A flame-retardant epoxy resin based on a reactive phosphorus-containing monomer of DODPP and its thermal and flame-retardant properties

A flame-retardant epoxy resin (EP) was synthesized based on a novel reactive phosphorus-containing monomer, 4-[(5,5-dimethyl-2-oxide-1,3,2-dioxaphosphorinan-4-yl)oxy]-phenol (DODPP), and its structures were characterized by FTIR, ¹H NMR and ³¹P NMR spectra. The DODPP-EP₃/LWPA (low molecular weight polyamide), which contains 2.5% phosphorus, can reach UL-94 V-0 rating and a limiting oxygen index (LOI) value of 30.2%. The thermal properties and burning behaviours of cured epoxy resins were investigated by differential scanning calorimeter (DSC), thermogravimetry (TG), LOI, UL-94 tests and cone calorimetry. The morphologies of residues of cured epoxy resins were investigated by scanning electron microscopy (SEM). DSC shows that the glass-transition temperatures of cured epoxy resins decrease with increasing phosphorus content. TGA shows that the onset decomposition temperatures and the maximum-rate decomposition temperatures decrease, while char yields increase, with the increase of phosphorus content. The data from the cone calorimeter tests give the evidence that heat release rate (HRR), peak heat release rate (PHRR), average heat release rate (Av-HRR), average mass loss rate (Av-MLR) and the fire growth rate index (FIGRA) decrease significantly for DODPP-EP₃/LWPA. SEM shows that the DODPP-EP₃/LWPA forms lacunaris and compact charred layers which inhibit the transmission of heat during combustion.     

Thermal degradation characteristics of a novel flame retardant coating using TG-IR technique

A novel phosphate acrylate monomer (TGMAP) has been synthesized by allowing phosphoric acid to react with glycidyl methacrylate. Its structure was characterized by Fourier transformed infrared spectroscopy (FTIR) and ¹H nuclear magnetic resonance spectroscopy (¹H NMR). The thermal degradation mechanism was characterized using thermogravimetric analysis/infrared spectrometry (TG-IR). The char yield was 36.3% at 600 °C. TG data indicate that the material undergoes degradation in three characteristic temperature stages, which can be attributed to the decomposition of the phosphate, thermal pyrolysis of aliphatic chains, and degradation of an unstable structure in char, respectively. The volatilized products formed on thermal degradation of TGMAP indicated that the volatilized products are CO, CO₂, carboxylic acid, acid anhydride, water, alkane, and aromatic compounds according to the temperature of onset formation.     

Preparation and expansion properties of a novel UV-curable intumescent flame-retardant coating

Journal of Thermal Analysis and Calorimetry - N,N′-bis(2,4-di(acryloyloxyethyl)-[1,3,5]-triazin-2-yl)-hexane-1,6-diamine(BDAETH) and 2,2-dimethyl-1,3-propanediol glycerol-methacrylate...     

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.     

Preparation and thermal properties of a novel flame retardant copolymer

A monomer, acryloxyethyl phenoxy phosphorodiethyl amidate (AEPPA), was synthesized and characterized using Fourier transform infrared (FTIR), ¹H nuclear magnetic resonance spectroscopy (¹H NMR) and ³¹P NMR. The copolymer with various amounts of styrene (St) was obtained by the free radical bulk polymerization between AEPPA and St, and characterized using ¹H NMR. The thermal properties of the copolymers were investigated with thermogravimetric analysis (TGA) in air and nitrogen atmosphere, and differential scanning calorimetry (DSC). The TGA results in air indicated the copolymers with AEPPA show higher thermal stability than those without AEPPA. However, the TGA results in nitrogen showed that the decomposition temperature decreased and the char residue increased with the increase of AEPPA. The glass transition temperature (T_g) of the copolymers from DSC indicated that a inverse proportion was observed between T_g and the amount of AEPPA incorporated. The flammability of the copolymers was evaluated by microscale combustion calorimeter (MCC). The MCC results showed that AEPPA can decrease the peak heat release rate (PHRR) and the heat release capacity (HRC), and the sample CP10 shows the lowest PHRR and HRC.     

Synthesis and properties of a novel hyperbranched polyphosphate acrylate applied to UV curable flame retardant coatings

A series of hyperbranched polyphosphate acrylates (HPPAs) being used for UV curable flame retardant coatings were prepared by the reaction of tri(acryloyloxyethyl) phosphate (TAEP) with piperazine at given ratios, and characterized using FTIR, ¹H NMR and GPC measurements. HPPA was blended with TAEP in different ratios to obtain a series of UV curable resins. Their maximum photopolymerization rates and final unsaturation conversion (P^f) in the cured films at the presence of a photofragmenting initiator were investigated. The results showed that the P^f increased along with HPPA content and the pure HPPA has the maximum value of 82.1% in the photo-DSC analysis. The data from dynamic mechanical thermal analysis showed that HPPA has good miscibility with TAEP. The crosslinking density and T_g of the cured film decrease along with the content of HPPA in the blend. The mechanical properties of the cured films were also investigated. Less than 20% HPPA addition improved both the tensile strength and elongation at break without damaging the modulus. The HPPA₂₀TAEP₈₀ film with 20% HPPA addition has the highest tensile strength of 31.7 MPa and an elongation at break two times that of cured TAEP. The flame retardancy of the UV cured films was investigated by the limiting oxygen index (LOI). The cured TAEP/HPPA samples greatly expanded when burning, and the degree of expansion increased along with HPPA content. However, the LOI values decreased from 47.0 to 34.0 along with HPPA content, which can be ascribed to that the flame retardancy of TAEP is mainly acting in the gas phase, whereas HPPA mainly acting in condensed phase, and the gas phase mechanism holds the dominant effect while their blends are burning.     

The effects of irradiation cross-linking on the thermal degradation and flame-retardant properties of the HDPE/EVA/magnesium hydroxide composites

High-density polyethylene/ethylene vinyl-acetate copolymer/magnesium hydroxide composites were crosslinked via high-energy electron beam irradiation in the presence of triallylisocyanurate. The structure of the cross-linking network was determined with the help of rheological measurements through advanced rheological extended systems (ARES). The thermal and flame-retardant properties of the irradiated composites were investigated by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and cone calorimetry. Results showed that the cross-linking network structure could enhance the thermal stability of composites, and did favor to smoke suppression. However, the peak heat release rate (PHRR) increased and the time to PHRR shortened, inferring that the composites after irradiation cross-linking were easier to combust. The char microstructure after cone calorimetry test was observed and used to give explanation of the above results.     

Synthesis of a novel ferrocene derivative having flame-retardant and smoke-suppressant properties

Reaction of ferrocene with chlorendic anhydride (1,4,5,6,7,7-hexachloro-5-norbornene-2,3-dicarboxylic acid anhydride) under Friedel–Crafts reaction conditions affords a new monosubstituted dervative of ferrocene which has significant flameretardant and smoke-suppressant properties when incorporated into poly(vinyl chloride) (PVC). The monocarboxylic acid from the above reaction undergoes smooth methylation with diazomethane to give the corresponding methyl ester. ¹H and ¹³C NMR spectra of these compounds have been compared with those obtained from similar compounds, namely β-ferrocenoylpropanoic acid and its methyl ester. Distant asymmetric centres in the chlorendic anhydride substituent markedly affect the proton spectra of the ferrocene derivative.     

Unsaturated polyester resins modified with phosphorus-containing groups: Effects on thermal properties and flammability

A novel reactive phosphorus-containing monomer [1-oxo-2,6,7-trioxa-1- phosphabicyclo-[2.2.2]octane-methyl diallyl phosphate, PDAP] was synthesized, and various amounts of PDAP were combined with unsaturated polyester by radical bulk polymerization. The resulting flame-retardant unsaturated polyester resin (FR-UPR) samples were investigated by thermogravimetric analysis (TGA), microscale combustion calorimetry (MCC), and limiting oxygen index (LOI) tests. Due to the relatively high phosphorus content of PDAP (18.2 wt%), incorporation of this monomer into unsaturated polyester resin (UPR) led to a marked decrease in the heat release capacity (HRC), the total heat release (THR), an increase in the LOI and the char yield upon combustion. In order to elaborate the interactions between the UPR and PDAP in degradation, differences between the experimental and theoretical mass losses of a FR-UPR sample were evaluated. Furthermore, thermogravimetry-Fourier transform infrared (TG-FTIR) and real-time Fourier transform infrared (RTIR) spectroscopy were employed to investigate the degradation behavior of UPRs, providing insight into the degradation mechanism.     

Preparation and electrochemical properties of Co3O4-coated layered manganese oxide by a novel coating method

Potassium type birnessite (K-bir) was synthesized by O₂ oxidizing Mn²⁺ in aqueous solution of KOH. Co₃O₄-coated K-bir (Co-K-bir) was prepared by employing a novel coating method, in which the remaining OH⁻ ions on the particle surface of the as-precipitated K-bir reacted with Co²⁺ ions in aqueous solution, forming CoOOH coverage; the coating layer of CoOOH was subsequently annealed at 300 °C to transform into Co₃O₄. All the K-bir and Co-K-birs were investigated by scanning electron microscopy, transmission electron microscopy, inductive coupled plasma–atomic emission spectroscopy, Brunauer–Emmett–Teller specific area, and laser particle size analyzing techniques. Their electrochemical properties were also studied by discharging–charging at constant current. The results show that the covering layers of Co₃O₄ are incompact, and their average thickness are about 0.65–0.78 μm. Compared to the as-prepared and the annealed K-bir, the Co₃O₄-coated samples have higher initial discharge capacities and show distinctly improved cycleability performance.     

Thermally stable and flame-retardant poly(vinyl alcohol)/montmorillonite aerogel via a facile heat treatment

The PVA/MMT aerogels prepared by a simple freeze-drying and heat treatment process exhibited a significant improvement of thermal stability and flame retardant property.     

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.     

Preparation and flammability of a novel intumescent flame-retardant poly(ethylene-co-vinyl acetate) system

A phosphorus-containing flame retardant, 4-(5,5-dimethyl-2-oxo-1,3,2-dioxaphosphorinan-2-yloxymethyl)-2,6,7-trioxa-1-phospha-bicyclo[2.2.2]octane-1-oxide (MOPO), was synthesized successfully and characterized. The flame retardancy and thermal behavior of a new intumescent flame-retardant (IFR) system for EVA, which was made of MOPO and ammonium polyphosphate (APP), were investigated by limiting oxygen index (LOI) test, vertical burning test (UL-94), cone calorimeter, and thermogravimetric analysis (TGA). An LOI value of 28.4 and UL-94 V-0 rating can be achieved when the total loading of MOPO and APP was 30 wt.%. The results from cone calorimeter indicate that both the heat release rate (HRR) and the total heat release (THR) of IFR-EVA decreased significantly compared with those of neat EVA. TG curves showed that the amount of residues increased significantly when intumescent additives were added; it also could be found that the LOI values increased with the increase in char residues. Meanwhile, morphology of the residues obtained from burning IFR-EVA in LOI test was studied through the SEM observations and rich compact char layers could explain the excellent flame retardance.     

Preparation and thermal properties of a novel core‐shell structure flame‐retardant copolymer

In order to improve the flame retardancy of polystyrene (PS), a phosphorus and nitrogen comonomer, named AC₂NP₂, was synthesized and then incorporated into various amounts of PS by seeded emulsion polymerization. The modified methacrylate (AC₂NP₂) was used as the core phase, the styrene as the shell phase, then flame‐retardant effect copolymers with core‐shell structure were prepared successfully. The particle size was ranged from 40 to 60 nm, and the structure and properties of the copolymers were characterized in detail. Notably, despite a few amounts of the AC₂NP₂ units in the copolymers, all the copolymers exhibited significantly enhanced thermal stability and reduced flammability as compared with pure PS. Furthermore, from differential scanning calorimetry test, it was observed that the glass transition temperature was tinily influenced with the incorporation of commoner. The incorporation of P‐N comonomer into PS backbone did not lead to negative effect on the glass transition behavior of PS.     

Effect of a phosphorus-containing flame retardant on the thermal properties and ease of ignition of poly(lactic acid)

An aryl polyphenylphosphonate, poly(9-oxa-10-(2,5-dihydro-xyphenyl) phospha-phenanthrene-10-oxide) phenylphosphonate (WLA-3), was used to prepare a flame-retardant poly(lactic acid) (PLA) by direct melt compounding. The thermal behaviour, burning behaviour and mechanical properties of the flame-retardant PLA systems have been investigated by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), vertical burning test (UL-94), limiting oxygen index (LOI), cone calorimeter test (CCT) and tensile test. The flame retardance mechanism has been studied via Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), and P content analysis. The UL-94 ratings of PLA’s containing 7phr (W_7P) and 10phr (W_10P) of WLA-3 were enhanced to V-0 from no rating for neat PLA. However, the cone calorimetry of flame-retardant PLA (W_7P) only showed a little decrease in heat release rate (HRR), peak of heat release rate (PHRR) and total heat release (THR) compared to neat PLA. TGA results showed that the PLA containing different amounts of WLA-3 presented more complicated thermal decomposition behaviours than neat PLA. Additionally, the results from DSC and tensile tests showed that the addition of WLA-3 into PLA had a slight impact on the crystallization behaviours and tensile properties.     

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.     

Intrinsically flame retardant epoxy resin - Fire performance and background - Part I

The flame retardant effect of newly synthesized phosphorus-containing reactive amine, which can be used both as crosslinking agent in epoxy resins and as a flame retardant, was investigated. The effect of montmorillonite and sepiolite additives on the fire induced degradation was compared to pristine epoxy resin. The effect of combining the organophosphorous amine with clay minerals was also studied. It could be concluded that the synthesized phosphorus-containing amine, TEDAP can substitute the traditional epoxy resin curing agents providing additionally excellent flame retardancy: the epoxy resins flame retarded this way reach 960 °C GWFI value, 33 LOI value and V-0 UL-94 rating - compared to the 550 °C GWFI value, 21 LOI value and “no rate” UL-94 classification of the reference epoxy resin. The peak of heat release was reduced to 1/10 compared to non-flame retarded resin, furthermore a shift in time was observed, which increases the time to escape in case of fire. The flame retardant performance can be further improved by incorporating clay additives: the LOI and the HRR results showed that the optimum of flame retardant effect of clay additives is around 1 mass% filler level in AH-16-TEDAP system. Applying a complex method for mechanical and structural characterization of the intumescent char it was determined that the flame retarded system forms significantly more and stronger char of better uniformity with smaller average bubble size. Incorporation of clay additives (owing to their bubble nucleating activity) results in further decrease in average bubble diameter.     

阻燃共聚酯/粘土复合物热降解动力学研究

用插层共聚方法合成了含磷共聚酯／粘土复合物。用热重(TG)方法考察热降解动力学。通过在空气中以不同的升温速率升温至设定温度,用Kissinger法和Hymn-Wall-Ozawa法对数据进行处理。结果表明,粘土组分含量较高的反应活化能较大,热稳定性较好。     

Effects of carbon nanotubes on the thermal stability and flame retardancy of intumescent flame-retarded polypropylene

Flame retardant mixtures of carbon nanotubes (CNTs) and intumescent flame retardant (IFR) were embedded in polypropylene (PP) to investigate what will happen if the additives exhibit two different flame retardation mechanisms. TEM tests showed that CNTs dispersed homogenously in PP matrix without any visible agglomeration. The effects of CNTs on thermal stability and flammability of PP were investigated by thermogravimetry (TG) and cone calorimetry tests, respectively. Results indicated that the introduction of CNTs only enhanced thermal stability of materials in a certain temperature range, but caused a severe deterioration of flame retardancy due to the interaction of the network structure and the intumescent carbonaceous char. Furthermore, conditions for an intumescent flame retardation system to behave with high efficiency were also discussed by a secondary combustion test.     

Polymeric nanocomposite materials: Preparation and characterization of star-shaped PbS nanocrystals and their influence on the thermal stability of acrylonitrile-butadiene-styrene (ABS) copolymer

Star-shaped PbS nanocrystals were synthesized via a simple hydrothermal reaction between Pb(NO₃)₂·4H₂O and thioglycolic acid at a relatively low temperature. The PbS nanostructures were then combined in a acrylonitrile-butadiene-styrene copolymer. The effect of the PbS nanostructures on the thermal stability of the nanocomposite products has been investigated. The nanostructures and nanocomposite were characterized by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectra, thermogravimetric-differential thermal analysis and atomic force microscopy. Cone calorimeter measurements showed that the heat release rate significantly decreased in the presence of PbS.