Ultraviolet/sunlight stability

Polymers that are unstable in sunlight and require ultraviolet light stabilizer, like poly(vinyl chloride), polypropylene, nylons, rubbers, and cellulose. 

Ultraviolet Aging. Nylon parts exposed to sunlight and uv rays undergo a similar free-radical aging process. Again, this can be reduced with appropriately stabilized materials. 

The role of CFCs in the destruction of ozone in the stratosphere was something of a surprise to some researchers because those compounds are normally quite stable. In fact, their stability is one of their most desirable properties for many industrial and commercial applications. But, when CFCs escape into the atmosphere and drift upward, they are exposed to ultraviolet radiation in sunlight and, as is oxygen itself, are dissociated by that radiation. In the case of Freon-12 (CCI2F2), photodissociation results in the formation of free chlorine atoms ... 

Exposure to sunlight Many explosives which contain nitrogen groups (primary explosives such as LA, MF etc.) decompose rapidly on exposure to the ultraviolet (UV) rays of the sun, and thus affect their stability. 

Ultraviolet absorbers are added to polypropylene resins which are used where exposure to sunlight is high. These chemicals are essentially ineffective as heat or processing stabilizers. 

Ultraviolet radiation from the sun can be veiy destructive to polymers used in vinyl siding, windows, doors and outdoor furniture. UV Stabilizers help prevent discoloration, cracking, embrittlement and loss of physical properties in these products that may occur upon exposure to sunlight. 

IFP s paper on their Spanish plant described their hydrocracked stocks as having about the same stability to oxidative storage conditions as those from solvent refining. This has generally not been industry experience elsewhere. In fact, unfinished first-stage hydrocracked base oils, waxy or dewaxed, have been found to darken in color over relatively short times and form haze or insoluble deposits, and these effects are accelerated when samples are exposed to high (about 100°C) temperatures or sunlight in so-called window tests, which were later replaced by more specific exposure to ultraviolet (UV) sunlamps. This was... 

Unstabilized PPS tends to degrade in sunlight. This is caused by the overlap of the absorption spectrum of PPS and the spectrum of the sun in the ultraviolet light. A systematic study has been performed to find suitable light stabilizers. A wide number of UV absorbers, quenchers, and antioxidants have been added in bulk to PPS. The effectiveness of the additives in suppressing UV degradation was evaluated. 

Improved stability, because these materials have ultraviolet stabilizing properties that prevent decay because of sunlight, reduce moisture absorption, ensure consistent color, and prevent curling. 

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