By George Wypych
This publication, the second one variation of the 1st monograph absolutely dedicated to UV degradation and stabilization ever released in English, has 12 chapters discussing various facets of UV comparable phenomena happening while polymeric fabrics are uncovered to UV radiation.
In the creation the present literature has been reviewed to determine how crops, animals and people shield themselves opposed to UV radiation. This evaluate allows review of mechanisms of safeguard opposed to UV utilized by residing issues and capability software of those mechanisms in safeguard of average and artificial polymeric fabrics. this can be through chapters with a extra specific examine extra particular features of UV degradation and stabilization.
- A sensible and up to date reference advisor for engineers and scientists designing with plastics, and formulating plastics materials
- Explains the consequences of UV mild on plastics, and the way to mitigate its results by using UV stabilizers
- Surveys the diversity of UV stabilizers out there, and offers suggestion on their choice and use
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Additional resources for Handbook of UV Degradation and Stabilization, Second Edition
Some PVC stabilizers also seem to be capable of eliminating ketoallylic chlorine. By doing so, they can break the sequence of conjugated double bonds that changes polymer color. Organotin chloride is believed to cause double bond migration (or isomerization), which breaks the sequence of conjugated double bonds and preserves color: organotin chloride CH CH CH CH CH Cl CH CH CH CH CH Cl These are not numerous examples but they may generate more interest in the search for other methods that would increase our ability to preserve the original properties of polymers.
2 Tinuvin 123 tions. 1 shows pKa constants of some >N-C(O)CH3 2 Tinuvin 440 HAS. The selection of particular HAS Mechanisms of UV Stabilization 47 depends on properties of the system. The general rule stipulates selection of basic HAS for basic compositions and vice versa. 7. 21 Phenol-type antioxidants are known as radical scavengers. 25 Carbon black is frequently mentioned26-29 as participating in radical scavenging but no credible mechanism responsible for this action was ever proposed. 4 SINGLET OXYGEN QUENCHING Many materials do not absorb in the ultraviolet range, therefore they cannot undergo direct degradation process, but some admixtures may absorb UV radiation and cause indirect degradation of these materials:32 Sensitizer Sensitizer* 1 O2 + light + 3 Sensitizer* Quencher Sensitizer* + 1 O2 3 O2 O2 Quencher + + Sensitizer Quencher* Sensitizer + Quencher* The schemes of reactions show that sensitizer may absorb radiation energy and get excited; excited sensitizer may react with triplet oxygen (common form of oxygen in air) and produce singlet oxygen (high energy, reactive form of oxygen).
The fate of this energy is discussed in the next section. Inorganic particles may also reflect and refract incoming radiation. Reflection of radiation which occurs on the material surface is the most desired outcome because energy is reflected into the surrounding space and therefore it does not affect material. If energy is reflected internally from the surface of an inorganic Mechanisms of UV Stabilization 43 particle into, for example, a polymeric matrix, then this energy can be utilized for photochemical processes because light reflection does not affect its energy.