A P/N-containing flame retardant constructed by phosphaphenanthrene,phosphonate, and triazole and its flame retardant mechanism in reducing fire hazards of epoxy resin

A P/N-containing flame retardant (PPT) constructed by phosphaphenanthrene, phosphonate, and triazole groups was successfully synthesized and used as a reactive co-curing agent for epoxy resin (EP). The curing behavior, thermal property, combustion behavior, and flame retardant mechanism of EP thermosets were comprehensively investigated. According to the analysis of DSC and TGA, PPT accelerated the crosslinking reaction and enhanced the charring ability for EP thermosets at high temperature. The results of combustion test indicated that PPT endowed epoxy thermoset with outstanding flame retardancy. When the phosphorus content was 0.71 wt%, EP/DDS/PPT-2 achieved a LOI value of 33.2% and passed V-0 rating in UL-94 test, and its peak heat release rate and total heat release were decreased by 63.7 and 30.5%, respectively, relative to EP/DDS. Moreover, the FIGRA of EP/DDS/PPT-2 was reduced from 9.7 to 3.5 kW m⁻² s⁻¹, manifesting the significantly improved fire safety of EP thermoset. The flame retardant mechanism was summarized as two parts: (a) the barrier effect of continuous phosphorus-rich char layers in condensed phase, (b) the quenching effect of phosphorous radicals and diluting effect of nonflammable gases in gaseous phase.     

Preparation and smoke suppression mechanism of flame-retardant PBS composites with BNNS@DOPA

Currently, the flame-retardant modification of polybutylene succinate (PBS) is mainly focused on improving flame-retardant efficiency, ignoring the negative impact of the smoke produced by combustion on the human respiratory tract. To address this problem, PBS composites were prepared by melt blending method in this study. The effect of boron nitride-grafted DOPO flame retardant (BNNS@DOPA) on flame retardancy and smoke suppression of PBS composites was investigated. Incorporating 3% BNNS@DOPA into PBS composites results in a 90% improvement in thermal conductivity. This resulted in a reduction of the peak heat release rate, total heat release rate, and actual smoke rate to 453.7 kW m⁻², 86.3 MJ m⁻², and 1035.9 m², respectively, compared with pure PBS. The latter indicated a decrease of 34.0%, 37.6%, and 51.2%, respectively. Furthermore, the ignition time was extended by 45 s and the limiting oxygen index value increased by 12.5%. This functionalization approach presents a new way to study PBS flame retardancy improvement, consequently boosting its application in fire safety for polymer materials.     

Synergistic Effect of Mesoporous Nanocomposites with Different Pore Sizes and Structures on Fire Safety and Smoke Suppression of Epoxy Resin

Epoxy resin (EP) is extremely flammable, and smoke release during combusting is considered toxic and harmful for human health. Mesoporous materials offer reliable desorption performance due to their large specific surface area. Therefore, the construction of mesoporous nanocomposites is a novel method for enhanced smoke suppression effect of EP. In this work, zinc hydroxystannate (ZHS)‐mesoporous silica (SBA‐15 and MCM‐41) modified reduced graphene oxide (RGO) is successfully prepared and used to enhance the fire safety of EP. SBA‐15‐RGO‐ZHS/EP exhibits the lowest total smoke production (22.8 m²) and peak heat release rate (416 kW m^?2), which are reduced by 55% and 37% compared with pure EP, respectively. Furthermore, the effect of mesoporous nanoparticles is also investigated. Apparently, the smoke suppression effect and flame retardancy of SBA‐15‐RGO‐ZHS/EP is even more remarkable than that of MCM‐41‐RGO‐ZHS/EP, which indicates that the pore size and structure of mesoporous are important factors for reducing the smoke toxicity of EP. Finally, it is verified that its enhanced fire safety is attributed to the synergistic action of physical barrier properties of RGO, “labyrinth” effect of SBA‐15, and catalytic ability of ZHS.     

锥形量热法研究木质素基膨胀型阻燃剂对环氧树脂阻燃抑烟效果

以来自自然界储量第二的木质素作为膨胀型阻燃剂的基体,通过接枝氮、磷元素成功合成碳源、酸源、气源三位一体的木质素基膨胀型阻燃剂(Lig?T),实现了良好的阻燃性能.将Lig?T按照不同含量添加到环氧树脂(EP)中制备EP/Lig?T复合材料,以锥形量热测试考察复合材料的热稳定性能和阻燃性能,并重点考察复合材料在接近真实火...     

Boosting flame retardancy of epoxy resin composites through incorporating ultrathin nickel phenylphosphate nanosheets

Ultrathin nickel phenylphosphate (NiPP) nanosheets with layered structure are successfully synthesized through a mixed solvothermal method. The results indicate that NiPP is Ni(O₃PC₆H₅)·H₂O and has good thermal stability. To ameliorate the thermal stability and flame ratardancy of epoxy resin (EP), EP/NiPP nanocomposites are prepared by incorporating NiPP into EP matrix. The results show that adding NiPP can availably enhance thermal stability at high temperature due to the remarkable catalytic char performance of NiPP, and the residues yield of EP/NiPP nanocomposites with 6 wt% NiPP is 24.1% while the pure EP had only 14.2% at 700°C. In contrast with pure EP, the peak heat release rate, total heat release, smoke production rate, CO production, and CO₂ production of EP/6wt%NiPP nanocomposites reduced by 35.2%, 20.2%, 27.1%, 45.8%, and 35.5%. The synergistic effect of catalytic char performance and fire retardancy of NiPP make the EP/NiPP nanocomposites possess prominent flame retardancy, smoke suppression, and thermal stability.     

Preparation and investigation of flame‐retardant epoxy resin modified with a novel halogen‐free flame retardant containing phosphaphenanthrene,triazine‐trione,and organoboron units

In this article, a novel flame retardant (coded as BNP) was successfully synthesized through the addition reaction between triglycidyl isocyanurate, 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide and phenylboronic acid. BNP was blended with diglycidyl ether of bisphenol‐A to prepare flame‐retardant epoxy resin (EP). Thermal properties, flame retardancy, and combustion behavior of the cured EP were studied by thermogravimetric analysis, limited oxygen index (LOI) measurement, UL94 vertical burning test, and cone calorimeter test. The results indicated that the flame retardancy and smoke suppressing properties of EP/BNP thermosets were significantly enhanced. The LOI value of EP/BNP‐3 thermoset was increased to 32.5% and the sample achieved UL94 V‐0 rating. Compared with the neat EP sample, the peak of heat release rate, average of heat release rate, total heat release, and total smoke production of EP/BNP thermosets were decreased by 58.2%–66.9%, 27.1%–37.9%, 25.8%–41.8%, and 21.3%–41.7%, respectively. The char yields of EP/BNP thermosets were increased by 46.8%–88.4%. The BNP decomposed to produce free radicals with quenching effect and enhanced the charring ability of EP matrix. The multifunctional groups of BNP with flame retardant effects in both gaseous and condensed phases were responsible for the excellent flame retardancy of the EP/BNP thermosets. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45291.     

Epoxy resin/phosphorus‐based microcapsules: Their synergistic effect on flame retardation properties of high‐density polyethylene/graphene nanoplatelets composites

Two types of microcapsule flame retardants are prepared by coating ammonium polyphosphate (APP) and aluminum diethylphosphinate (ADP) with epoxy resin (EP) as the shell via in situ polymerization, and blended with high density polyethylene (HDPE)/graphene nanoplatelets (GNPs) composites to obtain flame‐retardant HDPE materials. Fourier transform infrared spectroscopy, scanning electron microscopy (SEM), and water contact angle results confirm the formation of core–shell structures of EP@APP and EP@ADP. The limiting oxygen index (LOI), vertical burning test (UL‐94), cone calorimetry, and Raman spectroscopy are employed to characterize the HDPE/GNPs composites filled with EP@APP and EP@ADP core–shell materials. A UL94 V‐0 level and LOI of 34% is achieved, and the two flame retardants incorporated in the HDPE/GNPs composite at 20 wt % in total play a synergistic effect in the flame retardancy of the composite at a mass ratio of EP@ADP:EP@APP = 2:1. According to the cone‐calorimetric data, the compounding composites present much lower peak heat release rate (300 kW/m²) and total heat release (99.4 MJ/m²) than those of pure HDPE. Raman spectroscopic analysis of the composites after combustion reveals that the degree of graphitization of the residual char can reach 2.31, indicating the remarkable flame retarding property of the composites. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46662.     

Preparation of novel biomass humate flame retardants and their flame retardancy in epoxy resin

Humic acid (HA), a biomass material with plentiful oxygen-containing functional groups, showed huge potential to be considered as a promising charring agent in flame retardancy. In this study, this HA was modified with four different metal ions like Fe²⁺, Mn²⁺, Al³⁺, and Cu²⁺ and finally, introduced into the epoxy resin (EP) to enhance the flame retardancy of the EP and the dispersion of these flame retardants into the EP matrix. When 10 wt% of HA-Fe and HA-Mn were incorporated into EP matrix, the limiting oxygen index (LOI) was increased from 21.2% for EP to 26.6 and 25.3% for the EP composites and the peak heat release rate (pHRR) was reduced by 36 and 35.5%, respectively. Such a significant improvement in flame retardancy was attributed to the catalytic charring of HA in the presence of metal ions, which ultimately increased the residual char formation and produced compact char layers during the combustion process to retard the transfer of heat and combustible gases between the EP composites and the flame zone. Finally, this kind of application provided a feasible way for the development of an environmentally friendly flame retardant with high efficiency, which improved the fire safety of EP matrix.     

Phytic Acid-Iron/Laponite Coatings for Enhanced Flame Retardancy,Antidripping and Mechanical Properties of Flexible Polyurethane Foam

The use of flexible polyurethane foam (FPUF) is severely limited due to its flammability and dripping, which can easily cause major fire hazards. Therefore, choosing an appropriate flame retardant to solve this problem is an urgent need. A coating was prepared on the FPUF surface by dipping with phytic acid (PA), Fe₂(SO₄)₃·xH₂O, and laponite (LAP). The influence of PA-Fe/LAP coating on FPUF flame-retardant performance was explored by thermal stability, flame retardancy, combustion behavior, and smoke density analysis. FPUF/PA-Fe/LAP has a good performance in the small fire test, which can pass the UL-94 V-0 rating and the limiting oxygen index reaches 24.5%. Meanwhile, the peak heat release rate values and maximum smoke density of FPUF/PA-Fe/LAP are reduced by 38.7% and 38.5% compared with those of neat FPUF. After applying PA-Fe/LAP coating, the value of fire growth rate index decreases from 10.5 kW/(m²·s) to 5.1 kW/(m²·s), dramatically reducing the fire risk. Encouragingly, the effect of PA-Fe/LAP coating on cyclic compression and permanent deformation is small, which is close to that of neat FPUF. This work provides an effective strategy for making a flame-retardant FPUF with antidripping and keeping mechanical properties.     

Effect of Bio-Based Cobalt Alginate on the Fire Safety and Mechanical Properties for Epoxy Resin

There is a growing demand to develop epoxy resins (EP) with smoke suppression as well as satisfactory flame retardancy. Herein, bio-based cobalt alginate is successfully fabricated and incorporated into EP to prepare EP/Cobalt Alginate composites with better fire safety performance. The addition of cobalt alginate reduces the thermal-decomposition rate, temperature at maximum weight-loss rate of EP, whereas obviously improves the thermal stabilities at a higher temperature range. Furthermore, the addition of cobalt alginate substantially reduces the fire hazard of EP, resulting in 56.2% reduction in peak heat release rate, as well as 17.8% and 56.3% reduction in total smoke production and peak smoke production rate, respectively, compared with EP matrix. Moreover, the presence of cobalt alginate increases smoke-suppressant properties, according to the smoke density test. Additionally, the incorporation of cobalt alginate has no obviously destructive effect on the mechanical properties of EP, while EP/Cobalt Alginate-3 exhibits a 27.0% improvement in impact strength. In prospective, this study may provide a significant method for producing eco-friendly flame retardant EP.     

Self-emulsification synthesis of epoxy phosphate ester and its flame-retardant mechanism in flexible poly(vinyl chloride)/magnesium hydroxide composites

A trade-off dilemma exists for simultaneously improving the mechanical properties and flame resistance of flexible polyvinyl chloride (fPVC)/magnesium hydroxide (MH) composites. In this study, epoxy phosphate ester (EPE), a hydrophobic surface modifier of MH, was synthesized using a self-emulsification method. After modification, EPE was bonded to the surface of MH (MHEPE) without altering its morphology. The results of limiting oxygen index and cone calorimetry tests indicated that fPVC/MHEPE exhibited better flame retardancy and smoke suppression effects than did fPVC/MH. The peak of the heat release rate, total heat release, peak of the smoke production rate, and total smoke production of the fPVC/MHEPE composite were 206.0 kJ m⁻², 45.90 MJ m⁻², 0.0729 m² s⁻¹, and 9.88 m², which were 8.64%, 14.00%, 27.61%, and 9.02% lower than those of the fPVC/MH composite, respectively. For the fPVC/MHEPE composite, a compact and continuous char residue formed, which could inhibit heat and flammable volatile migration between the matrix and burning zones. In the gas phase, the dilution effect of H₂O vapor reduced the concentrations of O₂ and flammable volatiles. The free-radical quenching effect of ·PO and ·PO₂ also played a vital role in extinguishing flame and terminating combustion. Further, the introduction of EPE improved the tensile and impact strengths of the fPVC/MH composites because of the excellent interfacial compatibility between MHEPE and the fPVC matrix. This study provides a simple and workable solution for the trade-off dilemma, and the remarkable flame retardancy and mechanical properties of the fPVC/MHEPE composite render it a promising cable material.     

用锥形量热仪研究无卤阻燃HDPE体系的燃烧性

在35kW／m^2热辐照条件下,利用锥形量热仪研究了膨胀型阻燃剂／Mg(OH)2阻燃高密度聚乙烯(HDPE)体系的燃烧性。结果表明：膨胀型阻燃剂／Mg(OH)2能明显降低HDPE的热释放速率、总热释放量、最大生烟速率及总烟释放量。与膨胀型阻燃剂单独使用相比,Mg(OH)2与膨胀型阻燃剂复合使用的阻燃效果明显,总烟释放量减少了38％,总热释放量减少了10％,达到了低发炯、高效阻燃的目的。     

Influences of 4ZnO·B2O3·H2O whisker based intumescent flame retardant on the mechanical,flame retardant and smoke suppression properties of polypropylene composites

In this work, the influences of 4ZnO·B₂O₃·H₂O zinc borate (ZB) whisker based intumescent flame retardant (IFR) containing ammonium polyphosphate and dipentaerythritol on the mechanical, flame retardant and smoke suppression properties of polypropylene (PP) composites were characterized by the universal testing machine, UL-94, limiting oxygen index (LOI), and cone calorimeter tests, respectively. The results indicate that only 1 phr of ZB could effectively improve the LOI value and slow down the burning rate of PP composite. The peak heat release rate, average of HRR, total heat release, peak smoke production rate, and total smoke production values are all decreased from 413.8 kW/m², 166.3 kW/m², 82.3 MJ/m², 0.0995 m²/s, and 17.9 m² for PPc/20IFR composite to 267.8 kW/m², 128.3 kW/m², 66.8 MJ/m², 0.0478 m²/s, and 12.6 m² for PPc/20IFR/1ZB composite, respectively. The scanning electron microscopy images, energy dispersive spectrometry, and Raman spectra of char residue reveal that ZB is helpful to form a compact and graphitized intumescent char residue so that the heat diffusion and oxygen transmission are greatly hindered. The thermogravimetry analysis-fourier transform infrared spectroscopy (TGA-FTIR) results show that less combustible volatiles and more H₂O vapor are generated with the appearance of ZB. Hence, the combustion mechanism in gas phase is suppressed.     

Ni-MOF与焦磷酸哌嗪对环氧树脂的协同阻燃及抑烟

将含镍金属有机框架材料（Ni-MOF）与焦磷酸哌嗪（PPAP）复配后添加到环氧树脂（EP）中,通过极限氧指数（LOI）、垂直燃烧（UL 94）及锥形量热（CONE）测试研究了材料的阻燃性能及烟释放行为。结果表明,添加6%（质量分数,下同）的PPAP时,材料的LOI值为27.9%,垂直燃烧测试通过了UL 94 V-0级;当PPAP与Ni-MOF以质量比99∶1混合,总添加量为5%时,材料的LOI值达到29.3%并通过了UL 94 V-0级;极少量Ni-MOF的加入,有效提高了材料的阻燃效率。CONE测试表明,在相同阻燃剂添加量下,EP/PPAP/Ni-MOF材料的热释放速率、总热释放量、烟释放速率及总烟释放量,与EP/PPAP材料相比均得到了明显降低;Ni-MOF的引入,降低了材料的燃烧强度,减少了烟气的释放;Ni离子与PPAP受热分解形成的磷酸及多聚磷酸发生交联,将更多的磷留在了凝聚相中,促进了材料形成更加丰富、强度更高的炭层,有效抑制EP燃烧过程中热量和烟气的释放,从而提高了EP材料的火安全性能。     

Superior thermal stability and smoke suppression of epoxy resin composites with graphene/LDH phosphorus-rich hybrids

In this article, graphene/LDH phosphorus-rich triple hybrid was prepared by a mild method and used to effectively improve the thermal stability and smoke suppression of epoxy resin (EP). The graphene was firstly reacted with hexamethylenediamine (HA) and followed by the treatment with the layered double hydroxide (LDH) and NaH₂PO₄ solutions. Compared to the unmodified graphene, the initial decomposition temperature of the triple hybrids increases significantly from 168.6 to 292.5°C. The residual carbon content is greatly improved and the residual mass is up to 84.1%. Elemental analysis reveals the content of phosphorus in EP composites is as high as 10 wt%. In flame retardancy tests, the peak heat release rate of the EP composite with 5 wt% graphene/LDH phosphorus-rich hybrids decreases to 786.15 KW/m², 41.19% drastic reduction compared to that of EP. These results indicate that the triple functionalization process effectively expands the interval distribution of heat release and makes the heat release process more gradual and spread flames smaller. The smoke production rate and total smoke production rate of EP composite with 5 wt% graphene/LDH phosphorus-rich hybrids are 0.32 m²/s and 40.91 m², which are significantly reduced by 65.22 and 57.83%, respectively. This gentle and efficient process provides a new approach to multi-functional design to improve the thermal stability and smoke suppression of resin-based composites.     

壳聚糖/聚磷酸铵膨胀阻燃PP的阻燃及抑烟性能

为了提高聚丙烯(PP)的阻燃和抑烟性能,将壳聚糖(CS)作为膨胀型阻燃剂的碳源、聚磷酸铵(APP)作为膨胀型阻燃剂的酸源和气源,在此基础上通过熔融共混的方法制备了PP/CS/APP复合材料。采用极限氧指数仪、锥形量热仪等仪器研究了PP/CS/APP复合材料的的抑烟性及阻燃性。研究结果表明:CS/APP添加量为30%时,复合材料的极限氧指数值最大可达28.1%;且复合材料在烟气释放总量、CO和CO_2排放上明显降低,抑烟性得到了提升;热释放速率峰值、平均热释放速率值、平均有效燃烧热值、总热释放量值降低,成炭率升高,PP/CS/APP复合材料更难点燃;火灾性能指数明显提高,阻燃性能得到了大幅度提升,火灾蔓延指数显著减小,同时火灾危险性也相应降低。     

Synergistic flame retardant effects of activated carbon and molybdenum oxide in poly(vinyl chloride)

The synergistic effects of activated carbon (AC) and molybdenum oxide (MoO₃) in improving the flame retardancy of poly(vinyl chloride) (PVC) were investigated. The effects of AC, MoO₃ and their mixture with a mass ratio of 1:1 on the flame retardancy and smoke suppression properties of PVC were studied using the limiting oxygen index and cone calorimeter tests. It was found that the flame retardancy of the relatively cheaper AC was slightly weaker than that of MoO₃. In addition, the incorporation of AC and MoO₃ greatly reduced the total heat release and improved smoke suppressant property of PVC composites. When the total content of AC and MoO₃ was 10 phr, PVC/AC/MoO₃ had the lowest peak heat release rate and peak smoke production rate values of 173.80 kW m^?2 and 0.1472 m² s^?1, which represented reductions of 47.3 and 59.9%, respectively, compared with those of PVC. Furthermore, thermogravimetric analysis and gel content tests were used to analyze the flame retardant mechanism of AC and MoO₃, with results showing that AC could promote early crosslinking in PVC. Char residue left after heating at 500 °C was analyzed using scanning electron microscopy and Raman spectroscopy, and the results showed that MoO₃ produced the most compact char, with the smallest and most organized carbonaceous microstructures. © 2017 Society of Chemical Industry     

An efficient approach to improving fire retardancy and smoke suppression for intumescent flame‐retardant polypropylene composites via incorporating organo‐modified sepiolite

In this work, an efficient approach to improving the fire retardancy and smoke suppression for intumescent flame‐retardant polypropylene (PP) composites is developed via incorporating functionalized sepiolite (organo‐modified sepiolite [ONSep]). The PP composites with different amounts of intumescent flame retardants and ONSep were prepared by melt compounding. The morphology, thermal behavior, fire retardancy, smoke suppression, and mechanical property of flame‐retardant PP composites were studied. The results indicate an appropriate amount of ONSep in the flame‐retardant PP composites can increase thermal degradation temperature and char formation as well as a reduction of the peak heat release rate and total heat release; moreover, the addition of ONSep significantly decreases the CO production, total smoke production, smoke production rate, and smoke temperature. Simultaneously, the impact strength of intumescent flame‐retardant PP composite is also maintained by introducing an appropriate amount of ONSep as compared with that without ONSep.     

A high-efficiency DOPO-based reactive flame retardant with bi-hydroxyl for low-flammability epoxy resin

A high-efficiency DOPO-based reactive flame retardant (DPE) with bi-hydroxyl was successfully synthesized via reacting DOPO with imine obtained from the condensation of ethanolamine and 1,4-phthalaldehyde, and used as co-curing agent to improve the fire safety of epoxy resin (EP). Its chemical structure was characterized by Fourier transform infrared (FTIR) spectra, ¹H, ³¹P nuclear magnetic resonance (NMR) spectra and elemental analysis. The curing behavior, thermal properties, flame-retardant properties of EP/DPE systems were investigated. The results revealed that DPE slightly decreased the glass transition temperature (T_g), but accelerated the curing cross-linking reaction of EP. Furthermore, DPE decreased thermal degradation rate of epoxy matrix and promoted the formation of residual char at high temperature. After adding DPE, the flame retardant of epoxy thermosets was greatly improved. Especially, the thermoset modified with 5 wt% DPE achieved limiting oxygen index (LOI) value of 33.6% and V-0 rating in UL-94 test, demonstrating the highly efficient flame retardancy. While its peak heat release rate (PHRR), total heat release (THR) and total smoke production (TSP) were respectively decreased by 32.6%, 17.8%, and 13.9% compared with neat EP. Moreover, the research on flame retardant mechanism disclosed that DPE played dual flame-retardant effect in the gaseous and condensed phases.     

Flame retardancy and pyrolysis behavior of an epoxy resin composite flame-retarded by diphenylphosphinyl-POSS

To reduce the flammability of epoxy resin (EP), a flame retardant (designated as D-POSS) containing diphenylphosphinyl and polyhedral oligomeric silsesquioxane (POSS) was constructed by aminopropyl-isobutyl POSS and diphenylphosphinyl chloride. The chemical structure of D-POSS was fully characterized, then it was used to enhance the flame retardancy of EP. When the flame-retardant EP composite contained 4 wt% D-POSS, its limiting oxygen index value was 29.0% and it achieved UL 94 V-1 rating. Also, its peak of heat release rate (pk-HRR), total heat release (THR) and total smoke production were decreased by 35.3%, 30.3%, and 38.3%, respectively. Moreover, the results from cone calorimeter disclosed that diphenylphosphinyl group and POSS group in D-POSS showed a strong synergistic effect in inhibiting pk-HRR, THR, and smoke production, promoting the charring formation of EP material, and forming an intumescent char layer. Additionally, the theoretical THR reduction of flame-retardant EP composite was calculated by the equation deduced from the standard, and it was almost same with the practical THR reduction. Notably, some silicon oxide enriched on the residue's surface. The phenomenon led to form a double-layer residue that consisted of white yarn-like outer char and normal intumescent inner char. This double-layer residue was contributed to enhance EP composite's flame retardancy.