Weathering color changes

Published by the Plastics Design Library, PDLCOM is an exhaustive reference source of how exposure environments influence the physical characteristics of plastics. Data include resistance to thousands of chemicals, weathering and UV exposure (i.e. color change after accelerated weathering or outdoor exposure) sterilization (radiation, ethylene oxide, steam, etc.) thermal air and water aging environmental stress cracking and much more. 

P.Y.129 is not employed in plastics. The type of metal in the stabilizer defines how much of a color change is observed as the chelated metal in the pigment molecule is exchanged. Tin stabilizers produce red complexes, which, like corresponding lead or zinc chelates, respond very poorly to light and weather (see also Sec. 1.6.7). 

Figure 18.4 Effect on color of Weather-Ometer testing with ( wet ) and without ( dry ) water spray for Spectar copolymer sheeting [7a]. From Fagerburg, D. R. and Donelson, M. E., Effect of water spray and irradiance level on changes in copolyester sheeting with xenon arc exposure, ANTEC 98 Conference Proceedings, Paper 808, Atlanta, GA, April 30,1998, and reproduced with permission of the Society of Plastics Engineers...

Survey coatings for signs of weathering (color change, powdering, thinning of coat). 

A "humidity sensor" consists of a cardboard square that is colored blue in dry weather and red in humid weather. The color change is due to the reaction ... 

Weathering, Contaminants, and Color Change to Hair Fibers.128... 

Figure 5. ArtisFs rendition of color changes and surface ux)od change during the outdoor weathering process of a typical softwood.

This erosion or weathering is not to be confused with decay. Decay is caused by fungi and can lead to rapid deterioration throughout the volume of the wood. Weathering, on the other hand, is a surface deterioration and, although the initial color changes can be seen within days or even hours, the surface erosion proceeds very slowly. The erosion rate for solid wood in temperate zones is in the order of 1/8 to 1/2 inch per century and depends mainly on amount of UV exposure and the wood species (1, 2). Other degrading factors include moisture, mechanical abrasion, temperature, and pollution (3). 

TABLE 17.11 Influence the Combination of a Phenolic Antioxidant, a Phosphite, a UVA and a HALS on the UV Stability (Time Until a Color Change AE 10 in a Weather-Ometer (Black Standard Temperature 80° C, Intensity 0.55 W/m2 (at 340 nm), and 18 min Rain/2 h) of Gray-Pigmented PA6)... 

A color change in a material that involves a weakening or lightening with time, usually as a result of exposure to light, weather, among others. 

Chemical Composition. The extenders should be chemically inert in the paint. Secondary constituents (e.g., iron ions) may produce color changes. Sulfates, sulfides, alkali, alkaline-earth, and heavy-metal ions may cause problems due to their chemical reactivity and toxicity, and also affect abrasion and weather resistance. 

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