Ultraviolet screening agents

See Free-radical scavengers, Peroxide decomposers, Quenchers, Ultraviolet absorbers, Ultraviolet screening agents. 

Dipropylene Glycol Monosalicylate n (salicylic acid, dipropylene glycol monoester) A light-colored oil used in ultraviolet-screening agents and plasticizers. 

Ultraviolet-screening agents that absorb ultraviolet rays from the sun in exposed coatings and reduce ultraviolet degradation in the film, which drastically reduces the life expectancy of certain vehicles, such as the vinyl chloride resins. Plasticizers increase the flexibility and adhesion of film formers in fact,... 

CF4, chloroform, etc.), it has become absolutely necessary to use sun screen agents to prevent penetration of both ultravio-let-A and ultraviolet-B into the screen. Direct penetration of sunrays without the use of sunscreen agents in the body would cause both sunburn and suntan. 

Figure 27 shows that these compounds have a higher ultraviolet absorbance and a steeper long wavelength cut-off than the ultraviolet absorbers of the first two families [129]. These factors make them slightly better screening agents. 

Products and Uses Found in sunscreening products and protective coatings as a UV (ultraviolet) light screening agent. 

Products and Uses Found in cosmetics and sunscreen cream, lotion, gel, and spray preparations. Used as an ultraviolet (UV) screening agent. 

If exposed to sunlight, an ultraviolet absorber or screening agent should be in the formulation to protect it from degradation. Thermal oxidative degradation, particularly where copper is involved will pose a problem. 

Ultraviolet Stabilizer n An additive that protects plastics against Ultraviolet Degradation, and that may accomplish its protection in various ways. An additive that preferentially absorbs UV radiation and dissipates the associated energy in a harmless manner is sometimes called an ultraviolet absorber or ultraviolet screen-ing agent. Additives that do not actually absorb UV radiation but protect the polymer in some other manner are called ultraviolet stabilizers or other names indicative of the mechanism of stabilization. For example, products that remove the energy absorbed by... 

Ultraviolet protective agents fall into two categories, those operating as UV screens, and those which operate by interfering with a degradation chain reaction in the polymer that has been initiated or catalysed by the radiation. 

Reactions (d) and (e) occur much less frequently than reactions (a)-(c) but do so at a sufficient rate to cause changes in most polymers. There are three methods available for combating such effects light screens, ultraviolet absorbers and quenching agents. 

To improve the resistance to ultraviolet light carbon black is often useful as a light screen. Its use in fibres and films is clearly very restricted and in these instances ultraviolet absorbers and/or quenching agents are used. Recent developments include the greater use of hindered amine and nickel compounds. 

Tretinoin or retinoic acid is the acid form of vitamin A. Actually it is the all-trans isomer of retinoic acid. It is an effective topical agent for acne vulgaris. Its mechanism of action is believed to be associated with increased epidermal cell turnover. Some 10% of the topically applied dose is absorbed, metabolized by the liver and excreted in the urine and bile. To be effective tretinoin should be applied in a concentration that results in mild irritation and erythema. Patients should be advised to avoid or minimize sun exposure and use a protective sun screen as animal studies have raised some concern about possible carcinogenic effects under the influence of ultraviolet radiation. There are no indications that topical tretinoin is associated with an increased risk for birth defects. 

Products and Uses Commonly used in suntan oil and lotion products as a sun-screen. Found in wall paints as a pigment and whitening agent. A UV (ultraviolet) light absorber. 

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