MECHANISMS OF PHOTOLYTICALLY INDUCED DEGRADATION

The photolytic oxidation process--attack by sunlight--is perhaps the most widespread form of irreversible degradation in paint films, and is, in large part, responsible for the deterioration of their aesthetic and protective properties. This review considers the photo-oxidative degradation of organic coatings by light. The degradation of polymeric coating binders by ultraviolet (UV) light is a multistage process involving initiation, propagation, and termination phases. The two principal structural results of these degeneration processes are crosslinking and chain scission. Crosslinking tends to increase the hardness, strength, and modulus of the film while reducing its elongation at break. Chain scission leads to molecular weight reduction, depolymerization, reduced glass transition temperature, and loss of low molecular weight reaction products. These processes weaken the film, induce increased water sensitivity, and reduce its tensile strength. Specific degradation reaction pathways are discussed for polystyrene/butadiene copolymers, acrylates, melamine-crosslinked systems, polyurethanes, and epoxy coatings. The absorptive protection and the photolytic degradation of coating film binders containing entrained pigmentation is discussed in the next unit of the series.

• Availability:
  • Find a library where document is available. Order URL: http://worldcat.org/issn/87551985
• Supplemental Notes:
  • Page Range: pp 73, 75-78, 80, 82, 84-86
• Corporate Authors:

  Technology Publishing Company

  2100 Wharton Street, Suite 310
  Pittsburgh, PA  United States  15203
• Authors:
  • Hare, C H
• Publication Date: 2000-3

Language

• English

Media Info

• Features: Figures; References; Tables;
• Pagination: 10 p.
• Serial:
  • Journal of Protective Coatings & Linings
  • Volume: 17
  • Issue Number: 3
  • Publisher: Steel Structures Painting Council
  • ISSN: 8755-1985

Subject/Index Terms

• TRT Terms: Acrylic resins; Binders; Butadiene; Coatings; Copolymers; Degradation failures; Deterioration; Epoxy coatings; Films (Coatings); Light; Organic coatings; Oxidation; Paint; Photolysis; Pigments; Polymers; Polystyrene; Polyurethane resins; Protective coatings; Sunlight; Tensile strength; Ultraviolet light; Weathering
• Subject Areas: Geotechnology; Highways; Materials; I35: Miscellaneous Materials;

Filing Info

• Accession Number: 00790586
• Record Type: Publication
• Files: TRIS
• Created Date: Apr 3 2000 12:00AM