With the aim of obtaining halogen-free polybenzoxazazines with reduced flammability, phosphazene-containing benzoxazines (PhBZ) were synthesized in a two-stage method. In the first stage of the reaction of hexachlorocycotriphosphazene with bisphenol A at molar ratios of 1:12, 1:16, and 1:24, respectively, mixtures of bisphenol and hydroxyaryloxycyclotriphosphazenes were obtained, which mainly contained P₃N₃[OC₆H₄C(CH₃)₃C₆H₄OH]₆. In the second stage, when these mixtures interacted with aniline and an excess of paraformaldehyde in toluene at 80–90 °C, PhBZ containing 20–50% of the phosphazene component with M_w 1200–5800 were formed. According to ¹H and ¹³C NMR spectroscopy, PhBZ contain a small amount of oligomeric compounds with Mannich aminomethylene bridges. With an increase of the content of the phosphazene component, the curing temperature of PhBZ decreases from 242 °C to 215 °C. Cured PhBZ samples with a phosphorus content of more than 1.5% have increased flammability resistance according to UL-94.

GRAPHICAL ABSTRACT ABSTRACT Hydroxyaryloxycyclophosphazenes containing 2–4 OH groups have been synthesized by the substitution of chlorine atoms of hexachlorocyclotriphosphazene via the reaction with sodium phenolates of halogenophenols followed by the interaction with sodium monophenolate of diphenylolpropane. Oligoepoxyphosphazenes (OEPs) with molecular masses up to 2000 and the contents of epoxy groups, phosphorus, and halogens atoms about 5–8, 5–8, and 5–11%, respectively, have been obtained via the interaction of the aforementioned phosphazenes with epichlorohydrin. The curing of the OEPs with amines or acid anhydrides gives rise to the formation of self-extinguishing composites. The incorporation of the OEPs (5–75 wt %) into commercial epoxy resins followed by their curing, results in the formation of composites with excellent nonflammability or capability of self-quenching, and good dielectric, heat resistant and mechanical properties. It has been established that mixtures of common epoxides with different amounts of the OEPs can be synthesized by a “single-reactor” method.

Phosphazene-containing epoxy oligomers (PEO) were synthesized by the interaction of hexachlorocyclotriphosphazene (HCP), phenol, and bisphenol A in a medium of excess of epichlorohydrin using potassium carbonate and hydroxide as HCl acceptors with the aim of obtaining a product with lower viscosity and higher phosphazene content. PEOs are mixtures of epoxycyclophosphazene (ECP) and a conventional organic epoxy resin based on bisphenol A in an amount controlled by the ratio of the initial mono- and diphenol. According to ³¹P NMR spectroscopy, pentasubstituted aryloxycyclotrophosphazene compounds predominate in the ECP composition. The relative content in the ECP radicals of mono- and diphenol was determined by the MALDI-TOF mass spectrometry method. The organic epoxy fraction, according to gas chromatograpy-mass spectrometry (GC-MS), contains 50–70 wt % diglycidyl ether of bisphenol A. PEO resins obtained in the present work have reduced viscosity when compared to other known phosphazene-containging epoxy resins while phosphazene content is still about 50 wt %. Resins with an epoxy number within 12–17 wt %, are cured by conventional curing agents to form compositions with flame-retardant properties, while other characteristics of these compositions are at the level of conventional epoxy materials.

Oligomers of hexakis(4-allyl-2-methoxyphenoxy)cyclotriphosphazene have been synthesized and their molecular structure studied by X-ray and NMR analysis. The nonplanar character of a phosphazene cycle is established, and the bond lengths P-N and valence angles N-P-N are shown to change in narrow ranges (1.5771–1.5894 Å and 117.80°–118.37°, respectively). During epoxidation of hexakis(4-allyl-2-methoxyphenoxy)cyclotriphosphazene by m-chloroperbenzoic acid or peracetic acid, in addition to hexaepoxy derivatives, the corresponding dimer is formed due to partial intermolecular interaction of epoxy groups.

By partial substitution of the chlorine atoms in hexachlorocyclotriphosphazene for halophenols and subsequent reaction of the resulting halogenated phenoxy phosphazene and...

To reveal the effect of chlorine substituents in the ring of aromatic amine on the synthesis process of benzoxazine monomer and on its polymerization ability, as well as to develop a fire-resistant material, a previously unreported benzoxazine monomer based on 3,3′-dichloro-4,4′-diaminodiphenylmethane was obtained in toluene and mixture toluene/isopropanol. The resulting benzoxazine monomers were thermally cured for 2 h at 180 °C, 4 h at 200 °C, 2 h at 220 °C. A comparison between the rheological, thermal and fire-resistant properties of the benzoxazines based on 3,3′-dichloro-4,4′-diaminodiphenylmethane and, for reference, 4,4′-diaminodimethylmethane was made. The effect of the reaction medium on the structure of the oligomeric fraction and the overall yield of the main product were studied and the toluene/ethanol mixture was found to provide the best conditions; however, in contrast to most known diamine-based benzoxazines, synthesis in the pure toluene is also possible. The synthesized monomers can be used as thermo- and fire-resistant binders for polymer composite materials, as well as hardeners for epoxy resins. Chlorine-containing polybenzoxazines require more severe conditions for polymerization but have better fire resistance.