Flame retardancy mechanisms of melamine cyanurate in combination with aluminum diethylphosphinate in epoxy resin

A novel flame-retardant (FR) epoxy (EP) composite based on melamine cyanurate (MCA) and aluminum diethylphosphinate (AlPi) was successfully prepared and its flame retardancy was systematically investigated. Firstly, the facile surface modification was adopted to effectively solve the aggregation of FRs in EP matrix during the curing process. The influence of modified MCA/AlPi on the fire behavior and thermal degradation of EP were studied by using limiting oxygen index (LOI), vertical burning (UL94) tests, thermogravimetric analysis and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). The experimental results showed that EP/MCA/AlPi composite achieved UL-94V0 rating and LOI value of 33.0% at the optimum mass fraction of MCA/AlPi of 2/1. The chemical composition and structure of residue were characterized by X-ray photoelectron spectroscopy, Fourier transform infrared spectrometry and scanning electron microscopy. MCA mainly acted in gaseous phase during the initial combustion stage, and therefore to provide enough time for the formation of carbon layer in condenses phase. As a result, the synergistic effect of MCA and AlPi can effectively promote the formation of the char layer and the FR efficiency. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47223.     

高效液相色谱法测定焦磷酸三聚氰胺-焦磷酸哌嗪混合阻燃剂中的三聚氰胺

通过调节pH溶解样品,以离子对缓冲液及乙腈的混合液作为流动相,C18色谱柱作为分析柱,VWD可变波长紫外检测器作为检测器,应用高效液相色谱仪对焦磷酸三聚氰胺-焦磷酸哌嗪混合阻燃剂中的三聚氰胺含量进行了测定。结果显示,样品溶液中三聚氰胺质量浓度在0～80μg/mL范围内线性良好。重复测定相对标准偏差在1.2%以内,加标回收率在98.3%～104.0%。     

The investigation on the flame retardancy mechanism of nitrogen flame retardant melamine cyanurate in polyamide 6

Melamine cyanurate (MCA) flame retardant polyamide 6 (PA6) shows good flame retardancy, but the corresponding mechanisms have not been completely understood. In this paper, Fourier transform infrared spectra (FTIR), elemental analysis (EA), scanning electronmicroscope (SEM), energy dispersive scanning (EDS), thermogravimeric analysis (TGA) and pyrolysis-gas chromatogram-mass spectrometer (Py-GC-MS) were conducted to investigate the processes including melt-drip phase, gaseous phase and condensed phase of MCA/PA6 system. Compared with original PA6, it is found that MCA flame retardant PA6 mainly undergoes predominant weak bond-breakage degradation forming oligomers rather than oxidative degradation producing low-boiling point fuel as original PA6 does. The produced oligomers can accelerate the formation of the melt drips which effectively removes the combustion heat and latent fuel, also the self-condensation of these oligomers is advantageous to form stable cross-linking structure, thus greatly consolidating the char layer.     

次磷酸铝协效MCA阻燃三元乙丙橡胶的研究

以三聚氰胺氰尿酸盐（MCA）为阻燃剂、二乙基次膦酸铝（ADP）和次磷酸铝（PAH）为阻燃协效剂,制备了无卤阻燃三元乙丙橡胶（EPDM）材料,并研究了其阻燃性能和力学性能。结果表明,当阻燃剂MCA用量为76份、ADP用量为14份、PAH用量为10份时,EPDM垂直燃烧级别达到FV-0,氧指数为30%,拉伸强度为6.7 MPa,拉断伸长率为330%。     

Preparation and investigation of efficient flame retardant TPE composites with piperazine pyrophosphate/aluminum diethylphosphinate system

The piperazine pyrophosphate (PPAP) combined with aluminum diethylphosphinate (AlPi) with a certain mass fraction and then incorporated into thermoplastic elastomer (TPE) composites composed of oil extended styrene–ethylene–butadiene–styrene block copolymer and polypropylene. The fire retardancy, thermal behavior, mechanical performance, and flame retardant mechanism of TPE materials were investigated in detail. The results demonstrated that 1.6 mm TPE composites reached UL-94 V-0 grade during vertical burning tests and the limiting oxygen index value was 28.5% when 25 wt % PPAP/AlPi with the mass ratio of 4:1 was incorporated. The introduction of PPAP/AlPi improved the residual mass and thermal stability, and stimulated to produce the char layer with high quality. The formed char layer exerted shielding effect and AlPi could inhibit the flame in gas phase. Consequently, the PPAP/AlPi system evoked fire retardant effects in condensed and gas phase simultaneously, and the fire resistance of the TPE composites was enhanced. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 47711.     

改性三聚氰胺氰尿酸盐阻燃环氧树脂研究

采用分子复合技术合成了改性MCA(M-MCA)阻燃环氧树脂,采用UL94垂直燃烧测试及微型量热分析对其性能进行了研究,同时采用热失重分析方法研究其降解历程和阻燃机理。结果表明,该材料实现了阻燃剂粒子在环氧溶液及基材中超细及均匀分散,解决了常规MCA阻燃剂在环氧树脂胶液中分散困难、易团聚等问题,改性MCA阻燃树脂比传统MCA具有更佳阻燃效果,该体系阻燃机理以气相阻燃为主。     

磷系阻燃剂FR/APP协效阻燃PP

采用氧指数测定仪、热重分析仪和锥形量热仪研究了磷系阻燃剂1,3,5-三(5,5-二甲基-1,3-二氧杂环己内磷酸基)苯(FR)和聚磷酸铵(APP)复配体系对聚丙烯(PP)材料阻燃性能的影响.结果表明,FR/APP提高了PP的极限氧指数(LOI)、热稳定性和残炭率,降低了热释放速率.当w(FR)为15%和w(APP)为10%复配阻燃PP时,复合材料的LOI为29.6%.阻燃级别达到UL 94 V-0级.     

Enhanced mechanical properties and fire retardancy of polyamide 6 nanocomposites based on interdigitated crystalline montmorillonite–melamine cyanurate

Polyamide 6 (PA6)–montmorillonite (MMT)–melamine cyanurate (MCA) nanocomposites were prepared by the incorporation of interdigitated crystalline MMT–MCA. Their morphologies were assessed by X‐ray diffraction, scanning electron microscopy, transmission electron microscopy, thermal stability measurement by thermogravimetric analysis, mechanical properties measurement by tensile tests, and fire retardancy measurement by limiting oxygen index testing and vertical burning testing (UL‐94). The results indicate that MMT–MCA was homogeneously nanodispersed in PA6. Compared with PA6–MCA, the PA6–MMT–MCA nanocomposites showed enhanced thermal stability. The mechanical properties and fire retardancy show that the PA6–MMT–MCA nanocomposites with 5 wt % total loading of MMT–MCA reached UL‐94 V‐2 rating (3.2 mm) and significantly increased the tensile strength of PA6 up to 24.8 % with only 1 wt % MMT in PA6. Through the control the weight ratio of MMT and MCA in MMT–MCA, the Young's modulus of PA6 could be adjusted in a very wide range (300–1100 MPa) because of the dual role of the rigid MMT and nonrigid MCA layers. The reinforced mechanism of the mechanical properties was also investigated. Consequently, the PA6–MMT–MCA nanocomposites with a good nanodispersing ability, improved thermal stability, excellent mechanical properties, and good flame retardancy were obtained and could provide broad prospects for wider applications for PA6 materials. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46039.     

焦磷酸哌嗪/MCA对聚丙烯的阻燃作用

通过垂直燃烧试验、极限氧指数(LOI)测定和锥形量热分析,对焦磷酸哌嗪(DPP)与三聚氰胺氰尿酸盐(MCA)复合而成的膨胀型阻燃剂(IFR)阻燃聚丙烯(PP)进行了研究。结果表明:当m(MCA):m(DPP)为1.0∶2.5,IFR质量分数为26%时,PP的LOI为34.2%,垂直燃烧试验可通过V-0级;与PP相比,阻燃PP的热释放速率(HRR)、总热释放量(THR)分别降低了91.34%,31.42%。该IFR对PP的阻燃机理与聚磷酸铵基IFR的类似,主要是通过凝聚相阻燃。     

Preparation of polyamide resin‐encapsulated melamine cyanurate/melamine phosphate composite flame retardants and the fire‐resistance to glass fiber‐reinforced polyamide 6

In this study, melamine cyanurate (MCA)/melamine phosphate (MP) composite flame retardants were synthesized in the solution of phosphoric acid/polyamide 6 (PA6). Phosphoric acid acted as the solvent of PA6, catalyst of melamine‐cyanurate self‐assembly reaction and reactant of melamine‐phosphoric acid reaction. With the consumption of the acid, the pH value of the system increased, and the solved PA6 precipitated on the surface of the flame retardant particles to form polymeric encapsulation. This technology realized the synthesis and surface modification of the flame retardants in one process. The catalyst and solvent, phosphoric acid, was finally converted into the product MP, and need no an additional removing process. The encapsulated MCA/MP (EMCMP) composite flame retardants were successfully applied in the fire‐resistance to glass fiber (GF)‐reinforced PA6. Because the encapsulated layer of EMCMP was also PA6, good interfacial compatibility and effective dispersion of EMCMP in PA6 resin can be obtained, and the corresponding flame retardant materials showed excellent flame retardancy and mechanical performance. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1773–1779, 2006     

Synergistic effect of supported nickel catalyst with intumescent flame‐retardants on flame retardancy and thermal stability of polypropylene

Supported nickel catalyst (Ni‐Cat) was used as a catalyst to improve the flame retardancy of intumescent flame‐retardants (IFR) systems based on ammonium polyphosphate and pentaerythritol (PETOL) in polypropylene (PP) matrix. Limited oxygen index (LOI), UL‐94 rating, and thermogravimetric analysis were used to characterize the flame retardancy and thermal stability of the PP systems, and field emission scanning electron microscopy (FE‐SEM) and Fourier transformed infrared spectroscopy (FTIR) were used to analyze the microstructure and composition of the chars formed during measuring LOI value and after combustion at 800°C. The catalytic effect of Ni‐Cat was shown in an increase of LOI, a change in the char microstructure, and improvement of the thermal stability in the PP systems, which result from the synergistic effect of Ni‐Cat and IFR. The results from FE‐SEM and FTIR spectra of the char can explain how this synergistic effect happened. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5988–5993, 2006     

磷酸三苯酯和甲基八溴醚在阻燃聚苯乙烯中的协同行为研究

为获得基于甲基八溴醚（MOBE）的高效阻燃聚苯乙烯（PS）复合体系,采用极限氧指数仪、锥形量热仪、热重分析仪（TG）和差示扫描量热仪（DSC）等对纯PS及其复合材料的阻燃性能及机理和热稳定性等进行了测试和表征,探索了MOBE与磷酸三苯酯（TPP）复配阻燃PS的行为规律。结果表明,TPP和MOBE复合体系比二者各自单独作为阻燃剂使用时赋予了PS材料更高的极限氧指数（LOI）,PS/3 %（质量分数,下同）TPP/4 %MOBE的LOI可达27.7 %, 明显高于PS/4 %MOBE（26.1 %）;3 %TPP/4 %MOBE能够在4 %MOBE的基础上进一步抑制PS复合材料的燃烧强度,降低有效燃烧热,降低热释放速率峰值（PHRR）与总热释放量（THR）;TPP和MOBE能够在PS复合材料热降解时将阻燃元素集中释放,同时发挥气相淬灭效应;此外,TPP的加入能够提高PS复合材料的熔体流动速率,降低其玻璃化转变温度,从而使PS热分解产生的熔滴更快地带走热量,最终使TPP与MOBE发挥更好的阻燃效果。     

PP/纳米蒙脱土复合材料炭层结构对阻燃性能的影响

采用熔融插层法制备了不同纳米蒙脱土含量的聚丙烯(PP)/有机蒙脱土(OMMT)和PP/无机蒙脱土(MMT)复合材料,且评价了复合材料的阻燃性能:采用数码相机、扫描电子显微镜观察了燃烧残余物结构.加入OMMT可显著提高PP/OM MT的阻燃性能:纯PP的热释放速率(HRR)峰值为1 337.59 kW/m2;w(OMMT...     

Enhancement of flame retardancy and mechanical properties of polyamide 6 by incorporating melamine cyanurate combined with attapulgite

In this study, the nanocomposites are prepared which used polyamide 6 (PA6) composite as matrix, melamine cyanurate (MCA) as fire retardant and attapulgite (AT) as synergistic agent. The mathematical model between MCA content, AT content, and limited oxygen index (LOI) is established by multiple linear regression fitting. The polymer materials are characterized using Fourier transform infrared spectroscopy, X-ray diffraction, Thermogravimetric Analysis, and scanning electron microscopy. Through response surface methodology, the important variables (polymerization time, the content of MCA, and the content of AT) affecting the mechanical strength of composites are modeled. Results demonstrate that when the t is 0.6 h, the AT content is 6.2%, and the MCA content is 11.5%, the mechanical properties of the PA6/MCA/AT composite are up to 44.81 MPa, and the sample passes the UL-94 V-0 flammability rating, and the LOI reaches 27.9%. Therefore, polymers with highly effective flame retardancy and optimal mechanical properties are prepared. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 47298.     

二乙基次膦酸铝/三聚氰胺聚磷酸盐复配阻燃三元乙丙橡胶的性能

采用二乙基次膦酸铝(ADP)与三聚氰胺聚磷酸盐(MPP)复配填充三元乙丙橡胶(EPDM),制备了EPDM阻燃材料,研究了ADP/MPP填充量及配比对EPDM燃烧性能及力学性能的影响。结果表明,ADP与MPP复配使用,可提高EPDM的阻燃性能,二者具有协同作用;当二者总添加量为30份、质量比为2∶1时,材料的极限氧指数可达到36%,最大热释放速率下降50.2%,总释放热降低25.9%,总生烟量降低22.3%,且EPDM的力学性能能够满足使用要求,拉伸强度为19.5 MPa,扯断伸长率为427%,邵尔A硬度为78,300%定伸应力为10.3 MPa。     

The effect of morphology on the flame‐retardant behaviors of melamine cyanurate in PA6 composites

Three types of melamine cyanurate (MCA) with micrometer‐size sphere‐like, micrometer‐scale rod‐like, and nanometer‐scale flake‐like morphologies were synthesized by changing the chemical circumstances of the reactions. The microcosmic morphologies of MCA were characterized via scanning electron microscopy and X‐ray diffraction. After the MCAs with different morphologies were incorporated into polyamide 6 (PA6), the flame‐retardant properties of the MCA/PA6 composites were investigated using the limited oxygen index (LOI), UL94, and cone calorimeter tests. The MCA/PA6 composites with nanometer‐scale flake‐like MCA obtained an LOI value of 29.5% and a UL94 V‐0 rating, which were higher than those with micrometer‐size sphere‐like and rod‐like MCAs. However, the different morphologies did not affect the heat release rate, total smoke release, average carbon monoxide yield, and average carbon dioxide yield based on the cone calorimeter. The flame‐retardant mechanism of MCAs with different morphologies was investigated via thermal gravimetric analysis (TGA) and TGA‐Fourier transform infrared spectra. The results show that the different morphologies of MCA resulted in different dispersed evenness of MCA. Further, the nanometer‐scale flake‐like morphology of MCA brought more interactions of hydrogen bond between MCA and PA6, which resulted in the delay of MCA decomposition and the enhancement of MCA flame‐retardant effect. The nanometer‐scale flake‐like MCA had a better performance compared with the other samples because of the delaying and even release of flame‐retardant effect by the decomposition of evenly dispersed MCA. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40558.     

Effect of a novel phosphorus‐containing compound on the flame retardancy and thermal degradation of intumescent flame retardant polypropylene

A novel flame retardant, tetra(5,5‐dimethyl‐1,3‐ dioxaphosphorinanyl‐2‐oxy) neopentane (DOPNP), was synthesized successfully, and its structure was characterized by FT‐IR, ¹H NMR, and ³¹P NMR. The thermogravimetric analysis (TGA) results demonstrate that DOPNP showed a good char‐forming ability. Its initial decomposition temperature was 236.4°C based on 1% mass loss, and its char residue was 41.2 wt % at 600°C, and 22.9 wt % at 800°C, respectively. The flame retardancy and thermal degradation behavior of novel intumescent flame‐retardant polypropylene (IFR‐PP) composites containing DOPNP were investigated using limiting oxygen index (LOI), UL‐94 test, TGA, cone calorimeter (CONE) test, and scanning electron microscopy (SEM). The results demonstrate that DOPNP effectively raised LOI value of IFR‐PP. When the loading of IFR was 30 wt %, LOI of IFR‐PP reached 31.3%, and it passed UL‐94 V‐0. TGA results show that DOPNP made the thermal decomposition of IFR‐PP take place in advance; reduced the thermal decomposition rate and raised the residual char amount. CONE results show that DOPNP could effectively decrease the heat release rate peak of IFR‐PP. A continuous and compact char layer observed from the SEM further proved the flame retardance. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Improving the flame retardancy of polypropylene by nano metal–organic frameworks and bioethanol coproduct

In this work, a novel flame retardant system based on nano zeolitic imidazolate framework‐8 (ZIF‐8) and the distiller's dried grains with solubles (DDGS) without traditional flame retardants has been designed and blended with polypropylene (PP) to prepare the green flame retarded composites. The influences of nano ZIF‐8 and DDGS on mechanical properties and flame retardancy of PP are studied. The results indicate that combination of nano ZIF‐8 and DDGS improves the mechanical properties of PP, and the tensile strength of the composites containing 29 wt% of DDGS and 1 wt% of nano ZIF‐8 reaches 34.0 MPa compared with 24.7 MPa of pure PP. The limiting oxygen index (LOI) of the composites containing 27 wt% DDGS and 3 wt% of nano ZIF‐8 is about 25.0% compared with 17.5% of pure PP. Besides, its horizontal burning velocity also decreases significantly. The char residues after burning of the PP composites are analyzed, and the mechanism is discussed in detail.     

Improving the flame retardancy of polypropylene foam with piperazine pyrophosphate via multilayering coextrusion of film/foam composites

A series of 16-layer polypropylene/flame retardant (PP/FR) film/foam composite structures were produced by microlayer coextrusion. A highly branched PP was used in the foam layers to increase strain hardening and cell stability, while the PP used in the film layers was a high shear viscosity grade to confine bubble growth. In addition to improved tensile properties, the PP/FR composite film/foams exhibited five times the compression modulus of PP/FR composite foams at each FR loading level. The thermal stabilities of the composites were investigated, exhibiting three step decompositions. The FR particles were effective in decreasing flammability by forming intumescent char. The PP/FR-film/foam-20 showed self-extinguishing behavior in a modified vertical burn test, while the PP/FR-foam-20 sample continued to burn. Cone calorimetry demonstrated that PP/FR film/foams had lower heat release than PP/FR foams due to the unique alternating film/foam structure of PP/FR film/foams. Scanning electron microscopy imaging of the residual chars from fire testing that the PP/FR composite film/foams showed a more continuous protective char surface when compared with PP/FR composite foams at each FR concentration. The combined data indicate that the formation of a surface film on top of a foam ensures a robust intumescent fire protective barrier for partly foamed materials and shows a new way toward lightweight materials with improved fire safety performance. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48552.