Oxydation photothermique d'élastomères de polyuréthannes thermoplastiques, 4. Influence d'un oxyde à caractère photocatalytique

✍ Scribed by Gardette, Jean-Luc ;Lemaire, Jacques

• Publisher: Wiley (John Wiley & Sons)
• Year: 1984
• Weight: 461 KB
• Volume: 185
• Category: Article
• ISSN: 0025-116X
• DOI: 10.1002/macp.1984.021850305

✦ Synopsis

Abstract

A photocatalyst like TiO~2~ may be introduced into a polymer to control the initiation process, to protect the photo‐instable products, and to limit the oxidation to a surface phenomenon. In the case of aromatic polyurethanes, the quantum yields of photocatalytic oxidation are low as compared with the quantum yields of direct photooxidation. Photoactive pigments behave as stabilisers for the oxidation pathway. On the other hand, the photocatalyst acts as a screen for the Fries photorearrangement products and inhibits their photooxidation. Yellowing of polyurethanes is partly due to the photoinduced oxidation and partly to the Fires photorearrangement products. It is shown that in the presence of photoactive pigments the yellowing of polyurethanes due to Fires photorearrangement is the most determental process.