Thermal-oxidative degradation behavior and process of vulcanized styrene-butadiene rubber

Abstract

The thermal oxidative degradation behavior and process of vulcanized styrene-butadiene rubber (SBR) at high temperature was studied by the sol-gel analysis, equilibrium swelling method, Fourier transform infrared spectroscopy coupled with mass spectrometry (FTIR-MS) and in-situ Fourier transform infrared spectroscopy.The chemical structure changes of degradation process of the SBR vulcanizate at 210 ℃ were compared with those of 150 ℃.The results showed that the sol content of the SBR vulcanizate at 210 ℃ gradually increased in the initial stage of the reaction, reached a maximum value of 28.1% at 10 min, and then a significant decline occurred.The trend of the reaction at 150 ℃ was similar to that at 210 ℃, but the reaction rate was relatively slower.The vulcanized SBR produced a small amount of sulfur dioxide gas at 7 min and a relatively large amount of other oxidation products containing carboxyl group and thioheterocyclic group at 12 min were observed by FTIR-MS.The cross-linking bonds of the vulcanized SBR were initially converted from polysulfur bonds to monosulfur bonds, part of which were then oxidized to sulfoxide groups and further to sulfonyl groups or sulfates.The backbone oxidation of the SBR vulcanizate was an autocatalytic oxidation, and the carbonyl group content remained stable during the late stage of oxidation.

Keywords

• styrene-butadiene rubber
• thermal-oxidation degradation
• sol content
• gel cross-linking density
• sulfur bond
• backbone