Ultraviolet weathering

Polymer Engineering and Science 42, No.8, Aug.2002, p.1657-66 ACCELERATED ULTRAVIOLET WEATHERING OF PVC/WOOD-FLOUR COMPOSITES... 

L.M. Matuana, S. Jin, and N.M. Stark, Ultraviolet weathering of HDPE/wood-flour composites coextruded with a clear HDPE cap layer. Polym. Degrad. Stabil. 96, 97-106 (2011). 

N.M. Stark and L.M. Matuana, Ultraviolet weathering of photostabilized wood-flour-filled high-density polyethylene composites. /. Appl. Polym. Sci. 90,2609-2617 (2003). 

K.B. Adhikary, S. Pang, and M.P. Staiger, Accelerated ultraviolet weathering of recycled polypropylene—Sawdust composites. J. Thermoplast. Compos. Mater. 22,661-679 (2012). 

Matuana, L.M., Kamdem, D.P. Accelerated ultraviolet weathering of PVC/wood flour composites. Polym. Eng. Sci. 42, 1657-1666 (2002)... 

Stark, N.M., Mamana, L.M. Ultraviolet weathering of photostabilized wood-flour-filled high-density polyethylene composites. J. Appl. Polym. Sci. 90(10), 2609-2617 (2003) Bouza, R., Abad, M.J., Barral, L., et al. Efficacy of hindered amines in woodflour-polypropylene composites compatibilized with vinyltrimethoxysilane after accelerated weathering and moisture absorption. J. Appl. Polym. Sci. 120(4), 2017—2026 (2011)... 

Wea.ther lbillty. One of the more destmctive elements is exposure to sunlight specifically, ultraviolet (uv) light. AH sealants are affected by weathering, but there is much difference in the effect of weathering on different sealants. Most sHicones are stable with respect to uv exposure. Urethanes and polysulfides show effects of uv exposure, but can be formulated with uv absorbers to provide reasonable lifetimes in most appHcations. However, there are exceptions in aH classes of sealants and specifiers must be carehil to look for test data that has proven a specific sealant s durabHity. The source of the test data is also important data from an independent testing laboratory is generaHy apt to be more reHable. 

Small amounts of stabiliser (1-5%) are normally added to improve weather resistance. These materials are the usual ultraviolet light absorbers such as phenyl salicylate and various benzoates. Triphenyl phosphate also has a beneficial influence. 

From a practical review, perhaps it can be stated that buildings and construction materials are exposed to the most severe environments on earth, particularity when the long time factor is included. The environments include such conditions as temperature, ultraviolet, wind, snow, corrosion, hail, wear and tear, etc. Basically the following inherent potentials continue to be realized in different plastics ease of maintenance, light weight, flexibility of component design, combine with other materials, corrosion/abrasion/weather resistance, variety of colors and decorative appearance, multiplicity of form, ease of fabrication by mass production techniques, and total cost advantages (combinations of base materials, manufacture and installation). 

The specimen may be any shape. Artificial weathering has been defined by ASTM as The exposure of plastics to cyclic laboratory conditions involving changes in temperature, relative humidity, and ultraviolet (UV) radiant energy, with or without direct water spray, in an attempt to produce changes in the material similar to those observed after long-term continuous outdoor exposure. ... 

Light-stable and weather-resistant Resistant to weather and ultraviolet degradation. Structural panels, skylighting, glazing. 

Here, we shown a "conventional" system. It consists of a light source, an etched, transparent circuit diagram and a lens to focus the pattern upon the wafer which has a photoresist layer. Upon exposure, the unexposed part of the photoresist is wzished off. Sometimes, the exposed area is removed, depending upon weather the photoresist is positive or negative. Contrast this simple system with a method under development is the "Extreme Ultraviolet (EUV) system, using radiation from excited Xe gas, i.e.- 157 nm. The EUV system is shown in the following ... 

Applications. Ultraviolet detectors are ideally suited for applications where rapidly developing fire can occur in a relatively open area. UV detectors can be used to monitor ammunition assembly lines, gunpowder troughs, or open areas that are stocked with hazardous materials. These detectors are not typically affected by extremes of temperature or pressure, adverse weather conditions, high humidity, nor are they sensitive to solar radiation. 

They can withstand exposure to ozone, ultraviolet light and weathering. They have excellent dielectric properties and are not affected by oils. They get more easily tom than mbber and dissolve in aromatic solvent. 

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