Facile preparation of an efficient flame retardant and its application in ethylene vinyl acetate

Abstract

A novel phosphorus-nitrogen-clay flame retardant (PD-LDH@MF) was prepared via intercalating pentaerythritol diphosphate (PEDP) into MgAl hydrotalcite (LDH) interlayers and then capping melamine resin (MF) on the surface using in-situ copolymerization. The structure, morphology thermal stability and flame retardancy of the PD-LDH@MF material were characterized by various analytic methods. The results revealed that PEDP anions were intercalated successfully into the interlayers of the LDH, and the PEDP-intercalated LDH (PD-LDH) was also encapsulated in MF. The PD-LDH@MF exhibited better compatibility with EVA matrix than the EVA/PD-LDH due to higher hydrophobicity by capping MF on the surface of the PD-LDH particles. The incorporation of the PD-LDH@MF into EVA could improve not only the thermal stability but also the thermal oxidative resistance for EVA matrix. The limiting oxygen index (LOI) of the EVA/PD-LDH@MF composite with 15 wt% loading was about 27.5%, while the composite attained V-0 rating. The observable improvement in flame retardancy of the EVA/PD-LDH@MF composite was because intercalated PEDP could promote to remain more N and C elements, and P species in PEDP participated into the connecting reaction to form the more continuous and more compact char layer on the char surface, thus hindering heat diffusion and oxygen transmission effectively.