Synthesis and anti-aging property in acrylonitrile-butadiene rubber of non-aromatic dendritic antioxidant with amine groups

A novel kind of antioxidant with dendritic structure and amine groups for acrylonitrile-butadiene rubber (NBR) was synthesized via the combination of Michael addition and nucleophilic reactions. Structures of the synthesized non-aromatic dendritic antioxidants, namely first-generation (1.0 G), second-generation (2.0 G), third-generation (3.0 G) dendritic polyamidoamine (DPAMAM) and hyperbranched polyamidoamine (HPAMAM), were confirmed by Fourier Transform Infrared Spectroscopy (FT-IR) and Hydrogen Nuclear Magnetic Resonance Spectroscopy (¹H NMR). Anti-aging properties of the antioxidants for NBR vulcanizates were evaluated by accelerated thermal aging tests and extraction resistance tests. The decomposition of vulcanizates containing dendritic antioxidants were investigated by thermogravimetric (TGA) curves, and the thermo-oxidative aging kinetic parameters were calculated by the Dakin-Ozawa-Doyle (DOD) method. Compared with conventional aromatic antioxidant N-isopropyl-N′-phenyl-p-phenylene diamine (4010NA), the anti-aging properties of 1.0 G and 2.0 G DPAMAM were at the same level, while that of 3.0 G DPAMAM and HPAMAM were further improved. Meanwhile, HPAMAM and 3.0 G PAMAM showed better extraction resistance in NBR vulcanizates than 4010NA, thus indicating superior anti-aging performances. Maximum service temperatures (T_max) under 30 years of service life span of NBR vulcanizates containing HPAMAM and 3.0 G DPAMAM were 219°C and 221°C, 15°C and 17°C higher than that of sample with 4010NA respectively.