The effect of carbon nanotubes/NiFe2O4 on the thermal stability, combustion behavior and mechanical properties of unsaturated polyester resin

Multi-walled carbon nanotubes (MWCNTs) decorated with NiFe2O4 (MWCNT@NiFe2O4) were synthesized by a chemical co-deposition method at ambient temperature, followed by a post-annealing treatment. The structure and morphology of MWCNT@NiFe2O4 nanohybrids were characterized by X-ray diffraction, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and transmission electron microscopy. Then the MWCNT@NiFe2O4 nanohybrids were incorporated into unsaturated polyester resin (UPR) to obtain its composites via polymerization. From thermogravimetric analysis and thermogravimetric analysis-infrared spectrometry results, the char residue yield increased and the combustible organic volatiles and toxic gases were effectively suppressed during the thermal decomposition, in contrast to the case of pure UPR. Meanwhile, the addition of C@NF-3 endowed excellent fire resistance to the UPR matrix. The protective nanotube network structure of the MWCNTs and the catalytic charring function of the NiFe2O4 nanoparticles in the MWCNT@NiFe2O4 nanohybrids were responsible for the enhanced fire resistance, which was evidenced by the dramatically reduced peak heat release rate and total heat release values obtained from microscale combustion calorimeter tests. In addition, the MWCNT@NiFe2O4 nanohybrids dispersed well in the UPR matrix to significantly improve the mechanical properties of UPR composites. Compared to pure UPR matrix, the storage modulus (E′) and glass-transition temperature (Tg) of UPR composites by the addition of 2 wt% C@NF-3 nanohybrid were significantly increased by 69.77% and 21 °C, respectively. The increases in E′ and Tg values could be ascribed to the well-dispersed CNTs and the formation of a nanotube network.