A novel phosphorus-containing copolyester/montmorillonite nanocomposites with improved flame retardancy

A novel phosphorus-containing flame-retardant copolyester/montmorillonite nanocomposite (PET-co-HPPPA/O-MMT) was synthesized by the in situ intercalation polycondensation of terephthalic acid, ethylene glycol, and 2-carboxyethyl(phenylphosphinic) acid (HPPPA) with montmorillonite (O-MMT). The morphology was characterized by wide-angle X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The effects of organoclay on the thermal properties and melting behaviors of the nanocomposites were investigated by thermogravimetric analysis and differential scanning calorimetry. The flammability of the nanocomposites was characterized by the limiting oxygen index test and the UL-94 vertical test. The results showed that a small amount of organoclay was able to improve the thermal stabilities and the flame retardancy of PET-co-HPPPA copolyesters, and however there was no significant increase in the melting points of nanocomposites when the content of diethylene glycol was controlled as a certain value. The overall crystallization rate of the nanocomposites is greater than that of neat copolyester. The nanocomposites have better flame retardancy than PET-co-HPPPA.