Novel flame‐retardant epoxy based on zinc methylethyl phosphinate

A novel flame retardant zinc methylethylphosphinate (Zn(MEP)) was used to fill epoxy resins (EPs). The structure of Zn(MEP) was conformed with Fourier transform infrared, hydrogen nuclear magnetic resonance and phosphorus nuclear magnetic resonance, and X‐ray fluorescent and X‐ray diffraction. The flammability, decomposition behavior, and glass transition temperature (T_g) of cured EP/Zn(MEP) were investigated. Zn(MEP) is stable below 406°C. EP containing 20 phr of Zn(MEP) achieves 27.5% of limiting oxygen index and UL‐94 V0 rating. Scanning electron microscopy‐energy‐dispersive X‐ray and Fourier transform infrared spectroscopy investigations show that a condensed char layer with carbon‐rich and phosphorus‐rich components was formed during heating Zn(MEP)/EP, the atomic ratio of P to Zn on the surface of the char is reduced compared with the initial sample. The P‐rich components and lower atomic ratio of P/Zn on the char surface implies that the Zn(MEP) acts in both condensed phase and gas phase. TGA investigation shows that there are interactions between Zn(MEP) and EP when they are copyrolyzed. The interactions lead to a modification in degradation process and promote the char forming. Compared with aluminum diethylphosphinate Zn(MEP) filled EP shows lower limiting oxygen index but higher T_g. In addition, the interactions between polymer and additive are different when aluminum diethylphosphinate instead of Zn(MEP) is added into EP. Copyright © 2013 John Wiley & Sons, Ltd.     

Highly dispersed melamine cyanurate flame‐retardant epoxy resin composites

Ultrafine dispersion of flame retardants in polymer matrices favors improving the performance of flame‐retardant polymers, but is still a challenge on most occasions. In the present research, an efficient method was employed to realize satisfactory dispersion of a nitrogen flame retardant, melamine cyanurate (MCA), in epoxy resin (EP) composites, and meanwhile integrated the synthesis of MCA with the preparation of the flame‐retardant composites. In the conventional technology, EP pre‐polymer glue with added MCA powder (synthesized in water, then dried and pulverized) is used to coat glass fabrics, which are compressed into laminated boards. Here, MCA was synthesized in a good solvent for EP, and then EP pre‐polymer was directly dissolved in the MCA suspension to obtain the in situ synthesized flame‐retardant glue. In this way, MCA could keep perfect dispersion whether in the glue or cured resin. Compared with the conventional addition system easily resulting in the aggregation of MCA particles, the in situ synthesized MCA flame‐retardant system exhibited much better stability of the coating glue, and markedly improved flame retardancy and mechanical properties. © 2016 Society of Chemical Industry     

Synergistic effect of mesoporous silica SBA‐15 on intumescent flame‐retardant polypropylene

Mesoporous silica SBA‐15 synthesized from Pluronic P123 and tetraethoxysilane was used as a synergistic agent on the flame retardancy of polypropylene (PP)/intumescent flame‐retardant (IFR) system. Limiting oxygen index (LOI), UL‐94 rating and thermogravimetric analysis were used to evaluate the synergistic effect of SBA‐15 on PP/IFR system. It showed that PP/IFR system could reach V‐0 with loading of SBA‐15 ranging from 0.5 to 3 wt%, while without SBA‐15 it had no rating at UL‐94 test. The LOI value increased from 25.5 to 32.2 when the loading of SBA‐15 was 1 wt%. The thermal stability of PP/IFR was improved in the presence of SBA‐15 and the amount of the char residue at 600° C was increased from 8.96 to 16.42 wt% when loading of SBA‐15 varied from 0.5 to 5 wt%. Laser Raman spectroscopy (LRS) and scanning electron microscopy were employed to study the morphology of the char residue of PP/IFR system with and without SBA‐15. Copyright © 2010 John Wiley & Sons, Ltd.     

Synergistic flame‐retardant effect of halloysite nanotubes on intumescent flame retardant in LDPE

Synergistic flame‐retardant effect of halloysite nanotubes (HNTs) on an intumescent flame retardant (IFR) in low‐density polyethylene (LDPE) was investigated by limited oxygen index (LOI), vertical burning test (UL‐94), thermogravimetric analysis (TGA), cone calorimeter (CC) test, and scanning electronic microscopy (SEM). The results of LOI and UL‐94 tests indicated that the addition of HNTs could dramatically increase the LOI value of LDPE/IFR in the case that the mass ratio of HNTs to IFR was 2/28 at 30 wt % of total flame retardant. Moreover, in this case the prepared samples could pass the V‐0 rating in UL‐94 tests. CC tests results showed that, for LDPE/IFR, both the heat release rate and the total heat release significantly decreased because of the incorporation of 2 wt % of HNTs. SEM observations directly approved that HNTs could promote the formation of more continuous and compact intumescent char layer in LDPE/IFR. TGA results demonstrated that the residue of LDPE/IFR containing 2 wt % of HNTs was obviously more than that of LDPE/IFR at the same total flame retardant of 30 wt % at 700°C under an air atmosphere, and its maximum decomposing rate was also lower than that of LDPE/IFR, suggesting that HNTs facilitated the charring of LDPE/IFR and its thermal stability at high temperature in this case. Both TGA and SEM results interpreted the mechanism on the synergistic effect of HNTs on IFR in LDPE, which is that the migration of HNTs to the surface during the combustion process led to the formation of a more compact barrier, resulting in the promotion of flame retardancy of LDPE/IFR. In addition, the mechanical properties of LDPE/IFR/HNTs systems were studied, the results showed that the addition of 0.5–2 wt % of HNTs could increase the tensile strength and the elongation at break of LDPE/IFR simultaneously. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40065.     

Synergistic effects of fumed silica on intumescent flame‐retardant polypropylene

The synergistic effects of fumed silica on the thermal and flame‐retardant properties of intumescent flame retardant (IFR) polypropylene based on the NP phosphorus‐nitrogen compound have been studied by Fourier transfer infrared (FTIR) spectroscopy, cone calorimeter test (CCT), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), limiting oxygen index (LOI), and UL‐94 tests. The LOI and UL‐94 data show that when ≤1 wt % fumed silica substituted for the IFR additive NP can increase 2 to 4% LOI values of the PP blends and keep the V‐0 rating. The data obtained from the CCT tests indicate the heat release rates (HRR) reduce by about 23% for the PP/NP sample with 0.5 wt % fumed silica, whereas the mass loss rates (MLR) and total heat release (THR) values are much lower than those of the PP/NP samples without fume silica. The TGA data demonstrate that a suitable amount of fumed silica can increase the thermal stability and charred residue of the PP/IFR/SiO₂ blends after 500°C. The morphological structures of charred residues observed by SEM give positive evidence that a suitable amount of fumed silica can promote the formation of compact intumescent charred layers and prevent the charred layers from cracking, which effectively protects the underlying polymer from burning. The dynamic FTIR spectra reveal that the synergistic flame‐retardant mechanism of a suitable amount of fumed silica with IFR additive is due to its physical process in the condensed phases. However, a high loading of fumed silica restricts the formation of charred layers with P? O? P and P? O? C complexes formed from burning of polymer materials and destroys the swelling behavior of intumescent charred layers, which deteriorates the flame retardant and thermal properties of the PP/IFR blends. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

A novel intumescent flame‐retardant epoxy resins system

Pentaerythritol diphosphonate melamine–dicyandiamide–formaldehyde resin salt, a novel macromolecular intumescent flame retardants (IFR), was synthesized, and its structure was a caged bicyclic macromolecule containing phosphorus characterized by IR, NMR and element analysis. The flame retardancy and thermal behavior of a new IFR system for epoxy resin were investigated by LOI, UL‐94 test, TG, and IR. Activation energy for the decomposition of samples was obtained using Kissinger equation. 25% of weight of IFR were doped into epoxy resin to get 27.5 of LOI and UL 94 V‐0. The TG curves and IR spectra show that IFR decreases the initial decomposition temperature and the maximum weight loss rate of epoxy resin, and enhances the thermal stability of epoxy resin at high temperatures and char yield. The activation energy for epoxy resin containing IFR was decreased by 44.8 kJ/mol, which shows that IFR can catalyze decomposition of epoxy resin. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synergistic action of expandable graphite on fire safety of a self-intumescent flame retardant epoxy resin

Previously, it was reported that epoxy resin (EP) filled with ammonium polyphosphate (APP) and copper (I) oxide (Cu₂O) at a mass ratio of 8/2 (APP8-Cu₂O2) as a self-intumescent system demonstrated promising fire retardancy. To further improve the flame retardant efficiency, the possibility of expandable graphite (EG) as an effective synergist for the self-intumescent EP system was revealed by limiting oxygen index (LOI) test. The results showed that the incorporation of EG increased the LOI value of EP/APP8-Cu₂O2 obviously. The highest LOI value was obtained at the EG/APP8-Cu₂O2 mass ratio of 3/7, indicating the optimal synergistic effect being achieved. Furthermore, UL-94 test results showed that the excellent synergistic effect resulted in the addition of 13 wt% EG/APP8-Cu₂O2 of 3/7 not only endowed EP a relatively high LOI value of 34.3%, but also made it pass UL-94 V-0 rating. Moreover, the main fire hazard parameters obtained from cone calorimeter tests, such as peak heat release rate, total smoke production, and peak CO production were reduced 40.3%, 30.3%, and 46.2%, respectively by the combination effect of EG/APP8-Cu₂O2 with mass ratio of 3/7, suggesting the excellent improvement in the fire safety of EP significantly. Finally, a possible action mode, which would be beneficial for developing other flame retardant polymers with high fire safety, was proposed.     

Synthesis of a novel DOPO‐based polyphosphoramide with high char yield and its application in flame‐retardant epoxy resins

A novel and highly effective flame retardant (FR), DOPO‐TPMP oligomer, was synthesized by a simple condensation of 4‐(hydroxymethyl)‐2,6,7‐trioxa‐1‐phosphabicyclo[2.2.2]octane‐1‐oxide and phosphorus oxychloride followed by a polycondensation reaction with 6‐(2,5‐dihydroxyphenyl)‐6H‐dibenzo[c,e][1,2]oxaphosphinine‐6‐oxide. The chemical structure of DOPO‐TPMP was well characterized using Fourier transform infrared and NMR spectra. DOPO‐TPMP was used as an additive‐type FR for epoxy resin (EP). The FR properties of the resultant EP composites were investigated by limiting oxygen index (LOI) test, UL‐94 vertical burning test and cone calorimeter measurements. Specifically, the EP composite containing 10.0% DOPO‐TPMP achieved a LOI value of 36.1%, V‐0 rating in the UL‐94 test and a 58% reduction in peak heat release rate. Further mechanism analysis attributed the enhanced flame retardancy to the increased char yield on the addition of DOPO‐TPMP. © 2019 Society of Chemical Industry     

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.     

环氧树脂体系阻燃技术的发展

阐述了改善热固性环氧树脂体系阻燃性能的目的和意义，介绍了环氧树脂体系的阻燃方法。以气相机理和凝聚相机理为基础，讨论了几种常用阻燃剂的阻燃机理。分析了环氧树脂体系阻燃技术的研究现状，指出环氧树脂阻燃技术将向着安全化、复合功能化、新技术化和研究系统化的趋势发展。     

Synergistic effect of expandable graphite and melamine phosphate on flame‐retardant polystyrene

The halogen‐free flame‐retardant polystyrene (PS) composites containing expandable graphite (EG) and melamine phosphate (MP) were prepared successfully, and the thermal degradation behavior and fire performance were investigated by various measurements. The experimental results show that EG and MP have a synergistic effect on flame‐retardant PS, which can catalyze the char formation from PS. PS/MP/EG_(1:2) composite achieves limited oxygen index value of 28.0% and UL‐94V‐0 (1.6 mm) rate. The mass retention at high temperature (800 °C) under air atmosphere of PS composites have a large increase by the introduction of EG and MP. Microscale combustion calorimeter (MCC) and cone calorimetric analysis indicate that the heat release rate and total heat release of PS/MP/EG_(1:2) composite are reduced significantly, because the formed thick char layer has a notable barrier property. The study on the char residue of PS/MP/EG_(1:2) composite by X‐ray photoelectron spectroscopy (XPS) analysis confirms the formation of the stable structures containing P? O? C. Furthermore, the mechanical properties of PS composites were also investigated; compared with neat PS, the addition of flame retardants leads to the decrease of tensile strength and flexural strength, but the impact strength of PS/MP/EG_(1:2) has increased by 44.2%. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45474.     

Synergistic effect of ammonium polyphosphate and expandable graphite on flame‐retardant properties of acrylonitrile‐butadiene‐styrene

A new intumescent flame‐retardant (IFR) system consisting of expandable graphite (EG) and ammonium polyphosphate (APP) was applied in acrylonitrile–butadiene–styrene (ABS) resin. A synergistic effect between EG and APP on the flame retardancy of ABS was observed. Fixing the total loading of flame retardant at 15 wt %, the limited oxygen index (LOI) could reach 31 vol % at a weight ratio of 3 : 1 for EG and APP. While LOI values of EG‐ and APP‐filled ABS were only 26.0 and 21.5 vol % at the same loading, respectively. The UL‐94 vertical burning test suggested that samples with different ratios of EG and APP could all pass V‐0 rating while the samples containing EG and APP alone only passed V‐1 rating. Thermogravimetric analysis indicated that the addition of EG and APP (3 : 1 by weight) to ABS led to an increase in the amount of high‐temperature residue by 11.8 wt %, and a decrease of mass loss rate by 0.7%/°C compared with pure ABS. Scanning electronic microscopy revealed a homogeneous compact intumescent char layer of ABS/EG/APP samples. Based on our experiment and combined with others' previous studies, the synergistic mechanism is inferred. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Phosphaphenanthrene‐containing borate ester as a latent hardener and flame retardant for epoxy resin

Borate ester containing the phosphaphenanthrene group with N → B coordination structure (PBN) was synthesized by transesterification of tributyl borate, 2‐(6‐oxido‐6H‐dibenz?c,e??1,2?oxaphos‐phorin‐6‐yl) methanol and N,N‐dimethylethanolamine. A thermally latent curing utility for diglycidyl ether of bisphenol A epoxy resin (E51) was confirmed by differential scanning calorimetry. Additionally, its flame‐retarding function in the cured epoxy was demonstrated in terms of the limiting oxygen index (LOI) and vertical burning test. The cured epoxy with 100:20 mass ratio of E51 to PBN passed UL94 V‐0 rating with 34.3% of LOI. The flame retardation mode and thermal and mechanical properties of the cured epoxy were carefully evaluated. The results of this work suggest that application of PBN would permit the formulation of environmentally friendly one‐pot flame‐retardant epoxy resin. © 2015 Society of Chemical Industry     

Fire retardant synergism of hydroquinone bis(diphenyl phosphate) and novolac phenol in acrylonitrile–butadiene–styrene copolymer

Hydroquinone bis(diphenyl phosphate) (HDP) has been adopted to prepare acrylonitrile–butadiene–styrene copolymer (ABS)/HDP/novolac phenol (NP) composites. The limiting oxygen index (LOI) of ABS/HDP/NP composites is tested in this paper. The LOI value first grows with increasing ratio of HDP to NP, after reaching its maximum it decrease with further increasing ratio. The synergistic effect of HDP and NP exerted on the microstructure and the flame retardancy of ABS/HDP/NP composites are carefully analyzed by thermogravimetric analysis (TGA), cone calorimeter (CCT), scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). The results of CCT show that the synergistic action of HDP and NP reduces its heat release rate and smoke production rate. The results of TGA and SEM demonstrated that the introduction of NP and HDP is conducive to the improvement of the thermal stability and the formation of the intumescent char with homogeneous cavities and holes. The EDS results indicate that the introduction of NP could help retain phosphorus in the chars. As a result, the synergistic action of HDP and NP is favorable to the enhancement of flame retardancy of ABS/HDP/NP composites. Copyright © 2014 John Wiley & Sons, Ltd.     

Synergistic flame retardant effect of cerium oxide in ethylene‐vinyl acetate/aluminum hydroxide blends

The flammability characterization and synergistic flame retardant effect of cerium oxide (CeO₂) in the ethylene‐vinyl acetate/aluminum hydroxide blends were studied using limiting oxygen index (LOI), UL‐94 test, and cone calorimeter test (CCT). The results showed that the addition of a given amount of CeO₂ apparently increased the LOI value and UL‐94 rating. The data obtained from the CCT indicated that the addition of CeO₂ greatly decreased the heat release rate and prolonged the combustion time. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Thermal behaviors of flame‐retardant polycarbonates containing diphenyl sulfonate and poly(sulfonyl phenylene phosphonate)

Potassium diphenyl sulfonate (SSK), poly(sulfonyl phenylene phosphonate) (PSPPP), and their mixtures are proved to be effective flame‐retardants for polycarbonates (PCs) by measuring the limited oxygen index values and UL‐94 of blends. The flame‐retardant systems are characterized by thermogravimetric analysis under dynamic conditions. The resulting data, together with the analysis of the activation energies, demonstrates that the additives accelerate thermodegradation, especially in the early stage, and different additives cause a different process in the final stage. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 882–889, 2003     

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.     

硼酸锌在膨胀型无卤阻燃ABS中的协同作用

采用熔融共混法制备了丙烯腈-丁二烯-苯乙烯共聚物(ABS)/膨胀型阻燃剂(IFR)/硼酸锌(ZB)无卤阻燃复合材料。利用热重分析仪、氧指数测定仪、扫描电子显微镜等研究了ZB对复合材料热失重行为、阻燃性能、微观结构及力学、加工性能的影响。较低含量的ZB与IFR存在较好的阻燃协同作用,且ZB可促进IFR成炭,使ABS/IFR复合材料的氧指数及其残炭量分别由未加ZB时的27.4%、21.29%提高到30.1%和23.05%。ZB的加入能够提高ABS/IFR复合材料的弯曲性能和加工性能,但对复合材料的冲击、拉伸性能产生了不利影响。     

Halogen‐free flame retardant epoxy resins from hybrids of phosphorus‐ or silicon‐containing epoxies with an amine resin

Epoxy–melamine hybrid resins were obtained from in situ polymerization of siliconized (SE500) and phosphorylated (PE690) epoxy resins with hexakis(methoxymethyl)melamine (HMMM). The hybrid resins having HMMM contents less than 15 wt % exhibited high transparency and homogeneity. The compatibilities between SE500 and melamine as well as that between PE690 and melamine were poor than the compatibility between general bisphenol‐A epoxy and melamine. Incorporation of HMMM altered the degradation mechanisms and enhanced the thermal stability of the epoxy resins, especially for PE690 based resins. Excellent flame retardant property was observed with the hybrid resins because of the Si? N and P? N synergisms of flame retardation. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1071–1077, 2006     

环氧树脂纳米阻燃材料研究进展

综述了目前环氧树脂纳米阻燃材料的制备方法,介绍了环氧树脂/层状硅酸盐纳米阻燃材料和环氧树脂/SiO2纳米阻燃材料的优异性能并展望了环氧树脂阻燃材料的应用前景。