Flame retardancy of organic-anion-intercalated layered double hydroxides in ethylene vinyl acetate copolymer

摘要

To gain high efficiency flame retardant, the twin organic anions intercalated layered double hydroxides (PD(x)CA(y)-LDH) were designed and prepared via calcination-reconstruction, where the organic anions were pentaerythritol diphosphate (PD) and cyanuric acid (CA). The morphology, chemical composition and structure of the PD(x)CA(y)-LDH materials were characterized, revealed that the PD(x)CA(y)-LDH materials were successfully intercalated by the PD and CA anions in single or combining form. The incorporation of the PD(x)CA(y)-LDH with ethylene vinyl acetate copolymer (EVA) not only could significantly improve the thermal stability of EVA matrix but also promote the formation of char layer during combustion, owing to the combined advantages of CA, PD and LDH. It was found that the flame retardancy of the PD(x)CA(y)-LDH depended on the mass ratio of PD to CA anions, where the PD(7)CA(3)-LDH with a 7:3 mass ratio of PD/CA had the best flame retardancy due to the presence of an excellent char layer. The EVA/PD(7)CA(3)-LDH composite achieved a LOI value of 28.0% and a UL 94 V-0 rating compared with the EVA/LDH composite with 19.5% and a HB rating, and the peak heat release rate (PHRR) and total heat release (THR) decreased to 340.2 kW.m(-2) and 132.7 MJ.m(-2), respectively. These improvements could be attributed to the catalyzing carbonization of the PD and CA to EVA matrix to form more protective char layers.