Effects of layered lanthanum phenylphosphonate on flame retardancy of glass-fiber reinforced poly(ethylene terephthalate) nanocomposites

•MRP and LaPP had effective flame synergism in PET/GF composites.•Interaction between phenyl ring and PET promoted homogenous dispersion of LaPP.•Acid sites formed in decomposition of phenyl ring catalyzed carbonization.•LaPP was capable of initiating the compact and homogeneous char.

Effects of layered metal phosphonate lanthanum phenylphosphonate (LaPP) on the thermal stability, flame retardancy and mechanical properties of glass-fiber reinforced poly(ethylene terephthalate) (PET/GF)/microencapsulated red phosphorus (MRP) systems were investigated. The result of transmission electron microscopy (TEM) measurements indicated that LaPP particles were homogenously dispersed in PET matrix and no obvious signs of LaPP aggregation were detected. Thermogravimetric (TG) analysis showed that incorporating LaPP into PET/GF-MRP enhanced the thermal stability and increased the char residue compared to the sample without LaPP. In the existence of LaPP, the PET/GF-MRP composites could pass the UL 94 V-0 rating test, and the limited oxygen index (LOI) could be enhanced. The structures of char residues observed by scanning electron microscopy (SEM) demonstrated that LaPP could promote to form the homogenous and compact char layer. What is more, the presence of LaPP improved the tensile strength and storage moduli of PET/GF-MRP composites.

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