Novel flame retardant zirconia-reinforced nanocomposites containing chlorinated poly(amide-imide): synthesis and morphology probe

In the present investigation, a thermally stable poly(amide-imide) (PAI) was synthesised from the polymerisation reaction of 4,4′-methylenebis(3-chloro-2,6-diethyl trimellitimidobenzene) as a chlorinated diacid with 4,4′-methylenebis(3-chloro-2,6-diethylaniline) using molten tetra-n-butylammonium bromide and triphenyl phosphite as a condensing agent and green media. This methodology offers enhancements for the synthesis of polymers with regard to yield of products, simplicity in operation, and green aspects by avoiding volatile solvents. From the chemical point of view, the chloride and ethylene groups impart to the polymer's chain increased solubility of obtained polymer in organic solvent. Then, the surface of zirconia nanoparticles (ZrO2-NPs) was modified with 3-aminopropyltriethoxylsilane as a coupling agent. The obtained polymer and inorganic metal oxide NPs were used to prepare PAI/ZrO2 nanocomposites through ultrasonic irradiation. The formation of PAI was confirmed by 1H-NMR, FT-IR spectroscopy, and elemental analysis. The obtained polymer was synthesised with good yield (90%) and moderate inherent viscosity (0.48 dL/g). The resulting NP filled composites were also characterised by FT-IR, XRD, FE-SEM, TEM and TGA. The TEM and FE-SEM results indicated a high dispersion level of the nanoscale inorganic particles in the polymer matrix. In this article, ZrO2-NPs are employed to improve flame retardancy of nanocomposites. TGA thermographs confirmed that the heat stability of the prepared NP-reinforced composites was improved in the presence of ZrO2 nanocrystals.