Nitrogen-containing Flame Retardant Research Articles

Fabricating of flame retardant and antibacterial lyocell fabrics through the finishing of phosphorus and nitrogen-containing flame retardant and coating of copper nanoparticles

Fabricating of flame retardant and antibacterial lyocell fabrics through the finishing of phosphorus and nitrogen-containing flame retardant and coating of copper nanoparticles

A novel sustainable phosphorus-containing heteroatom-based coating for polyamide 6.6 textiles: Enhanced flame retardancy and hydrophilicity

The demand for "green" materials increases due to concerns about the effects of flame-retardant textiles. Using natural plant-base compounds such as phytic acid (PA) and the most abundant green amino polysaccharide chitosan (CS) as effective and durable flame retardants for textiles is essential for creating sustainable and ecological textile products. This study aims to develop a novel, eco-friendly, phosphorus- and nitrogen-containing flame retardant known as ammonium phytate (AP), intending to improve the flame retardant properties of polyamide 6.6 (PA6.6) textiles. UV-induced grafting with 2-acrylamide-2-methylpropane sulfonic acid (AMPS) increases the surface functional groups of PA6.6 fabrics. Later, the surface-modified fabrics were coated with phosphorus-containing heteroatom-based components, namely, sulfur, nitrogen, silicon, and boron, onto a single flame retardant system via layer-by-layer (LBL) deposition of positively charged chitosan/boron drop (3-aminopropyl) triethoxysilane/silicon dioxide (CS/BAPTES/SiO2) sole solution and negatively charged AP solution to enhance superior hydrophilic and durable flame retardant performance. According to the data, a weight pick-up of 56.5% is attributable to only 4 BLs. However, all the flame-retardant-coated fabrics can completely stop the melting-dripping tendency and achieve B-3 to B-2 ratings after the UL-94 vertical burning test. In addition, the LOI values of treated fabrics increase from 18.5% to 23.5% compared to a pure sample. The AMPS grafted with a 4BL-deposited fabric sample exhibits a maximum decrease in peak heat release rate (PHRR) of more than 54%. Moreover, the thermogravimetric analysis (TGA) test reveals a significant increase in thermal stability and char yield. Additionally, the as-prepared phosphorus-containing heteroatom-based coatings impart a water contact angle value of approximately 0⁰ within 2 s, demonstrating that the treated fabrics exhibit superior hydrophilic performance. Moreover, using AMPS-grafted and only 2-BL-deposited treatments improves coating stability in washing and imparts durable flame retardancy that can resist up to 20 washing cycles. It is proposed that the sustainable phosphorus-containing heteroatom-based coating may be a potentially effective replacement for existing durable flame retardants routinely used in textile finishing operations.

Synthesis of a phosphorus- and nitrogen-containing flame retardant and the fabrication of flame retardant cotton

A novel phosphorus- and nitrogen-containing flame retardant (APNTHE) was synthesized through the reaction of N, N, N′, N′-tetrakis (2-hydroxypropyl) ethylenediamine, phosphoric acid and urea. Then, the APNTHE solution with a concentration of 120 g/L was used for the preparation of flame retardant cotton (FR-cotton). The elemental compositions, surface morphology, thermal stability and combustion behavior of the cotton before and after modification were investigated. Thermogravimetric (TG) analysis showed that the char residue of the treated fabric at 800°C was as high as 35.09% under a nitrogen atmosphere. Flammability tests after different LCs indicated that FR-cotton had durable flame retardancy. Compared to the blank sample, the peak of heat release rate and total heat release of the FR-cotton decreased by 91.89% and 90.53%, respectively. The char residual and TG-Fourier transform infrared spectroscopy analysis illustrated that APNTHE played a flame retardant role both in the gas phase and the condensed phase. All the results demonstrated that APNTHE can be regarded as a prospective flame retardant for cotton.

Clays as Inhibitors of Polyurethane Foams' Flammability.

Polyurethanes are a very important group of polymers with an extensive range of applications in different branches of industry. In the form of foams, they are mainly used in bedding, furniture, building, construction, and automotive sectors. Due to human safety reasons, these applications require an appropriate level of flame retardance, often required by various law regulations. Nevertheless, without the proper modifications, polyurethane foams are easily ignitable, highly flammable, and generate an enormous amount of smoke during combustion. Therefore, proper modifications or additives should be introduced to reduce their flammability. Except for the most popular phosphorus-, halogen-, or nitrogen-containing flame retardants, promising results were noted for the application of clays. Due to their small particle size and flake-like shape, they induce a “labyrinth effect” inside the foam, resulting in the delay of decomposition onset, reduction of smoke generation, and inhibition of heat, gas, and mass transfer. Moreover, clays can be easily modified with different organic compounds or used along with conventional flame retardants. Such an approach may often result in the synergy effect, which provides the exceptional reduction of foams’ flammability. This paper summarizes the literature reports related to the applications of clays in the reduction of polyurethane foams’ flammability, either by their incorporation as a nanofiller or by preparation of coatings.

A novel synthesis of ditrimethylolpropane biphosphoramide diethyleneamine as flame retardant and antistatic textiles

A novel phosphorous- and nitrogen-containing flame retardant, ditrimethylolpropane biphosphoramide diethyleneamine (DBD), was synthesized. Its chemical structure is characterized by Fourier-transform infrared spectroscopy and 1H nuclear magnetic resonance spectroscopy. The effect of DBD on the physical, mechanical, and antistatic properties, thermal stability, and flame retardancy of wool fabric was systematically investigated. Thermogravimetric analysis showed that the initial decomposition temperature of DBD was 165 oC and 243 oC under nitrogen and air atmosphere, respectively. Furthermore, after 30 washes, the treated wool fabric exhibited excellent wash durability and good antistatic properties. Vertical burning tests indicated that both the burning time and char length of the treated wool fabric were lower than those of the flame-retardant standard, leading to a B1 flame retardant rating for the treated wool fabric. Compared to untreated wool fabric, the limiting oxygen index value of treated wool fabric increased significantly from 25.7% to 34.7%.

Construction of Charring-Functional Polyheptanazine towards Improvements in Flame Retardants of Polyurethane.

Nitrogen-containing flame retardants have been extensively applied due to their low toxicity and smoke-suppression properties; however, their poor charring ability restricts their applications. Herein, a representative nitrogen-containing flame retardant, polyheptanazine, was investigated. Two novel, cost-effective phosphorus-doped polyheptazine (PCN) and cobalt-anchored PCN (Co@PCN) flame retardants were synthesized via a thermal condensation method. The X-ray photoelectron spectroscopy (XPS) results indicated effective doping of P into triazine. Then, flame-retardant particles were introduced into thermoplastic polyurethane (TPU) using a melt-blending approach. The introduction of 3 wt% PCN and Co@PCN could remarkably suppress peak heat release rate (pHRR) (48.5% and 40.0%), peak smoke production rate (pSPR) (25.5% and 21.8%), and increasing residues (10.18 wt%→17.04 wt% and 14.08 wt%). Improvements in charring stability and flame retardancy were ascribed to the formation of P–N bonds and P=N bonds in triazine rings, which promoted the retention of P in the condensed phase, which produced additional high-quality residues.

Recent developments in s-triazine holding phosphorus and nitrogen flame-retardant materials

Flame retardants are chemical compounds when mixed or incorporated in to polymers provide varying degrees of flammability protection. Flammable polymeric materials are ubiquitous with a wide array of applications. However, recent studies have shown potential environmental and health concerns with certain halogen-containing flame retardants. Thus, it has now become a necessity to explore new and effective materials that are safer and environmentally benign. In this context, halogen-free phosphorus- and nitrogen-containing flame retardants have attracted much attention worldwide. Moreover, s-triazine is the central focus because of its excellent charring effect. General strategies for synthesizing s-triazine compounds mostly via nucleophilic substitution reaction have been highlighted. This review provides a comprehensive description on design and synthesis of flame-retardant materials with significant flammability performance.

Synthesis of a novel phosphorus and nitrogen-containing flame retardant and its application in rigid polyurethane foam with expandable graphite

A novel phosphorus and nitrogen containing flame retardant named 1,4-bis(Diethyl methylenephosphonate) piperazine (BDEMPP) was synthesized. The chemical structures of BDEMPP were determined by Fourier transform infrared spectrum (FTIR), nuclear magnetic resonance (NMR) and gas chromatography-mass spectrometry (GC-MS). The flame retardant rigid polyurethane foams (FR-RPUFs) were prepared by one-pot and free foaming with incorporating BDEMPP/expanded graphite (EG) with polyether polyol and polymethylene polyphenyl isocyanate. The limit oxygen index (LOI), vertical burning (UL94) and cone calorimeter (CONE) test showed that the fire-retardant properties were improved due to the barrier effect of EG and residual char. With addition of 10 wt % EG and 15 wt % BDEMPP, RPUF/10EG/15BDEMPP passed UL94 V-0 with the LOI value of 25.7%. The thermogravimetric analysis (TGA) results revealed that the initial decompose temperature (T5%) of RPUF/10EG/15BDEMPP was decreased compared with pure RPUF. However, the yield of residual char was increased from 0.35% for pure RPUF to 30.52% for RPUF/10EG/15BDEMPP at 800 °C. EG and BDEMPP had a slight influence on density and compression strength. The density and compression strength of pure RPUF was 45.42 kg m−3 and 213 kPa. As for RPUF/10EG/15BDEMPP, the density and compression strength was 44.18 kg m−3 and 180 kPa. The morphology and composition of residual char were investigated. The results demonstrated that the intact, compact and thick residual char with abundant of phosphorus and nitrogen was formed to enhance the flame retardancy and smoke suppression.

Synthesis of a phosphorus–nitrogen-containing flame retardant and its application in epoxy resin

In this article, a phosphorus–nitrogen-containing flame retardant (DOPO-T) was successfully synthesized by nucleophilic substitution reaction between 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and cyanuric chloride. The chemical structure of DOPO-T was characterized by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance (NMR) and phosphorous-31 NMR, and elemental analysis. DOPO-T was then blended with diglycidyl ether of bisphenol-A to prepare flame-retardant epoxy resins. Thermal properties, flame retardancy, and combustion behavior of the cured epoxy resins were evaluated by differential scanning calorimetry, thermogravimetric analysis, limited oxygen index (LOI) measurement, UL94 vertical burning test, and cone calorimeter test. The results indicated that the glass transition temperature ( Tg) and temperature at 5% weight loss of epoxy resin (EP)/DOPO-T thermosets were gradually decreased with the increasing content of DOPO-T. DOPO-T catalyzed the decomposition of EP matrix in advance. The flame-retardant performance of EP thermosets was significantly enhanced with the addition of DOPO-T. EP/DOPO-T-0.9 sample had an LOI value of 36.2% and achieved UL94 V-1 rating. In addition, the average of heat release rate, peak of heat release rate, average of effective heat of combustion, and total heat release (THR) of EP/DOPO-T-0.9 sample were decreased by 32%, 48%, 23%, and 31%, respectively, compared with the neat EP sample. Impressively, EP/DOPO-T thermosets acquired excellent flame retardancy under low loading of flame retardant.

Flame-retarding epoxy resin with an efficient P/N/S-containing flame retardant: Preparation, thermal stability, and flame retardance

To further study the effect of the phosphorus, sulfur, and nitrogen-containing flame retardant on epoxy resin, a DOPO-based phenol derivative 4-[(benzothiazolyl 2-amino)(6-oxido-6H-dibenz[c,e][1,2]oxaphosphorin-6-yl) methyl] phenol namely D-P-A, was successfully synthesized from 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), p-hydroxybenzaldehyde (PHBA), and 2-aminobenzothiazole (ABZ), and used to flame retard epoxy resin (EP). As expected, D-P-A imparted flame retardance to epoxy resin. For example, with 7.5 wt% loading of D-P-A, epoxy thermoset passed a UL-94 V-0 rating, and got a LOI value of 29.6%. Besides, D-P-A played an effective role in inhibiting heat release of EP, that EP/7.5% D-P-A showed a peak of heat release rate (PHRR) of 713 kW/m2 much lower than 1137 kW/m2 of EP. However, it decomposed in advance owing to the lower thermal stability of D-P-A. Finally, through Scanning electron microscopy (SEM), Raman spectra and X-ray photoelectron spectroscopy (XPS) and pyrolysis-gas chromatograph/mass spectrometer (Py-GC/MS), it disclosed that D-P-A exerted its flame-retardant activity both in the vapor and condensed phase.

Synthesis and application of aminophenyl-s-triazine derivatives as potential flame retardants in the modification of epoxy resins.

In order to develop new phosphorus–nitrogen-containing flame retardants, three novel compounds of DOPO-substituted aminophenyl-s-triazine (TAT-DOPO) with different P/N element ratios were synthesized by Kabachnik–Fields reaction. TAT-triDOPO possessing three DOPO units in one molecule exhibited the best thermal stability. Besides, TAT-triDOPO and TAT-hexaDOPO possessing active hydrogen displayed the characteristics of reactive-type retardant, while TAT-enneaDOPO without active hydrogen represented additive-type retardant. The influences of three TAT-DOPO compounds on the thermal stability, flame retardancy and mechanical properties of the cured EP composites were investigated. Compared with pure EP, the char yields of EP/TAT-DOPO were increased. The LOI value and the UL-94 ratings of EP/TAT-triDOPO with a 5% loading were improved to 34.0% and V-0 grade. The PHRR, THR and HRC of EP/TAT-triDOPO were decreased by 25.7%, 21.1% and 25.4%, respectively. Furthermore, the incorporation of TAT-triDOPO could also improve the flexural strength and elastic modulus of cured EP. It was explained that the existence of active hydrogen atoms within TAT-triDOPO molecule can act as effective chemical cross-linking points in EP network. Finally, based on the SEM and TGA-FTIR analysis of pyrolytic products of cured EP/TAT-DOPO, it was deduced that the prepared TAT-DOPO flame retardant could exhibit both condensed phase and gas phase flame-retardancy mechanism.

Synthesis of a novel phosphorus and nitrogen-containing bio-based polyols and its application in flame retardant polyurethane sealant

A novel ricinoleic acid (RA) based phosphorus and nitrogen-containing flame retardant polyols (FRPE) was successfully synthesized and characterized by FTIR, 1H NMR and 13C NMR. The flame retardant polyurethane sealants (FR-PUS) were prepared by curing FRPE with methylene diphenyl diisocyanate (MDI-50). The flame retardant properties and thermal decomposition of FR-PUS were investigated by the limiting oxygen index (LOI), cone calorimeter testing (CCT) and thermogravimetric analysis (TGA). The results showed that FRPE could enhance the thermal stability and improve the flame retardancy of polyurethane sealants (PUS) without any other flame retardant. Moreover, the gaseous degradeation products of FR-PUS were analyzed by thermogravimetric analysis/infrared spectrometry (TG-IR), providing insight into the thermal degradation mechanism. FTIR and dynamic mechanical analysis (DMA) were used to explore the chemical components of the char after CCT and mechanical properties of PUS.

Aluminum hypophosphite microencapsulated to improve its safety and application to flame retardant polyamide 6

Aluminum hypophosphite (AHP) is an effective phosphorus-containing flame retardant. But AHP also has fire risk that it will decompose and release phosphine which is spontaneously flammable in air and even can form explosive mixtures with air in extreme cases. In this paper, AHP has been microencapsulated by melamine cyanurate (MCA) to prepare microencapsulated aluminum hypophosphite (MCAHP) with the aim of enhancing the fire safety in the procedure of production, storage and use. Meanwhile, MCA was a nitrogen-containing flame retardant that can work with AHP via the nitrogen-phosphorus synergistic effect to show improved flame-retardant property than other capsule materials. After microencapsulation, MCA presented as a protection layer inhibit the degradation of AHP and postpone the generation of phosphine. Furthermore, the phosphine concentration could be effectively diluted by inert decomposition products of MCA. These nonflammable decomposition products of MCA could separate phosphine from air delay the oxidizing reaction with oxygen and decrease the heat release rate, which imply that the fire safety of AHP has been improved. Furthermore, MCAHP was added into polyamide 6 to prepare flame retardant polyamide 6 composites (FR-PA6) which show good flame retardancy.

Enhanced thermal and flame retardant properties of flame-retardant-wrapped graphene/epoxy resin nanocomposites

Functionalized reduced graphene oxide (FRGO) wrapped with a phosphorus and nitrogen-containing flame retardant (FR) was successfully prepared via a simple one-pot method and well characterized.

Flame-retardant wrapped ramie fibers towards suppressing “candlewick effect” of polypropylene/ramie fiber composites

In this work, a flame-retardant polypropylene (PP)/ramie fiber (RF) composite was prepared. The ramie fibers were wrapped chemically by a phosphorus- and nitrogen-containing flame retardant (FR) produced via in situ condensation reaction so as to suppress their candlewick effect. Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) demonstrated that the ramie fibers wrapped chemically by FR (FR-RF) were obtained successfully. Thermogravimatric test showed that the PP/FR-RF composite had more residue and better thermal stability at high temperatures than the PP/RF composite. Cone calorimeter (CC) results indicated that the peak of heat release rate (PHRR) and total heat release (THR) correspondingly decreased by 23.4% and 12.5% compared with the values of neat PP/RF. The PP/FR-RF composite created a continuous and compact char layer after the combustion. Combining FTIR analysis of char residue after CC test with heat conduction coefficient results, it could be concluded that the charring of FR on RF greatly weakened the candlewick effect of RF, and more char residue in the RF domain facilitated the formation of more continuous and compact char layer in the whole combustion zone, consequently protected PP composites during combustion, resulting in the better flame retardancy of PP/FR-RF composite than that of PP/RF composite.

Syntheses and characterization of two novel 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide-based flame retardants for epoxy resin

Two novel phosphrous–nitrogen-containing flame retardants (3) and (4) were successfully synthesized from two steps: condensation reaction between 4-aminopenol and 1,4-phthaladehyde (or 4,4′-biphenyldicarboxaldehyde) and addition reaction between the above condensation compounds and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide. The structures of (3) and (4) were characterized by Fourier transform infrared, nuclear magnetic resonance, and mass spectroscopy methods. The results show that (3) and (4) can serve as co-curing agents of diaminodiphenylmethane (DDM) for the curing reaction of epoxy resin. The epoxy thermosets-containing DDM and (3) or (4) exhibit moderate changes in glass transition temperature, thermal stability, and show improvement in flame retardancy: UL94 V-0 grade can be obtained when phosphorus content of the epoxy thermoset is only 1.0%; the limiting oxygen index of epoxy resin system containing (4) reaches 40.9 when phosphorus content is up to 1.5%.

Material resistance of flame retarded wood-plastic composites against fire and fungal decay

Flame retarded wood-plastic composites (WPCs) should allow safe application in areas of fire risk. Halogen-free flame retardants can contain high amounts of nitrogen, phosphorus or sulphur, which may serve as nutrition source for wood degrading fungi and accelerate wood decay. Therefore, the material resistance of WPCs with each of four flame retardants against both fire or fungal decay was examined in comparison to WPC without flame retardant. Expandable graphite showed the best performance against fire in cone calorimetry and radiant panel testing. Two ammonium polyphosphates and a third nitrogen-containing flame retardant were not as effective. Contrary to the possibility that flame retardants might enhance fungal decay of WPC, the opposite effect occurred in case of the wood-degrading fungi Trametes versicolor and Coniophora puteana according to determination of mass loss and decrease of bending modulus of elasticity. Only the surface mould Alternaria alternata slightly increased the degradation of WPCs with nitrogen-containing flame retardants compared to WPC without flame retardant according to mass loss data and FTIR-ATR analyses. Finally, WPC including expandable graphite as flame retardant was effective against both fire and fungal decay.

Studies on the effect of different levels of toughener and flame retardants on thermal stability of epoxy resin

A thermoplastic toughener, polyether sulphone (PES) and a number of different types of flame retardants were blended in different ratios with a commercial epoxy resin triglycidyl-p-aminophenol (TGAP) and 4,4-diamino diphenyl sulphone (DDS) a curing agent. The effect of type and levels of flame retardants (FR) and the toughening agent on the curing, thermal decomposition and char oxidation behaviour of the epoxy resin was studied by the simultaneous differential thermal analysis and thermogravimetric techniques. It was observed that the toughener slightly increases the curing temperature (by up to 20 °C) but had minimal effect on the decomposition temperature of the resin. Flame retardants, however affected all stages depending upon the type of flame retardant used. The curing peak for samples containing tougher and flame retardants although slightly changed depending upon the type of FR, was not more than ± 20 °C compared to that of samples containing toughener only. All flame retardants lowered the decomposition temperature of the epoxy resin. Phosphorus- and nitrogen-containing flame retardants reduced the char oxidation leading to more residual char, whereas halogen- containing flame retardants had less effect on this stage.

Preparation of microencapsulated red phosphorus through melamine cyanurate self-assembly and its performance in flame retardant polyamide 6

A novel technology was developed to prepare microencapsulated red phosphorus (RP) with a coating of melamine cyanurate (MCA) serving as both a nitrogen-containing flame retardant and as a solid lubrication agent. We took advantage of the self-thickening effects during the MCA self-assembly process to realize effective encapsulation on the surface of predispersed RP powder. The technology described in this article can overcome several drawbacks of current microencapsulation processes including (1) relatively complicated preparation processes, (2) use of formaldehyde or other noxious modifiers, and (3) poor compatibility with flame retardant fillers and polymer matrix resulting in poor physical properties. Additionally, this novel technology can also modify various properties of RP with regard to lubrication performance, ignition point, moisture absorption ratio, and color. As a composite system of flame retardant phosphorus encapsulated by a nitrogen-containing flame retardant, the microencapsulated RP showed nitrogen-phosphorus (N-P) synergism with further improved flame retardancy. The action and mechanisms of the microencapsulated RP flame retardant polyamide 6 (PA6) were investigated by limiting oxygen index, vertical burning experiment (UL94), thermogravimetric analysis, and scanning electron microscope observations. The results indicated that the flame retardant PA6 possessed desired flame retardancy because of effective char-formation of the condensed phase and it also showed satisfactory mechanical properties as the result of the good compatibility between flame retardant and PA6 resin. POLYM. ENG. SCI., 46:1548–1553, 2006. © 2006 Society of Plastics Engineers

Interactions between Phosphorus- and Nitrogen-Containing Flame Retardants

A halogen-free, flame-retardant polystyrene containing polyphenylene ether (PPE) with excellent melt flow, impact resistance, and heat resistance can be obtained through concurrent use of hydroxyphenyl-containing phosphate (resorcinyl diphenyl phosphate: triphenyl phosphate (TPP)-OH) as phosphorus-containing flame retardant and melamine cyanurate (MC) as nitrogen-containing flame retardant. Investigation of interactions between these two flame retardants showed that an intumescent process, which involves the formation of char that swells and foams, occurs upon the burning of this resin composition and lowers the burning surface temperature by 130°C compared with the resin composition without MC, in which the intumescent process does not occur. The resin composition containing TPP-OH/MC has higher impact resistance than that containing TPP/MC (TPP: contains no hydroxyl group). Viscoelastic measurement indicated significant interactions between TPP-OH and MC, including particularly hydrogen bonding between their hydroxyl and amino groups, which suggests that TPP-OH acts as a compatibilizer of MC.