A multi-element flame retardant for rail transit to improve the flame retardant performance of epoxy resin while reducing smoke density

A P/N/Si structure flame retardant DTBD was successfully synthesized by 3,5-diaminobenzoic acid, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), triphenylsilanol, and benzaldehyde. The chemical structure of DTBD was analyzed by Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectra, which showed that DTBD was successfully synthesized. By analyzing the curing behavior, the addition of DTBD promoted the curing of epoxy resin (EP). According to the limited oxygen index (LOI) and UL-94 vertical combustion tests, it can be shown that the introduction of DTBD makes the epoxy resin have good self-extinguishing properties. Py-GC/MS analysis showed that the phosphorus free radicals and ammonia generated in the gas phase of DTBD could quench and dilute by capturing reactive free radicals and refractory gases. DTBD could improve the tensile and flexural properties of epoxy resin. According to the European flame retardant standard EN45545-2, the Ds of EP-15 and EP-20 obtained HL1 grade. With the increase in DTBD content, the VOF₄ of modified EP also gradually decreased, and both EP-15 and EP-20 obtained HL2 grade.     

磷酸二氢铵的提纯工艺研究

研究了用离子交换法提纯磷酸二氢铵的方法。以树脂的三价铁离子、二价钴离子、二价镍离子、二价铜离子吸附容量和再生性能为考查指标，从3种树脂中选出了性能最佳的一种——亚氨基二乙酸螯合树脂D401，并探讨了溶液pH、温度等因素对该树脂吸附容量的影响。结果表明提纯磷酸二氢铵的最佳条件为：pH4．0～4．5，温度30～40℃。在该实验条件下，D401可将分析纯磷酸二氢铵中三价铁离子、二价钴离子、二价镍离子、二价铜离子的总质量分数降至2．3×10^-6。[第一段]     

Preparation of DOPO-derived magnesium phosphate whisker and its synergistic effect with ammonium polyphosphate on the flame retardancy and mechanical property of epoxy resin

In this study, a magnesium phosphate whisker (DPM-H) was synthesized by the acid–base neutralization reaction between magnesium hydroxide and 10-hydroxy-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO-OH) at 120°C. A new synergistic intumescent flame retardant (IFR) for epoxy resin (EP), which was composed of DPM-H and ammonium polyphosphate (APP) was thoroughly studied. When the IFR loading was 8%, with the DPM-H to APP weight ratio at 1:7, the prepared flame-retardant EP (EPDA-2) passed the vertical burning tests (UL-94) V-0 rating and obtained the limiting oxygen index (LOI) value of 29.3%. Microscale combustion calorimetry (MCC) results showed that the total heat release (THR) of EPDA-2 reduced by 32.1% compared with pure EP. Meanwhile, the addition of DPM-H can partially solve the problem of the decrease of the EP mechanical property caused by the addition of APP. Compared with the flame-retardant EP with the 8% loading of APP, the impact strength of EPDA-2 increased 152.3%.     

Preparation of thermally stable and flame-retardant sugarcane bagasse-ammonium dihydrogen phosphate/epoxy composites and their performance

Epoxy resin was often applied in fiber-reinforced composite materials, adhesives, and encapsulation materials. However, epoxy was easily flammable and limited its usage in certain applications. The study recycled and reused agricultural waste sugarcane bagasse to prepare a halogen-free bio-based intumescent flame retardant and then mixed with epoxy resin to prepare a composite containing polymer with improved thermal properties and flame retardancy of the materials. The work followed the concept of circular economy and sustainability. Bagasse-ammonium dihydrogen phosphate (ADP) flame retardant was added to an epoxy resin to prepare epoxy/bagasse-ADP composites, an effective flame-retarding composite material through hydrothermal method. Adding bagasse-ADP increased the thermal stability and flame retardancy of the composite materials compared with that of pure epoxy. For the material with 30 wt% added bagasse-ADP, the char yield was 32.3 wt%, which was 18.2 wt% higher than that of pure epoxy (14.1 wt%) through thermogravimetric analysis. In addition, the limiting oxygen index increased from 21% to 30%, and the UL-94 classification improved from “Fail” to “V-0.” This performance was attributed to the nitrogen, phosphorus, and silicon content of the flame retardant.     

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     

Effect of Ni2+ chelated to the surface of PBFA on the charring flame retardant and smoke suppression properties of epoxy resin

Here, a phosphazene-based flame retardant (PBFA) containing active amine groups was synthesized by hexachlorocyclotriphosphazene and N-aminoethylpiperazine and nickel ion (Ni²⁺) was chelated to the surface of PBFA (named as PBFA-Ni²⁺). Incorporation into epoxy resin (EP) with a loading of 6 wt% (named as EP/PBFA-Ni²⁺-6.0), enabled the composite to pass the vertical burning test (UL-94) V 0 rating. Peak heat release rate and the total smoke release of EP/PBFA-Ni²⁺-6.0 were decreased by 41.02% and 22.74% as measured by cone calorimeter tests. The production rate of CO was inhibited when PBFA-Ni²⁺ was incorporated into EP.     

Synthesis of aluminum ethylphenylphosphinate flame retardant and its application in epoxy resin

A novel flame retardant additive, aluminum ethylphenylphosphinate (AEPP), was synthesized from diethyl phenylphosphonite and aluminum chloride hexahydrate, and characterized by FTIR, ¹H NMR, and ³¹P NMR. AEPP was added into diglycidyl ether of bisphenol A epoxy resin (EP) cured by bisphenol A‐formaldehyde novolac resin. The flame retardancy of the cured EP was investigated by limited oxygen index, UL 94 test, and cone calorimeter test. The results revealed that the EP composite containing 15% AEPP had a limited oxygen index value of 28.2% with a UL 94 V‐0 rating. The incorporation of AEPP effectively decreased the peak heat release rate and the total heat release in cone calorimeter test analysis. Scanning electron microscopy results showed that the introduction of AEPP benefited to the formation of a smooth and continuous char layer during combustion of the flame retarded EP. The thermogravimetric analysis results indicated that the incorporation of AEPP promoted the initial decomposition of EP matrix, but AEPP/EP composites had a higher char yield at high temperatures. Moreover, the flexural properties of the flame retarded EP composites were studied.     

Organophosphorous additive for fortification,processibility, and flame retardance of epoxy resins

Amine‐cured epoxy resins are prepared containing an aliphatic phosphonate additive which aids in the processing of the epoxy by reducing the viscosity of the resin mixture. The additive also acts as an antiplasticizer in the cured epoxy by increasing the modulus and yield strength under uniaxial tension and compression. Additionally, phosphonates are known to behave as flame retardants and dimethyl methyl phosphonate (DMMP) demonstrates a reduction in the rate of thermal degradation and the heat‐release rate upon pyrolysis. Addition of the antiplasticizer reduces the T_g and suppressed β‐relaxations, while effectively increasing the density of the material. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 302–309, 2002; DOI 10.1002/app.10329     

A novel flame retardant of spirocyclic pentaerythritol bisphosphorate for epoxy resins

A novel flame retardant for epoxy resins, bisdiglycol spirocyclic pentaerythritol bisphosphorate (BDSPBP) was synthesized from the reaction of diglycol with spirocyclic pentaerythritol bisphosphorate diphosphoryl chloride, which was obtained from the reaction of phosphoryl chloride with pentaerythritol. Flammability of the cured epoxy resin systems consisted of diglycidyl ether of bisphenol A (DGEBA), low‐molecular‐weight polyamide and BDSPBP are investigated by vertical burning test (UL‐94) and limiting oxygen index test (LOI). The results indicate that BDSPBP has good flame retardance on epoxy. The thermogravimetric analysis (TGA) shows that the epoxy resin containing BDSPBP has a high yield of residual char at high temperatures, indicating that BDSPBP is an effective charring agent. From the SEM observations of the residues of the flame retardant systems burned, the compact charred layers can be seen, which form protective shields to protect effectively internal structure, and inhibit the transmission of heat and heat diffusion during contacting fire. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4978–4982, 2006     

膨胀型阻燃剂/二乙基次磷酸铝阻燃改性不饱和树脂基复合材料

采用密胺包覆聚磷酸铵（APP）、季戊四醇（PER）和三聚氰胺（MEL）作为膨胀型阻燃剂（IFR）对不饱和树脂（UP）进行改性,研究了APP、PER和MEL不同复配比例及用量对不饱和树脂基复合材料阻燃性能和力学性能的影响。基于IFR最佳用量,以二乙基次磷酸铝（ADP）为协效剂,研究了ADP用量对IFR/UP阻燃复合材料阻燃性能、力学性能及热稳定性的影响。结果表明,当APP∶PER∶MEL复配比例为4∶1∶1,IFR添加量为15 %（质量分数,下同）时,复合材料综合性能最佳,其极限氧指数为27.4 %,UL 94垂直燃烧达到V?1等级,弯曲强度和冲击韧性分别为100.3 MPa和6.3 kJ/m²;ADP的引入能够进一步提高IFR/UP复合材料阻燃性能,且随着ADP质量分数的增加而增强;当ADP质量分数为2 %时,IFR?ADP/UP复合材料极限氧指数为28.5 %并达到V?0阻燃等级,弯曲强度和冲击韧性分别为110 MPa和7.8 kJ/m²,与IFR/UP复合材料相比,分别提高了9.7 %和23.8 %;ADP能够促进IFR/UP复合材料表面成炭,缓解基体的热降解。     

卡拉胶包覆APP/MnO2增强水性环氧树脂阻燃抑烟性能

用反相乳液法，以卡拉胶（KC）为壳材，聚磷酸铵（APP）和二氧化锰（MnO2）为芯材，制备了KC包覆APP/MnO2阻燃剂（KC-FR）。通过FTIR、 XRD、 SEM和 EDS对KC-FR进行了表征。结果表明：卡拉胶已成功包覆APP和MnO2，合成的样品具有微胶囊结构。将KC-FR应用于水性环氧树脂（EP）中，考察KC、APP、MnO2 三者质量比对EP阻燃、抑烟性能的影响。用极限氧指数（LOI）、垂直燃烧（UL-94）和锥形量热（CCT）测试了涂层的阻燃、抑烟性能。结果发现，当KC/APP/MnO2的质量比为2∶1∶1，并且在EP中添加量为20%时，制备的阻燃涂层EP2的LOI达到29.1%，UL-94达到V-0级，表现出较好的阻燃性能。EP2相比于其它涂层热释放峰值（pHRR）、热释放总量（THR）和烟释放总量（TSP）最低，相比于EP0分别下降了42%、37%和46%，表现出较好的抑烟性能。另外，热重分析（TGA）测试结果显示EP2在800℃残炭量（W800）为33%，表明KC-FR具有促进EP成炭的功能。通过SEM对残炭表面分析发现，EP2表面炭层更加致密，这表明KC-FR对促进形成稳定并且致密的炭层起到至关重要的作用。     

Polyamide‐enhanced flame retardancy of ammonium polyphosphate on epoxy resin

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

Synthesis of bio-based reactive N/P flame retardant and its curing and flame retarding behavior in epoxy resins

In this study, a pioneering bio-based nitrogen–phosphorus flame retardant and curing accelerator named oxime-phosphazene hexakis [(4-(hydroxyimino) 2-methoxy) phenoxy] cyclotriphosphazene (HAPV) was successfully synthesized using hexachlorocyclotriphosphazene and vanillin. When 5 wt % HAPV was added into epoxy, the limiting oxygen index increased from 22% to 27% and passed UL-94 V-0 (UL is defined as Underwriters Laboratories) rating. Meanwhile, with the addition 5 wt% HAPV, the apparent activation energy (E_a) of HAPV/EP decreased from 20.22 to 67.15 kJ/mol, and the pHRR value was suppressed from 581.21 to 330.18 kW/m². It was due to that the HAPV quenched the combustion chain reaction through the gas phase and condensed phase, forming a dense char layer for blocking the heat transfer. Overall, the study provides an environmentally friendly epoxy flame retardant curing accelerator that shows great potential in epoxy flame retardant applications.     

磷酸二氢铵结晶介稳区宽度的研究

溶液的介稳区宽度是结晶过程的基础研究内容之一,本文用激光散射法测定了纯磷酸二氢铵溶液和含有杂质或添加剂的磷酸二氢铵溶液在不同饱和温度下的结晶介稳区宽度,并用多元线性回归拟合得出磷酸二氢铵介稳区宽度与饱和温度及添加剂用量的回归方程.结果表明:磷酸二氢铵溶液的介稳区宽度随溶液饱和温度的升高而线性下降:添加剂硫酸铵、柠檬酸钠和硫脲均能使磷酸二氢铵溶液的介稳区变宽.     

新型含磷阻燃环氧树脂的合成与表征

以2-(5,5-二甲基-4-苯基-2-氧代-1,3,2-二氧磷杂环已烷膦酸酯基)-对苯二酚和双酚A 二缩水甘油酯合成了一新型的含环状膦酸酯结构的阻燃环氧树脂(DPODB-EP).采用元素分析、红外光谱(FTIR)和凝胶渗透色谱(GPC)对该含磷环氧树脂的结构和相对分子质量分布进行了表征.采用示差扫描量热法(DSC))和热失重法(TG)对DPODB-EP/PN固化物热性能进行了测试,发现该固化物具有较高的玻璃化转变温度(165℃)和较高的燃烧残炭率(700℃,31%).阻燃性能测试表明该固化物具有较好的阻燃效果,在磷的质量分数为2.25%时其极限氧指数可达29.5%.     

PEPA-EG/EP复合涂料的制备及其阻燃防腐性能

以季戊四醇磷酸酯(PEPA)与可膨胀石墨(EG)作为复合填料,添加到水性环氧树脂(EP)中制备出PEPA-EG/EP复合涂料。通过耐火极限分析、热失重分析、极限氧指数测试、垂直燃烧测试、残炭扫描电镜分析、残炭红外分析、电化学实验和附着力实验,考察了不同质量配比的复合填料对PEPA-EG/EP复合涂料阻燃性能和防腐性能的影响。结果表明:当复合填料与水性环氧树脂的质量比为15∶100时,涂料具有最佳的阻燃性能和防腐性能,其钢片背温达到500℃的时间是38 min,极限氧指数达到27.2%,垂直燃烧等级达到V-1级,800℃时残炭量为27.79%,并且在480 h的电化学测试中,其阻抗值达到最大,为9.24*10~6Ω×cm~2。     

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.     

磷酸二氢铵结晶动力学研究

运用连续流化床结晶装置，测定了不同饱和温度的磷酸二氢铵在15℃和25℃结晶温度下晶体的成核、生长速率。实验结果表明，随饱和温度的增加，磷酸二氢铵的成核、生长速率随之增加；同时根据实验数据，应用多元线性回归得出磷酸二氢铵晶体的生长动力学模型：B0=1．45×10^6G^0.189MT^1.608（15℃），B0=1．05×10^7G^0.458MT^0.980（25℃）。实验还研究了添加剂对磷酸二氢铵晶体生长速率的影响，结果表明，有添加剂时晶体的生长速率更高；而且随着饱和温度的升高，磷酸二氢铵晶体的生长速率上升趋势更显著。     

Fire retardance and smoke suppression of polypropylene with a macromolecular intumescent flame retardant containing caged bicyclic phosphate and piperazine

A macromolecular intumescent flame retardant (FR) named PPPAP was designed and synthesized with phosphorus chloride (the acid source), 2,6,7-trioxa-l-phosphabicyclo[2.2.2]-octane-4-methanol (the charring agent), and anhydrous piperazine (the blowing agent). Then, it was used to prepare an intumescent flame-retardant polypropylene (FR-PP). The thermal stability, flame retardancy, and fire performance of the FR-PPs were investigated. The results show that the initial decomposition temperature and char residue at 700 °C of PPPAP were 260.8 °C and 31.8%, respectively. The limiting oxygen index (LOI) value of polypropylene (PP) was enhanced with increasing PPPAP content. With the addition of 40 wt % PPPAP, the LOI value of FR-PP was 29%, and it passed the vertical burning UL-94 V-0 rating. The cone calorimetry results indicate that not only the peak heat-release rate but also the total smoke production of PP significantly decreased to 65.7 and 79.5%, respectively, with the incorporation of only 20 wt % PPPAP. The FR mechanism suggested that PPPAP played a part in both the gas and condensed phases, and the formation of the intumescent char layer during combustion was the dominant FR mechanism. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47593.