Ultraviolet radiation, polymers

When the polymers are exposed to ultraviolet radiation, the activated ketone functionahties can fragment by two different mechanisms, known as Norrish types I and II. The degradation of polymers with the carbonyl functionahty in the backbone of the polymer results in chain cleavage by both mechanisms, but when the carbonyl is in the polymer side chain, only Norrish type II degradation produces main-chain scission (37,49). A Norrish type I reaction for backbone carbonyl functionahty is shown by equation 5, and a Norrish type II reaction for backbone carbonyl functionahty is equation 6. 

Degradation of polyolefins such as polyethylene, polypropylene, polybutylene, and polybutadiene promoted by metals and other oxidants occurs via an oxidation and a photo-oxidative mechanism, the two being difficult to separate in environmental degradation. The general mechanism common to all these reactions is that shown in equation 9. The reactant radical may be produced by any suitable mechanism from the interaction of air or oxygen with polyolefins (42) to form peroxides, which are subsequentiy decomposed by ultraviolet radiation. These reaction intermediates abstract more hydrogen atoms from the polymer backbone, which is ultimately converted into a polymer with ketone functionahties and degraded by the Norrish mechanisms (eq. 

The oxidation of hydrocarbons, including hydrocarbon polymers, takes the form of a free-radical chain reaction. As a result of mechanical shearing, exposure of ultraviolet radiation, attack by metal ions such as those of copper and manganese as well as other possible mechanisms, a hydrocarbon molecule breaks down into two radicals... 

Acrylamide readily undergoes polymerization by conventional free radical methods, ionizing radiation, ultrasonic waves, and ultraviolet radiation. The base-cata-lized hydrogen transfer polymerization of acrylamide yields poly-/3-alanine (Nylon 3) a water insoluble polymer that is soluble in certain hot organics. All current industrial production is believed to be by free radical polymerization. 

Ultraviolet radiation, effect on commercial polymers, 201 Ultraviolet-cured coatings hydroxy-benzotriazolc, 213 photostabilization of PVC, 213 Ultraviolet-visible spectrum,... 

The most stable resin for many of our purposes has proven to be a copolymer of ethyl methacrylate and methyl acrylate. This comes as little surprise the Rohm and Haas Company has for years sold a durable resin based on these two monomers, Acryloid B-72 (6,28). We have also prepared polymers of similar physical properties based on methyl methacrylate and ethyl acrylate and have found that their behavior is practically the same - the methyl and ethyl groups apparently do not become seriously involved in crosslinking. As reported elsewhere( 23), rather than crosslink, Acryloid B-72 tends to chain break under visible and near-ultraviolet radiation, although at a very slow rate. Polyvinylacetate is another polymer used in the care of museum objects that tends more to chain break than crosslink under these conditions(23), but it is not our purpose to discuss its properties at this time. 

Feller, R. L., "Cross-Linking of Methacrylate Polymers by Ultraviolet Radiation", Preprints of papers presented at the New York Meeting, Division of Paint, Plastics and Printing Ink Chemistry, American Chemical Society, Sept., 1957, 17, No. 2, 465-470. 

A large number of polymeric materials have been developed over the past two decades which are photochemically reactive. In many cases, such polymers are initially soluble in organic solvents prior to exposure with insolubilization accompanying ultraviolet radiation. This often presents a problem in practical applications where handling of organic solvents is objectionable or expensive. A need exists to develop functional polymers which are both water soluble and photochemically labile. 

However, Jellinek and Chaudhuri exposed Nylon 66 films to nitrogen dioxide, ozone, and ultraviolet radiation. The degree of degradation of polymer a was measured by... 

Jellinek, H. H. G., and A. K. Chaudhuri. Inhibited degradation of nylon 66 in presence of nitrogen dioxide, ozone, air, and near-ultraviolet radiation. J. Polymer Sci. Part A-1. 10 1773-1778, 1972. 

Dimensional instability and susceptibility to degradation by biological organisms, heat, and ultraviolet radiation can be greatly reduced by modification of lignocellulosic cell wall polymers. 

Here PNO2 partial pressure of nitrogen dioxide in pascals (1 Pa = 0.000145 psi), and the activation energy is 3870 kJ/mol. Other saturated polymers are less susceptible to attack by NO2 than most unsaturated polymers such as synthetic rubbers (polyiso-prene, polybutadiene, and butyl rubber). The presence of oxygen also tends to accelerate degradation by NO2. The reaction of sulfur dioxide with saturated polymers is complex, but appears to be activated by ultraviolet radiation. 

Unsaturated polymers, such as polydienes, react with chlorine and bromine at normal temperatures and in the absence of ultraviolet radiation. The... 

The initiation of polymerization by ultraviolet radiation has been of particular interest in the study of free radical processes [1,2]. The test tube demonstration described here is simple and may be used to evaluate the polymerizabil-ity of new monomers or to study some of the physical properties of a polymer. Although the method is particularly effective for acrylic and methacrylic monomers, it may also be applied to the polymerization of a wide range of vinyl -type monomers. 

Hexamethylphosphoramide has been produced commercially in relatively small quantities in several countries of Europe, in Japan and in the United States. It is used as a solvent for polymers, a selective solvent for gases and as a thermal and ultraviolet radiation degradation stabilizer in various polymers (lARC, 1977). 

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