Ultraviolet light stabilization carbon black

Ultraviolet Light Stabilizers. Both titanium dioxide and carbon black are strong ultraviolet light absorbers and effective in protecting the PVC. For ultraviolet light absorption in transparent PVC oi foi impiovement of pigmented systems, various derivatives of benzotnazole are used. 

Ultraviolet Light Stabilization. UV light stabilization is produced by fillers that reflect UV, particularly aluminum flake and Ti02, and by fillers that absorb UV radiation and reduce it to harmless wavelengths, particularly carbon black and zinc oxide (Sec. 5.1.4). 

Since acetal resins are degraded by ultra violet light, additives may be included to improve the resistance of the polymer. Carbon black is effective but as in the case of polyethylene it must be well dispersed in the polymer. The finer the particle size the better the ultra violet stability of the polymer but the poorer the heat stability. About 1.5% is generally recommended. For white compounds and those with pastel colours titanium dioxide is as good in polyacetals as most transparent ultraviolet absorbers, such as the benzophenone derivatives and other materials discussed in Chapter 7. Such ultraviolet absorbers may be used for compounds that are neither black, white nor pastel shade in colour. 

The commercial polymers are of comparatively low molecular weight (M = 25 000-60 000) and whilst being essentially linear may contain a few branches or cross-links arising out of thermal oxidation. Exposure to ultraviolet light causes a rapid increase in gel content, whilst heating in an oven at 125°C causes gelation only after an induction period of about 1000 hours. Eor outdoor applications it is necessary to incorporate carbon black. The polymers, however, exhibit very good hydrolytic stability. 

Many materials are subject to deterioration by ultraviolet light (UV). particularly many of the plastics and fiberglass materials. Fiberglass materials for outside use should be specified as UV-stabilized, and most plastics installed outdoors should be carbon-impregnated (black in color). It is particularly recommended that plastic cable ties, which secure cables in cable trays, be carbon-impregnated if installed outdoors. 

Light. Ultraviolet (uv) light promotes free-radical oxidation at the mbber surface which produces discoloration and a brittle film of oxidized mbber (35). This skin cracks in random directions to form a pattern called crazing, which can be prevented by the addition of carbon black fillers or uv stabilizers. Black stocks are more resistant to uv light than are gum or light-colored stocks. Nonblack compounds require larger quantities of nonstaining antioxidants which should bloom to the surface as the surface uv stabilizers deplete. 

Nylons require modification or stabilization to improve their resistance to certain environmental effects. Unstabilized nylon is degraded by ultraviolet light. The most widely used stabilizer has been approximately 2% well-dispersed carbon black, which has proved effective in the absorption of ultraviolet light. The nylons are considered adequate for outdoor applications if they are not exposed to direct sun-hght,... 

Deterioration occurs in uncolored polyethylene exposed to weather. Ultraviolet light causes photoactivated oxidation. Satisfactory weathering formulations contain 2-2.5% well-dispersed carbon black and stabilizers, The carbon black prevents ultraviolet light penetration. 

Antioxidants are key ingredients used in the compounding of PE and PP due to the limited stability of PO to high temperatures and ultraviolet (UV) light [47]. Antistatic plastic materials are frequently made by compounding a thermoplastic with a conductive filler, such as carbon black, carbon fibres or metal fibres [48]. 

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