Material propertiesMelt processed polyethylene/fullerene nanocomposites with highly improved thermo-oxidative stability

The thermo-oxidative stability of melt processed polyethylene composites with the two fullerenes C60 and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) was studied with the aim of comparing the stabilization effect of both fullerenes on three different polyethylenes (PE). The results obtained show that, irrespective of the specific polyethylene being considered, C60 loadings as low as 1.0 wt% cause a dramatic increase in the thermo-oxidative stability of the corresponding composites (up to 64.8 °C at T2% and 113.8 °C at T5%, TX% being the temperature corresponding to a mass loss of X wt%), in agreement with previous reports. Furthermore, and more importantly, this work shows for the first time that the thermo-oxidation stability effect caused by PCBM is even higher than that of C60, the difference between both being particularly significant in the early stages of degradation, i.e. for mass losses ≤2 wt%. For example, polyethylene composites with 1.0 wt% PCBM show T2% values which are systematically higher than those of the corresponding composites with 1.0 wt% C60, the difference between the T2% values of the two composites being 38.8 °C, 67.1 °C and 26.4 °C in the three different polyethylenes considered. Therefore, when compared with C60, PCBM is particularly more effective at delaying the beginning of the thermo-oxidative degradation. According to our results, PCBM loadings as low as 1.0 wt% can increase the thermo-oxidative stability of polyethylene composites by more than 130 °C and these are, as far as we know, the highest thermo-oxidative stability results induced by nanoparticles ever reported in the literature for polyethylene.