Construction of Carbon Microspheres-Based Silane Melamine Phosphate Hybrids for Flame Retardant Poly(ethylene Terephthalate)

To improve the flame retardancy and inhibit the smoke of poly(ethylene terephthalate) (PET), carbon microspheres (CMSs)-based melamine phosphate (MP) hybrids (MP-CMSs) were constructed in situ with the introduction of CMSs into the hydrothermal reaction system of MP. The integrated MP-CMSs were modified by 3-Aminopropyltriethoxysilane (APTS) to obtain the silane MP-CMSs (SiMP-CMSs) to strengthen the interface binding between the MP-CMSs and PET matrix. The results showed that the SiMP layer was loaded on the CMSs surface. The addition of only 3% SiMP-CMSs increased the limiting oxygen index (LOI) value of the PET from 21% ± 0.1% to 27.7% ± 0.3%, reaching a V-0 burning rate. The SiMP-CMSs not only reduced heat damage, but also inhibited the smoke release during PET combustion, whereupon the peak heat release rate (pk-HRR) reduced from 513.2 to 221.7 kW/m², and the smoke parameters (SP) decreased from 229830.2 to 81892.3 kW/kg. The fire performance index (FPI) rose from 0.07 m²s/kW to 0.17 m²s/kW, demonstrating the lower fire risk. The proportion of the flame-retardant mode in the physical barrier, flame inhibition, and char effects were recorded as 44.53%, 19.04%, and 9.04%, respectively.