Synthesis and Investigation of Silatrane Complex as a New Flame Retardant in Poly(ethylene terephthalate)/Montmorillonite Nanocomposites

The purpose of this research was to improve the flame retardant properties of PET using silatrane complex synthesized from silica through one pot process. In addition, the synergistic effect of flame retardant agents between silatrane complex and montmorillonite (MMT) at various concentrations was investigated. The characteristics of the obtained silatrane complex were studied by FT-IR, Si-29-NMR, SEM, and TGA. Different ratios of PET/MMT/silatrane complex nanocomposites were prepared by melt bending process using a twin screw extruder and compressed into various shapes by a compression molding machine, respectively. The effects of single flame retardant and co-flame retardant agents on morphology, flame retardant properties, and mechanical properties of PET nanocomposites were evaluated. LOT values and UL-94V rating were used as parameters for determine flame retardant properties of PET nanocomposites. The results showed that LOI values of PET/MMT/silatrane complex nanocomposites were evidently greater than that of neat PET and increased with increasing the silatrane complex concentration. The LOT value of PET/2%MMT/7%silatrane nanocomposites was highest and increased up to 60.75%, compared with that of neat PET. While neat PET was classified into V-2 rating since it showed sustainable burning and melt-dripping behavior during burning process, PET/MMT/silatrane complex nanocomposites did not show such behavior and thus could be designated as V-0 rating. The enhancing of flame retardant properties for PET nanocomposites was attributed from the synergistic effect of MMT and silatrane complex. When they undergo decomposition through an endothermic reaction, MMT and silatrane complex can form homogeneous carbonaceous char and highly silicate-crosslink structure, respectively, in the condensed phase while burning. This multilayer can significantly improve the flame retardant properties of PET/MMT/silatrane complex nanocomposites. The mechanical properties of PET/2%wt MMT nanocomposites were better than those of neat PET but further increasing the amount of MMT and silatrane complex, phase separation and agglomeration occurred leading to the reduction in the mechanical properties.