Exposing polymers to environmental atmosphere changes their external appearance and their properties and modifies their surface. Protection from photoaging of polymers with aromatic structures such as bisphenol-A polycarbonate (PC), poly(ethylene tereph- thalate) (PET), or poly(ethylene naphthalate) (PEN) is a difficult challenge as their monomer units strongly absorb UV light. UV radiations induce chemical reactions such as the rupture of covalent bonds initiating photolytic (without intervention of oxygen) and photooxidation (fixation of oxygen) reactions. This causes, in turn, breakdown of the materials, with yellowing and embrittlement as major consequences. To prevent these damages, a very effective method to protect the polymer is the dep- osition of ceramic coatings that are transparent in the visible light range. A ceramic coat- ing physically screens the incident radiation, which reduces the undesirable effects of photochemical processes. In addition, the photooxidation rate decreases because the coat- ing acts as an oxygen barrier. Low temperature crystalline deposition is of particular interest for polymers that cannot tolerate high temperatures.

Enhancement of Photoprotection and Mechanical Properties of Polymers by Deposition of Thin Coatings”

FABBRI, PAOLA
2009

Abstract

Exposing polymers to environmental atmosphere changes their external appearance and their properties and modifies their surface. Protection from photoaging of polymers with aromatic structures such as bisphenol-A polycarbonate (PC), poly(ethylene tereph- thalate) (PET), or poly(ethylene naphthalate) (PEN) is a difficult challenge as their monomer units strongly absorb UV light. UV radiations induce chemical reactions such as the rupture of covalent bonds initiating photolytic (without intervention of oxygen) and photooxidation (fixation of oxygen) reactions. This causes, in turn, breakdown of the materials, with yellowing and embrittlement as major consequences. To prevent these damages, a very effective method to protect the polymer is the dep- osition of ceramic coatings that are transparent in the visible light range. A ceramic coat- ing physically screens the incident radiation, which reduces the undesirable effects of photochemical processes. In addition, the photooxidation rate decreases because the coat- ing acts as an oxygen barrier. Low temperature crystalline deposition is of particular interest for polymers that cannot tolerate high temperatures.
Service Life Prediction of Polymeric Materials Global Perspectives
327
343
A. Rivaton; J-L. Gardette; S. Morlat-Therias; B. Mailhot; E. Tomasella; O. Awitor; K. Komvopoulos; P. Fabbri
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11585/474199
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