Ultraviolet stabilizers mechanisms

Mechanisms of Photodegradation of Ultraviolet Stabilizers and Stabilized Polymers... 

Typical, ultraviolet absorbers are salicylate esters, -amino-benzoate esters, a-cyano-0-phenylcinnamate esters, 2-hydroxybenzo-phenones, 2(2-hydroxyphenyl)2H-benzotriazoles (Figure 1), and more recently diaminodiphenyloxamides. Some pigments and various types of carbon blacks are also known as effective ultraviolet stabilizers. Another mechanism by which the stabilization of the polymers can be accomplished is by quenching the excited state of the molecules. 

The sheathing is usually made of the same resin for the power cables and the telecommimication cables. The main functions of the jacket are the mechanical and environmental protection of the cable therefore, the cable jackets are commonly filled with carbon black, the best ultraviolet stabilizer known today. 

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... 

After briefly describing the classical types of ultraviolet stabilizers and their mode of operation, we will consider the new mechanisms of photostabilization of the polymers which act by quenching the electronic states excited by UV light. 

Stability. Mechanical properties are retained up to about 140°C. The polymer has good electrical insulation properties and is self-extinguishing it also has very good resistance to ultraviolet light. Polyarylates thus find use in a number of outdoor applications such as traffic light components and solar collectors. 

How does the primary mechanism of stabilization differ between ultraviolet radiation stabilizers and thermal stabilizers ... 

As a rule, however, most of the ESIPT dyes exhibit weak to very weak fluorescence quantum yields, i.e., the quantum yield of the nonradiative processes is near unity. Such dyes, if they show little permanent photodestruction, can be used as ultraviolet (UV)-stabilizers of polymers, such as Tinuvin (a hydroxy-benzotria-zole),(45) because they efficiently convert UV radiation, harmful for the polymer, into harmless heat. The mechanisms of these nonradiative decay paths are often linked to... 

This study was therefore undertaken to prepare and evaluate acrylonitrile—butadiene-styrene (ABS) and methyl methacrylate-butadiene-styrene (MBS) polymers under similar conditions to determine whether replacement of acrylonitrile by methyl methacrylate could improve color stability during ultraviolet light aging, without detracting seriously from the good mechanical and thermal-mechanical properties of conventional ABS plastics. For purposes of control, the study also included briefer evaluation of commercial ABS, MBS, and acrylonitrile-butyl acrylate-styrene plastics. 

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