Poly(vinyl alcohol)/melamine phosphate composites prepared through thermal processing: thermal stability and flame retardancy

摘要

Poly(vinyl alcohol)/melamine phosphate composites (PVA/MP) as a novel halogen-free, flame-retardant foam matrix were prepared through thermal processing, and then their thermal stability and flame retardancy were investigated by thermo-gravimetric analysis, micro-scale combustion calorimeter, cone calorimeter, vertical burning test, and limiting oxygen index (LOI) test. It was found that the thermal stability and combustion properties of the PVA/MP composites could be influenced by the addition of MP. Compared with the control PVA sample (B-PVA), in the PVA/MP (75/25) composites, the temperature at 5% mass loss (T 5%) decreased about 10℃, the residual chars at 600℃ increased by nearly 27%, the temperature at the maximum peak heat release rate (TP) shifted from 292℃ to 452℃, and the total heat released and the heat release capacity (HRC) decreased by 28% and 14%, respectively. Moreover, the PVA/MP composites could reach LOI value up to 35% and UL94 classification V-0, showing good flame retardancy. At the same time, both Fourier transform infrared and X-ray photoelectron spectroscopy spectra of the residual chars from the PVA/MP composites demonstrated that the catalytic effect of MP on the dehydration and decarboxylation reactions of PVA, and the chemical reactivity of MP during the chars-forming reactions could be used to account for the changed thermal stability and flame retardancy of the PVA/MP composites.