Weathering carbon arc

Artificial weathering of plasticized PVC 1 mm (40 mil) thick. Plasticizer 50 phr OOP. Stabilizer systems Curve 1, no stabilizer Curve 2, ESO 3 phr, Ba/Cd/Zn/organic phosphite 2.25 phr Curve 3, same as for Curve 2 plus 1 phr of 2-hydroxy-4-raethoxybenzophenone UV absorber. Weathering Carbon Arc Weather-Ometer, black panel temperature 145 °F (63 °C), water spray 18 min every 2 h (52). 

Specification for electroplated coatings of 65/35 tin/nickel alloy Method for the evaluation of results of accelerated corrosion tests on metallic coatings Methods of test for paints Cross-cut test Pull-off test for adhesion Resistance to artificial weathering (enclosed carbon arc) and Addendum No. 1 Resistance to continuous salt spray Notes for guidance on the conduct of natural weathering test... 

Three types of light sources for artificial weathering are in common use (1) enclosed UV carbon arc [7.5 UV energy output, approx. (x sunlight)], (2) open-flame sunshine carbon, and (3) water-cooled xenon arc. Selection of the light source involves many conditions and circumstances, such as the type of material being tested, product service conditions, previous testing experience, or the type of information desired. 

The general requirements for accelerated weathering apparatus are given in ISO 4892-1 [29], whilst ISO 4892 Parts 2-4 [26-28] deal more specifically with xenon arcs, fluorescent tubes and carbon arcs respectively. ISO 4892 refers to ISO 9370 [30] (Instrumental determination of radiant exposure in weathering tests), and CIE publication 85 (Solar spectral irradiance) [31]. 

Presently, there is a great number of apparatus and methods for accelerating weathering in the laboratory (DEF - 1053 No 26, ASTM G23 Carbon-arc type, ASTM G26 xenon-arc type, ASTM G53 fluorescent UV-Condensation typ etc.). However, even though these devices exist, it is difficult to obtain reproducible results. Hence, the rather pessimistic statement of Papenroth ( ) "A general accelerated weathering method which is valid in all cases does not exist today and there will never be one". 

Atlas Weather-Ometer described In reference 2. Samples were exposed 50 cm from a bare carbon arc (no filters) and with a 90 sector immediately preceedlng the water spray blocked off by a metal baffle to simulate night conditions. 

Ca-stearate (HALS-III, without AO-II). Test specimens compression-molded plates (2.0 mm thick). Weathering test sunshine carbon arc lamp weather meter (WEL-SUN-HC, Suga Test Instruments Co., Ltd.). Black panel temperature 63 3 C, without water spray. Failure criterion time to 507, loss of original elongation (half life time = H.L.T.). IF = H.L.T. with stabilizer/H.L.T. without stabilizer. (b) Test specimens compression-molded sheets (0.5 mm thick). Aging test forced air circulation oven at 150 C. 

The principal sources of ultraviolet radiation are carbon arcs, xenon arcs, mercury arcs and derived fluorescent lamps. Comparison of the emission spectra of these light sources with sunlight is shown in Fig. 10 [15]. Energy characteristics of various light sources and their relation to the weatherability of plastics have been discussed by Hirt and Searle [16]. 

The most decisive technical problem with respect to weathering devices is to achieve an adequate simulation of solar radiation. When artificial weathering first began in the 1920s, the only source of intense radiation available was the carbon arc. The spectral energy distribution of this radiation bears but a faint similarity to that of solar radiation. 

Test method for accelerated weathering test conditions and procedures for bituminous materials (carbon-arc method). 

Test method for rubber deterioration in carbon-arc weathering apparatus. 

Early accelerated weathering apparatus utilized carbon arc lamps with various filters to generate a spectrum that reproduced some of the harmful effects of sunlight. Improved versions of these are still in use and are specified for certain applications. However, many users and specifiers have turned to xenon arc lamp-based machines as these produce a spectrum that more closely matches that of sunlight (Fig. 6.1). Additionally, they are generally less expensive to purchase and to run than the carbon arc machines. Both types nowadays have facilities for the provision of controlled humidity, water spray, periodic water immersion and/or variable temperature cycles. 

The light sources commonly used for laboratory-accelerated weathering tests include filtered xenon arcs, two types of filtered carbon arcs, fluorescent UV lamps, and metal halide lamps. The spectral power distributions are shown in Figures 8.3 through 8.6 in comparison with solar radiation. The spectral emission characteristics of the sources differ significantly in both the UV and visible regions. 

Accelerated weathering test conditions (DIN 53387, ASTM G26-70, ISO 4892) defining cycles of exposure to light, humidity and water spraying, have been developed. Xenon light but also carbon arc is still used as light source in weatherometers. 

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

Those grades meet the color UV weathering requirements of car body paints in a broad variety of colors Accelerated weathering by carbon arc leads to no obvious visual color change between original, 500 or 1600 hrs exposed samples equivalent to 12 months Florida outdoor ageing. 

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