For structural composites used in vehicles and aircraft, flame retardant chemistries which enhance char formation and reduce heat release are preferred. Phosphorus-based and phosphorus–nitrogen flame retardants for epoxies have been well studied to date, but phosphorus hydrazides have not been studied for their flame-retardant potential in epoxy. These hydrazides offer some novel structures and they can potentially offer a combination of vapor and condensed phase flame retardant action. A series of eight compounds were systematically investigated in this study as reactive flame retardants in a bisphenol F epoxy/aliphatic amine resin system at a level of 2.5 wt% phosphorus. Results suggest that the phosphorus hydrazides react with the epoxy during thermal decomposition, and they also release nitrogen during flaming combustion of the epoxy matrix. The observed reactions resulted in increased char yields and reduced total heat release, while simultaneously lowering heat of combustion and total smoke release.
MouritzAPGibsonAG (eds). Fire properties of polymer composite materials. Dordrecht: Springer, 2006.
3.
ElmughrabiAERobinsonMGibsonAG.Effect of stress on the fire reaction properties of polymer composite laminates. Polym Degrad Stab2008; 93: 1877–1883.
4.
GibsonAGBrowneTNAFeihS, et al. Modeling composite high temperature behavior and fire response under load. J Composit Mater2012; 46: 2005–2022.
5.
CorreiaJRBaiYKellerT. A review of fire behavior of pultruded GFRP structural profiles for civil engineering applications. Composit Struct2015; 127: 267–287.
6.
WeilEDLevchikS. A review of current flame retardant systems for epoxy resins. J Fire Sci2004; 22: 25–40.
7.
LevchikSVWeilED. Thermal decomposition, combustion and flame—retardancy of epoxy resins—a review of the recent literature. Polym Int2004; 53: 1901–1929.
8.
LevchikSPiotrowskiAWeilE, et al. New developments in flame retardancy of epoxy resins. Polym Degrad Stab2005; 88: 57–62.
9.
WuTPiotrowskiAMYaoQ, et al. Curing of epoxy resin with poly(m-phenylene methylphosphonate). J App Polym Sci2006; 101: 4011–4022.
WilkieCAMorganAB. Fire retardancy of polymeric materials. 2nd ed.Boca Raton, FL: Taylor and Francis, 2009.
14.
KandolaBKMylerPHorrocksAR, et al. Empirical and numerical approach for optimization of fire and mechanical performance in fire-retardant glass-reinforced epoxy composites. Fire Saf J2008; 43: 11–23.
15.
KandolaBKAkondaMHHorrocksAR. Use of high-performance fibres and intumescents as char promoters in glass-reinforced polyester composites. Polym Degrad Stab2005; 88: 123–129.
16.
KandolaBKPornwannachaiW. Enhancement of passive fire protection ability of inorganic fire retardants in vinyl ester resin using glass frit synergists. J Fire Sci2010; 28: 357–381.
17.
KandareEChukwudoleCKandolaBK. The use of fire-retardant intumescent mats for fire and heat protection of glass fibre-reinforced polyester composites: thermal barrier properties. Fire Mater2010; 34: 21–38.
18.
KandareEChukwunonsoAKKandolaBK. The effect of fire-retardant additives and a surface insulative fabric on fire performance and mechanical property retention of polyester composites. Fire Mater2011; 35: 143–155.
19.
HertzbergT. Dangers relating to fires in carbon-fibre based composite material. Fire Mater2005; 29: 231–248.
20.
EiblS. Potential for the formation of respirable fibers in carbon fiber reinforced plastic materials after combustion. Fire Mater2017; 41: 808–816.
21.
MorganABGagliardiNAPriceWA, et al. Cone calorimeter testing of S2 glass reinforced polymer composites. Fire Mater2009; 33: 323–344.
22.
MorganABToubiaE. Cone calorimeter and room corner fire testing of balsa wood core/phenolic composite skin sandwich panels. J Fire Sci2014; 32: 328–345.
23.
ZilbermanJYoffeDPiotrowskiA, et al. Comparative study of reactive flame retardant based on 9:10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide. J Fire Sci2017; 35: 235–256.
24.
ZwierzakASulewskaA. Solid-liquid phase-transfer-catalysed phosphorylation of hydrazine: preparation of Dialkyl Phosphorohydarzidates and N, N’-Bis[dialkoxyphosphoryl]hydrazines. Synthesis1976; (12): 835–838.
25.
FelchtURegitzM. N-Phosphorylierung von Aminen, Glycin-Ethylester, Hydrazin, Hydrazonen und Natriumazid. Liebigs Ann Chem1977; 8: 1309–1320.
26.
HargerM. Phopshorochloridates from Phosphorohydrazides with ButOCl: stereospecificity, selectivity and phosphorylium ion intermediates.Tetrahedron Lett2001; 42: 6749–6752.
FrischMJPopleJABinkleyJS. Self-consistent molecular orbital methods 25. Supplementary functions for Gaussian basis sets. J Chem Phys1984; 80: 3265–3269.
31.
LeeCYangWParrRG. Development of the Colle-Salvetti correlation-energy formula into a functional of the electron density. Phys Rev B1988; 37: 785–789.
32.
PengCAyalaPYSchlegelHB, et al. Using redundant internal coordinates to optimize equilibrium geometries and transition states. J Comp Chem1996; 17: 49–56.
33.
PengCSchlegelHB. Combining synchronous transit and quasi-newton methods to find transition states Israel. J Chem1994; 33: 449–454.
34.
Bin SulaymanA. Novel amine-functionalized phosphoryl hydrazine flame retardants for epoxy resin systems. MSc Thesis, University of Dayton, Dayton, OH, 2018.
35.
BeninVCuiXMorganAB, et al. Synthesis and flammability testing of epoxy functionalized phosphorus-based flame retardants. J App Polym Sci2015; 132. DOI: 10.1002/app.42296.
36.
WangKMorganABBeninV. Preparation and studies of new phosphorus-containing diols as potential flame retardants. Fire Mater2017; 41: 973–982.
37.
ByardBWangKMorganAB, et al. New polyether diols as flame retardants for polyurethane: derivatives of epoxy functionalized phosphonates and phosphates. Fire Mater2018; 42: 3–7.
38.
LiQJiangPWeiP. Synthesis, characteristic, and application of new flame retardant containing phosphorus, nitrogen, and silicon. Polym Eng Sci2006; 46: 344–350.
39.
BabrauskasVPeacockRD. Heat release rate: the single most important variable in fire hazard. Fire Saf J1992; 18: 255–272.
