Highly aging-resistant elastomers doped with antioxidant-loaded clay nanotubes.

A novel aging-resistant styrene-butadiene rubber (SBR) composite is prepared using the antioxidant N-isopropyl-N'-phenyl-p-phenylenediamine (4010NA) loaded inside of halloysite clay nanotubes and used as filler. Loading the antioxidant inside of halloysite allows for its sustained release for nine months in the rubber matrix. By utilizing modified halloysite, the antioxidant concentration in this rubber nanoformulation is tripled without causing "blooming" defects. Furthermore, the halloysite is silanized to enhance its miscibility with rubber. The aging resistance of SBR-halloysite composites is studied by comparing the mechanical properties before and after thermal-oxidative aging. A seven-day test at 90 °C shows preservation of mechanical properties, and no 4010NA blooming is observed, even after one month. Styrene-butadiene rubber with 27 wt % halloysite loaded with 4010NA shows marked increase in aging resistance and promising future of halloysite as a functional rubber filler.