English Abstract
Discoloration Mechanism of Thermoplastic Elastomer
gStyrene-Butadiene-Styrene Block CopolymerhProducts

Jun HATAKEYAMA
Hiroki FUJIMURA
Yoshiharu MITSUHASHI
Panwashlet Co., Ltd., Material Reseach Sec., Kokuraminami-ku, Kitakyusyu, Japan
Yoshito OHTAKE
Chemicals Evaluation and Research Institute, Japan, Kitakatsushika-gun, Saitama
Mutsuhisa FURUKAWA
Department of Materials Science, Graduate School of Science and Technology, Nagasaki University, Nagasaki, Japan
Nippon Gomu Kyokaishi,(2005),78(11),413-418 Original Paper in Japanese


Abstract
Discoloration mechanism of styrene-butadiene-styrene block copolymer (SBS) containing phenolic antioxidants by human excrement and urine was studied. The phenolic antioxidants react with SBS to give bright pink, discolored products. They were analyzed by color-difference measurement, FT-IR, TOF-SIMS, and ESR. Products of high activation state were formed on the discolored surface by reaction of the phenolic antioxidant with nitrogen compounds and metallic elements that were metabolized from a human body.
The colored substance is a 3,3',5,5'-tetra-tert-butyl-4,4'-stilbenequinone derivative. This discoloration is disappeared by the ative. This discoloration is disappeared by the addition of the phosphoric antioxidant to SBS products.

(Received on December 27, 2004)

(Accepted on September 16, 2005)

Keywords:
Thermoplastic elastomer, Styrene-butadiene-styrene block copolymer, Phenolic antioxidant, Elucidation of discoloration mechanism, 3,3',5,5'-tetra-tert-butyl-4,4'-stilbenequinone, TOF-SIMS, ESR
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