Thermal properties and flame retardancy of novel epoxy based on phosphorus‐modified Schiff‐base

Through addition reaction of Schiff‐base terephthalylidene‐bis‐(p‐aminophenol) ( DP‐1 ) and diethyl phosphite (DEP), a novel phosphorus‐modified epoxy, 4,4'‐diglycidyl‐(terephthalylidene‐bis‐(p‐aminophenol))diphosphonate ether ( EP‐2 ), was obtained. An modification reaction between EP‐2 and DP‐1 resulted in an epoxy compound, EP‐3 , possessing both phosphonate groups and C?N imine groups. The structure of EP‐2 was characterized by Fourier transform infrared (FTIR), elemental analysis (EA), ¹H, ¹³C, and ³¹P NMR analyses. The thermal properties of phosphorus‐modified epoxies cured with 4,4'‐diaminodiphenylmethane (MDA) and 4,4'‐diaminodiphenyl ether (DDE) were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The activation energies of dynamic thermal degradation (E_d) were calculated using Kissinger and Ozawa's methods. The thermal degradation mechanism was characterized using thermogravimetric analysis/infrared spectrometry (TG‐IR). In addition, the flame retardancy of phosphorus‐modified epoxy thermosets was evaluated using limiting oxygen index (LOI) and UL‐94 vertical test methods. Via an ingenious design, phosphonate groups were successfully introduced into the backbone of the epoxies; the flame retardancy of phosphorus‐modified epoxy thermosets was distinctly improved. Due to incorporation of C?N imine group, the phosphorus‐modified epoxy thermosets exhibited high thermal stabilities; the values of glass‐transition temperatures (T_gs) were about 201–210°C, the values of E_d were about 220–490 kJ/mol and char yields at 700°C were 49–53% in nitrogen and 45–50% in air. These results showed an improvement in the thermal properties of phosphorus‐modified epoxy by the incorporation of C?N imine groups. Copyright © 2010 John Wiley & Sons, Ltd.     

Effect of a triazine ring‐containing charring agent on fire retardancy and thermal degradation of intumescent flame retardant epoxy resins

A triazine ring‐containing charring agent (PEPATA) was synthesized via the reaction between 2,6,7‐trioxa‐l‐phosphabicyclo‐[2.2.2]octane‐4‐methanol (PEPA) and cyanuric chloride. It was applied into intumescent flame retardant epoxy resins (IFR‐EP) as a charring agent. The effect of PEPATA on fire retardancy and thermal degradation behavior of IFR‐EP system was investigated by limited oxygen index (LOI), UL‐94 test, microscale combustion calorimetry (MCC), thermogravimetric analysis (TGA) and thermogravimetric analysis/infrared spectrometry (TG‐IR). The glass transition temperatures (T_g) of IFR‐EP systems were studied by dynamic mechanical analysis (DMA). The LOI values increased from 21.5 for neat epoxy resins (EPs) to 34.0 for IFR‐EP, demonstrating improved flame retardancy. The TGA curves showed that the amount of residue of IFR‐EP system was largely increased compared to that of neat EP at 700 °C. The new IFR‐EP system could apparently reduce the amount of decomposing products at higher temperatures and promotes the formation of carbonaceous charred layers that slowed down the degradation. Copyright © 2010 John Wiley & Sons, Ltd.     

Flame‐retardant performance and mechanism of epoxy thermosets modified with a novel reactive flame retardant containing phosphorus,nitrogen, and sulfur

A novel phosphorus‐containing, nitrogen‐containing, and sulfur‐containing reactive flame retardant (BPD) was successfully synthesized by 1‐pot reaction. The intrinsic flame‐retardant epoxy resins were prepared by blending different content of BPD with diglycidyl ether of bisphenol‐A (DGEBA). Thermal stability, flame‐retardant properties, and combustion behaviors of EP/BPD thermosets were investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), limited oxygen index (LOI) measurement, UL94 vertical burning test, and cone calorimeter test. The flame‐retardant mechanism of BPD was studied by TGA/infrared spectrometry (TGA‐FTIR), pyrolysis‐gas chromatography/mass spectrometry (Py‐GC/MS), morphology, and chemical component analysis of the char residues. The results demonstrated that EP/BPD thermosets not only exhibited outstanding flame retardancy but also kept high glass transition temperature. EP/BPD‐1.0 thermoset achieved LOI value of 39.1% and UL94 V‐0 rating. In comparison to pure epoxy thermoset, the average of heat release rate (av‐HRR), total heat release (THR), and total smoke release (TSR) of EP/BPD‐1.0 thermoset were decreased by 35.8%, 36.5% and 16.5%, respectively. Although the phosphorus content of EP/BPD‐0.75 thermoset was lower than that of EP/DOPO thermoset, EP/BPD‐0.75 thermoset exhibited better flame retardancy than EP/DOPO thermoset. The significant improvement of flame retardancy of EP/BPD thermosets was ascribed to the blocking effect of phosphorus‐rich intumescent char in condensed phase, and the quenching and diluting effects of abundant phosphorus‐containing free radicals and nitrogen/sulfur‐containing inert gases in gaseous phase. There was flame‐retardant synergism between phosphorus, nitrogen, and sulfur of BPD.     

Effect of a novel charring-foaming agent on flame retardancy and thermal degradation of intumescent flame retardant polypropylene

A new triazine polymer was synthesized by using cyanuric chloride, ethanolamine and ethylenediamine as raw materials. It is used both as a charring agent and as a foaming agent in intumescent flame retardants, designated as charring-foaming agent (CFA). Effect of CFA on flame retardancy, thermal degradation and mechanical properties of intumescent flame retardant polypropylene (PP) system (IFR-PP system) has been investigated. The results demonstrated that the intumescent flame retardant (IFR) consisting of CFA, APP and Zeolite 4A is very effective in flame retardancy of PP. It was found that when the weight ratio of CFA to APP is 1:2, that is, the components of the IFR are 64 wt% APP, 32 wt% CFA and 4 wt% Zeolite 4A, the IFR presents the most effective flame retardancy in PP systems. LOI value of IFR-PP reaches 37.0, when the IFR loading is 25 wt% in PP. It was also found that when the IFR loading is only 18 wt% in PP, the flame retardancy of IFR-PP can still pass V-0 rating, and its LOI value reaches 30.2. TGA data obtained in pure nitrogen demonstrated that CFA has a good ability of char formation itself, and CFA shows a high initial temperature of the thermal degradation. The char residue of CFA can reach 35.7 wt% at 700 °C. APP could effectively promote the char formation of the APP-CFA system. The char residue reaches 39.7 wt% at 700 °C, while it is 19.5% based on calculation. The IFR can change the thermal degradation behaviour of PP, enhance T_max of the decomposition peak of PP, and promote PP to form char, based upon the results of the calculation and the experiment. This is attributed to the fact that endothermic reactions took place in IFR charring process and the char layer formed by IFR prevented heat from transferring into inside of IFR-PP system. TGA results further explained the effective flame retardancy of the IFR containing CFA.     

Synthesis of a novel phosphate‐containing highly transparent PMMA copolymer with enhanced thermal and flame retardant properties

A novel poly(methyl methacrylate) (PMMA)‐based copolymer (PMMA‐co‐BDPA) rich in aromatic rings was synthesized via radical copolymerization between a phosphorus‐containing acrylic monomer (BDPA) and methyl methacrylate (MMA). UV‐vis spectroscopy demonstrated that the copolymer had high transparency. Thermogravimetric analysis (TGA) and a differential scanning calorimeter (DSC) were used to test the thermal properties of the composites. Additionally, the PMMA‐co‐BDPA‐15 copolymer exhibited a 23% increase in the limited oxygen index (LOI) value. A cone calorimeter test indicated that the peak heat release rate (pk‐HRR) of PMMA‐co‐BDPA was reduced by 29.2% compared with that of pure PMMA, and the carbon yield of burning was obviously increased. The combined test results demonstrated that the prepared copolymer material had good transparency, thermal stability, and flame retardancy.     

Flammability and thermal degradation of epoxy acrylate modified with phosphorus‐containing compounds

A series of UV‐curable flame retardant resins was obtained using epoxy acrylate (EA) modified with 1‐oxo‐4‐hydroxymethyl‐2,6,7‐trioxa‐1‐phosphabicyclo[2.2.2]octane (PEPA). The flammability was characterized by limiting the oxygen index (LOI), UL 94 and cone calorimeter, and the thermal degradation of the flame retardant resins was studied using thermogravimetric analysis (TGA) and real time Fourier transform infrared (RTFTIR). The results indicated that the flame retardant efficiency increases and the heat release rate (HRR) decreases greatly with the content of PEPA. The TG data showed that the modified epoxy acrylates (MEAs) have lower initial decomposition temperatures and higher char residues than pure EA. The RTFTIR study indicates that the MEAs have lower thermal oxidative stability than the pure EA. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis and property of phosphorus‐containing bismaleimide by a novel method

A series of novel addition products (phosphorus content: 0.5, 1, 2, and 3 wt %) were synthesized from the reaction of 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene 10‐oxide (DOPO) and 4,4′‐bismaleimidodiphenylmethane (BMI). NMR and IR were used to confirm the structures of the synthetic bismaleimides. Dynamic mechanical analysis scans showed the glass‐transition temperatures of these cured BMIs decreased with phosphorus content. Thermal gravimetric analysis heating scans indicated that they had high thermal stability. Limiting oxygen index measurements implied that the flame retardancy was improved by the incorporation of DOPO. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2260–2268, 2000     

Water resistance,thermal stability,and flame retardation of polypropylene composites containing a novel ammonium polyphosphate microencapsulated by UV‐curable epoxy acrylate resin

In this work, ammonium polyphosphate (APP) was microencapsulated by UV‐curable epoxy acrylate (EA) resin. The resulting novel EA‐microencapsulated APP (EA‐APP) was characterized by Fourier transform infrared spectra, X‐ray photoelectron spectroscopy, X‐ray diffraction, scanning electron microscopy, granulometry, and thermogravimetric (TG) analysis. EA‐APP was used to flame retard polypropylene (PP). The water solubility of EA‐APP and the water resistance of PP/EA‐APP systems were investigated. The thermal stability and combustion behaviors of PP/EA‐APP composites were studied through TG and cone calorimeter (CC) tests, respectively. The water resistance test showed that the EA shell could significantly improve the water resistance of PP/APP. TG data illustrated that the char residue of EA‐APP greatly increased by 149% compared with uncoated APP, and the thermal stability of PP/EA‐APP composite was improved because of the microencapsulation of APP, with an increment of 248% for the char residue compared with PP/APP. CC test results indicated that the peak value of heat release rate, the total heat release, and the peak of smoke production rate of PP/EA‐APP decreased in comparison with PP/APP. The mechanism for the improvement of flame retardancy in CC test was discussed based on the experimental results. EA resin containing a large number of hydroxyl groups might promote the dehydration reaction in EA‐APP, which facilitated the formation of char residue and the stabilization of APP. Consequently, the flame‐retardant efficiency for APP was improved because of the presence of EA shell. Copyright © 2014 John Wiley & Sons, Ltd.     

A novel phosphorus‐containing thermotropic liquid crystalline poly(ester‐imide) with high flame retardancy

A novel phosphorus–nitrogen thermotropic liquid crystalline poly(ester‐imide) (PN‐TLCP) derived from p‐acetoxybenzoic acid (ABA), terephthalic acid (TPA), acetylated 2‐(6‐oxide‐6H‐dibenz<c,e><1,2>oxa phosphorin‐ 6‐yl)‐1,4‐dihydroxy phenylene (DOPO‐AHQ) and N,N'‐hexane‐1,6‐diylbis(trimellitimide) was prepared by melt transesterification. The chemical structure, the mesophase behavior, and the thermal properties of the copolymer were investigated with Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance spectroscopy (¹H NMR), elemental analysis, wide‐angle X‐ray diffraction (WAXD), hot‐stage polarized light microscopy (PLM), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). PN‐TLCP exhibited a nematic mesophase with a strong birefringence at a low and broad mesomorphic temperature ranging from 220 to 350°C, an initial flow temperature as low as about 190°C and a glass transition temperature of about 160°C. PN‐TLCP has also good thermal stability, high char residues and excellent flame retardancy (limiting oxygen index, LOI = 71 and UL‐94 V‐0 rating). Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis and characterization of a novel phosphorus–nitrogen‐containing flame retardant and its application for textile

The economic and environmentally friendly flame‐retardant compound, tetramethyl (6‐chloro‐1,3,5‐triazine‐2,4‐diyl)bis(oxy)bis(methylene) diphosphonate ( CN‐1 ), was synthesized by a simple two‐step procedure from dimethyl phosphate, and its chemical structure was characterized by ¹H, ¹³C, and ³¹P nuclear magnetic resonance and gas chromatography mass spectroscopy. Using the traditional pad–dry–cure method, we obtained several different add‐ons (wt%) by treating cotton twill fabric with flame retardant ( CN‐1 ). Thermogravimetric analysis, in an air and nitrogen atmosphere, of the modified cotton showed that decomposition occurred ~230°C with 16% residue weight char yield at 600°C, indicating high thermal stability for all treated levels. Limiting oxygen index (LOI) and the vertical flammability test were employed to determine the effectiveness of the flame‐retardant treatments on the fabrics. LOI values increased from ~18 vol% oxygen in nitrogen for untreated fabric to maximum of 34 vol% for the highest treatment level. Fabrics with higher levels of flame retardant also easily passed the vertical flammability test. Furthermore, Fourier transform infrared and scanning electron microscopy were utilized to characterize the chemical structure as well as the surface morphology of the flame‐retardant treated twill fabrics, including char area and the edge between unburned fabric and char area. Copyright © 2011 John Wiley & Sons, Ltd.     

Flame‐retardant rigid polyurethane foam with a phosphorus‐nitrogen single intumescent flame retardant

A phosphorous‐nitrogen intumescent flame‐retardant, 2,2‐diethyl‐1,3‐propanediol phosphoryl melamine (DPPM), was synthesized and characterized by Fourier transform infrared spectroscopy and nuclear magnetic resonance. Flame‐retardant rigid polyurethane foams (RPUFs) with DPPM (DPPM‐RPUF) as fire‐retardant additive were prepared. Scanning electron microscope (SEM) and mechanical performance testing showed that DPPM exhibited a favorable compatibility with RPUF and negligibly negative influence on the mechanical properties of RPUF. The flame retardancy of DPPM on RPUF was investigated by the limiting oxygen index (LOI), vertical burning test and cone calorimeter. The LOI of DPPM‐RPUF could reach 29.5%, and a UL‐94 V‐0 rating was achieved, when the content of DPPM was 25 php. Furthermore, the DPPM‐RPUF exhibited an outstanding water resistance that it could still obtain a V‐0 rating after water soaking. Thermogravimetric analysis showed that the residual weight of RPUF was relatively low, while the charring ability of DPPM‐RPUF was improved greatly. Real‐time Fourier transform infrared spectroscopy was employed to study the thermo‐oxidative degradation reactions of DPPM‐RPUF. The results revealed that the flame‐retardancy mechanism of DPPM in RPUF was based on the surface charred layer acting as a physical barrier, which slowed down the decomposition of RPUF and prevented the heat and mass transfer between the gas and the condensed phases.     

Preparation,flame retardancy,and thermal degradation of epoxy thermosets modified with phosphorous/nitrogen‐containing glycidyl derivative

Phosphorus/nitrogen‐containing advanced epoxy resins were obtained by chain‐extension of the diglycidyl ether of bisphenol‐A epoxy (DGEBA) resin with phosphorus‐modified triglycidyl isocyanurate (TGICP). The structure of TGICP was characterized by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR). Differential scanning calorimetry revealed that the EP/TGICP composites possessed higher glass transition temperatures than that of phosphorus free EP. The thermal stability and flame retardant properties of the epoxy resin/TGICP systems were investigated by thermogravimetric analysis (TGA), limiting oxygen index (LOI), and vertical burning test (UL‐94) test. When the TGICP content was 10 wt%, the LOI value of epoxy resin system was as high as 35.0% and it can obtain the V‐0 grade in UL‐94 protocol. From microscale combustion calorimetry (MCC) measurement, it was found that the addition of TGICP reduced the value of peak heat release rate and total heat release. The thermal degradation process of EP and EP/TGICP composite was monitored by real time FTIR. Moreover, scanning electron microscopy (SEM) and X‐ray photoelectron spectroscopy (XPS) were used to explore the morphology and chemical components of the char residues. Copyright © 2010 John Wiley & Sons, Ltd.     

Preparation of a novel phosphorus‐containing organosilicon and its effect on the flame retardant and smoke suppression of polyethylene terephthalate

A novel phosphorus‐containing silicone flame retardant (PDPSI) was prepared by Mannish reaction, and a series of PDPSI/PET composites were prepared by melt blending method. The nuclear magnetic resonance (¹H NMR), Fourier transformation infrared (FTIR), and the thermogravimetric analyzer (TGA) results indicated that PDPSI showed network structure and owned good thermal stability, with the char residue of 62.2% at 800°C. The flame retardancy of PDPSI/PET composites was characterized by limiting oxygen index (LOI), vertical burning tests (UL‐94), and cone calorimeter (CCT). The results revealed that the addition amount of PDPSI was 5%, the LOI value of PDPSI/PET composites increased to 27.3%, and UL‐94 test passed V‐0 rating. When the PDPSI loading was 3%, PET composites showed excellent flame retardancy and smoke suppression, with a decrease in the peak heat release rate (PHRR) by 71.19% and the total smoke release (TSP) reduced from 14.4 to 11.1m². The scanning electron microscopy (SEM) and FTIR results of char residue demonstrated that the flame‐retardant mechanism of PDPSI was solid phase flame retardant. PDPSI catalyzed the aromatization reaction of PET to promote the formation of a dense and continuous carbon layer, finally improving the flame retardancy and smoke suppression properties of PET.     

The effect of hBN on the flame retardancy and thermal stability of P-N flame retardant PA6

A novel thermally conductive Polyamide 6 (PA6) with good fire resistance was prepared by introducing a phosphorous-nitrogen flame retardant (FR) and platelet-shaped hexagonal boron nitride (hBN) into the matrix. With high thermal conductivity and good flame retardancy, the material is suitable for applications in electronic and electrical devices. The limiting oxygen index (LOI) changes for various loadings content of FR. However this formulation still does not show an ideal fire resistance, due to the appearance of melt dripping behavior during the UL 94 test. With the extra introduction of 3 vol% and 5 vol% hBN, the melt dripping behavior during the burning process completely disappeared. The hBN also increased the thermal conductivity. Furthermore PA6 compounded with FR and hBN showed a better thermal stability than neat PA6. The morphology of the char residues was investigated by scanning electron microscopy (SEM). The flaky hBN acted as the framework in the char structure and the rigid hBN could effectively break the bubble-shaped char on the surface of the residues which resulted in the enhancement of the strength and compactness of the char.     

Preparation and thermal properties of a novel UV‐cured star polyurethane acrylate coating

A novel star polyurethane acrylate (SPUA) used for UV‐curable coating was prepared from 2,4‐toluene diisocyanate, 2‐hydroxyethyl arcylate, and hexakis(2‐hydroxyethyl)melamine, and characterized using FTIR, ¹H‐NMR, and elemental analysis. Its UV curing behaviors investigated via FTIR clearly indicated that this monomer could be cured rapidly at air atmosphere. The conversion of the unsaturated bond of the cured monomer sample is near to 72% after exposed under UV light for 40 sec. The hardness, flexibility, and mechanical properties of the cured film were also investigated. The thermal stability of the cured film was studied using thermogravimetric analysis (TGA) and real time Fourier transform infrared (RTFTIR). Results showed that this oligomer has some superior properties and can be used for UV curing coating. Copyright © 2007 John Wiley & Sons, Ltd.     

Development of an environmentally friendly halogen‐free phosphorus–nitrogen bond flame retardant for cotton fabrics

A novel flame retardant diethyl 4‐methylpiperazin‐1‐ylphosphoramidate (CN‐3) containing phosphorous and nitrogen was prepared. Its chemical structure was confirmed by nuclear magnetic resonance (¹H‐, ¹³C‐, and ³¹P‐NMR), Fourier transform infrared spectroscopy, and elemental analysis. Print cloth and twill fabrics were treated with CN‐3 to achieve different levels of add‐on (7–22 wt% add‐ons for print cloth and 3–18 wt% add‐ons for twill). Thermogravimetric analysis, vertical flame test, and limiting oxygen index (LOI) were performed on the treated cotton fabrics and showed promising results. When the treated print cloth and twill fabric samples were tested using the vertical flame test (ASTM D6413‐08), we observed that the ignited fabrics self‐extinguished and left behind a streak of char. Treated higher add‐ons fabrics were neither consumed by flame nor produced glowing ambers upon self‐extinguishing. LOI (ASTM 2863–09) was used to determine the effectiveness of the flame retardant on the treated fabrics. LOI values increased from 18 vol% oxygen in nitrogen for untreated print cloth and twill fabrics to maximum of 28 and 31 wt% for the highest add‐ons of print cloth and twill, respectively. The results from cotton fabrics treated with CN‐3 demonstrated a higher LOI value as well as a higher char yield because of the effectiveness of phosphorus and nitrogen as a flame retardant for cotton fabrics. Furthermore, FT‐IR and SEM were used to characterize the chemical structure on the treated fabrics as well as the surface morphology of char areas of treated and untreated fabrics. Published 2012. This article is a US Government work and is in the public domain in the USA.     

Synthesis and characterization of UV‐curable ladder‐like polysilsesquioxane

Various ladder‐like structured poly(phenyl‐co‐methacryl silsesquioxane)s (LPMSQ)s with high molecular weight (M_w = 10,000 ～ 40,000) were synthesized by direct hydrolysis and polymerization in the presence of base catalyst at 25 °C. Synthesized LPMSQs mainly showed ladder‐like structure and photo‐cure reaction by 100 mW/cm² (360 nm) for 10 s without any photo‐cure initiators. Chemical composition and structural analysis of the obtained LPMSQs were characterized using ¹H NMR, ²⁹Si NMR, Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), and X‐ray diffraction (XRD). Physical properties of LPMSQs before and after photcuring were analyzed by Nanoindentation. Surface modulus increased to 8GPa and hardness of thin films increased from 100 to 400 MPa. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Renewable epoxidized cardanol‐based acrylate as a reactive diluent for UV‐curable resins

A novel kind of biobased monomer, epoxidized cardanol‐based acrylate (ECA), was successfully synthesized from cardanol via acrylation and epoxidization. The chemical structure was confirmed by Fourier transform infrared spectroscopy and proton nuclear magnetic resonance. Then, the ECA was employed to produce UV‐curable films and coatings copolymerized with castor oil‐based polyurethane acrylate. Compared to coatings from petroleum‐based diluent hydroxyethyl acrylate‐based castor oil‐based polyurethane acrylate resins, ECA‐based biomaterials exhibited a little inferior dilution ability but overcome the drawback of high volumetric shrinkage with a special lower value. Moreover, ultimate properties of the UV‐cured biomaterials such as thermal, mechanical, coating, swelling, and hydrophobic properties were investigated. The UV‐curing behavior was investigated using real‐time IR, and the overall double bond conversion was more than 90%. This biobased UV‐curable cardanol‐based diluent shows a promise in “green + green” materials technologies.     

In situ synthesis of a novel transparent poly (methyl methacrylate) resin with markedly enhanced flame retardancy

A novel phosphorus‐containing monomer, (6‐oxido‐6H‐dibenzo[c,e][1,2]oxaphosphinin‐6‐yl)methyl acrylate (DOPO‐AA), is first synthesized and characterized by Fourier transform infrared spectra (FTIR), ¹H nuclear magnetic resonance (NMR) and ³¹P NMR. The monomer is then introduced into poly (methyl methacrylate) (PMMA) matrix via in situ copolymerization to produce a new PMMA based copolymer (PMMA/DOPO‐AA). From UV–vis spectra, microscale combustion calorimeter (MCC) and thermogravimetric analyses (TGA) results, the as‐fabricated PMMA/DOPO‐AA copolymers not only keep relatively high transparency, but also exhibit remarkable improvements in the flame retardancy and thermal stability, such as increased T_0.5 by 60.2°C and limited oxygen index (LOI) by 4.1, and decreased peak heat released rate (PHRR) by 34.7%. Thermal degradation behaviors investigated by real time Fourier transform infrared spectra (RTIR), char structure analysis studied by scanning electron microscope (SEM) and pyrolysis gaseous products studied by TGA coupled with FTIR (TGA‐FTIR) demonstrate that the catalytic charring function of DOPO‐AA in condensed phase and DOPO flame retardant systems in the gas phase are two key factors for the property enhancements. This work not only provides a promising flame‐retardant monomer for polymers, but also will stimulate more efforts on the development of DOPO‐containing flame‐retardant monomers. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis and properties of poly(bisphenol A acryloxyethyl phosphate) as a UV curable flame retardant oligomer

Poly(bisphenol A acryloxyethyl phosphate) (BPAAEP) being used for UV curable flame retardant coatings and adhesives, was synthesized from phosphorus oxychloride, hydroxylethyl acrylate and bisphenol A as raw materials, and characterized using ¹³C NMR, ³¹P NMR, FTIR, MS and GPC measurements. A series of formulations with different ratios of BPAAEP to urethane acrylate, EB220, were prepared to obtain flame retardant resins. The flame retardancy of the UV cured films was investigated by the limiting oxygen index (LOI). A synergistic effect between phosphorus and nitrogen was observed when 1.5 wt% phosphorus was presented in the resin. Their maximum photopolymerization rates and final unsaturation conversion (P^f) in the cured films at the presence of a 3 wt% photofragmenting initiator were investigated. The results showed that the P^f increased with increasing EB220 content photo-DSC analysis. The data from dynamic mechanical thermal analysis showed that BPAAEP has good miscibility with EB220. Moreover, the crosslink density and T_g of the cured film decreased along with the content of BPAAEP in the blend.