Flame retardancy,mechanical, and thermal properties of waterborne polyurethane conjugated with a novel phosphorous‐nitrogen intumescent flame retardant

A novel phosphorous‐nitrogen intumescent flame retardant with reactive diamino groups, benzoguanamine spirocyclic pentaerythritol bisphosphonate (BSPB), was synthesized and used as a chain extender, and then a series of flame retardant waterborne polyurethanes (FRWPU) were prepared by covalently conjugating the BSPB into waterborne polyurethane (WPU) backbone. Their structures were characterized by Fourier transformed infrared spectrometry (FTIR), ¹H and ³¹P nuclear magnetic resonances (NMR), respectively. Simultaneously, the flame retardancy and the thermal stability of FRWPU were systematically investigated by limiting oxygen index (LOI) test, UL‐94 vertical burning test and thermogravimetric analysis (TGA). The results indicated that with the increase of BSPB content from 0 to 8 wt%, the LOI value of FRWPU increased from 18.6 to 27.3%, showing significant improvement by 8.7%. Compared with WPU, FRWPU showed decreased thermal stability but promoted char residue ratio. Conjugation of BSPB could obviously enhance the mechanical properties of FRWPU, the Young's modulus and tensile strength dramatically increased with the increase of BSPB. Investigation of char forming mechanism of BSPB through real time Fourier transform infrared spectra (RTFTIR) and scanning electronic microscopy (SEM) revealed that the polyphosphoric acid and phosphorus oxynitrides rich outer intumescent char layer could form protective shields to inhibit effectively internal polyurethane to heat and flame diffusion during contacting fire. POLYM. COMPOS., 38:452–462, 2017. © 2015 Society of Plastics Engineers     

Flame retardation and thermal stability of novel phosphoramide/expandable graphite in rigid polyurethane foam

A novel flame retardant named diethylene N,N',N''‐tri (diethoxy)phosphoramide (DTP) was synthesized using diethyl phosphate and diethylenetriamine via Atherton–Todd reaction. Then, series of flame‐retardant water‐blown rigid polyurethane foams (RPUFs) with expandable graphite (EG) and DTP were prepared through box‐foaming. The results of thermogravimetric analysis showed that DTP/EG changed thermal degradation process of RPUF and promoted enhancing char residues. The complex flame‐retardant system (EG/DTP) endowed RPUF higher limiting oxygen index (LOI) values (29.1%–30.2%) and lower heat release rate peak (PHRR) values according to LOI and microscale combustion calorimeter tests. More importantly, the synergistic flame‐retardant effect between EG and DTP in RPUF was proved by the analysis of synergistic effectivity values. Based on the analysis of cone calorimetric tests, EG/DTP revealed remarkable effects to inhibit the fire intensity and smoke release of RPUF with decreased PHRR and total smoke production due to good char‐forming action. To further investigate the char‐residues of the foams after combustion, scanning electron microscope and energy dispersive X‐ray spectroscopy analyses were conducted. The results suggested that EG/DTP flame‐retardant system promoted RPUF forming a compact, continuous and phosphorus‐rich char layer as a good fire barrier in combustion. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46434.     

Polyamide‐enhanced flame retardancy of ammonium polyphosphate on epoxy resin

An attractive intumescent flame retardant epoxy system was prepared from epoxy resin (diglycidyl ether of bisphenol A), low molecular weight polyamide (cure agent, LWPA), and ammonium polyphosphate (APP). The cured epoxy resin was served as carbonization agent as well as blowing agent itself in the intumescent flame retardant formulation. Flammability and thermal stability of the cured epoxy resins with different contents of APP and LWPA were investigated by limited oxygen index (LOI), UL‐94 test, and thermogravimetric analysis (TGA). The results of LOI and UL‐94 indicate that APP can improve the flame retardancy of LWPA‐cured epoxy resins. Only 5 wt % of APP can increase the LOI value of epoxy resins from 19.6 to 27.1, and improve the UL‐94 ratings, reaching V‐0 rating from no rating when the mass ratio of epoxy resin to LWPA is 100/40. It is much interesting that LOI values of flame retardant cured epoxy resins (FR‐CEP) increase with decreasing LWPA. The results of TGA, FTIR, and X‐ray photoelectron spectroscopy (XPS) indicate that the process of thermal degradation of FR‐CEP consists of two main stages: the first stage is that a phosphorus rich char is formed on the surface of the material under 500°C, and then a compact char yields over 500°C; the second stage is that the char residue layer can give more effective protection for the materials than the char formed at the first stage do. The flame retardant mechanism also has been discussed according to the results of TGA, FTIR, and XPS for FR‐CEP. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis of amino trimethylene phosphonic acid melamine salt and its application in flame‐retarded polypropylene

Amino trimethylene phosphonic acid melamine salt (MATMP) was synthesized and used as acid source and blowing agent in intumescent flame‐retarded polypropylene (PP); its compositions were characterized by Fourier transform infrared spectroscopy and X‐ray powder diffraction. An intumescent flame retardant (IFR) system composed of MATMP, pentaerythritol (PER), and PP was tested by limiting oxygen index (LOI), UL‐94, cone calorimeter tests, and thermogravimetric analysis and compared with an ammonium polyphosphate (APP)/PER system. The results showed that MATMP had better water resistance than APP, the LOI value of PP/MATMP/PER composite can reach 30.3%, and a UL‐94 V‐0 rating can be reached at 25 wt % IFR loading. The amount of residual char of IFR MATMP/PER was 20.3 and 9.5 wt % at 400 and 600 °C, respectively. A thermooxidative degradation route and a possible flame‐retardant mechanism of IFR were proposed according to the analysis of evolved gases and residual chars. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46274.     

Synergistic effects of tetrabutyl titanate on intumescent flame‐retarded polypropylene

The synergistic mechanism of tetrabutyl titanate (TBT) in the intumescent flame‐retardant polypropylene (PP) composites was investigated in this work. The intumescent flame‐retardant was composed of pentaerythritol (PER) as a carbonizing agent ammonium polyphosphate (APP) as a dehydrating agent and blowing agent. Five different concentrations (1, 1.25, 1.5, 1.75, 2 wt %) of TBT were incorporated into flame retardant formulation to investigate the synergistic mechanism. The thermal degradation and flammability of composites were characterized by thermogravimetric analysis (TGA), limiting oxygen index (LOI), and UL‐94 tests. The morphology and chemical structure of char layer was characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and energy dispersive spectrometer (EDS). The results showed that LOI was increased from 27.8 to 32.5%, with the increase of TBT content from 0 to 1.5 wt %. Results from SEM, and FTIR demonstrated that TBT could react with APP and PER to form the stable char layer. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4255–4263, 2013     

A novel halogen‐free intumescent flame retardant containing phosphorus and nitrogen and its application in polypropylene systems

A novel halogen‐free intumescent flame retardant, pentaerythritol spirobisphosphoryl‐dicyandiamide (SPDC), was synthesized and characterized by FTIR, ¹H NMR, and ³¹P NMR spectra. The new flame retardant was used in polypropylene (PP) to prepare flame‐retardant materials whose flammability and thermal behavior were studied by the limiting oxygen index (LOI) method, thermogravimetric analysis (TGA), and cone calorimetry (CONE). The mechanical properties were also investigated. The results indicated that when the addition of SPDC reached 30 wt%, the material showed both excellent flame retardancy and anti‐dripping abilities for PP. Moreover, the LOI value of the PP‐IFR(30%) was 32.5, and it passed the UL‐94 V‐0 rating test. The CONE results revealed that in PP, SPDC(30%) significantly decreased the peak heat release, total heat release, and smoke relative to their values for pure PP. The morphological structures observed by SEM demonstrated that SPDC could promote the formation of a homogeneous and compact intumescent char layer. The TGA data showed that SPDC could enhance the thermal stability of PP and effectively increase the char residue formation. J. VINYL ADDIT. TECHNOL., 2010. © 2010 Society of Plastics Engineers     

Highly effective flame-retarded polyester diol with synergistic effects for waterborne polyurethane application

In this article, a novel bi-reactive flame retardant (FRD) was successfully synthesized for waterborne polyurethane (WPU). The chemical structures of FRD were characterized by Fourier-transform infrared spectra and ¹H and ³¹P nuclear magnetic resonance. Then, the FRD was incorporated into polyurethane backbone to prepare a series of flame-retarded WPU (FRWPU). The flammability characteristics of FRWPU were measured by limited oxygen index (LOI), UL-94, and cone calorimeter (CCT) tests. The FRPWU-7 had a high LOI value of 30.5% with UL94 V-0 rating. Moreover, the CCT values indicated that FRD induced the gaseous phase quenching effect of phosphorus-containing free radicals derived from the decomposed phosphaphenanthrene group on the gas-phase flame retardancy. Scanning electron micrographs and Raman spectra exhibited that FRD promoted the charring formation of phosphorus-rich char layer with graphitized surface and honeycomb-like intumescent structure in WPU matrix during burning. This study provides a new way to design a novel reactive P–P flame retardant consisted of the phosphaphenanthrene group and intumescent flame retardant for WPU application. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48444.     

Preparation of a chitosan‐based flame‐retardant synergist and its application in flame‐retardant polypropylene

A novel flame‐retardant synergist, chitosan/urea compound based phosphonic acid melamine salt (HUMCS), was synthesized and characterized by Fourier transform infrared spectroscopy and ³¹P‐NMR. Subsequently, HUMCS was added to a fire‐retardant polypropylene (PP) compound containing an intumescent flame‐retardant (IFR) system to improve its flame‐retardant properties. The PP/IFR/HUMCS composites were characterized by limiting oxygen index (LOI) tests, vertical burning tests (UL‐94 tests), microscale combustion calorimetry tests, and thermogravimetric analysis to study the combustion behavior and thermal stability. The addition of 3 wt % HUMCS increased the LOI from 31.4 to 33.0. The addition of HUMCS at a low additive amount reduced the peak heat‐release rate, total heat release, and heat‐release capacity obviously. Furthermore, scanning electron micrographs of char residues revealed that HUMCS could prevent the IFR–PP composites from forming a dense and compact multicell char, which could effectively protect the substrate material from combusting. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40845.     

Flame‐retarding mechanism of organically modified montmorillonite and phosphorous‐Nitrogen flame retardants for the preparation of a halogen‐free,flame‐retarding thermoplastic poly(ester ether) elastomer

In this study, thermoplastic poly(ester ether) elastomer (TPEE) nanocomposites with phosphorus–nitrogen (P–N) flame retardants and montmorillonite (MMT) were prepared by melt blending. The fire resistance of the nanocomposites was analyzed by limiting oxygen index (LOI) and vertical burning (UL 94) tests. The results show that the addition of the P–N flame retardants increased the LOI of the material from 17.3 to 27%. However, TPEE containing P–N flame retardants only obtained a UL 94 V‐2 ranking; this resulted in a flame dripping phenomenon. On the other hand, TPEE containing the P–N flame retardant and organically modified montmorillonite (o‐MMT) achieved better thermal stability and good flame retardancy; this was ascribed to its partially intercalated structure. The synergistic effect and synergism were investigated by Fourier transform infrared spectroscopy and thermogravimetry. The introduction of o‐MMT decreased the inhibition action of the P–N flame retardant and increased the amount of residues. The catalytic decomposition effect of MMT and the barrier effect of the layer silicates are discussed in this article. The residues after heating in the muffle furnace were analyzed by scanning electron microscopy, energy‐dispersive X‐ray spectroscopy and laser Raman spectroscopy. It was shown that the intercalated layer silicate structure facilitated the crosslinking interaction and promoted the formation of additional carbonaceous char residues in the formation of the compact, dense, folded‐structure surface char. The combination of the P–N flame retardant and o‐MMT in TPEE resulted in a better thermal stability and fire resistance because of the synergistic effect of the mixture. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41094.     

Improving thermal and flame‐retardant properties of epoxy resins by a novel reactive phosphorous‐containing curing agent

In an attempt to improve thermal and flame‐retardant properties of epoxy resins efficiently, a new reactive phosphorus‐containing curing agent called 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐yl‐(phenylimino)‐(4‐hydroxyphenyl)me‐thane (DOPO‐PHM) was synthesized and was combined with 4,4′‐diaminodiphenyl methane (DDM) to co‐cure epoxy resins (E51), which covalently incorporated halogen‐free DOPO organ groups into the epoxy networks. The chemical structure of this curing agent was confirmed by FTIR, 1D, and 2D NMR spectra. A reaction mechanism during the preparation was proposed, and the electron effect on the stabilization of the carbocation was discussed. Various DDM/DOPO‐PHM molar ratios were used to get the materials with different phosphorus contents. Their dynamic mechanical, thermal, and flame‐retardant properties were evaluated by dynamic mechanical thermal analysis, thermogravimetric analysis, and limiting oxygen index (LOI) respectively. All samples had a single T_g, showing that these epoxy resins were homogeneous phase for long‐term use in spite of adding DOPO‐PHM. Both char yields (under nitrogen and air atmospheres) increased with the increasing of phosphorus content and the LOI values increased from 24.5 for standard resin to 33.5 for phosphorus‐containing resins, indicating the significant enhancement of thermal stability and flame retardancy. POLYM. ENG. SCI., 54:1192–1200, 2014. © 2013 Society of Plastics Engineers     

Preparation and characterization of microcapsulated red phosphorus and its flame‐retardant mechanism in halogen‐free flame retardant polyolefins

Microcapsulated red phosphorus (MRP), with a melamine–formaldehyde resin coating layer, was prepared by two‐step coating processes. The physical and chemical properties of MRP were characterized by Fourier‐transform infrared spectroscopy (FTIR), X‐ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) and other measurements. The flame retardant action and mechanism of MRP in the halogen‐free flame retardant (HFFR) polyolefins (PO) blends have been studied using cone calorimeter, limiting oxygen index (LOI), thermogravimetric analysis (TGA) and dynamic FTIR spectroscopy. The results show that the MRP, which is coated with melamine–formaldehyde resin, has a higher ignition point, a considerably lower amount of phosphine evolution and of water absorption compared with red phosphorus (RP) itself. The data observed by cone calorimeter, LOI and TGA measurements from the PO/HFFR blends demonstrated that the MRP can decrease the heat release rate and effective heat of combustion, and increase the thermostability and LOI values of PO materials. The dynamic FTIR results revealed the flame‐retardant mechanism that RP can promote the formation of charred layers with the P–O and P–C complexes in the condensed phase during burning of polymer materials. Copyright © 2003 Society of Chemical Industry     

Synthesis,characteristic of a novel flame retardant containing phosphorus and its application in poly(ethylene‐co‐vinyl acetate)

A novel flame retardant (SPDH) containing phosphorus was synthesized through the reaction of 10‐(2, 5‐dihydroxyphenyl)‐9, 10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO‐HQ) and synthesized intermediate product 3, 9‐dichloro‐2, 4, 8, 10‐tetraoxa‐3, 9‐diphosphaspiro(5.5)undecane‐3, 9‐dioxide (SPDPC). The structure and properties of SPDPC and SPDH were characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR) spectroscopy and thermogravimetric analysis (TGA). After blending with poly(ethylene‐co‐vinyl acetate) (EVA), the flame‐retardant properties of EVA/SPDH composites were estimated by cone calorimeter, limited oxygen index (LOI) and UL‐94 tests, whereas the thermal stabilities were investigated using TGA. The morphological microstructure of the char formed by EVA/SPDH composite after combustion in cone calorimeter was investigated by scanning electron microscopy (SEM). The results indicate that the flame retardant and thermal stability were improved by incorporation of SPDH. The rich foamy char layers were observed from the residues after combustion in a cone calorimeter, which exactly benefits the improvement of thermal stability and flame retardant property of materials. Copyright © 2010 John Wiley & Sons, Ltd.     

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.     

Synergistic effect of phosphorus,nitrogen, and silicon on flame‐retardant properties and char yield in polypropylene

In this study, several flame retardants (FRs), containing phosphorus, nitrogen, and silicon, were synthesized. These synthesized FRs were blended with polypropylene (PP) to obtain mixture samples. The flame‐retardant properties of these mixture samples were estimated by the limiting oxygen index (LOI) value and thermal stabilities were characterized by thermogravimetric analysis. The LOI values of these samples were improved from 17.0 to 26.0 and the char yield increased from 0 to 27 wt %. A comparison of these samples, with respect to their LOI values and carbon yield, showed that the FRs, which simultaneously contained phosphorus, nitrogen, and silicon elements, can provide materials with the best flame‐retardant properties, suggesting that there is a synergistic effect among the three elements on the flame‐retardant properties and char yield when they are used in PP. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 854–860, 2005     

Synthesis of a novel cross‐linked organophosphorus‐nitrogen containing polymer and its application in flame retardant epoxy resins

A novel cross‐linked organophosphorus–nitrogen polymetric flame retardant additive poly(urea tetramethylene phosphonium sulfate) defined as PUTMPS was synthesized by the condensation polymerization between urea and tetrahydroxymethyl phosphonium sulfate. Its chemical structure was well characterized by Fourier transform infrared (FTIR) spectroscopy, ¹³C and ³¹P solid‐state nuclear magnetic resonance. The synthesized PUTMPS and curing agent m‐phenylenediamine were blended into epoxy resins to prepare flame retardant epoxy resin thermosets. The effects of PUTMPS on fire retardancy and thermal degradation behavior of EP/PUTMPS thermosets were investigated by limiting oxygen index (LOI), vertical burning test (UL‐94), cone calorimeter measurement, and thermalgravimetric analysis (TGA) tests. The surface morphologies and chemical compositions of char residues for cured epoxy resins were investigated by scanning electron microscopy and X‐ray photoelectron spectroscopy (XPS), respectively. Water resistant properties of epoxy resin thermosets were evaluated by putting the samples into distilled water at 70°C for 168 h. The results demonstrated that the EP/12 wt% PUTMPS thermosets successfully passed UL‐94 V‐0 flammability rating and the LOI value reached 31.3%. The TGA results indicated that the incorporation of PUTMPS promoted epoxy resin matrix decomposed and char forming ahead of time, which led to a higher char yield and thermal stability for epoxy resin thermosets at high temperature. The morphological structures and analysis of XPS for the char residues of the epoxy resin thermosets shown that PUTMPS benefited to the formation of a sufficient, more compact, and homogeneous char layer with rich flame retardant elements on the materials surface during burning, which prevented the heat transmission and diffusion, limited the production of combustible gases, inhibited the emission of smoke, and then led to the reduction of the heat release rate and smoke produce rate. After water resistance tests, EP/12 wt% PUTMPS thermosets still remained excellent flame retardancy. Copyright © 2015 John Wiley & Sons, Ltd.     

Flame retarding mechanism of Polyamide 6 with phosphorus‐nitrogen flame retardant and DOPO derivatives

A novel flame‐retardant composite was prepared by introducing a phosphorus‐nitrogen flame retardant and DOPO‐SiO₂ into PA6. DOPO‐SiO₂ was synthesized successfully in a one‐step process. PA6/OP1314/DOPO‐SiO₂ achieved a UL 94 V‐0 rating with an LOI value of 31%. The maximum mass loss rate of decomposition decreased significantly and char residue increased to 11.6 wt % compared with that of pure PA6. The compacted and dense char was formed due to the combination of the P‐N flame retardant and DOPO‐SiO₂. The complex viscosity of PA6/OP1314/DOPO‐SiO₂ increased considerably which tend to prevent the dripping phenomenon. The flame‐retardant mechanism of PA6/OP1314/DOPO‐SiO₂ was also investigated by Fourier transform infrared spectroscopy FTIR at different temperatures and the pyrolysis products were investigated by pyrolysis gas chromatography/ mass spectrum (Py‐GC/MS). It was assumed that DOPO‐SiO₂ and the hypophosphite of OP1314 possess excellent flame retardancy during the gaseous phase. Meanwhile, melamine and phosphate reacted with the pyrolytic products of PA6 to protect the matrix during the condensed phase. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42932.     

ZnO对PP/MPP/PEPA膨胀阻燃体系的协同作用

以ZnO为阻燃协效剂,采用多聚磷酸蜜胺(MPP)和笼状季戊四醇磷酸酯(PEPA)复配阻燃剂,制备了具有良好阻燃性能的无卤阻燃PP。研究了ZnO用量对PP阻燃性能和协效作用的影响。结果表明:添加少量的ZnO即可显著提高PP的阻燃性能。当MPP、PEPA和ZnO添加量分别为12%、8%和1%时,阻燃PP的氧指数高达29.5%。TGA、FTIR分析和体式显微镜观测结果表明:添加ZnO可以催化MPP/PEPA间的酯化反应,促进体系成炭,形成更致密的炭层,从而提高材料的阻燃性能。     

Role of caged bicyclic pentaerythritol phosphate alcohol in flame retardancy of PA6 and mechanism study

A series of PA6/PEPA composites were prepared by mixing caged bicyclic pentaerythritol phosphate alcohol (PEPA) and polyamide 6 (PA6) at different feed ratios by the melt‐blending method in a twin‐screw extruder. The influence of PEPA on the flame‐retardant properties of PA6 was investigated using the limiting oxygen index (LOI), the Underwriters Laboratories UL‐94 test, and the cone calorimeter method. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy, X‐ray photoelectron spectroscopy, thermogravimetry (TG), and TG‐FTIR were conducted to study the influence of PEPA on the thermal decomposition and the mechanism of performance of PA6 from products of condensed and gaseous phases. The results show that the LOI value and the content of residual char of PA6/PEPA composites increased with increasing PEPA content, and an LOI value of 38% could be reached when the feed ratio of PEPA was 30 wt %. The average heat release rate and total heat release drastically decreased with increasing content of PEPA, and the amount of carbon residue increased by 52.9% over neat PA6 after TG tests. The inorganic acid produced by PEPA during combustion can be used as an acid source to promote the dehydration of PA6 and the processes of esterification crosslinking, arylation, and carbonization. Moreover, there was less CO₂ released than by PA6, and more carbon‐containing compound remained in the composites so that a stable carbon layer structure was formed. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46236.     

A formaldehyde‐free flame retardant wood particleboard system based on two‐component polyurethane adhesive

To address the problem of formaldehyde‐free flame retardation of wood particleboard, a novel phosphorus‐containing compound, di(2,2‐dimethyl‐1,3‐propanediol phosphate) urea (DDPPU) was synthesized. DDPPU was used as flame retardant for wood particleboard. The flammability of treated wood particleboard systems consisted of wood particles, polyurethane (PU) adhesive, and different flame retardant formulations were investigated by limiting oxygen index (LOI). The results of LOI indicate that DDPPU could improve the flame retardancy of wood particleboard. However, when H₃BO₃ was used as the second flame retardant component and combined with DDPPU, the flame retardant wood particleboard could obtain the highest LOI value (46.0) in these experiments. Thermogravimetric analysis shows that treated wood particleboard can decrease the initial decomposition temperature, and that at higher temperatures the degradation rate are lower than the untreated wood particleboard. Furthermore, wood particleboard treated with DDPPU/H₃BO₃ has a higher yield of residue char at 600°C than that treated with other flame retardant systems. The ability of char formation of these samples agrees with the order of LOI values. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Flame‐retardant and thermal degradation mechanism of low‐density polyethylene modified with aluminum hypophosphite and microencapsulated red phosphorus

Aluminum hypophosphite (AHP), a novel flame retardant, was used to improve the flame retardancy of low‐density polyethylene (LDPE) with microencapsulated red phosphorus (MRP). The synergistic effect between MRP and AHP was investigated by the limiting oxygen index (LOI), vertical burning test (UL‐94), and thermogravimetric analysis. When the contents of MRP and AHP were 10 and 30 phr, the LOI of LDPE/10MRP/30AHP composite was 25.5%, and it passed the UL‐94 V‐0 rating (the number before “MRP” and “AHP” is the loading of MRP and AHP, In LDPE/10MRP/30AHP, the content of the LDPE, MRP and AHP is 100phr, 10phr and 30phr, where phr refers to parts per hundreds of resin). The results of cone calorimetry testing show that the heat release rate of the composites was significantly reduced, and the strength of the char layer improved when the loading of AHP increased. The thermal stability of the LDPE/10MRP/30AHP composite was enhanced. The structure of the char was investigated by Fourier transform infrared spectrometry and scanning electron microscopy/energy‐dispersive spectrometry. The results indicate that AHP promoted the formation of stable char. This research provided a good way to prepare flame‐retardant materials with a halogen‐free flame retardant and contributed to environmental protection. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43225.