Halogen‐free flame‐retardant waterborne polyurethane with a novel cyclic structure of phosphorus−nitrogen synergistic flame retardant

A novel phosphorus?nitrogen flame retardant, octahydro‐2,7‐di(N,N‐dimethylamino)‐1,6,3,8,2,7‐dioxadiazadiphosphecine (ODDP), with bi‐phosphonyl in a cyclic compound, was synthesized by the reaction of POCl₃, NH(CH₃)₂·HCl with OHCH₂CH₂NH₂ in CH₂Cl₂ solution, and characterized by Fourier transform infrared spectrometer, nuclear magnetic resonance, and mass spectrum. ODDP has been successfully reacted with polyurethane (PU) as a chain extender to prepare phosphorus–nitrogen synergistic halogen‐free flame‐retardant waterborne PU (DPWPU). Limiting oxygen index (LOI), UL‐94, thermogravimetric analysis and scanning electron microscopy suggest the excellent flame retardancy of the DPWPU polymer. When the content of ODDP was 15 wt %, the LOI of DPWPU was 30.6% and UL‐94 achieved a V‐0 classification. Compared with the unmodified WPU, the thermodecomposition temperature of the DPWPU was reduced and the amount of carbon residue was increased to 18.18%. The surface of carbon residue was shown to be compact and smooth without holes, which would be favorable for resisting oxygen and heat. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41288.     

Effect of boron‐containing materials on the flammability and thermal degradation of polyamide 6 composites containing melamine

Three different boron‐containing substances—zinc borate (ZnB), borophosphate (BPO₄), and a boron‐ and silicon‐containing oligomer (BSi)—were used to improve the flame retardancy of melamine in a polyamide 6 (PA‐6) matrix. The combustion and thermal degradation characteristics of PA‐6 composites were investigated with the limiting oxygen index (LOI), the UL‐94 standard, thermogravimetric analysis (TGA)/Fourier transform infrared (FTIR) spectroscopy, and differential scanning calorimetry (DSC). A slight increase was seen in the LOI values of a sample containing BSi (1 wt %). BPO₄ at high loadings showed a V0 rating (indicating the best flame retardancy) and slightly lower LOI values in comparison with samples with only melamine. For ZnB and BSi, glassy film and char formation decreased the dripping rate and sublimation of melamine, and this led to low LOIs. According to the TGA–FTIR results, the addition of boron compounds did not change the decomposition product distribution of melamine and PA‐6. The addition of boron compounds affected the flame retardancy by physical means. The TGA data showed that boron compounds and melamine reduced the decomposition temperature of PA‐6. According to the DSC data, the inclusion of boron compounds increased the onset temperature of sublimation of melamine and also affected the flame retardancy negatively. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Melamine amino trimethylene phosphate as a novel flame retardant for rigid polyurethane foams with improved flame retardant,mechanical and thermal properties

Melamine amino trimethylene phosphate (MATMP) as a novel nitrogen‐phosphorus flame retardant, was synthesized by the reaction of melamine with amino trimethylene phosphonic acid (ATMP) in aqueous solution. The structure of MATMP was characterized by Fourier transform infrared spectroscopy, solid state 31 P nuclear magnetic resonance, and thermogravimetric analysis. Rigid polyurethane (RPU) foams were prepared by one‐shot and free‐rise method, using MATMP as a flame retardant. The flame retardant, mechanical and thermal properties of MATMP in RPU foams were studied. It is found that the RPU foam containing 15 wt % MATMP (sample RPUMA‐15) can pass the UL‐94 V0 test with a limiting oxygen index of 25.5%. The cone calorimeter test results show that the peak heat release rate of RPUMA‐15 is reduced about 34% compared with that of untreated RPU foam. SEM results indicate that the RPU foams with MATMP can form the good and compact char during burning which provides better flame retardancy. The compressive strength of the RPU foams filled with MATMP first increases and then slightly decreases with an increase in the MATMP content comparing with that of untreated RPU foam. Moreover, thermal conductivities of the MATMP filled RPU foams are about 0.03 W/m K. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45234.     

Fire‐retardant copolymer of acrylonitrile with O,O‐diethyl‐O‐allyl thiophosphate

A novel halogen‐free flame retardant, O,O‐diethyl‐O‐allyl thiophosphate (DATP), which simultaneously contained phosphorus and sulfur, was synthesized through a simple method. The structure of DATP was characterized by Fourier transform infrared spectroscopy, ¹H‐NMR, and mass spectroscopy. The flame‐retardant copolymer was obtained by the free‐radical copolymerization of DATP with acrylonitrile. The flammability and thermal degradation characteristics of the copolymer were assayed by limiting oxygen index measurement, thermogravimetric analysis, and differential scanning calorimetry. The results show that the incorporation of a small percentage of DATP into the copolymer had a significant effect on the retarding combustion of the copolymer, with the limiting oxygen index of the copolymer reaching 28.5% and the char yield being 68.63 wt % at 554°C. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Blends of modified epoxy resin and carboxyl‐terminated polybutadiene. I

Six blend samples were prepared by the physical mixing of epoxidized resole (EDR) with different weight ratios of carboxyl‐terminated polybutadiene (CTPB) liquid rubber ranging from 0 to 25 wt % in intervals of 5 wt %. The formation of various reaction products during the curing of unblended EDR and CTPB‐blended EDR were studied with Fourier transform infrared spectroscopy. The curing time at 100°C for the blend sample containing 15 wt % CTPB was the least among all of the blend samples. This blend sample, also, showed the highest initial degradation temperature, as obtained from thermogravimetric analysis thermograms, which indicated that it was the most thermally stable matrix system. The films of coatings based on the blend of EDR with 15 wt % CTPB offered the highest resistance toward different concentrations of acids and alkalis compared to the films having 5, 10, 20, and 25 wt % CTPB in the EDR/CTPB blends. Solvents showed almost the same behavior as acids and alkalis for these films except for hydrocarbon solvents such as mineral turpentine oil, toluene, and xylene. The resistance toward these solvents was poor and slightly inferior to those found with EDR unblended with CTPB. The tensile, flexural, and impact strengths of the molded specimens derived from the EDR/CTPB blends initially increased up to 15 wt % CTPB addition in the blend and then decreased, whereas the elongation at break remained constant for all blend compositions. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1802–1808, 2006     

Thermal degradation and pyrolysis study of phosphorus‐containing polysulfones

This article deals with the thermal decomposition behavior of a polysulfone containing 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide versus the initial chloromethylated polysulfone under an inert atmosphere and in air. Thermogravimetric characteristics from thermogravimetry and differential thermogravimetry data revealed important differences related to the employed atmosphere, the types of substituted functional groups, or the degree of substitution. The introduction of the 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide pendent group into polysulfone enhanced the thermal stability of the initial chloromethylated polysulfone in both an inert atmosphere and air. Thermal degradation in nitrogen consisted of one degradation step, whereas thermooxidative degradation in air involved more steps. In air, the degradation mechanism was more complex. The volatile products and solid residues that resulted after pyrolysis in an inert atmosphere and in air were analyzed with Fourier transform infrared and mass spectrometry. Environmental scanning electron microscopy showed that the char residues had different morphologies, which suggested that a more compact structure led to better resistance to heat and oxygen. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci 000: 000–000, 2011     

Synthesis of a novel phosphorus‐containing dicyclopentadiene novolac hardener and its cured epoxy resin with improved thermal stability and flame retardancy

A novel phosphorus‐containing dicyclopentadiene novolac (DCPD‐DOPO) curing agent for epoxy resins, was prepared from 9,10‐dihydro‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) and n‐butylated dicyclopentadiene phenolic resin (DCPD‐E). The chemical structure of the obtained DCPD‐DOPO was characterized with FTIR, ¹H NMR and ³¹P NMR, and its molecular weight was determined by gel permeation chromatography. The flame retardancy and thermal properties of diglycidyl ether bisphenol A (DGEBA) epoxy resin cured with DCPD‐DOPO or the mixture of DCPD‐DOPO and bisphenol A‐formaldehyde Novolac resin 720 (NPEH720) were studied by limiting oxygen index (LOI), UL 94 vertical test and cone calorimeter (CCT), and differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), respectively. It is found that the DCPD‐DOPO cured epoxy resin possess a LOI value of 31.6% and achieves the UL 94 V‐0 rating, while its glass transition temperature (T_g) is a bit lower (133 °C). The T_g of epoxy resin cured by the mixture of DCPD‐DOPO and NPEH720 increases to 137 °C or above, and the UL 94 V‐0 rating can still be maintained although the LOI decreases slightly. The CCT test results demonstrated that the peak heat release rate and total heat release of the epoxy resin cured by the mixture of DCPD‐DOPO and NPEH720 decrease significantly compared with the values of the epoxy resin cured by NPEH720. Moreover, the curing reaction kinetics of the epoxy resin cured by DCPD‐DOPO, NPEH720 or their mixture was studied by DSC. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44599.     

The flame retardant and thermal performances of polypropylene with a novel intumescent flame retardant

A novel mono-component intumescent flame retardant(m-IFR), called poly-(spirocyclic pentaerythritol bisphosphonate-1,3,5-triazine-O-bicyclic pentaerythritol phosphate) (PSTBP) was synthesized and characterized. PSTBP was used in polypropylene (PP) to obtain PP/PSTBP mixture whose flame retardancy, thermostability, and water resistance were studied by limiting oxygen index (LOI), vertical burning test (UL-94 V) and thermogravimetric analysis (TGA). In addition, flame-retardant mechanism of the PSTBP was investigated. The results showed that the residue of PSTBP reached 34.58% at 800°C and the volume of the PSTBP increased by dozens of times. When the content of PSTBP was 30.0 wt%, the PP/PSTBP mixture could achieve an LOI value of 32.5% and an UL-94 V-0 rating. Compared with PP/APP/PER system, PP/PSTBP mixture showed better water resistance. The TGA and Fourier transform infrared spectroscopy (FTIR) results showed that PSTBP could generate free radicals and capture the free radicals of the thermal decomposition of PP, and form a dense, strong, and thick intumescent char on the substrate, thus effectively retard the degradation and combustion of PP.     

Nonhalogen flame retarded poly(butylene terephthalate) composite using aluminum phosphinate and phosphorus‐containing deoxybenzoin polymer

Synergistic charring effect was observed between aluminum diethlyphosphinate (AlPi) and 4,4‐bishydroxydeoxybenzoin‐polyphosphonate (BHDB‐PPN) in the poly(butylene terephthalate) composite. By combining them together, robust UL 94 V0 rating was achieved at 0.8 mm thickness for poly(butylene terephthalate)/AlPi/BHDB‐PPN composite which exhibited better mechanical properties than the samples without BHDB‐PPN. The thermal degradation behavior of BHDB‐PPN was investigated by analyzing its evolution and residues under different temperatures. It was found that the radical termination reaction of formed benzyl group may play a critical role in the high charring capacity of BHDB‐PPN. Part of the volatile diethlyphosphinate fragments reacted with the degradation intermediates from BHDB‐PPN to form big chain structure for further carbonization was a possible reason for the synergistic charring effect between AlPi and BHDB‐PPN. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45537.     

Flame retardant modification of acrylic fiber with hydrazine hydrate and sodium ions

The sodium ions were introduced into the acrylic fibers by post‐treating the fibers with hydrazine hydrate and aqueous sodium hydroxide to improve the flame resistance of the fibers. The molecular structure of the modified acrylic fibers was characterized by FTIR spectra. The flame resistance of the acrylic fibers was significantly increased after post‐treatment and was relied mostly on the content of sodium ions. The flame‐retardant mechanism of the modified fiber was studied in details. The micro calorimeter tests showed that the total heat release and the peak heat release rate were largely reduced after post‐treatment. Photographs of the char residues and the results of TGA and TG‐IR technique revealed that the flame retardance of the modified acrylic fiber was provided through the combination effect of the gas phase and condensed phase. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41996.     

Preparation of flame‐retardant leather pretreated with pyrovatex CP

Resistance to burning is one of the most useful properties that can be imparted to leather. Pyrovatex CP is rich in phosphorus and nitrogen and has been successfully used as a flame‐retardant agent in the presence of etherified methylolated melamine (EMM). The effects of a finishing formulation containing Pyrovatex CP and EMM on the flame retardancy and other properties of modified leather have been studied under different conditions. The synergistic effect of the N/P ratio has been thoroughly investigated through the estimation of the nitrogen and phosphorus contents, and their impact on the flame retardancy, tensile strength, and elongation at break of the treated leather has been studied. An investigation of the different factors has led to the following conclusions: (1) the P and N percentages increase with increasing curing temperature and time, (2) increases in the Pyrovatex CP and EMM concentrations are accompanied by an enhancement of the P and N percentages, and (3) all samples exhibit loss in their tensile properties but within an acceptable range (20%). © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Green synthesis and characterization of phosphorus flame retardant crosslinking agents for epoxy resins

The flame‐retardant efficacy of phosphorus‐containing reactive amine hardeners for epoxy resins is well‐known; however their synthesis often applies hazardous, objectionable reagents. The aim of this work is to develop an effective synthesis method for the preparation of P‐containing amines, which can act as flame‐retardant crosslinking agent in epoxy resins. The syntheses and testing of an aliphatic and two aromatic amines are described: curing properties, glass transition temperature, thermal stability, and flame‐retardant performance of the amines are studied. On the basis of these results, the scaling‐up and the optimization of the synthesis of the phosphorus‐containing aliphatic amine hardener in ReactIR? in situ FTIR apparatus is discussed. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40105.     

A phosphorus‐containing inorganic compound as an effective flame retardant for glass‐fiber‐reinforced polyamide 6

A novel inorganic compound, aluminum hypophosphite (AP), was synthesized successfully and applied as a flame retardant to glass‐fiber‐reinforced polyamide 6 (GF–PA6). The thermal stability and burning behaviors of the GF–PA6 samples containing AP (flame‐retardant GF–PA6) were investigated by thermogravimetric analysis, vertical burning testing (with a UL‐94 instrument), limiting oxygen index (LOI) testing, and cone calorimeter testing (CCT). The thermogravimetric data indicated that the addition of AP decreased the onset decomposition temperatures, the maximum mass loss rate (MLR), and the maximum‐rate decomposition temperature of GF–PA6 and increased the residue chars of the samples. Compared with the neat GF–PA6, the AP‐containing GF–PA6 samples had obviously improved flame retardancy: the LOI value increased from 22.5 to 30.1, and the UL‐94 rating went from no rating to V‐0 (1.6 mm) when the AP content increased from 0 to 25 wt % in GF–PA6. The results of CCT reveal that the heat release rate, total heat release, and MLR of the AP‐containing GF–PA6 samples were lower than those of GF–PA6. Furthermore, the higher additive amount of AP affected the mechanical properties of GF–PA6, but they remained acceptable. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Pyrolysis properties and kinetic model of an asphalt binder containing a flame retardant

In this study, thermogravimetry (TG) experiments were employed to study the influence of magnesium hydroxide (MH) on the pyrolysis characteristics of an asphalt binder. Pyrolysis models of the asphalt binder were developed to reveal the flame‐retarding mechanism of MH. The TG experimental results showed that the pyrolysis process of the asphalt binder in N₂ was a one‐stage reaction. The asphalt binder containing MH had a higher residue yield ratio at a high temperature, and TG and differential TG curves showed a dramatic shift toward higher temperatures with an increase in the MH concentration; this indicated that MH inhibited the thermal decomposition of the asphalt binder. By optimal identification of the pyrolysis mechanism function, the pyrolysis reaction of the asphalt binder was found to follow the model of one‐dimensional diffusion (parabolic law), whereas that of the flame‐retarding asphalt binder followed the model of three‐dimensional diffusion (the Ginstling–Brounshtein equation). On the basis of the models, the calculation results for the pseudo activation energy indicated that the thermal stability of the asphalt binder in the pyrolysis process was obviously improved by the addition of MH. We conclude that the flame retardancy of asphalt binders can be enhanced by the use of MH, and MH may be a potential flame retardant for asphalt binders used in tunnel asphalt pavement. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effect of boric acid and melamine on the intumescent fire‐retardant coating composition for the fire protection of structural steel substrates

Intumescent coating is an insulating material designed to decrease heat transfer to a substrate structure. The coating presented in this research article was based on expandable graphite, ammonium polyphosphate, melamine, and boric acid. Bisphenol A epoxy resin BE‐188 was used as a binder with ACR hardener H‐2310 polyamide amine. Different formulations were developed to study the effect of expansion and heat shielding after fire testing. The coating was tested at 950°C for 1 h. The results show that the coating was stable and well bonded with the substrate. The coating was characterized with thermogravimetric analysis (TGA, Parkin Elmer, Norwalk, CT, 06859, USA), Fourier transform infrared (FTIR, Nicolet 400 D Shimadzu spectrometer) spectroscopy, X‐ray diffraction (XRD, Bruker D8 advance Diffracto meter, Bruker Germany), and scanning electron microscopy (SEM, Carl Zeiss Leo 1430VP, UK). The morphology of char was studied by SEM on the coating after fire testing. XRD and FTIR spectroscopy showed the presence of graphite, boron phosphate, boron oxide, and sassolite in the residual char. TGA (Pyris 1, manufactured by Parkin Elmer, Norwalk, CT, 06859, USA) and differential thermal gravimetric analysis (DTGA) showed that boric acid enhanced the residual weight of the intumescent fire‐retardant coating. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Photopolymerization and thermal behavior of phosphate diacrylate and triacrylate used as reactive‐type flame‐retardant monomers in ultraviolet‐curable resins

Tri(acryloyloxyethyl)phosphate (TAEP) and di(acryloyloxyethyl)ethyl phosphate (DAEEP) were used as reactive‐type flame‐retardant monomers along with commercial epoxy acrylate and polyurethane acrylate oligomers in ultraviolet (UV)‐curable resins. The concentrations of the monomers were varied from 17 to 50 wt %. The addition of the monomers greatly reduced the viscosity of the oligomers and increased the photopolymerization rates of the resins. The flame retardancy and thermal degradation behavior of the UV‐cured films were investigated with the limiting oxygen index (LOI) and thermogravimetric analysis. The results showed that the thermal stability at high temperatures greater than 400°C and the LOI values of the UV‐cured resins, especially those containing epoxy acrylate, were largely improved by the addition of the monomers. The dynamic mechanical thermal properties of the UV‐cured films were also measured. The results showed that the crosslink density increased along with the concentrations of the monomers. However, the glass‐transition temperature decreased with an increasing concentration of DAEEP because of the reduction in the rigidity of the cured films, whereas the glass‐transition temperature increased with the concentration of TAEP because of the higher crosslink density of the cured films. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 185–194, 2005     

Effect of charring agent THEIC on flame retardant properties of polypropylene

Tris(2‐hydroxyethyl) isocyanurate (THEIC) was used as charring agent and combined with ammonium polyphosphate (APP) to form an intumescent flame retardant (IFR) for polypropylene (PP). The flame retardancy and combustion performance of PP/IFR composite was tested by limiting oxygen index (LOI), UL‐94 vertical burning test and cone calorimeter. The results showed that PP/IFR composite had highest LOI of 34.8 and obtained V‐0 rating when 30 wt % IFR was loaded and mass ratio APP/THEIC was 2 : 1. The peak heat release (PHRR) and total heat release (THR) values of PP composite containing FRs were remarkably reduced compared with that of pure PP. However, water resistant test demonstrated the PP/IFR composite had poor flame retardant durability, both the LOI value and UL‐94 V‐rating decreased when PP/IFR composite was soaked in water at 70°C after 36 h. The degradation process and the char morphology of IFR and PP/IFR composite were investigated by TGA and SEM images. The possible reaction path between APP and THEIC in the swollen process was proposed. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41214.     

Preparation and solid‐state polyamidation of hexamethylenediammonium adipate: The effect of sodium 5‐sulfoisophthalic acid

The effect of sodium 5‐sulfoisophthalic acid (NaSIPA) on the solid‐state polymerization of hexamethylenediammonium adipate was studied. In particular, different polyamide salt grades, such as a model salt of hexamethylenediamine and NaSIPA and a polyamide 6,6 salt containing NaSIPA, were prepared through alternative procedures based on the solution–precipitation technique. Furthermore, selected salt grades were solid‐state‐polymerized in a thermogravimetric analysis chamber under static and flowing nitrogen. Critical reaction parameters, such as the reaction temperature, surrounding gas, and presence of NaSIPA, were investigated to determine the rate‐controlling mechanism of the process. More specifically, NaSIPA significantly influenced solid‐state polyamidation by reducing the reaction rate and changing the prevailing mechanism. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1609–1619, 2007     

Flame retardation of dibromoneopentyl glycol on intumescent flame‐retardant/low‐density polyethylene composites

On the basis of ammonium polyphosphate (APP) microencapsulated with pentaerythritol/dibromoneopentyl glycol (DBNPG) mixed phosphate melamine salt as an intumescent flame retardant (IFR), the influence of DBNPG on the flame retardancy of IFR/low‐density polyethylene was investigated. The results prove that DBNPG could influence the combustion heat and the thermal barrier properties of the char layer in combustion. The intumescent degree (ID), compactness, and closure were the determinants of the thermal barrier properties of the char layer. A greater ID below 500°C and then a more compact and closed char layer above 500°C contributed to the better thermal barrier properties. An appropriate DBNPG reduced the combustion heat and promoted the formation of a compact and closed char layer by increasing of the melting viscosity of the composites. However, excessive DBNPG destroyed the closure of the char layer and increased the combustion heat because of a decrease in the melting viscosity of the composites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41244.     

Improving the flame‐retardant efficiency of aluminum hydroxide with fullerene for high‐density polyethylene

The influence of fullerene (C₆₀) on the flame retardancy and thermal stability of high‐density polyethylene (HDPE)/aluminum hydroxide (ATH) composites was studied. After the addition of three portions of C₆₀ to an HDPE–ATH (mass ratio = 100:120) composite, a V‐0 rating in the UL‐94 vertical combustion test was achieved, and the limiting oxygen index increased by about 2%. The results of cone testing also showed that the addition of C₆₀ effectively extended the time to ignition and the time to maximum heat‐release rate while cutting down the peak heat‐release rate. Thus, fewer flame retardants were needed to achieve a satisfactory flame retardance. Consequently, the adverse effects on the mechanical properties because of the high level of flame‐retardant loading was reduced, as evidenced by the obvious enhancements in the tensile strength, elongation at break, and flexural strength. Electron spin resonance spectroscopy proved that C₆₀ was an efficient free‐radical scavenger toward HO· radicals. Thermogravimetric analysis coupled to Fourier transform infrared spectroscopy demonstrated that in both N₂ and air atmospheres, C₆₀ increased the onset temperature of the matrix by about 10 °C because of its enormous capacity to absorb free radicals evolved from the degradation of the matrix to form crosslinked network, which was covered by aluminum oxide. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44551.