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A novel flame retardant heax-[N,N′,N″-tris-(2-amino-ethyl)-[1,3,5] triazine-2,4,6-triamine] cyclotriphosphazene (HTTCP) containing phosphazene and triazine groups was synthesized and characterized by Fourier transform infrared spectroscopy (FTIR), solid-state 1H and 13C nuclear magnetic resonance (NMR) spectroscopy. HTTCP was applied to PLA matrix. The results of thermal gravimetric analysis (TGA), the limited oxygen index (LOI), and cone calorimeter test indicated that the HTTCP enhanced the thermal stability and flame retardant properties of PLA. When the mass fraction of HTTCP was 25 wt %, the PLA composite acquired a LOI value of 25.2% and the lower pk-HRR at 290 kW/m2. The excellent flame retardancy of HTTCP was attributed to the group synergistic effect between phosphazene and triazine groups. However, when combined HTTCP with APP (the total amount remaining 25 wt %, the ratio of HTTP to APP are 1:1 and 1:2), high values of LOI (over 40%) and UL94 V-0 rating without dripping reached simultaneously. Meanwhile, the heat release rate, total heat release and mass loss rate were all decreased dramatically. Scanning electron microscopy (SEM) demonstrated that HTTCP/APP system benefited to the formation of more intumescent, dense, compact char layer on the materials surface which could effectively prevent the underlying material from degradation during burning. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 134, 44660.

A series of flame-retardant rigid polyurethane foams (RPUFs) containing nonreactive phosphonate (5-ethyl-2-methyl-1,3,2-dioxaphosphorinan-5-yl) methyl dimethyl phosphonate P-oxide (EMD) and expandable graphite (EG) were prepared by water blown. The flame-retardant properties and mechanism of EMD/EG on RPUFs were systematically investigated. The EMD/EG system effectively increased the limiting oxygen index (LOI) value and decreased the values of total heat release (THR), av-effective heat of combustion (EHC), pk-heat release rate (HRR), total smoke release (TSR) of RPUFs. The impact values of LOI, THR, and av-EHC resulted by EMD/EG system are nearly equal to the sum of the impact values by EMD and EG individually in RPUFs, which implies the addition flame-retardant effect from EMD and EG. EMD alone exerted excellent gas-phase flame-retardant effect by releasing PO fragments with quenching effect. The firm residue produced by EMD combined well with the loose and worm-like expanded graphite from EG further to form compact and expanded char layer, which brought excellent barrier effect and filtration effect to matrix. That's why pk-HRR and TSR values of RPUF reduced. Depending on the simultaneous actions of EMD/EG system in gas phase and condensed phase during combustion, the flame-retardant effects from nonreactive phosphonate and EG on RPUFs were added together. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45960.

A phosphorus/silicon flame retardant, MVC-DOPO, was synthesized from 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and 2,4,6,8-tetra-methyl-2,4,6,8-tetra-vinyl-cyclo-tetrasiloxane (MVC) via addition reaction. Its flame-retardant effect on polycarbonate (PC) was investigated. The phosphorus/silicon flame retardant increased the limited oxygen index and UL-94 rating and reduced the heat release rate and total heat release of DOPO-MVC/PC composites during combustion, indicating the excellent flame-retardant effect of MVC-DOPO on PC. MVC-DOPO inhibited the burning intensity of PC material in the gaseous phase and promoted the formation of a more viscous residue in the condensed phase. Through releasing phosphorus-containing pieces and phenoxy radicals from the phosphaphenanthrene group, MVC-DOPO quenched the combustion chain reaction in the gaseous phase; through promoting formation of a more viscous residue and a dense char layer from the main actions of the cyclotetrasiloxane group, MVC-DOPO reduced fuel release and generated a barrier effect in the condensed phase. Hence, MVC-DOPO effectively exerted a flame-retardant effect on PC material in both the gaseous and condensed phases during combustion. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45815.

A functional surface-modification agent was synthesized via a reaction between hexachlorocyclotriphosphazene and γ-aminopropyl triethoxysilane. Ammonium polyphosphate (APP) was modified with this agent and then incorporated into a rigid polyurethane foam (RPUF). Fourier transform infrared spectroscopy, 1H-NMR, and X-ray photoelectron spectroscopy were used to characterize the modified ammonium polyphosphate (M-APP). The results show that the dispersibility was improved and the particle size decreased after the modification. The limiting oxygen index and cone calorimetry test results show that M-APP enhanced the flame-retardant properties of RPUF. The peak heat-release rate of polyurethane (PU)/20% M-APP decreased by 51.18% compared with that of PU–APP. The scanning electron microscopy results illustrate that M-APP facilitated the formation of intumescent and compact char. The excellent flame-retardant performance of M-APP resulted from the flame-inhibition and barrier effects, which were attributed to the phosphazene group and the intumescent char, respectively. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45369.

The synergistic flame-retardant (FR) effect of 1,1′-bis(4-hydroxyphenyl)-metheylene-bis(9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide-2-hydroxypropan-1-yl) (DPOH) and aluminum diethylphosphinate (AlPi) composites on glass fiber reinforced polyamide 66 (PA) was investigated by limiting oxygen index (LOI) tests, vertical burning (UL94) tests, and cone calorimeter tests. DPOH/AlPi system with 1:1 mass ratio increased UL94 ratings, suppressed heat release rate and increased residue yields of PA composites, and DPOH/AlPi system also imposed high LOI values and lower total heat release values to PA composites. All these results verified excellent synergistic FR effect between DPOH and AlPi. The reason of DPOH/AlPi system with higher flame-retardant efficiency was caused by the quenching effect as good as that of DPOH and also by the higher charring effect than that of AlPi. DPOH/AlPi system possesses good flame retardancy in gas phase and also the strengthened FR effect in condensed phase compared with DPOH and AlPi alone, which led to excellent synergistic FR effect between the two components DPOH and AlPi. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45126.

A hyperbranched derivative of triazine group (EA) was synthesized by elimination reaction between ethylenediamine and cyanuric chloride. The different-mass-ratio EA and ammonium polyphosphate (APP) were mixed and blended with polypropylene (PP) in a constant amount (25%) to prepare a series of EA/APP/PP composites. The component ratio effect of EA/APP on the flame-retardant property of the EA/APP/PP composites was investigated using the limiting oxygen index (LOI), vertical burning (UL-94), and cone calorimetry tests. Results indicated that the EA/APP/PP (7.50/17.50/75.00) composite with the appropriate EA/APP mass ratio had the highest LOI, UL94 V-0 rating, lowest heat release rate, and highest residue yield. These results implied that the appropriate EA/APP mass ratio formed a better intumescent flame-retardant system and adequately exerted their synergistic effects. Furthermore, average effective combustion heat values revealed that EA/APP flame retardant possessed the gaseous-phase flame-retardant effect on PP. Residues of the EA/APP/PP composites were also investigated by scanning electron microscopy, Fourier-transform infrared, and X-ray photoelectron spectroscopy. Results demonstrated that the appropriate EA/APP mass ratio can fully interact and lock more chemical constituents containing carbon and nitrogen in the residue, thereby resulting in the formation of a dense, compact, and intumescent char layer. This char layer exerted a condensed-phase flame-retardant effect on EA/APP/PP composites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41006.

Three types of melamine cyanurate (MCA) with micrometer-size sphere-like, micrometer-scale rod-like, and nanometer-scale flake-like morphologies were synthesized by changing the chemical circumstances of the reactions. The microcosmic morphologies of MCA were characterized via scanning electron microscopy and X-ray diffraction. After the MCAs with different morphologies were incorporated into polyamide 6 (PA6), the flame-retardant properties of the MCA/PA6 composites were investigated using the limited oxygen index (LOI), UL94, and cone calorimeter tests. The MCA/PA6 composites with nanometer-scale flake-like MCA obtained an LOI value of 29.5% and a UL94 V-0 rating, which were higher than those with micrometer-size sphere-like and rod-like MCAs. However, the different morphologies did not affect the heat release rate, total smoke release, average carbon monoxide yield, and average carbon dioxide yield based on the cone calorimeter. The flame-retardant mechanism of MCAs with different morphologies was investigated via thermal gravimetric analysis (TGA) and TGA-Fourier transform infrared spectra. The results show that the different morphologies of MCA resulted in different dispersed evenness of MCA. Further, the nanometer-scale flake-like morphology of MCA brought more interactions of hydrogen bond between MCA and PA6, which resulted in the delay of MCA decomposition and the enhancement of MCA flame-retardant effect. The nanometer-scale flake-like MCA had a better performance compared with the other samples because of the delaying and even release of flame-retardant effect by the decomposition of evenly dispersed MCA. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40558.

A flame retardant tri-(phosphaphenanthrene-(hydroxyl-methylene)-phenoxyl)-1, 3, 5-triazine (Trif-DOPO) and its control samples are incorporated into diglycidyl ether of bisphenol-A (DGEBA) and 4, 4′-diamino-diphenyl sulfone (DDS) to prepare flame retardant thermosets, respectively. According to the results of limited oxygen index (LOI), UL94 vertical burning test and cone calorimeter test, the Trif-DOPO/DGEBA/DDS thermoset with 1.2 wt % phosphorus possesses the LOI value of 36% and UL94 V-0 flammability rating, and Trif-DOPO can decrease the peak of heat release rate (pk-HRR) and reduce the total heat release (THR) of thermosets. All these prove better flame retardant performance of Trif-DOPO than that of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide(DOPO). The residue photos of thermosets after cone calorimetry test disclose that Trif-DOPO can promote the formation of thick and tough melting char layer for combined action of the flame retardant groups of Trif-DOPO. The results from thermo gravimetric analysis (TGA) and pyrolysis-gas chromatography-mass spectrometry(Py-GC/MS) show that the groups in Trif-DOPO can be decomposed and produce PO2 fragments, phosphaphenanthrene and phenoxy fragments, which can jointly quench the free radical chain reaction during combustion. Therefore, the excellent flame retardancy of Trif-DOPO is attributed to its flame retardant group-synergic-effect. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39709.