Magnesium hydroxide nanoparticles grafted by DOPO and its flame retardancy in ethylene-vinyl acetate copolymers

Magnesium hydroxide (MH) nanoparticles have been considered as an excellent nonhalogen flame-retardant. However, the drawbacks of easy aggregation and relatively low flame retardancy limit their applications in polymer materials. In this research, MH nanoparticles were successfully grafted by 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) through the bridge of vinyl silane coupling agents (WD70). The grafted MH nanoparticles (MH-WD70-DOPO) were characterized by Fourier transform infrared spectra, 31 P nuclear magnetic resonance spectra, thermogravimetric analysis, transmission electron microscopy, and X-ray photoelectron spectroscopy spectra. MH-WD70-DOPO nanoparticles were incorporated into ethylene-vinyl acetate copolymer (EVA) matrix by melt blending method. The results indicated that MH-WD70-DOPO nanoparticles were much homogenously dispersed in EVA matrix than unmodified MH particles. EVA/MH-WD70-DOPO nanocomposites with 51.32 wt% loading showed higher flame retardancy, better mechanical and processing properties compared with EVA/MH-WD70 sample. These findings could provide a novel method to enhance the flame-retardant efficiency of inorganic hydroxide flame retardants, while keeping good mechanical and processing properties of polymer materials.