The effect of graphene presence in flame retarded epoxy resin matrix on the mechanical and flammability properties of glass fiber-reinforced composites

The effect of adding graphene in epoxy containing either an additive (MP) or reactive-type (DOPO) flame retardant on the thermal, mechanical and flammability properties of glass fiber-reinforced epoxy composites was investigated using thermal analysis; flexural, impact, tensile tests; cone calorimetry and UL-94 techniques. The addition of MP or DOPO to epoxy had a thermal destabilization effect below 400 °C, but led to higher char yield at higher temperatures. The inclusion of 10 wt% flame retardants slightly decreased the mechanical behavior, which was attributed to the poor interfacial interactions in case of MP or the decreased cross-linking density in case of DOPO flame retarded resin. The additional graphene presence increased flexural and impact properties, but slightly decreased tensile performance. Adding graphene further decreased the PHRR, THR and burning rate due to its good barrier effect. The improved fire retardancy was mainly attributed to the reduced release of the combustible gas products.     

A effective flame retardant for epoxy resins based on poly(DOPO substituted dihydroxyl phenyl pentaerythritol diphosphonate)

Poly(DOPO substituted dihydroxyl phenyl pentaerythritol diphosphonate) (PFR) was synthesized via the reaction between 10-(2,5-dihydroxyl-phenyl)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO-BQ) and pentaerythritol diphosphonate dichloride (SPDPC). The structures of PFR were characterized by Fourier transformed infrared (FTIR) spectroscopy and ¹H nuclear magnetic resonance (¹H NMR). Thermal degradation behaviors and flame retardant properties of the epoxy resin (ER)/PFR systems were investigated from the thermogravimetric analysis (TGA), UL-94 test and the limiting oxygen index (LOI) test. Moreover, the surface morphology of the char residue was studied by scanning electron microscopy (SEM). When the PFR content reached 10 wt%, the epoxy resin system met the UL-94 V0 classification and the LOI value of 30.2. The microscale combustion calorimetry (MCC) was used to evaluate the combustion behaviors of the ER/PFR. It was found that the addition of PFR obviously decreased the value of peak heat release rate and total heat release of the hybrids. The TGA results showed that the epoxy resin with 10 wt% PFR exhibited high char yields. The high char yields and the high limiting oxygen index values were found to certify the excellent flame retardancy of this phosphorus-containing epoxy resin.     

Organic/inorganic flame retardants containing phosphorus,nitrogen and silicon: Preparation and their performance on the flame retardancy of epoxy resins as a novel intumescent flame retardant system

This paper presents the preparation of novel organic/inorganic flame retardants containing phosphorus, nitrogen and silicon (organic/inorganic FRs). The organic/inorganic FRs were highly water resistant, as suggested by the water contact angle and water solubility tests. The organic/inorganic FRs were then incorporated into epoxy resins (EP) at different phosphorus/nitrogen ratios and the flame retardancy of EP/FRs composites was characterized. The results showed that synergistic effects on the flame retardancy of EP composites existed between the DOPO-VTS and TGIC-KH. The char residues for EP/FRs composites were increased, and the highest char residues were obtained in air atmosphere (3.8 wt.%) when the DOPO-VTS/TGIC-KH is 4/1. The MCC results also showed that the THR of epoxy resins were also decreased when the DOPO-VTS/TGIC-KH is 4/1, which was in accordance with the highest LOI and UL-94 results. The SEM, FTIR, XPS and TG-FTIR results of pyrolysis products in both condensed and gases phases indicated that the strategy of organic/inorganic FRs combined condensed phase and gases phase flame retardant strategies such as the phosphorus–nitrogen synergism systems, the silicon reinforced effects in the condensed phase and DOPO flame retardant systems in the gases phase, resulting in significant improvements in the flame retardancy of epoxy resins.     

Facile preparation,characterization and performance of noncovalently functionalized graphene/epoxy nanocomposites with poly(sodium 4-styrenesulfonate)

Graphene was noncovalently functionalized with poly(sodium 4-styrenesulfonate) (PSS) and then successfully incorporated into the epoxy resin via in situ polymerization to form functional and structural nanocomposites. The morphology and structure of PSS modified graphene (PSS-g) were characterized with transmission electron microscopy, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. The effects of PSS-g additions on tensile, electrical and thermal properties of the epoxy/graphene nanocomposites were studied. Noncovalent functionalization improved interfacial bonding between the epoxy matrix and graphene, leading to enhanced tensile strength and modulus of resultant nanocomposites. The PSS-g additions also enhanced electrical properties of the epoxy/PSS-g nanocomposites, resulting in a lower percolation threshold of 1.2 wt%. Thermogravimetric and differential scanning calorimetric results showed the occurrence of a two-step decomposition process for the epoxy/PSS-g nanocomposites.     

Combination effect of carbon nanotubes with graphene on intumescent flame-retardant polypropylene nanocomposites

A novel polypropylene (PP) nanocomposite was fabricated by the incorporation of intumescent flame retardant (IFR), carbon nanotubes (CNTs) and graphene into the PP matrix. Results from TEM indicate that IFR, CNTs and exfoliated graphene nanosheets are dispersed finely in the PP matrix, which is supported by the XRD analysis results. Thermogravimetric (TGA) results show that the addition of IFR, CNTs and graphene improved the thermal stability and the char yields of PP. The PP/IFR/CNTs/RGO nanocomposites, filled with 18 wt% IFR, 1 wt% CNTs and 1 wt% graphene, achieve the limiting oxygen index value of 31.4% and UL-94 V0 grade. Cone calorimeter data reveal that combustion behavior, heat release rate peak (PHRR) and average specific extinction area (ASEA) of PP decrease substantially when combination effects of IFR, CNTs and graphene intervene. For the PP/IFR/CNTs/RGO nanocomposites, the PHRR exhibits an 83% reduction and the time of ignition is delayed 40 s compared with neat PP.     

Iron-montmorillonite and zinc borate as synergistic agents in flame-retardant glass fiber reinforced polyamide 6 composites in combination with melamine polyphosphate

This paper presents a preliminary investigation on the effects of organically modified iron-montmorillonite (Fe-OMT) and zinc borate (ZnB) on thermal degradation behaviors and flame retardancy of melamine polyphosphate (MPP) flame-retarded glass fiber reinforced polyamide 6 (GFPA6). The samples were characterized using limiting oxygen index (LOI), UL-94 tests, thermogravimetric analysis (TGA), Fourier transform infrared coupled with the thermogravimetric analyzer (TG-FTIR) and Microscale Combustion Calorimeter (MCC) measurements. The residue after LOI test was also analyzed by Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) and Raman spectroscopy. A substitution of a certain fraction of MPP with ZnB or Fe-OMT can significantly improve the UL-94 rating of GFPA6/MPP composites from no rating to V0 rating, exhibiting excellent flame retardacny. Based on the investigations, different flame retardant mechanisms were proposed for the two effective flame-retardant formulations.     

基于微胶囊化聚磷酸铵和微胶囊化膨胀石墨的阻燃硬质聚氨酯泡沫复合材料的制备及性能

采用原位聚合法,以聚氨酯为壳材,制备微胶囊化聚磷酸铵(PUAPP)和微胶囊化膨胀石墨(PUEG).采用XPS、FTIR、TG和SEM分别对PUAPP和PUEG进行表征,结果表明,聚氨酯有效包覆在聚磷酸铵和膨胀石墨表面,成功制备了 PUAPP和PUEG.在此基础上,采用一步法全水发泡工艺将PUAPP和PUEG引入到聚氨酯...     

Organophosphorus and DGEBA resins containing clay nanocomposites: flame retardant,thermal, and mechanical properties

Flame-retardant nanocomposites were prepared from diglycidylphenylphosphate (DGPP) and modified montmorillonite (MMT) clay blended with DGEBA in different ratio. T _g of all formulations increased with increasing clay content in the respective series while decreasing with increasing DGPP content. The TGA, LOI, and UL-94 data of all nanocomposites indicated that the materials were thermally stable with high flame retardancy resulting from synergetic effect of phosphorus and inorganic clay. The XRD analysis of the nanocomposites with 1 and 2% of clay indicated the intercalation of clay while rest of the samples displayed exfoliation at high clay content. As compared to neat epoxy system, a maximum increase of 59.3, 45.5, and 93% of tensile, flexural, and impact strengths were observed for the prepared nanocomposites. The SEM analysis of the failure surfaces of all DGPP containing samples showed rough with ridge patterns and river markings on the fracture surface that serves in improving the mechanical properties.     

磷杂菲三氮唑双基化合物高效阻燃环氧树脂

以对苯二甲醛、3,5-二氨基-1,2,4-三氮唑和9,10-二氢-9-氧杂-10-磷杂菲-10-氧化物(DOPO)为原料合成了一种磷杂菲三氮唑双基化合物(DTZ),将其用于高效阻燃环氧树脂。利用FTIR、NMR、GPC和元素分析表征了其分子结构,采用TG和DSC研究了环氧固化物的热性能,利用极限氧指数、垂直燃烧、锥形量热、拉伸性能测试仪探究了环氧固化物的阻燃和力学性能,通过分析DTZ的热裂解行为、热氧化降解行为及炭层的形貌和结构研究了其阻燃机制。结果表明,DTZ的引入会降低环氧固化物的起始降解温度和玻璃化温度,但会提高其高温残炭率和拉伸强力。DTZ可显著提升环氧固化物的阻燃性能,当添加量为6wt%时,所得固化物的极限氧指数(LOI)值为33.5%,UL-94测试等级达到V-0级,热释放速率峰值和总热释放量分别降低21.8%和18.2%。DTZ可通过猝灭自由基、稀释可燃气体、促进基体成炭,在气相和凝聚相同时发挥阻燃作用。      

Solvothermal synthesis of carbon nanostructure and its influence on thermal stability of poly styrene

Carbon nanostructures were synthesized via a novel solvothermal reaction between ferrocene and sulfur. Carbon nanostructures were then added to poly styrene (PS) matrix. The thermal stability behavior of PS filled with carbon nanostructures were investigated by thermogravimetric analysis (TGA). Nanostructures were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, energy-dispersive X-ray (EDS) analysis and atomic force microscopy (AFM). The flame retardancy behavior of PS–carbon was studied by UL-94 analysis.     

含磷聚合物型阻燃剂(PMP)对乙烯基酯树脂(VER)的阻燃改性

使三氯氧磷与4-甲氧基苯酚发生反应制备阻燃剂聚对甲氧基苯氧基磷酸-4,4’-二羟基联苯酯(PMP),用傅里叶变换红外光谱(FTIR)和核磁共振(¹H-NMR,¹³C-NMR,³¹P-NMR)等手段表征其结构,并测试其煅烧后残炭的X射线光电子谱(XPS)。用阻燃剂PMP复配聚磷酸铵(APP) 改性乙烯基酯树脂(VER),制备出PMP/APP/VER复合材料。用热失重分析(TGA)、极限氧指数(LOI)和垂直燃烧(UL-94)等手段研究了这种材料的阻燃性能和热稳定性能。结果表明,阻燃剂PMP/APP添加量为15%的PMP/APP/VER复合材料其UL-94测试等级达到V-1级;PMP/APP添加量为20%时LOI值达到25.0%,在温度为700℃时的残炭量为34.6%,是纯VER的3.72倍。这表明,PMP/APP能显著提高VER基体的阻燃性能和热稳定性。     

有机蒙脱土协同含磷木质素基成炭剂阻燃聚乳酸

将自制含磷木质素基成炭剂（Lig-P）和聚磷酸铵（APP）复配用于制备阻燃聚乳酸（PLA）基复合材料,考察了协效阻燃剂有机蒙脱土（OMMT）对阻燃PLA性能的影响。采用极限氧指数（LOI）仪、垂直燃烧（UL-94）测试仪、锥形量热仪、热失重分析仪分别对Lig-P-APP-OMMT/PLA阻燃复合材料的阻燃性能、热稳定性能和燃烧行为进行了研究。结果发现,OMMT与Lig-P-APP存在明显的协同阻燃作用,当OMMT替代3wt%的Lig-P-APP时,Lig-P-APP-OMMT/PLA阻燃复合材料的LOI由27%增加至32%,UL-94等级由V1级提高至V0级;且Lig-P-APP-OMMT/PLA阻燃复合材料的最大热降解速率有所降低,800℃的残炭量提高了将近50%;此外,OMMT的引入使PLA阻燃复合材料的热释放速率明显降低,热释放速率峰值（PHRR）、烟释放速率峰值（PSPR）及总烟释放量（TSR）分别降低了26.4%、60%及26.3%。OMMT可明显提高阻燃PLA炭层的致密度及石墨化程度。      

The influence of cobalt oxide–graphene hybrids on thermal degradation,fire hazards and mechanical properties of thermoplastic polyurethane composites

In this work, cobalt oxide nanoparticles decorated on graphene nanosheets was firstly synthesized by a facile hydrothermal method. The structure and morphology of the synthesized hybrids were characterized by X-ray diffraction, Raman spectrum and Transmission electron microscopy measurements. Subsequently, the hybrids were introduced into thermoplastic polyurethane matrix for acting as reinforcements. The hybrids were well dispersed in thermoplastic polyurethane and no obvious aggregation of graphene nanosheets was observed. The obtained nanocomposites exhibited significant improvements in thermal stability, flame retardancy, mechanical properties and reduced the fire toxicity effectively, compared with those of neat polyurethane. The obvious improvements of these properties were mainly attributed to the ‘‘tortuous path’’ effect of graphene nanosheets, catalytic char formation function of cobalt oxide–graphene hybrids and the synergism between the catalysis effect of cobalt oxide nanoparticles and the adsorption effect of graphene nanosheets.     

改性埃洛石复配聚磷酸铵对硅橡胶阻燃性能和力学性能的影响

为研究埃洛石对硅橡胶阻燃性能和力学性能的影响,将埃洛石经乙烯基三甲氧基硅烷(A-171)表面改性处理后与聚磷酸胺(APP)复配并用于硅橡胶基体中,经机械共混制备了复配填充改性埃洛石(m-HNTs)的阻燃硅橡胶复合材料(FRSR)。利用红外光谱、热重分析对m-HNTs进行表征分析,采用扫描电子显微镜、极限氧指数(LOI)、垂直燃烧、锥形量热、能谱仪、热重分析等对FRSR的力学性能、阻燃性能、残渣形貌及热降解行为进行研究,并与复配填充未改性HNTs的样品性能对比。结果表明,复配填充适量的m-HNTs后,FRSR阻燃性能明显改善,力学性能显著提高。当复配填充3phr m-HNTs时,拉伸强度达8.7 MPa,LOI值达31.4%,UL-94测试为V-0级,且残渣致密紧实,热阻隔效果好,残炭率高,热释放速率降低36%。     

环氧树脂/聚磷酸铵复合材料的阻燃性能与热降解行为

利用环氧树脂(EP)成炭能力,引入聚磷酸铵(APP)以提高其阻燃性能。当APP质量分数为9%时,EP/APP氧指数达30.5%,垂直燃烧性能通过V-0级。相比EP,EP/APP的热释放峰值与总热释放均有所下降。此外,利用热失重-红外联用设备研究了EP以及EP/APP的热降解行为并解释相关机理:EP在高温下会释放CO、甲醇等易燃性气体,剧烈燃烧并放出大量的热;APP在低温阶段的热裂解产物会催化EP的降解,但在高温下EP/APP却有热稳定性优异的炭层形成,在火灾中此炭层会覆盖在基体表面保护下部材料以免其遭到进一步的破坏。     

High concentration exfoliation of graphene in ethyl alcohol using block copolymer surfactant and its influence on properties of epoxy nanocomposites

In this work, high concentration exfoliation (～0.2 mg/ml) of graphene in ethyl alcohol is achieved in presence of block copolymer of polyethylene oxide–polypropylene oxide–polyethylene oxide (PEO–PPO–PEO) using sonication followed by centrifugation. The obtained graphene solution is used to prepare epoxy nanocomposites. Flexural tests were conducted over epoxy nanocomposites. The 0.018 wt% of PEO–PPO–PEO block copolymer exfoliated graphene in epoxy matrix shows 21.7% and 15.8% enhancement in flexural modulus and flexural strength respectively as compared to pure epoxy. Transmission electron microscopy reveals well dispersion of graphene in epoxy matrix; and fractography of flexural fractured sample shows graphene dispersion restricts the crack propagation. The well-dispersed graphene in epoxy matrix increase the dielectric constant and thermal stability of epoxy nanocomposites. Further, the enhanced graphene dispersion in epoxy nanocomposites reduces the glass transition temperature (T_g). Thus, enhanced mechanical properties achieved by dispersion of block copolymer exfoliated graphene in epoxy nanocomposites make it suitable for several applications.     

三聚氰胺氰尿酸盐与聚磷酸铵协同作用对环氧树脂阻燃性能的影响

采用氧指数法（LOI）、垂直燃烧法（UL-94）及热重分析法（TGA）对三聚氰胺氰尿酸盐（MCA）和聚磷酸铵（APP）阻燃环氧树脂的阻燃性及热稳定性进行了研究。TGA结果表明,MCA促进成炭的作用较弱,主要在气相起到阻燃的作用。而APP的添加虽然降低了环氧树脂的初始分解温度,但当温度高于400℃时,体系具有更好的热稳定...     

Synergistic flame retardancy effect of graphene nanosheets and traditional retardants on epoxy resin

Novel non-toxic halogen-free flame retardants are replacing traditional flame retardants in polymer and polymer matrix composite structures. In this study, graphene nanosheet (GNS) is investigated in combination with traditional layered double hydroxide (LDH), layered rare-earth hydroxide (LRH), and phosphorus-based flame retardant (DOPO) to enhance the flame retardancy of epoxy resin. A synergistic flame retardancy effect is achieved in GNS/LDH and GNS/DOPO systems where combined GNS and LDH increased the viscosity of the epoxy melt, and limited the flame propagation through inhibition of dripping. The limiting oxygen index of epoxy increased from 15.9 to 23.6 with addition of 0.5 wt.% each of GNS and LDH. With the addition of 2.5 wt.% of both GNS and LDH, the total heat release of epoxy resin also reduced from 33.4 MJ/m² to 24.6 MJ/m². The synergistic effect of GNS and DOPO adopted a different mechanism. The addition of 2.5 wt.% of GNS and DOPO reduced the peak heat release rate from 1194 kW/m² to 396 kW/m², and the total heat release rate from 72.5 MJ/m² to 48.1 MJ/m². The synergistic mechanisms of the flame retardants were closely analyzed and correlated with the flame retardant properties.     

纤维素改性环氧酚醛树脂与环氧酚醛树脂的阻燃性

用热塑性环氧酚醛树脂与纸泥制备纸泥/环氧酚醛复合材料,将含卤素的阻燃剂三-2-氯乙基膦酸盐和无机阻燃剂(如氢氧化铝)加入到环氧酚醛树脂和纸泥/环氧酚醛聚合物中,用UL-94等级燃烧测试法测定体系的燃烧等级;用热重分析仪和差示扫描量热仪对复合材料进行热分析,研究两体系的阻燃性。结果表明,含磷型阻燃剂和无机阻燃剂对环氧酚醛树脂有阻燃作用,但只有卤化和磷酸化的阻燃剂能增强纸泥/环氧酚醛复合材料的阻燃性,原因是环氧酚醛树脂材料和纸泥/环氧酚醛复合材料的阻燃性取决于本身的热容和热分解行为。     

纸泥/环氧酚醛树脂复合物与环氧酚醛树脂的阻燃性研究

将含各类阻燃剂加入到环氧酚醛树脂和纸泥/环氧酚醛聚合物中,用UL-94等级燃烧测试法测定体系的燃烧等级,结果表明:TCEP和无机阻燃剂对环氧酚醛树脂有阻燃作用,但卤化和磷酸化的阻燃剂能增强纸浆/环氧酚醛复合材料的阻燃性.用热重分析仪和差示扫描量热仪对复合材料进行热分析研究阻燃机理,结果显示环氧酚醛树脂材料和纸泥/环氧酚醛复合材料的阻燃性取决于本身的热容和热分解行为.