Weatherometer ageing

G.A. Van der Doelen, K.J. Van den Berg, and JJ. Boon, A Comparison of Weatherometer Aged Dammar Varnishes and Aged Varnishes from Paintings, in Proceedings of the Conference Art et Chimie La couleur, J. Goupy and J.P. Mohen (Eds), Paris, France, 1998, CNRS Editions, Paris, 2000, pp. 146 149. 

Figure 3. Weatherometer aging of transparent saturated acrylic...

Outdoor aging is currently being conducted on these polymers, and while accelerated aging may have limited value in predicting long term outdoor exposure, the accelerated aging studies of Jordan et al. (9) with poly (methyl methacrylate) copolymers and homopolymers indicated that a 2000-hour carbon-arc weatherometer period was a realistic exposure to screen the relative changes to be expected in about a two-year period in an outdoor environment—e.g., Florida or Arizona. 

Outside exposure to the elements can certainly take its toll on plastic materials, particularly those not properly protected by stabilizers. Unstabilized tensile bars of 40% glass-filled PPS were aged in an Atlas Weatherometer for 10,000 hours. Moderate stability was observed as shown in Table IX. The loss in tensile strength was reduced from 37% to 9% by adding 1 % Tinuvin 327 stabilizer. 

For sunlight stability, products can be evaluated after exposure in their packages to direct sunlight for various periods of time. Accelerated aging can also be evaluated in instruments such as the Atlas Weatherometer in which products can be subjected to intense radiation at elevated temperatures. 

Data on accelerated ageing (XI A weatherometer) have been reported by Lanza [431] it has been shown that irradiated polyethylene weathered somewhat better than unirradiated. 

Table 1 UV stability of Natural Rubber Adhesive After Accelerated Aging in a Carbon-Arc Weatherometer (1.0 Mil Thick)... 

Table 3 UV Stability of SEBS Sealant Film After Accelerated Aging in a Xenon-Arc Weatherometer (2.0 Mils Thick) ...

The Weatherometer is often used in comparing the weather resistance of paint coatings and the surface appearance of plastics parts. Although it is difficult to make a correlation to actual, real-time aging, the Weatherometer provides a useful instrument to measure the relative weather resistance of different materials. 

Figure 26.16 shows how well natural aging under mechanical and electrical stress is following the prediction from the WeatherOmeter. The data in Figure 26.16 is obtained from test terminations of 11 and 33 kV cables exposed to heavy industrial and marine pollution in various parts of the UK. 

The effects of curing time and some other formulation variables are summarized in Table 2, along with initial flexural strength, and tensile strength and modulus before and after 1,000 hours weatherometer accelerated aging. It is readily apparent... 

Figure 4 shows data for samples of PE mulch film exposed to artificial UV ageing in a Xenon weatherometer. The lifetime to embrittlement of transparent films can be reduced significantly by using the appropriate additive. Addition of carbon black to unmodified film produces a major stabilizing effect, which can easily be overcome by the additive. 

To accelerate degradation processes artificial aging with an Xe lamp is used [3]-The artificial simulated weathering was carried out in an Atlas Weatherometer Ci 5000 chamber equipped with a 6500W borosilicate glass-filtered xenon arc... 

Several commercial weatherometers provide similar temperatures and provided the UV shorter wavelength cut-off is not less than that experienced in sunshine ( 290 nm) [62], these are realistic practical conditions for plastics that end up on the soil particularly in the sunbelt countries, where they are wisely used. International standards describe the use of typical commercial laboratory techniques. Since ageing and weathering procedures have been standardised for the benefit of manufacturers and users of plastics, it is not considered that the details of the weathering procedure should be part of the standard itself, provided that full reference is made to the standard method chosen. ASTM D 5510-94 [60] describes a convenient heat-ageing oven for degradable plastics. 

Procedures that may be used to mimie heat ageing during eomposting and outdoor weathering inelude eonventional forced-air ovens and xenon arc weatherometers. Polyolefins treated in this way have been found to generate CO2 to over 60% of theoretical carbon dioxide formation in 18 months to two years in the presence of mature compost." Similarly, inoeulation with soil gives a similar result after two years (see section 12.6.3). 

After 1000 h aging in a xenon arc weatherometer % Elongation at break D2370 >100%... 

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