Effects of Incorporating Small Amounts of Fe3O4 Nanoparticles into Epoxidized Natural Rubber: Chemical Interactions, Morphology and Thermal Characteristics

Nanocomposites were synthesized from epoxidized natural rubber (ENR-50) and magnetite (Fe3O4) at 1, 5, and 9 wt.%, respectively. Various analyses were conducted to gain comprehensive insight into the properties of the nanocomposites. It was found that the ring epoxide units can be opened and bonded with the Fe moieties of the magnetite to form an Fe-O-C structure, as shown in FTIR spectra at 690 and 700 cm−1. Peaks in UV-vis spectra at the wavelength of 297 nm shifted to 299, 303, and 309 nm for the nanocomposite samples with 1, 5, and 9 wt.% Fe3O4, respectively. XRD showed a decrease in the amorphous peak intensity, while new diffraction peaks emerged at 33° and 43°, indicative of the crystalline structure of the Fe3O4 in the nanocomposites. Based on TEM micrographs, it was found that the average size of Fe3O4 particles in the rubber matrix with 1 wt.% Fe3O4 was around 20 and 33 nm. SEM micrographs proved that nanoparticles with 1 wt.% Fe3O4 were regularly dispersed in the rubber matrix, and that magnetite nanoparticles were spherical in shape, as well as having strong interactions and bonding with the rubber matrix. A TGA thermogram showed three thermal steps of degradation across a wide temperature range, from 81 °C to 592 °C, and resistance to thermal degradation of the nanocomposite samples as compared to the rubber sample could be clearly observed. Furthermore, DCS showed higher Tg for nanocomposites at 24.4, 25.1, and 26.3 °C, respectively, compared to purified ENR-50 at −18.6 °C.