Thermo-oxidative aging and strain softening behaviors of natural rubber composites mediated by a low-cost and multifunctional black talc filler: a comprehensive comparison with roles of carbon black, silica and talc as traditional fillers

Thermo-oxidative aging and strain softening would cause irreversible structural changes in the rubber composites accompanied by degradation of properties and eventual failure. Herein a novel strategy using black talc (BT) as filler is attempted for addressing the two long-standing issues by systematical regulation of vulcanization kinetics, crosslinking density, mechanical properties and thermal-oxygen stability of natural rubber (NR) composites. The results show that, for the composites with filler of 50 parts per hundred parts of rubber, the retentions of strain at break and tensile strength of the NR/BT composite after thermo-oxidative aging at 100 °C for 48 h are 93.6 % and 96.8 %, being superior to those of the composites filled with traditional fillers like carbon black (CB, 64.5 % and 50.0 %), silica (36.7 % and 53.6 %) and talc (82.8 % and 57.9 %). In comparison with CB and silica, BT can also weaken the damping and softening behaviors accompanying the Mullins effect during cyclic stretching and weaken Payne effect during large amplitude oscillation shear. It is suggested that the graphite-like carbon in BT is able to improve filler-rubber interfacial interaction and decrease the concentration of peroxyl radicals generated by NR aging while the MgO and SiO 2 components in BT play an important role in improving thermo-oxidative aging resistance. The findings pave the way to extend potential applications of BT resource and prolong the service life of NR products in an environmentally sustainable way.