PGS@B–N: an efficient flame retardant to improve simultaneously the interfacial interaction and the flame retardancy of EVA

A novel organic–inorganic hybrid flame retardant of PGS@B–N prepared via the decoration of palygorskite (PGS) by boric acid (B) and dodecylamine (N) was incorporated with an ethylene-vinyl acetate copolymer (EVA) to improve its flame retardance. The structure and morphology of PGS@B–N were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The flame retardance and burning behavior of the EVA/PGS@B–N/EG (expandable graphite) composite were studied through thermogravimetric analysis (TGA), limiting oxygen index (LOI), vertical burning test (UL-94), and cone calorimeter test (CCT). The results of the UL-94 and LOI tests indicated that the flame retardance of EVA/PGS@B–N/EG was better than that of EVA/PGS/EG flame-retardant composites. The data obtained from the CCT illustrated that the peak heat release rate (PHRR) of EVA with the addition of 30 wt% PGS@B–N/EG was reduced by about 25% compared to EVA with equivalent PGS/EG. The heat release rate (HRR), total release rate (THR), smoke production rate (SPR), and mass loss rate (MLR) of the composite were improved significantly. The TGA data showed that the thermal stability of EVA/PGS@B–N/EG was also well improved at high temperatures. SEM images of cryogenically fractured surfaces illustrated that EVA/PGS@B–N/EG had better interfacial interaction compared with that of EVA/PGS/EG.