One-Pot Synthesis of Cyclomatrix-Type Polyphosphazene Microspheres and Their High Thermal Stability

Highly cross-linked inorganic and organic hybrid cyclomatrix-polyphosphazenes microspheres (C-PPZs) have been successfully synthesized by a one-pot polymerization technique between hexachlorocyclotriphosphazene and p-phenylenediamine in the presence of triethylamine (TEA), and they were used for enhancing the flame retardancy of epoxy resins (EPs). A thermoset EP was prepared by incorporating different percentages (2, 5, and 10%) of C-PPZs into diglycidyl ether of bisphenol A (DGEBA). The results reveal that the size and morphology of the microspheres can be tuned by varying the synthesis temperature. The average size of C-CPPZs gradually increased from 3.1, 4.9, to 7.8 mu m as the temperature was increased from 100, 120, to 200 degrees C, respectively. The thermogravimetric analysis showed that the C-CPPZ microspheres have good thermal stability up to 900 degrees C with about similar to 10 wt % mass loss for C-CPPZs formed at 200 degrees C compared to similar to 30 wt % mass loss for those obtained at 100 and 120 degrees C. The 10% loss at 900 degrees C is much lower than the previous research concerning the thermal stability of cyclophosphazene, in which more weight losses were observed at lower temperatures. The resulting C-CPPZ microspheres were characterized by spectroscopic and imaging techniques including Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, elemental mapping, and X-ray photoelectron spectroscopy.

Automated summary

Highly cross-linked inorganic and organic hybrid cyclomatrix-polyphosphazenes microspheres (C-PPZs) were synthesized using a one-pot polymerization technique. These microspheres were incorporated into epoxy resins (EPs) to enhance their flame retardancy. The size and morphology of the microspheres could be controlled by varying the synthesis temperature. The C-CPPZ microspheres exhibited good thermal stability up to 900 degrees C.