Flame Retardation of Ethylene-Vinyl Acetate Copolymer Using Nano Magnesium Hydroxide and Nano Hydrotalcite

Abstract

The flame-retardant effects of nano magnesium hydroxide (NMH) and nano hydrotalcite (NLDH) in ethylene-vinyl acetate copolymer (EVA) are studied by using the limited oxygen index (LOI), UL-94 test, cone calorimeter test (CCT), thermogravimetric analysis (TGA), laser Raman spectroscopy (LRS), and scanning electron microscopy (SEM). The LOI values of both EVA-NMH and EVA-NLDH blends increase gradually on increasing the NMH and NLDH content, respectively. The LOI value of EVA-NLDH is higher than that of EVA-NMH at the same additive level. In the UL-94 test, for EVA-NMH blend, there are no ratings at all even if the loading of NMH is up to 150 phr (60%). However, the EVA-NLDH blend at the additive level of 120 phr reaches the V-1 rating, and the blend with 150 phr NLDH reaches the V-0 rating. The heat release rate (HRR) data of EVA-NLDH blends are much lower than that of the EVA-NMH blends. From the LOI, UL-94, and HRR data, it can be seen that the flame-retardant effect of NLDH is better than that of NMH. The TG and differential TG (DTG) data show that additives NMH and NLDH increase the thermal stability of the EVA copolymer. The LRS results confirm that the charred layers formed during the burning of the nano EVA blends have a graphite-like structure. The mechanical properties of EVA-NMH blends are better than those of EVA-NLDH blends.