Synthesis of a novel flame retardant containing phosphorus and sulfur and its application in polycarbonate

A novel flame retardant containing phosphorus and sulfur, bis(2‐tienyl)phenylphosphine (BTPP) was synthesized and characterized with Fourier transform infrared spectroscopy, ¹H, ¹³C, and ³¹P nuclear magnetic resonance. BTPP was used to impart flame retardancy to polycarbonate (PC). Combustion behaviors and thermal degradation properties of PC/BTPP system were assayed by limiting oxygen index (LOI), vertical burning test (UL‐94), cone calorimeter test, and thermogravimetric analysis. PC/3 wt% BTPP passed UL‐94 V‐0 rating with 3.0 mm samples and the LOI value was 36.5%. PC/6 wt% BTPP passed UL‐94 V‐0 rating with 1.6 mm samples and the LOI value was 38.5%. Scanning electron microscopy revealed that char properties had direct effects on the flame retardancy. Mechanical properties and water resistance of PC/BTPP system were also examined. After water resistance test, PC/3 wt% BTPP with 3.0 mm samples and PC/6 wt% BTPP with 1.6 mm samples kept V‐0 rating and mass loss were only 0.2%. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

Synthesize and Characterization of Flame Retardant Copolyesters PET/Phosphorus Compound

The aim of this study was to achieve a fiber‐grade poly(ethylene terephthalate) (PET) with flame retardancy properties. Flame retardant copolyesters based on ethylene glycol, terephthalic acid, and 3‐(hydroxyphenyl phosphinyl) propionic acid (HPP), as a flame retardant comonomer, were synthesized in presence of antimony trioxide catalyst at laboratory and semi‐industrial scales. At first, copolyesters with the lowest amount of flame retardant comonomer were synthesized at laboratory scale in a one‐pot reactor setup. In the second stage, flame retardant PET was synthesized in semi‐industrial pilot with HPP (PET‐HPP). The obtained copolyesters demonstrated almost identical intrinsic viscosities and other characteristics such as PET. Fourier transform infrared spectroscopy (FTIR), 1H‐NMR spectroscopy, and RMS test were performed. Flame retardancies were evaluated by a limiting oxygen index (LOI) test. The results indicated that the presence of FR significantly improved the flame retardancy and thermal stability of PET‐HPP. LOI values increased from 28% (PET) to 33 (PET‐HPP) (at laboratory scale) and 44% (at semi‐industrial scale). Differential scanning calorimetry analysis showed that the HPP polyester chain had a higher flexibility compared to PET, due to lower glass transition temperature. The effect of adding FR with regard to the thermal stability of PET‐HPP was investigated via thermogravimetric analysis. The physical properties of both the polymers are similar and suitable for textile application. J. VINYL ADDIT. TECHNOL., 25:262–270, 2019. © 2018 Society of Plastics Engineers     

Preparation and characterization of new flame retardant polyurethane composite and nanocomposite

In this work, a new flame retardant additive [2‐phenyl‐1,3,2 oxazaphospholidine 2‐oxide (POPO)] containing phosphorus and nitrogen is synthesized using phenyl phosphonic dichloride, ethanol amine, and copper (II) chloride, as catalyst. POPO is characterized by ¹H‐NMR, ¹³C‐NMR, and ³¹P‐NMR and used as additive in polyurethane composites. Moreover, two commercial flame retardant additives [tricalcium diphosphate and hexabromocyclododecane (HBCD)] as well as nanoclay are used to compare flame retardancy of the synthesized additive. Limited oxygen index (LOI) and time burning (flammability test) of polyurethane composites and nanocomposites are evaluated. The results of the LOI test demonstrate that POPO is an excellent flame retardant additive and can be used to improve flame retardancy of polyurethane composites. In addition, increasing the additive content leads to an improvement of the flame retardancy of the samples. The LOI results show, however, that POPO is a good flame retardant, but the high synthesis cost of this flame retardant is a major disadvantage. Thermogravimetric analysis results show that using POPO in polyurethane matrices leads to low thermal stability and high char residue. Moreover, the nanocomposite has better thermal stability than the other samples. Scanning electron microscope micrographs have been used to evaluate the char residue of the samples. These micrographs indicate that POPO is an intumescent flame retardant and HBCD follows a nonintumescent mechanism. Exfoliated/intercalated structures have been shown for nanocomposites by transmission electron microscope. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Flame retardant performance of a carbon source containing DOPO derivative in PET and epoxy

The combination of gas‐phase and condensed‐phase action will contribute to high quality flame retardant. A novel 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO)‐based flame retardant (DOPO‐DOPC), which contains carbon source was synthesized in favor of conducting the effect of gas‐phase as well as promoting the char formation in condensed‐phase. The chemical structure of DOPO‐DOPC was characterized by nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FTIR). DOPO–DOPC was used as an additive in poly(ethylene terephthalate) (PET) and epoxy resin (EP). The flame retardancy of PET/DOPO‐DOPC and EP/DOPO‐DOPC composites were studied by limiting oxygen index (LOI) and UL‐94 test. The results showed that the incorporation of DOPO–DOPC into PET or EP could obviously improve their flame retardancy. The LOI values of modified PET or EP, which contained 10 wt % DOPO‐DOPC reached 42.8 and 31.7%, respectively. The thermogravimetric analysis (TGA) results revealed that DOPO–DOPC enhanced the formation of char residues. The Laser Raman spectroscopy (LRS) was used to investigate the carbon structure of thermal oxidation residues. Because of the combination of the gas phase flame retardant effect of DOPO moiety and the promoting formation of char residues in condensed phase, the PET and EP composites exhibited significant improvement toward flame retardancy. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44639.     

Flammability properties of paper coated with poly (methylenephosphine), an organophosphorus polymer

The flame retardant properties of paper coated with either poly(methylenephosphine) ( PMP ) or poly(methylenephosphine oxide) ( PMP‐O ) are evaluated. Paper sheets made from thermomechanical pulp were coated with PMP (M_n = 27,000 g mol^?1, polydispersity index (PDI) = 1.47), PMP‐O (M_n = 30,000 g mol^?1, PDI = 1.24), or monobasic ammonium phosphate (MAP) to achieve an approximate loading of 0.8 mmol P/g paper. Thermal stability studies by thermogravimetric analysis show that the paper degrades in two main stages, with the second thermo‐oxidative stage having a slower rate of degradation for paper treated with flame retardants. The flame retardancy of the sheets was evaluated by Technical Association of Pulp and Paper Industry Standard Method T461 cm‐00 and by limiting oxygen index (LOI) according to ASTM D2863. After leaching with water, samples coated with PMP or PMP‐O show no loss of flame retardancy, while those coated with MAP lose all flame retardancy. The LOI of paper coated with PMP (23.1%) or PMP‐O (25.9%) is higher than those of uncoated paper (19.6%), but lower than MAP‐coated paper (34.7%). Analysis of the char provided evidence that the flame retardant mechanism of PMP and PMP‐O involves the formation of phosphorus oxides and acids. Copyright © 2014 John Wiley & Sons, Ltd.     

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     

Effect of methyl methacrylate on the properties of transparent flame retardant unsaturated phosphate ester copolymer

The effect of methyl methacrylate (MMA) on the properties of transparent flame retardant unsaturated phosphate ester copolymer (poly[UPE‐co‐MMA]) prepared by bulk polymerization technique was investigated. Fourier transform infrared spectra, gel fraction (G) test, and dynamic mechanical analysis revealed the structure and crosslinking density of poly(UPE‐co‐MMA) copolymers. The thermal degradation and flame retardancy of copolymers were indicated by thermogravimetric analysis, limiting oxygen index (LOI), and microscale combustion calorimeter (MCC) test. Besides, the mechanical properties and transparency were tested with testing machines and solid ultraviolet absorption spectra. As the MMA content increased to 50%, the copolymer contained 50 wt% MMA showed the maximal G (88.93%) and transmittance was up to 91.72%. From the poly(UPE‐co‐MMA) copolymers, the tensile strength increased from 14.62 to 26.95 MPa, assigned to the increase of crosslinking density of copolymers. The char yield of poly(UPE‐co‐MMA) was up to 21.18 wt%, which was a result of decomposition of phosphate groups, producing a phosphorus‐rich layer that increased the thermal stability of the residues. LOI and MCC results confirm that the introduction of MMA can retain the flame retardancy of copolymer remarkably. POLYM. ENG. SCI., 59:2103–2109, 2019. © 2019 Society of Plastics Engineers     

Construction of novel silicon‐phosphorus linear polymers with DDSQ and DOPO derivatives for effective flame retardancy of PC/ABS

Two kinds of novel silicon‐phosphorus linear polymers were synthesized by the hydrosilylation reaction of double‐decker‐shaped silsesquioxane (DDSQ) and 9,10‐dihydro‐9‐oxa‐10‐ phosphaphenanthrene‐10‐oxide (DOPO) derivatives and characterized using ¹H NMR, ³¹P NMR, and ²⁹Si NMR. Flame‐retardant polycarbonate/acrylonitric‐butadiene‐styrene (PC/ABS) blends were prepared with different contents of silicon‐phosphorus linear polymers. The flame‐retardant properties of silicon‐phosphorus linear polymers as well as the morphology were investigated in detail by using thermogravimetric analysis (TGA), limiting oxygen index (LOI), (Underwriters Laboratory) UL‐94, microscale combustion calorimetry (MCC), and scanning electron microscopy (SEM), respectively. The silicon‐phosphorus linear polymers containing DDSQ and DOPO units can synergistically improve the flame retardancy and thermal stability of PC/ABS blends. Flame‐retardant polymers with different linkers between DDSQ and phosphate units show comparable effect on the flame retardancy of PC/ABS.     

Improving thermal and flame‐retardant properties of epoxy resins by a new imine linkage phosphorous‐containing curing agent

A new reactive phosphorus‐containing curing agent with imine linkage called 4, 4′‐[1, 3‐phenyl‐bis(9, 10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐yl)dimethyneimino)]diphenol (2) was synthesized both via two‐pot and one‐pot procedure. The chemical structure of this curing agent was confirmed by FTIR, ¹H, ¹³C, and ³¹P NMR spectra. A series of thermosetting systems were prepared by using conventional epoxy resins (E51), 4, 4′‐diaminodiphenyl methane (DDM) and (2). Resins with different phosphorus contents were obtained by changing the DDM/(2) molar ratios. Their dynamic mechanical thermal, thermal and flame‐retardant properties were evaluated by dynamic mechanical thermal analysis (DMTA), thermogravimetric analysis (TGA), and limiting oxygen index (LOI), respectively. All samples had a single T_g, which showed that these epoxy resins were homogeneous phase. Both the two char yields under nitrogen and air atmospheres increased with increasing content of (2) and the LOI values increased from 24.5 for standard resin to 37.5 for phosphorus‐containing resin, which indicated that incorporation of (2) could impart good thermal stability and excellent flame retardancy to the conventional epoxy thermosets. POLYM. ENG. SCI., 56:441–447, 2016. © 2016 Society of Plastics Engineers     

The flame retardant effect of aluminum phosphinate in combination with zinc borate,borophosphate, and nanoclay in polyamide‐6

The effect of zinc borate (ZnB), borophosphate (BPO₄), and organoclay were studied to improve the flame retardancy of polyamide‐6 composites containing organic phosphinates. The flame retardancy of polyamide‐6 composites was investigated using limiting oxygen index (LOI), Underwriters Laboratories (UL‐94) standard, thermogravimetric analysis, Fourier transform infrared spectroscopy, and mass loss calorimeter. The addition of 15 wt% aluminum phosphinate (AlPi) increased the LOI value from 22.5 to 29.5, and V0 rating was obtained from UL‐94 test. The addition of organoclay, ZnB, and borophosphate does not change the predominant gas phase mechanism of AlPi during LOI and UL‐94 tests. The addition of organoclay increased the condensed phase mechanism of AlPi physically by the protective effect of layered silicate, whereas the addition of ZnB increased the condensed phase mechanism of AlPi chemically by the formation of boron aluminum phosphate species deducted from mass loss calorimeter studies. Copyright © 2012 John Wiley & Sons, Ltd.     

Synergism between hydrotalcite and silicate‐modified expandable graphite on ethylene vinyl acetate copolymer combustion behavior

Influence of independent Mg–Al‐layered double hydroxide (LDH), silicate modified expandable graphite (EG), mixture of LDH and EG at various ratios on ethylene vinyl acetate copolymer (EVA) combustion behavior and thermal stability was detected in sequence through the limiting oxygen index (LOI), vertical combustion (UL‐94) level, microscale combustion calorimeter (MCC) tests and thermal gravimetric/differential thermal gravimetric (TG/DTG) analysis. Results show that the 30 wt % LDH can improve the LOI of 70EVA/30LDH to 27.0%, but the combustion accompanies with serious melt‐dropping. While, the same amount of the EG can increase the LOI, UL‐94 level to 28.5%, V‐0 respectively. However, the combination of LDH and EG can further enhance the 70EVA/20LDH/10EG flame retardancy, it presents the LOI of 29.7%, UL‐94 level of V‐0, and total heat release of 29.5 kJ g^?1. The excellent flame retardancy is attributed to its compact residue. Compared with residue mass, the residue compactness plays a more important role in improving flame retardancy. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44634.     

Crystallization of 2‐methyl‐1,3‐propanediol substituted poly(ethylene terephthalate). I. Thermal behavior and isothermal crystallization

Differential scanning calorimetry (DSC) was used to evaluate the thermal behavior and isothermal crystallization kinetics of poly(ethylene terephthalate) (PET) copolymers containing 2‐methyl‐1,3‐propanediol as a comonomer unit. The addition of comonomer reduces the melting temperature and decreases the range between the glass transition and melting point. The rate of crystallization is also decreased with the addition of this comonomer. In this case it appears that the more flexible glycol group does not significantly increase crystallization rates by promoting chain folding during crystallization, as has been suggested for some other glycol‐modified PET copolyesters. The melting behavior following isothermal crystallization was examined using a Hoffman–Weeks approach, showing very good linearity for all copolymers tested, and predicted an equilibrium melting temperature (T_m⁰) of 280.0°C for PET homopolymer, in agreement with literature values. The remaining copolymers showed a marked decrease in T_m⁰ with increasing copolymer composition. The results of this study support the claim that these comonomers are excluded from the polymer crystal during growth. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2592–2603, 2006     

Flame retardancy and mechanical properties of pet‐based composites containing phosphorus and boron‐based additives

Flame retardancy of poly(ethylene terephthalate), PET, was improved using different flame retardant additives such as triphenylphosphate, triphenylphosphine oxide, zinc borate, and boron phosphate (BP). Composites were prepared using a twin screw extruder and subsequently injection molded for characterization purposes. The flame retardancy of the composites was determined by the limiting oxygen index (LOI) test. Smoke emission during fire was also evaluated in terms of percent light transmittance. Thermal stability and tensile properties of PET‐based composites were compared with PET through TGA and tensile test, respectively. The LOI of the flame retardant composites increased from 21% of neat PET, up to 36% with the addition of 5% BP and 5% triphenyl phosphate to the matrix. Regarding the smoke density analysis, BP was determined as an effective smoke suppressant for PET. Enhanced tensile properties were obtained for the flame retardant PET‐based composites with respect to PET. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42016.     

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.     

Novel flame retardant thermosets from nitrogen‐containing and phosphorus‐containing epoxy resins cured with dicyandiamide

A novel phosphorus‐containing epoxy resin (EPN‐D) was prepared by addition reaction of 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene 10‐oxide (DOPO) and epoxy phenol‐ formaldehyde novolac resin (EPN). The reaction was monitored by epoxide equivalent weight (EEW) titration, and its structure was confirmed by FTIR and NMR spectra. Halogen‐free epoxy resins containing EPN‐D resin and a nitrogen‐containing epoxy resin (XT resin) were cured with dicyandiamide (DICY) to give new halogen‐free epoxy thermosets. Thermal properties of these thermosets were studied by differential scanning calorimeter (DSC), dynamic mechanical analysis (DMA), thermal mechanical analyzer (TMA) and thermal‐gravimetric analysis (TGA). They exhibited very high glass transition temperatures (T_gs, 139–175°C from DSC, 138–155°C from TMA and 159–193°C from DMA), high thermal stability with T_{d,5 wt %} over 300°C when the weight ratio of XT/EPN‐D is ≥1. The flame‐retardancy of these thermosets was evaluated by limiting oxygen index (LOI) and UL‐94 vertical test. The thermosets containing isocyanurate and DOPO moieties showed high LOI (32.7–43.7) and could achieve UL‐94 V‐0/V‐1 grade. Isocyanurate and DOPO moieties had an obvious synergistic effect on the improvement of the flame retardancy. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Flame retardancy in fabric consisting of cellulosic fiber and modacrylic fiber containing fine‐grained MoO3 particles

Flame retardancy of fabrics consisting of modacrylic fiber containing with various dispersed metal compounds and cellulosic fiber has been investigated by means of flame test (ISO15025 procedure A) and limiting oxygen index (LOI). It has been found that excellent flame retardancy is achieved by fine‐grained MoO₃ particles. The afterflame time in flame test and the LOI value are improved with decreasing particle size of MoO₃. The flame retardancy of MoO₃ (particle size; 0.1 µm) is comparable to that of Sb₂O₃. On the other hand, significant improvement in flame retardancy is not observed for other metal compounds although some metal oxides and a hydroxide in the present study are known as flame retardant or smoke suppressing agent in halogen containing polymer in previous studies. In order to clarify the mechanism of the observed flame retardancy by the addition of fine‐grained MoO₃, we have carried out X‐ray fluorescence spectrometry (XRF) measurement of the fabric specimen after the flame test and thermogravimetric analysis (TGA) of various types of samples. These analytical data indicated that MoO₃ works as halogen synergist in solid phase and the char of modacrylic fiber formed by addition of MoO₃ suppresses decomposition of the cotton blended in the fabric in the range of the ignition temperature. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis of a novel flame retardant containing phosphazene and triazine groups and its enhanced charring effect in poly(lactic acid) resin

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. 2017 , 134, 44660.     

Research on properties of rigid polyurethane foam with heteroaromatic and brominated benzyl polyols

Rigid polyurethane foams (RPUFs) were prepared with specific heteroaromatic and brominated benzyl polyols. The mechanical properties and thermal stability were studied using dynamic mechanical analysis (DMA) and thermogravimetric analysis (TG). The limiting oxygen index (LOI) was used to investigate the flame retardancy of the RPUFs. The results showed that the glass transition temperature (T_g) of the RPUF prepared by heteroaromatic polyol was 182°C, demonstrating an improved thermal stability for this specific heteroaromatic polyol. Brominated benzyl polyol exhibited less negative influence on mechanical properties of the RPUFs at the same time of improving the flame retardancy. The LOI values increased with an increase in the brominated polyol content to 27.5%, and the char‐forming ability of the RPUF improved; the char residue rate reached 12.6% at 700°C, but it was only 6.2% without the flame retardant. Scanning electron microscope (SEM) and energy‐dispersive spectrometry (EDS) verified that the mechanism of flame retardancy was due to a synergistic effect of the gas phase and the condensed phase. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42349.     

A high-efficiency DOPO-based reactive flame retardant with bi-hydroxyl for low-flammability epoxy resin

A high-efficiency DOPO-based reactive flame retardant (DPE) with bi-hydroxyl was successfully synthesized via reacting DOPO with imine obtained from the condensation of ethanolamine and 1,4-phthalaldehyde, and used as co-curing agent to improve the fire safety of epoxy resin (EP). Its chemical structure was characterized by Fourier transform infrared (FTIR) spectra, ¹H, ³¹P nuclear magnetic resonance (NMR) spectra and elemental analysis. The curing behavior, thermal properties, flame-retardant properties of EP/DPE systems were investigated. The results revealed that DPE slightly decreased the glass transition temperature (T_g), but accelerated the curing cross-linking reaction of EP. Furthermore, DPE decreased thermal degradation rate of epoxy matrix and promoted the formation of residual char at high temperature. After adding DPE, the flame retardant of epoxy thermosets was greatly improved. Especially, the thermoset modified with 5 wt% DPE achieved limiting oxygen index (LOI) value of 33.6% and V-0 rating in UL-94 test, demonstrating the highly efficient flame retardancy. While its peak heat release rate (PHRR), total heat release (THR) and total smoke production (TSP) were respectively decreased by 32.6%, 17.8%, and 13.9% compared with neat EP. Moreover, the research on flame retardant mechanism disclosed that DPE played dual flame-retardant effect in the gaseous and condensed phases.     

Novel intumescent flame retardants: synthesis and application in polycarbonate

Novel phosphorus‐containing and nitrogen‐containing intumescent flame retardants, bis‐aminobenzyl spirocylic pentaerythritol bisphosphonate (BASPB) and arylene‐N,N′‐bis(2,2‐dimethyl‐1,3‐propanediol phosphoramidate) (ABDPP), were synthesized, and their structures were characterized with Fourier transform infrared spectroscopy and ¹H and ³¹P nuclear magnetic resonance. The phosphorus compounds were used to impart flame retardancy to polycarbonate (PC). Combustion behaviors and thermal degradation properties of the flame‐retarded‐PC composites were assayed by limiting oxygen index (LOI), vertical burning test (UL‐94), cone calorimeter test, and thermogravimetric analysis. PC/5 wt.% BASPB and PC/5 wt.% ABDPP composites passed UL‐94 V‐0 rating; their LOI values were 35.5% and 34.7%, respectively. Scanning electron microscopy revealed that the char properties had crucial effects on the flame retardancy. The mechanical properties and water resistance of the PC/BASPB and PC/ABDPP composites were also measured. After water resistance test, PC/5 wt.% BASPB and PC/5 wt.% ABDPP composites kept V‐0 rating, and the mass loss was only 1.0%. Copyright © 2012 John Wiley & Sons, Ltd.