Metal deactivator-suppressed degradation of trans-1,4-poly(isoprene-co-butadiene) rubber

Abstract

Trans-1,4-poly(butadiene-co-isoprene) rubber (TBIR) has excellent dynamic properties, such as a high anti-fatigue performance, low rolling resistance, good abrasion resistance, and low heat generation, for use in high-performance tires; however, these properties are degraded by Ziegler-Natta (Z-N) catalyst residues, which accelerate aging. Introducing metal deactivators into anti-aging agents, we demonstrated the suppressed degradation of TBIR using differential scanning calorimetry, gel permeation chromatography, and thermogravimetric analysis. The suppression extent was closely associated with the types and content of metal deactivators. Given the optimized content, TEA (0.5 phr) and oxine (0.1 phr) exerted a more profound effect than did MD697 (0.1 phr) and MD1024 (0.2 phr)), resulting in a higher oxidation induction time and retention rate of molecular weight of TBIR. It is demonstrated that the details of the suppression mechanism of metal deactivators obtained from the analysis of the ultraviolet spectrum could be accounted for the formation of stable chelates, thereby reducing the activity of the catalyst metal residues. Finally, we found that TEA and oxine had no significant negative effects on the physical and processing properties of TBIR. These results provide an important reference for improving the stability and aging resistance of TBIR, which could be extended to other polymers that are synthesized using a Z-N catalyst or may encounter metals or metallic compounds.