Anti-aging behavior of amino-containing co-condensed nanosilica in polyethylene

Physical loss of stabilizers by migration and extraction accelerates the degradation of polymer materials. In this work, amino-containing nanosilica with anti-aging properties was prepared simply by the co-condensation of tetraethoxysilane and N-(2-aminoethyl)-3-aminoproply-trimethoxysilane (AEAPS). AEAPS was used to introduce amino groups into silica nanoparticles and to act as a catalyst in this process. The co-condensed nanosilica (CCS) showed agglomerate structure similar to the typical fumed nanosilica (FS). The amino groups were distributed both on the surface and inside the nanoparticles. HDPE/CCS and HDPE/FS composites were prepared by melt blending. Thermogravimetric analysis and oxidative induction time showed that CCS has effectively improved the thermo-oxidative stability of HDPE. In the long-term accelerated thermo-oxidative aging and UV aging tests, HDPE/CCS composite showed superior stability to neat HDPE and HDPE/FS composite. The results of infrared spectroscopy and electron paramagnetic resonance suggested that the HDPE/CCS composite manifested a special degradation mechanism involving the nucleophilic addition of amino groups to carbonyl species as well as the oxidation of amino groups on CCS by peroxides. The amino groups on CCS consumed carbonyl species and peroxides, and generated hydroxylamines and nitroxide radicals which were able to eliminate free radicals, thus restrained the degradation of HDPE.