Hexaphenoxycyclotriphosphazene (HPCTP) and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) were used to flame retard N,N,N′,N′-tetraglycidyl-4,4′-diaminodiphenylmethane epoxy resins. The curing behaviors and glass transition temperature were investigated by differential scanning calorimetry. The limiting oxygen index (LOI), UL-94 vertical burning, and cone calorimetry tests were used to assess the flame retardancy of the cured epoxy resins. The increase in LOI value and UL-94 rating was strongly dependent on the phosphorus content. The reduction in peak of heat release rate and total heat release showed that the incorporation of flame retardants could improve the flame retardancy of epoxy resin. The higher smoke release and CO yield of the flame-retardant epoxy resins indicated that both DOPO and HPCTP showed a gas phase flame retardancy action. Thermogravimetric analysis of the flame-retardant epoxy resins indicated that the incorporation of the flame retardants reduced the initial decomposition temperature of epoxy resin.

Hexaphenoxycyclotriphosphazene (HPCTP) was synthesized by a nucleophilic substitution reaction between hexachlorocyclotriphosphazene and phenol. The chemical structure of HPCTP was then characterized by Fourier transform infrared spectroscopy as well as 1 H and 31 P nuclear magnetic resonance spectroscopy. The synthesized HPCTP was incorporated into the diglycidyl ether of bisphenol A to prepare epoxy resin (EP) composites using 4,4 0 -diamino diphenylmethane as curing agent. The thermal and flame-retardant properties of cured samples were investigated by differential scanning calorimetry, thermogravimetric analysis, UL-94 vertical burning test, and cone calorimetry. Evaluation of thermal properties demonstrated that the resulting composites achieved high thermal stability with high char yields. The UL-94 V-0 rating was easily achieved with the addition of HPCTP, and the heat release intensity simultaneously decreased. Results of scanning electron microscopy and energy-dispersive x-ray spectroscopy confirmed that HPCTP can enhance the thermal stability and flame retardancy of epoxy resin.

A novel phosphazene-based compound called hexaphenoxycyclotriphosphazene (HPCTP) was synthesized and characterized by Fourier transform infrared spectroscopy as well as proton and phosphorus nuclear magnetic resonance spectroscopies. Epoxy (EP) resin composites containing HPCTP and octapropylglycidylether polyhedral oligomeric silsesquioxane (OGPOSS) were prepared using 4,4 0 -diamino diphenylmethane as curing agent. Differential scanning calorimetry, thermogravimetric analysis, UL 94 vertical burning test, and cone calorimetry test were used to assess thermal stability and flame retardancy of the composites. Evaluation of thermal properties demonstrated that the resulting composites achieved less thermal stability compared with control EP resin but possessed high char yields at high temperatures. It indicated that both HPCTP and OGPOSS could induce the formation of intumescent char layer that retarded the degradation and combustion process of EP resin. The peak heat release rate of EP resin composite containing 15 wt% HPCTP was 61% less than that of control EP resin. Meanwhile, other flame-retardant parameters were also improved. Results of scanning electron microscopy and energy-dispersive x-ray spectroscopy of residual chars confirmed that both HPCTP and OGPOSS can enhance thermal stability and flame retardancy of EP resin.

A series of epoxy resin (EP) nanocomposites containing octaammonium polyhedral oligomeric silsesquioxane-modified montmorillonite (OAPOSS-MMT) was prepared via in situ polymerization using 4,4 0 -diaminodiphenyl sulfone as the curing agent. X-Ray diffraction and transmission electron microscopy were used to characterize the morphology of the resulting nanocomposites. Characterization results indicated the formation of intercalated and exfoliated structures. Thermogravimetric analysis (TGA) was performed to study the thermal properties of epoxy nanocomposites. Analysis results revealed that OAPOSS-MMT improved the thermal stability of EP matrix. TGA coupled with Fourier transform infrared spectrometry was used to detect pyrolytic gases. The gas species produced by epoxy nanocomposites were the same as those of control EP. A cone calorimeter was used to evaluate the flame retardancy of epoxy nanocomposites containing different concentrations of OAPOSS-MMT. Results showed that OAPOSS-MMT improved the flame retardancy of EP to some extent. The enhanced thermal oxidative stability was also confirmed by the data obtained through x-ray photoelectron spectroscopy.

Epoxy resin nanocomposites based on 3,3', 5,5' -4,4' tetramethylbiphenyl diglycidyl epoxy resins (TMBP) were prepared through in situ co-polymerization with 4, 4'-diaminodiphenylsulfone (DDS) in the presence of octapropylglycidylether silsesquioxane (OGPOSS). The thermal properties of the TMBP/OGPOSS nanocomposite were analyzed by DSC and TGA. The glass transition temperature (T g ) increased with increasing OGPOSS content. Additionally, the integrity of the epoxy networks was also demonstrated by thermal decomposition which occurred in one-step. The dielectric constant decreased with the increase of OGPOSS content. The morphology of TMBP/OGPOSS hybrids was characterized by Scanning Electron Microscopy (SEM).