Flame retarding glass fibers reinforced polyamide 6 by melamine polyphosphate/polyurethane‐encapsulated solid acid

Melamine polyphosphate and thermal‐plastic polyurethane (TPU)‐encapsulated solid acid were applied for flame retardant glass fibers reinforced polyamide 6 (GFPA6). The introduction of TPU would change the interfacial property between glass fibers (GFs) and polyamide 6 (PA6), weakening the “candlewick effects” of GFs in PA6. Serving as a synergist, solid acid containing sulfur (CAS) played the role of a strong acid source, which could promote the system to form much more condensed and closed char layers. Macromolecular charring agent, TPU, was able to accelerate the charring process. In addition, TPU encapsulating on the unstable solid acid could isolate CAS from PA6 resin, preventing the chemical interaction between them, which would cause the degradation of material. This established technology provided an effective approach to prepare halogen‐free flame retardant GFPA6 with UL94‐1.6 mm V0 rating and good mechanical performance, showing a promise in the future commercial application. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Synergistic effect of a novel charring agent with ammonium polyphosphate on flame retardancy and thermal degradation of acrylonitrile‐butadiene‐styrene copolymer

A novel charring agent poly(1,3‐propylene terephthalamide) (PPTA) was synthesized and characterized by Fourier transform infrared spectroscopy and ¹H nuclear magnetic resonance. This novel charring agent combined with ammonium polyphosphate (APP) was adopted as an intumescent flame retardant (IFR) to impart flame retardance and dripping resistance to acrylonitrile‐butadiene‐styrene copolymer (ABS). Flammability and thermal behaviors of the treated ABS were investigated by limiting oxygen index, vertical burning test and thermogravimetric analysis. The results showed that the IFR with the novel charring agent had both excellent flame retardant and anti‐dripping abilities for ABS. The thermogravimetric analysis curves indicated that there was a synergistic effect between PPTA and APP, which greatly promoted the char formation of IFR‐ABS composites. Meanwhile, the thermal degradation mechanism of PPTA and APP/PPTA was characterized using thermogravimetric analysis/infrared spectrometry. The results demonstrated that APP changed the thermal degradation behavior of PPTA and reacted with PPTA to form a crosslinked structure. Additionally, the structure and morphology of char residues were studied by Fourier transform infrared spectroscopy and scanning electron microscopy. Copyright © 2011 Society of Chemical Industry     

Simultaneously Improving the Thermal,Flame‐Retardant and Mechanical Properties of Epoxy Resins Modified by a Novel Multi‐Element Synergistic Flame Retardant

To obtain epoxy resins with satisfactory thermal, flame retardant, and mechanical properties, a novel multi‐element synergistic flame retardant (PPVSZ) is synthesized through the reaction between P? H of 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) and C?C of polysilazane (PVSZ) and utilized as a multi‐element synergistic flame retardant for epoxy resins. The flame retardant mechanism is explored by XPS and SEM, confirming that the excellent flame‐retardance efficiency owes itself to an optimal flame retardant way which jointly exerts the flame‐retardant effects in the gaseous and condensed phase. The thermal properties deduced from DSC, TGA, and DMA, indicate the glass transition temperature, maximum weight loss rate, and char yields at 700 °C for EP‐2 increase by about 5.0 °C, 8.4 °C and 8.8%, respectively. Furthermore, mechanical properties such as impact strength, tensile strength, and flexural strength are also increased by 45.38%, 14.16%, and 17.43%, respectively, which show that the incorporation of PPVSZ does not deteriorate the mechanical properties of modified resin. All the results demonstrate that epoxy resins modified by PPVSZ not only have good effect on the flame retardance, but also have good improvement on thermal and mechanical properties, indicating the potential for applications in many fields requiring fire safety.     

水滑石对PBS/Sb2O3阻燃PA6/GF性能的影响

研究了聚溴化苯乙烯(PBS)对玻纤增强尼龙6(PA6/GF)阻燃和力学性能的影响,并采用锥形量热仪研究了改性水滑石(HT)对PBS/Sb2O3阻燃PA6/GF抑烟作用和燃烧时热释放速率的影响。结果表明,随PBS用量增加,PA6/GF的氧指数增加,阻燃性提高,当PBS质量分数为20%时,PA6/GF的垂直燃烧达到FV-0级;HT燃烧后形成多孔、大比表面积的镁铝复合氧化物,能够有效吸附材料燃烧过程中产生的炭微粒,对PBS/Sb2O3阻燃PA6/GF具有显著的抑烟作用。当HT质量分数为5%时,烟释放速率降低27.6%,且对阻燃PA6/GF的力学性能影响不大。另外,HT使PA6/GF的氧指数和相比漏电起痕指数(CTI)提高。     

New developments in flame retardancy of glass‐reinforced epoxy composites

This work involves the development of novel glass fiber–reinforced composite materials containing a commercially available epoxy resin, a phosphate‐based intumescent, and inherently flame‐retardant cellulosic (Visil, Sateri) and phenol–formaldehyde (Kynol) fibers. The intumescent and flame‐retardant fiber components were added both as additives in pulverized form and fiber interdispersed with the intumescent as a fabric scrim for partial replacement of glass fiber. Thermal stability, char formation, and flammability properties of these novel structures were studied by thermal analysis, limiting oxygen index, and cone calorimetry. The results are discussed in terms of effect of individual additive component on thermal degradation/burning behavior of neat resin. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2511–2521, 2003     

The investigation of melamine polyphosphate flame retardant polyamide‐6/inorganic siliciferous filler with different geometrical form

Melamine polyphosphate (MpolyP) was used to flame retard polyamide‐6 filled with siliciferous fillers including fibrous wollastonite, laminar talc, and spherical glass bead. The mechanical performance, flame retardancy of these flame retarded materials, and the influence of these fillers on charring behavior were investigated. The results show that wollastonite/MpolyP/PA6 system has the best mechanical properties as compared with talc/MpolyP/PA6 and glass bead/MpolyP/PA6 system due to good reinforcing effects of the fibrous filler in resin matrix. Otherwise, the char morphology observation shows that spherical glass beads separates from the char matrix during the expansion of the char layer, which hardly improves the char quality. However, fibrous wollastonite and laminar talc can well combine with the char layer, thus enhancing the flame retardancy as a part of the charred layer. It is proved that the laminar talc favors the formation of more condensed char because of its barrier effects, and the fibrous wollastonite with quite high aspect ratio can effectively reinforce both the resin and the charred layer, which leads to the remarkable improvement of the flame retardancy. Consequently, polyamide‐6/MpolyP/wollastonite system shows the best flame retardancy among the above systems. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Using PA6 as a charring agent in intumescent polypropylene formulations based on carboxylated polypropylene compatibilizer and nano‐montmorillonite synergistic agent

The intumescent fire retardant polypropylene (IFP/PP) filled with ammonium polyphosphate (APP), melamine (M), and PA6 (charring agent) is discussed. Intumescing degree (ID) and the char yield were determined. Only when the three main components of IFR coexist at appropriate proportions, it has optimal ID and higher char yield. The appropriate proportion is PA6 : APP : M = 10 : 10 : 5. A new compatibilizer, carboxylated polypropylene (EPP), was added to PP/PA‐6 blend. Flow tests indicated that the apparent viscosity increased with the addition of EPP, thermal characterization suggested that EPP has reacted with PA6, PA6‐g‐EPP cocrystallized with PA6, and EPP‐g‐PA6 cocrystallized with PP; SEM micrographs illustrated that the presence of EPP improved the compatibility of PP and PA6. All the investigations showed that EPP was an excellent compatibilizer, and it was a true coupling agent for PP/PA6 blends. Using PA6 as a charring agent resulted in the IFR/PP dripping, which deteriorated the flammability properties. The addition of nano‐montmorillonite (nano‐MMT) as a synergistic agent of IFR enabled to overcome the shortcoming. The tensile test testified that the addition of nano‐MMT enhanced the mechanical strength by 44.3%. SEM showed that nano‐MMT improved the compatibility of the composites. It was concluded that the intumescent system with nano‐MMT was an effective flame retardant in improving combustion properties of polypropylene. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 739–746, 2006     

Synergistic flame‐retardant effect of phosphaphenanthrene derivative and aluminum diethylphosphinate in glass fiber reinforced polyamide 66

The synergistic flame‐retardant (FR) effect of 1,1′‐bis(4‐hydroxyphenyl)‐metheylene‐bis(9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide‐2‐hydroxypropan‐1‐yl) (DPOH) and aluminum diethylphosphinate (AlPi) composites on glass fiber reinforced polyamide 66 (PA) was investigated by limiting oxygen index (LOI) tests, vertical burning (UL94) tests, and cone calorimeter tests. DPOH/AlPi system with 1:1 mass ratio increased UL94 ratings, suppressed heat release rate and increased residue yields of PA composites, and DPOH/AlPi system also imposed high LOI values and lower total heat release values to PA composites. All these results verified excellent synergistic FR effect between DPOH and AlPi. The reason of DPOH/AlPi system with higher flame‐retardant efficiency was caused by the quenching effect as good as that of DPOH and also by the higher charring effect than that of AlPi. DPOH/AlPi system possesses good flame retardancy in gas phase and also the strengthened FR effect in condensed phase compared with DPOH and AlPi alone, which led to excellent synergistic FR effect between the two components DPOH and AlPi. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45126.     

A phosphorus‐containing inorganic compound as an effective flame retardant for glass‐fiber‐reinforced polyamide 6

A novel inorganic compound, aluminum hypophosphite (AP), was synthesized successfully and applied as a flame retardant to glass‐fiber‐reinforced polyamide 6 (GF–PA6). The thermal stability and burning behaviors of the GF–PA6 samples containing AP (flame‐retardant GF–PA6) were investigated by thermogravimetric analysis, vertical burning testing (with a UL‐94 instrument), limiting oxygen index (LOI) testing, and cone calorimeter testing (CCT). The thermogravimetric data indicated that the addition of AP decreased the onset decomposition temperatures, the maximum mass loss rate (MLR), and the maximum‐rate decomposition temperature of GF–PA6 and increased the residue chars of the samples. Compared with the neat GF–PA6, the AP‐containing GF–PA6 samples had obviously improved flame retardancy: the LOI value increased from 22.5 to 30.1, and the UL‐94 rating went from no rating to V‐0 (1.6 mm) when the AP content increased from 0 to 25 wt % in GF–PA6. The results of CCT reveal that the heat release rate, total heat release, and MLR of the AP‐containing GF–PA6 samples were lower than those of GF–PA6. Furthermore, the higher additive amount of AP affected the mechanical properties of GF–PA6, but they remained acceptable. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Influence of polyamide 6 as a charring agent on the flame retardancy,thermal, and mechanical properties of polypropylene composites

In this work, polyamide 6 (PA6) as a charring agent has been used in combination with thermoplastic polyurethane (TPU)‐microencapsulated ammonium polyphosphate (MTAPP) forming intumescent flame retardants (IFRs) which applies in polypropylene (PP). The effects of the IFRs on the flame retardancy, morphology of char layers, water resistance, thermal properties and mechanical properties of flame‐retardant PP composites are investigated by limiting oxygen index (LOI), UL‐94 test, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and mechanical properties test. The results show that the PP/MTAPP/PA6 composites exhibit much better flame‐retardant performances than the PP/MTAPP composites. The higher LOI values and UL‐94 V‐2 of the PP/MTAPP composites with suitable amount of PA6 are obtained, which is attributed to the thick and compact char layer structure evidenced by SEM. The results from TGA and DSC demonstrate that the introduction of PA6 into PP/MTAPP composites has a great effect on the thermal stability and crystallization behaviors of the composites. Furthermore, the mechanical properties of PP/MTAPP/PA6 composites are also improved greatly due to the presence of PA6 as a charring agent. POLYM. ENG. SCI., 55:1355–1360, 2015. © 2015 Society of Plastics Engineers     

硼酸锌对氮磷协效阻燃玻纤增强尼龙66性能的影响

为提高三聚氰胺聚磷酸盐(MPP)和二乙基次膦酸盐(OP)协效阻燃玻纤(GF)增强尼龙66(PA66)的综合性能,引入少量的无机阻燃剂硼酸锌(ZB)作为协效剂,系统研究了不同添加量的ZB对阻燃材料的阻燃性能、热稳定性、力学性能和白度的影响。结果表明,当MPP和OP的总添加量为15%,复配0.5%的ZB时,阻燃GF增强PA66的垂直燃烧阻燃等级达到UL94 V–0级,且热释放总量由MPP/OP体系的15.4 k J/g降为13.7 k J/g;ZB的引入促进了连续、致密炭层的形成,增强了凝聚相阻燃;ZB增强了阻燃材料的热稳定性,ZB复配量为1.0%的阻燃材料的初始降解温度提高到了301℃,有效避免了加工过程中的降解;当ZB添加量为1.0%时,阻燃材料的拉伸强度和缺口冲击强度分别为100.9 MPa和4.22 k J/m~2,均优于未添加阻燃剂的纯GF增强PA66;同时,样品的白度得到了明显提升,有利于阻燃GF增强PA66的工业化应用。     

Synergistic Effect between a Novel Hyperbranched Flame Retardant and Melamine Pyrophosphate on the Char Forming of Polyamide 6

A novel hyperbranched polyphosphate bisphenol-S ester (HPPES) flame retardant was prepared. The structure and thermal stability of the product were characterized. Polyamide 6 (PA6), HPPES and melamine pyrophosphate (MPP) were used to prepare flame retardant PA6 (FR-PA6) through melt blending. Limiting oxygen index (LOI), UL-94 vertical burning methods, thermogravimetric analysis (TGA), X-ray photoelectron spectroscope (XPS) and scanning electron microscope (SEM) were used to investigate the combustion properties, thermal degradation behaviours and char forming of FR-PA6. The results showed that synergistic effect between HPPES and MPP was present, which enhanced the char forming and flame retardance of PA6.     

一种三嗪阻燃剂对玻纤增强PET体系性能的影响

比较了新型阻燃剂无析出阻燃剂A和十溴联苯醚对玻纤增强聚对苯二甲酸乙二醇酯（PET）体系的阻燃和力学性能的影响以及阻燃剂在体系中的抗析出性能。结果表明，两种阻燃剂对体系性能的贡献几乎一样，但无析出阻燃剂A具有良好的抗析出性。借助扫描电镜（SEM）对体系的微观结构的分析发现无析出阻燃剂A在PET基体中分散均匀，颗粒尺寸小而一致。在不同工程塑料中加入无析出阻燃剂A后发现，PET体系的阻燃性能明显高于而力学性能则大大低于PBT和尼龙体系，这在很大程度上是由于无析出阻燃剂A体系使PET树脂摩尔质量降低所致。此外，还讨论了玻纤对十溴联苯醚阻燃PET的影响。适当提高玻纤的加入量，不仅可以提高体系的力学性能，还可以改善其阻燃性能。     

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     

Acidic buffer mechanism of cyclotriphosphazene and melamine cyanurate synergism system flame retardant epoxy resin

In this research, a new synergistic mechanism based on an acid‐buffer action for cyclotriphosphazene (CPZ)/melamine cyanurate (MCA) flame retardant epoxy resin (EP) was proposed. This mechanism broke through the conventional well‐recognized phosphorus–nitrogen interaction one. It revealed that CPZ had not only acid‐catalytic charring but also acid‐catalytic degrading effect on EP. The former that occurs in higher temperature range to improve the flame resistance in the condensed phase is a mechanism generally accepted for the phosphorus flame retardant, but the later that occurs in lower temperature range to deteriorate the flame retardance is usually ignored by the people. For CPZ/MCA flame retardant EP, the produced organic base from decomposed MCA can neutralize the acids from CPZ. Decline of the acidity effectively weakened the acid‐catalytic effect, and reduced the volatiles release rate of the degraded resin in the initial stage, thus slowing down the combustion in the gaseous phase. With increasing temperature, the neutralized products were converted to the phosphorus‐containing acids again to promote the formation of the chars. A series of characterizations such as vertical burning test, X‐ray photoelectron spectra, micro‐scale combustion calorimetry, thermogravimetric, and differential thermogravimetric analysis of the flame retardant materials and the pH value detection of the corresponding carbonation products were performed to investigate the acid‐buffer mechanism. The experimental results including no N? P forms in the condensed phase obviously improved flame retardance and increased degradation temperature of CPZ/MCA/EP compared with CPZ/EP, as well as the enhanced pH value of the former carbonation residue confirmed the above mechanism. POLYM. ENG. SCI., 55:1046–1051, 2015. © 2014 Society of Plastics Engineers     

Flame retardancy of glass fiber reinforced high temperature polyamide by use of aluminum diethylphosphinate: thermal and thermo‐oxidative effects

Glass fiber reinforced polyamide (PA) 6 T/DT flame retarded with aluminum diethylphosphinate (AlPi) was tested to assess its flame retardant properties. Models for the decomposition of PA 6T/DT with and without AlPi are presented. Thermal decomposition was measured by performing TGA with Fourier transform infrared (FTIR) spectroscopy and FTIR spectroscopy in the condensed phase. Fire behavior was studied using a cone calorimeter and flammability was tested with UL 94 and the limiting oxygen index. AlPi works as an effective flame retardant for glass fiber reinforced PA 6T/DT materials, acting in the gas phase. Also observed was condensed‐phase action, which occurs especially under oxidative conditions before the samples ignite. © 2013 Society of Chemical Industry     

阻燃大豆蛋白纤维的热性能研究

为了提高阻燃性,用四溴酞酐(TBPA)加有机二酸体系对大豆蛋白纤维进行了阻燃处理,然后用极限氧指数(LOI)、剩炭率表征了它的阻燃性能,用热分析和扫描电子显微镜研究了它的热性能。结果表明:与纯大豆蛋白纤维相比,阻燃处理后的大豆蛋白纤维的极限氧指数和剩炭率提高,热分解起始温度降低,阻燃性能得到了明显改进。     

PA‐6 clay nanocomposite hybrid as char forming agent in intumescent formulations

This work deals with new flame retardant (FR) intumescent formulations for ethylene‐vinyl acetate copolymers (EVA) using charring polymers polyamide‐6 (PA‐6) and polyamide‐6 clay nanocomposite hybrid (PA‐6‐nano) as carbonization agents. Use of PA‐6 nano improved both the mechanical and fire properties of FR EVA‐based materials. The part played by the clay in the improvement of the FR performance was studied using FTIR and solid state NMR. It is shown that the clay allowed the thermal stabilization of a phosphorocarbonaceous structure in the intumescent char which increased the efficiency of the shield and, in addition, the formation of a ‘ceramic’ which can act as a protective barrier. Copyright © 2000 John Wiley & Sons, Ltd.     

Effect of novel copolyamide charring agents on flame‐retarded polypropylene

In this article, two novel copolyamide charring agents, ES‐6 and M‐170, were served as charring agents or synergist with ammonium polyphosphate (APP) and dipentaerythritol (DPER) for the flame‐retarded polypropylene (PP). The flame‐retardant system was characterized by limiting oxygen index (LOI), tensile strength, Izod impact strength, thermogravimetric analyses, differential scanning calorimeter (DSC), and scanning electron microscope (SEM). Compared with polyamide 6 (PA6), ES‐6 and M‐170 had better dispersion and compatibility in the PP matrix and enhanced mechanical properties. Meanwhile, as low melting point polyamides, ES‐6 and M‐170 could decrease processing temperature and effectively inhibit side reaction, especially the degradation of APP. In addition, the synergistic effect between ES‐6 and DPER was also investigated. The results showed that the synergistic system containing ES‐6 had better flame retardancy and mechanical performance in comparison with the system only using DPER or the system containing PA6. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers     

三聚氰胺聚磷酸盐/硼酚醛协效体系阻燃PA66/GF复合材料的研究

采用氮磷型阻燃剂三聚氰胺聚磷酸盐(MPP)与硼改性酚醛树脂(BPF)组成的复合阻燃体系对玻纤(GF)增强尼龙66( PA66)复合材料进行阻燃,获得了阻燃性能优异、力学性能良好的增强复合材料,研究了协效阻燃剂BPF/MPP配比、BPF/MPP用量及GF用量对阻燃复合材料阻燃性能的影响,采用微型燃烧量热和质量保持率分析方法研究了阻燃复合材料的燃烧及成炭行为,对复合阻燃剂的协效机理进行了讨论.结果表明,当BPF在BPF/MPP中的质量分数为15％时,添加25％ BPF/MPP复合阻燃剂可使20％ GF增强PA66复合材料达到V-0( 1.6 mm)阻燃级别,极限氧指数增加至25.3％,拉伸强度、弯曲强度、缺口冲击强度分别为116 MPa,132 MPa,7.1 kJ/m2.该复合材料可满足高性能无卤阻燃的使用要求.