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The effect of acid-treated multi-walled carbon nanotubes (MWCNTs) on thermo-oxidative stability and degradation behavior of silicone rubber (SR) was evaluated. Raman microscopy, Fourier transformed infrared spectroscopy, X-ray photoelectron spectroscopy and thermogravimetric (TG) analysis were performed to characterize the surface states of MWCNTs samples. The results demonstrated that after acid treatment the nanodefects and surface oxygen-containing groups (mainly hydroxyl and carboxyl groups) were formed and the number of them was gradually increased by increasing the treatment time. Then these MWCNTs were embedded into SR matrix. Furthermore, the thermo-oxidative stability and degradation behavior of MWCNTs/SR composites were studied using thermogravimetric/infrared spectrometry (TG-IR). Thermo-oxidative stability test in air revealed that the degradation of SR, at relatively low temperature, was mainly due to the oxidation of Si-CH3 side groups and the generation of free radicals. This behavior was hindered by the MWCNTs’ surface nanodefects and hydroxyl groups, as proved by TG-IR study which revealed that the amount of carbonyl compounds was reduced more than 60%, compared with that of neat SR. Therefore, acid treatment led a better thermo-oxidative stability of MWCNTs/SR. For 4hAT-MWCNTs/SR, with maximum hydroxyl groups on MWCNTs surface, the Ti (defined as the temperature for 5% mass loss) of it is increased by 34.8 °C compared to that of neat SR, and even increased by 18.5 °C compared with that of raw-MWCNTs/SR.

To investigate the impact factors and action mechanism for the improved thermal oxidative stability of silicone rubber (SR) by incorporating reduced graphene oxide (rGO), graphene oxide (GO), and rGO were prepared, and subsequently graphite, GO and different amounts of rGO were introduced into SR. Transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction were performed to characterize morphology and surface chemical composition of particles (graphite, GO, and rGO). Scanning electron microscope and X-ray diffraction were employed to investigate the dispersion of particles in the SR matrix. Moreover, the effect of morphology and surface chemical composition of particles on the thermal oxidative degradation of SR and the action mechanism were studied via measuring the mechanical properties and the average molecular weight between crosslinking points of the SR before and after aging, as well as utilizing thermogravimetric/infrared spectrometry. The results showed that rGO exhibited the largest exfoliation extent, few oxygen-containing functional groups and better dispersion among these particles, causing the best thermal oxidative stability of rGO/SR nanocomposites, especially when its amount is 1 phr; incorporating rGO could increase the initial formation temperatures of pyrolysis products and decrease the concentrations of products from the oxidation and fracture of side groups of SR. POLYM. COMPOS., 2016. © 2016 Society of Plastics Engineers