Synergistic effects of rare earth oxides on intumescent flame retardancy of Nylon 1010/ethylene-vinyl-acetate rubber thermoplastic elastomers

Abstract

Synergistic effects of two kinds of rare earth oxides (REOs), samarium oxide (Sm2O3) or lanthanum oxide (La2O3) on the intumescent flame retardancy of Nylon 1010/ethylene-vinyl-acetate rubber (EVM) thermoplastic elastomers (TPE) were studied systemically. The limiting oxygen index (LOI) of intumescence flame retardant (IFR)-TPE increased from 30.5 to 32.5 and 34 when 0.5 wt% of IFR was substituted by La2O3 and Sm2O3, respectively. Sm2O3 showed higher synergistic effectivity than La2O3. Cone calorimetry tests confirmed that REOs enhanced flame retardancy of IFR-TPE. Smoke and CO production rate slightly decreased after incorporation of REOs as compared to IFR-TPEs without REOs, indicating relatively reduced combustion hazard. By thermalgravimetric analyses (TGA), it was found that the presence of REOs promoted the esterification and carbonization process in low-temperature range while enhanced the thermal stability of IFR and IFR-TPEs in high-temperature range. X-ray diffraction (XRD) proved that the interaction of Sm2O3 with IFR resulted in the formation of samarium phosphate (SmPO4) with high-thermal stability. Rheological measurements showed that the complex viscosities of the IFR-TPEs increased with the addition of REOs, which might aid in suppressing melt dripping. For mechanical properties, incorporation of REOs led to higher modulus, similar tensile strength but lower elongation at break as compared to IFR-TPEs without REOs.