English Abstract

Discoloration Phenomenon Induced by the Combination of Phenolic antioxidants and Hindered Amine Light Stabilizers

Takako KIKUCHI *1 *2
Yoshito OHTAKE *1
Keiji TANAKA *2 *3
*1:Chemicals Evaluation and Research Institute, Japan, Kitakatsushika-gun, Saitama, Japan
*2:Department of Automotive Science, Kyushu University, Nishi-ku, Fukuoka, Japan
*3:Department of Applied Chemistry, Kyushu University, Nishi-ku, Fukuoka, Japan
Nippon Gomu Kyokaishi,(2012),85(9),283-288 Original Paper in Japanese

Additives are generally mixed into polymeric materials to extend their lifetimes. However, the mixing of multiple additives may cause a negative synergy effect such as discoloration behaviors. We here report how the discoloration of a typical phenolic antioxidant, 2,6-di-tert-butyl-4-methylphenol(BHT), is promoted under the presence of hindered amine light stabilizers(HALS) on the basis of a temperature accelerated test. When BHT was used with HALS in n-decane solution at higher temperatures, quinone methide and stilbenequinone were produced via the oxidation of BHT, which can be catalyzed by titanium dioxide. This eventually leads to the discoloration of the reaction system.
Interestingly, the discoloration phenomenon was further proceeded with increasing concentration of HALS and strength of HALS basicity. Similar results could be obtained even in polymer materials.

Keywords: Discoloration, Phenolic antioxidant, BHT, HALS, Titanium dioxide(TiO2)