PHOTOLYTICALLY INDUCED DEGRADATION--EFFECTS OF ORGANIC LIGHT STABILIZERS

This article discusses the use of organic light stabilizers as a primary stabilizing device against paint film degradation in the presence of ultraviolet (UV) light. Organic light stabilizers are used when pigments are not an option for stabilizing light. UV absorbers (UVAs), like pigments, absorb UV light radiation, reducing the amount of UV light available for absorption by the resin. One of the most widely used liquid UVAs (from polyethylene glycol used to functionalize the absorber) has hydroxyl functionality. It will react into isocyanate- and melamine-cured systems, reducing the possibilities of loss by solvent leaching and of migration effects induced by high temperature. It is possible for a UVA to deteriorate chemically by free radical attack. Quenchers represent the next level of protection, dissipation of the excited state so that free radicals are not formed. UVAs and excited state quenchers work by similar mechanisms, depending on the additive and the coating system in which it is used. The role of the hindered amine light stabilizer (HALS) is to scavenge free radicals formed by the initial oxidation of the binder or impurity before further reaction can proceed. The article differentiates the HALS from other antioxidants, such as the hindered phenols. The latter are less effective than the HALS as light stabilizers, although they are used as thermal stabilizers to protect coatings against yellowing during high-temperature baking cycles. An introduction to the issues associated with accelerated testing for improved UV performance is appended.

  • Availability:
  • Supplemental Notes:
    • Page Range: pp 56-58, 60-61, 63-65
  • Corporate Authors:

    Technology Publishing Company

    2100 Wharton Street, Suite 310
    Pittsburgh, PA  United States  15203
  • Authors:
    • Hare, C H
  • Publication Date: 2000-5

Language

  • English

Media Info

Subject/Index Terms

Filing Info

  • Accession Number: 00793972
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Jun 10 2000 12:00AM