lower irradiance levels and additionally by an effective radiation loss in the night. - Relative humidity at specimen surfaces In weathering devices the relative humidity at specimen surfaces is very low if it is uncontrolled. If controlled by ultrasonic humidifiers or spray nozzles, the additional exposure to water droplets is quite likely. - Wetness on specimen surfaces All usual spray programs prescribed in weathering standards recommend frequently changing of short spray/dry periods and result in total times of wetness (TOW) of the exposed specimen surfaces which is only about 30 % of the outdoor TOW. - Acidic precipitation and bio films Acidic precipitation and bio films are usual outdoor conditions which are only considered in special weathering tests. T2 - 8th European Weathering Symposium CY - Vienna, Austria DA - 20.09.2017 KW - Artificial weathering KW - Natural weathering KW - Weathering parameters PY - 2017 SN - 978-3-9818507-1-0 VL - 18 SP - 63 EP - 75 CY - Karlsruhe AN - OPUS4-42127 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -