Synergistic effects of aluminum hypophosphite on intumescent flame retardant polypropylene system

The effects of aluminum hypophosphite(AHP) as a synergistic agent on the flame retardancy and thermal degradation behavior of intumescent flame retardant polypropylene composites(PP/IFR) containing ammonium polyphosphate(APP) and triazine charring-foaming agent(CFA) were investigated by limiting oxygen index(LOI), UL-94 measurement, thermogravimetric analysis(TGA), cone calorimeter test(CONE), scanning electron microscopy(SEM) and X-ray photoelectron spectroscopy(XPS). It was found that the combination of IFR with AHP exhibited an evident synergistic effect and enhanced the flame retardant efficiency for PP matrix. The specimens with the thickness of 0.8 mm can pass UL-94 V-0 rating and the LOI value reaches 33.5% based on the total loading of flame retardant of 24 wt%, and the optimum mass fraction of AHP/IFR is 1:6. The TGA data revealed that AHP could change the degradation behavior of IFR and PP/IFR system, enhance the thermal stability of the IFR and PP/IFR systems at high temperatures and promote the char residue formation. The CONE results revealed that IFR/AHP blends can efficiently reduce the combustion parameters of PP, such as heat release rate(HRR), total heat release(THR), smoke production rate(SPR) and so on. The morphological structures of char residue demonstrated that AHP is of benefit to the formation of a more compact and homogeneous char layer on the materials surface during burning. The analysis of XPS indicates that AHP may promote the formation of sufficient char on the materials surface and improve the flame retardant properties.     

A novel intumescent flame retardant imparts high flame retardancy to epoxy resin

Intumescent flame retardant (IFR) has received the considerable attention ascribed to the inherent advantages including non‐halogen, low toxicity, low smoke release and environmentally friendly. In this work, a novel charring agent poly (piperazine phenylaminophosphamide) named as PPTA was successfully synthesized and characterized by Fourier transform infrared spectra (FTIR) and X‐ray photoelectron spectroscopy (XPS). Then, a series of flame‐retardant EP samples were prepared by blending with ammonium polyphosphate (APP) and PPTA. Combustion tests include oxygen Index (LOI), vertical Burning Test (UL‐94) and cone calorimeter testing,these test results showed that PPTA greatly enhances the flame retardancy of EP/APP. According to detailed results, EP containing 10 wt% APP had a LOI value of 30.2%,but had no enhancement on UL‐94 rating. However, after both 7.5 wt% APP and 2.5 wt% PPTA were added, EP‐7 passed UL‐94 V‐0 rating with a LOI value of 33.0%. Moreover, the peak heat release rate (PHRR) and peak of smoke product rate (PSPR) of EP‐7 were greatly decreased. Meanwhile, the flame‐retardant mechanism of EP‐7 was investigated by scanning electron microscopy (SEM), thermogravimetric analysis/infrared spectrometry (TG‐IR) and X‐ray photoelectron spectroscopy (XPS). The corresponding results presented PPTA significantly increased the density of char layer, resulting in the good flame retardancy.     

Preparation and properties of an efficient smoke suppressant and flame‐retardant agent for thermoplastic polyurethane

APP@ETA, as a new type of flame retardant, was prepared by chemically modifying ammonium polyphosphate (APP) with ethanolamine (ETA) and applied to thermoplastic polyurethane (TPU) in this study. Then, the smoke suppression properties and flame‐retardant effects of APP@ETA in TPU composites were evaluated using smoke density test, cone calorimeter test, etc. And, the thermal degradation properties of flame‐retardant TPU composites were investigated by thermogravimetric analysis/infrared spectrometry. The smoke density test results indicated that APP@ETA could obviously improve the luminous flux of TPU composites in the test with or without flame. The cone calorimeter test results showed that total smoke release, smoke production rate and smoke factor of the composites with APP@ETA were significantly decreased than those of the composites with APP. For example, when the loading of APP@ETA or APP was 12.5 wt%, the total smoke release of the sample with APP@ETA decreased to 3.5 m²/m² from 6.0 m²/m², which was much lower than that of the sample with APP, reduced by 41.7%. The thermogravimetric analysis results demonstrated that APP@ETA could decrease the initial decomposition temperature and improve the thermal stability at high temperature for TPU composites. Copyright © 2017 John Wiley & Sons, Ltd.     

Aluminum hypophosphite in combination with expandable graphite as a novel flame retardant system for rigid polyurethane foams

The main aim of this work was to investigate the synergistic effect of expandable graphite (EG) and aluminum hypophosphite (AHP) on the flame retardancy of rigid polyurethane foams (RPUFs). A series of flame retardant RPUF containing EG and AHP were prepared by one‐shot and free‐rise method. The flame retardant, thermal degradation, and combustion properties of RPUF hybrids were characterized through limiting oxygen index (LOI) test, vertical burning (UL‐94) test, thermogravimetric analysis and microscale combustion calorimeter. The LOI and UL‐94 results showed that the RPUF sample with 10 wt% EG and 5 wt% AHP passed UL‐94 V‐0 rating and reached a relatively high LOI value of 28.5%, which is superior over other EG/AHP ratios in RPUF at the equivalent filler loading. Microscale combustion calorimeter results revealed that the incorporation of EG and AHP into RPUF reduced the peak heat release rate and total heat release, thus decrease the fire risk of RPUF significantly. Incorporation of EG and AHP improved the thermal stability of RPUF as observed from the thermogravimetric analysis results and also enhanced the thermal resistance of char layer at high temperature from scanning electron microscopy and Raman spectroscopy. Moreover, it could be seen from thermogravimetric analysis/infrared spectrometry spectra that the addition of EG and AHP significantly decreased the combustible gaseous products such as hydrocarbons and ethers. Finally, the synergistic mechanism in flame retardancy was discussed and speculated. Copyright © 2014 John Wiley & Sons, Ltd.     

Novel nanocomposites based on epoxy resin and modified magnesium hydroxide: Focus on flame retardancy and mechanical properties

In this work, a novel multifunctional organic‐inorganic hybrid flame agent (AM‐MEL) was prepared from magnesium hydroxide nanosheets decorated by nitrilotrimethylene triphosphonic acid and melamine. Then, an intrinsic flame‐retardant epoxy resin (EP) was prepared by covalently incorporating AM‐MEL nanoparticles. Meanwhile, ammonium polyphosphate (APP) was added into EP to form an intumescent flame retardant system with AM‐MEL. The chemical structure of AM‐MEL was characterized by Fourier transform infrared spectra, X‐ray photoelectron spectroscopy, and scanning electron microscopy. With the incorporation of 5 wt% AM‐MEL and 15 wt% APP, EP/AM‐MEL/APP could reach a limiting oxygen index value of 32.0% and achieve UL‐94 V‐0 rating, along with 88.0%, 70.0%, 81.5%, and 87.3% decrease in the peak heat release rate, total heat release, total smoke production, and the peak CO production rate, respectively, with respect to that of pure EP. The mechanisms of its flame retardant and smoke suppression were investigated.     

磷化淀粉的合成及其与聚磷酸铵协效阻燃聚乳酸的性能研究

利用9,10-二氢-9-氧杂-10-磷杂菲-10-氧化物(DOPO)和马来酸酐(MA)对淀粉进行改性得到磷化淀粉(DOPOMASt),通过红外光谱(FTIR)、核磁共振谱(1H-NMR)和X射线光电子能谱(XPS)确定其结构.利用DOPOMASt作为碳源,与聚磷酸铵(APP)复配后通过熔融共混制备了阻燃聚乳酸(PLA)...     

Preparation of Poly(phosphoric acid piperazine) and Its Application as an Effective Flame Retardant for Epoxy Resin

A phosphorus-nitrogen containing flame retardant additive of poly(phosphoric acid piperazine),defined as PPAP,was synthesized by the salt-forming reaction between anhydrous piperazine and phosphoric acid,and the dehydration polymerization under heating in nitrogen atmosphere.Its chemical structure was well characterized by Fourier transform infrared (FTIR) spectroscopy,13C and 31p solid-state nuclear magnetic resonance measurements.The synthesized PPAP and curing agent m-phenylenediamine were blended into epoxy resin (EP) to prepare flame retardant EP thermosets.The effects of PPAP on the fire retardancy and thermal degradation behavior of cured EP/PPAP composites were investigated by limiting oxygen index (LOI),vertical burning (UL-94),thermogravimetric analysis/infrared spectrometry (TG-IR) and cone calorimeter tests.The morphologies and chemical compositions of char residues for cured epoxy resin were investigated by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS),respectively.The results demonstrated that the flame retardant EP thermosets successfully passed UL-94 V-0 flammability rating and the LOI value was as high as 30.8％ when incorporating 5wt％ PPAP into the EP thermosets.The TGA results indicated that the synthesized PPAP flame retardant additive possessed high thermal stability and excellent charring capability.Meanwhile,the incorporation of PPAP stimulated the epoxy resin matrix to decompose and charring ahead of time due to its catalytic decomposition effect,which led to a higher char yield at high temperature.The morphological structures and the analysis results of XPS for char residues of EP thermosets revealed that the introduction of PPAP benefited the formation of a sufficient,more compact and homogeneous char layer containing phosphorus-nitrogen flame retardant elements on the material surface during combustion.The formed char layer with high quality effectively prevented the heat transmission and diffusion,limited the production of combustible gases,and inhibited the emission of smoke,leading to the reduction of heat and smoke release.     

“One‐pot” synthesis of crosslinked silicone‐containing macromolecular charring agent and its synergistic flame retardant poly(l‐lactic acid) with ammonium polyphosphate

A crosslinked silicone‐containing macromolecular charring agent (CSi‐MCA) was synthesized via “one‐pot” process, and it was combined with ammonium polyphosphate (APP) to synergistically improve the flame retardancy of poly(l ‐lactic acid) (PLA). The chemical structure of synthesized CSi‐MCA was characterized by Fourier transform infrared spectroscopy and solid‐state ¹³C nuclear magnetic resonance. The thermal gravimetric analyzer indicated that the CSi‐MCA displayed good thermal stability and high residue via the catalytic crosslinking. Furthermore, the flame retardant effect of CSi‐MCA and APP as intumescent flame retardants in PLA system was investigated by limited oxygen index, UL94, and cone calorimeter test. When the content of CSi‐MCA was 5 wt% and APP was 10 wt% (CSi‐MCA/APP = 1/2), the limited oxygen index value of composites was 33.6 and UL94 classed a V‐0 rating. The peak heat release rate and total heat release of PLA composites containing both APP and CSi‐MCA decreased significantly in comparison with those with APP or CSi‐MCA alone. The flame retardancy mechanism was investigated via analyzing residual chars by scanning electron microscopy and X‐ray photoelectron spectroscopy as well as the possible chemical reaction between APP and CSi‐MCA by thermal gravimetric analyzer and Fourier transform infrared spectroscopy. The results showed that the enhanced flame retardancy was attributed mainly to synergistic effect of CSi‐MCA and APP, which could form a compact, continuous, and protective layer during combustion. Copyright © 2017 John Wiley & Sons, Ltd.     

Improvement of thermoplastic polyurethane's flame retardancy and thermal conductivity by leaf‐shaped cobalt‐zeolitic imidazolate framework–modified graphene and intumescent flame retardant

In this work, a new type of leaf‐shaped cobalt‐zeolitic imidazolate framework–modified graphene (Co‐ZIF‐L@RGO) hybrid was successfully prepared and blended with an intumescent flame retardant (IFR). It was added into thermoplastic polyurethane (TPU) to study the effect of its combination with IFR on the thermal conductivity and flame retardant performance of TPU. The morphology and structure of the Co‐ZIF‐L@RGO hybrid were characterized by scanning electron microscope (SEM), Fourier transform infrared and X‐ray diffraction (XRD). The results showed that Co‐ZIF‐L were uniformly loaded on the surface of graphene. Furthermore, compared with pure TPU, the limiting oxygen index values of the composite material with 3 wt% Co‐ZIF‐L and 27 wt% IFR increased to 32.6%. Their UL‐94 rating reached V‐0 rating. Their peak heat release rate, total heat release, peak smoke production rate and total smoke production were also greatly reduced by 84.4%, 70.1%, 60.3% and 62.5%, respectively. The thermogravimetric‐infrared test results showed that the amount of toxic gas emissions was effectively suppressed. The residual carbon was analyzed by SEM, laser Raman spectroscopy and XRD, and flame retardant mechanism was further investigated. Besides, the addition of this hybrid improved the thermal conductivity of TPU.     

聚苯氧基磷酸联苯二酚酯/聚磷酸铵膨胀阻燃剂对环氧树脂阻燃性能影响研究

以聚苯氧基磷酸联苯二酚酯(PBPP)与聚磷酸铵(APP)组成复合阻燃剂,对环氧树脂(EP)进行阻燃改性.通过氧指数(LOI)、垂直燃烧(UL-94)、热失重(TGA)、锥形量热(CONE)和扫描电镜(SEM)等方法研究改性环氧树脂的阻燃性能和阻燃机理.结果表明,PBPP/APP体系对EP具有较好的阻燃性能,阻燃剂添加量为10%时能使环氧树脂的氧指数提高到29.6%,垂直燃烧等级达到UL94 V-0级,残炭量大大增加;平均热释放速率下降45.7%,热释放速率峰值下降51.0%,有效燃烧热平均值下降21.1%;TGA、CONE、SEM等综合分析显示了PBPP/APP改性后的环氧树脂比纯环氧树脂具有更高的热稳定性,燃烧后能够形成连续、致密、封闭、坚硬的焦化炭层,在聚合物表面产生有效覆盖、隔绝了氧气,改善了环氧树脂的燃烧性能.     

Simultaneous improvement in the flame retardancy and water resistance of PP/APP through coating UV-curable pentaerythritol triacrylate onto APP

To improve the flame-retardant efficiency and water resistance of ammonium polyphosphate(APP), the UV-curable pentaerythritol triacrylate(PETA) was used to microencapsulate APP via the UV curing polymerization method. The prepared PETA-microencapsulated APP(PETA-APP) was characterized by Fourier transform infrared spectroscopy(FTIR), scanning electron microscopy(SEM), and thermogravimetric(TG) analysis. PETA-APP was used as intumescent flame retardant(IFR) alone to flame retard polypropylene(PP). The water resistance of PP/PETA-APP composites was investigated, and the effect of PETA on the combustion behaviors of PP/APP composites was studied through limiting oxygen index(LOI), vertical burning test(UL-94) and cone calorimeter(CC) test, respectively. With 40 wt% of PETA-APP, the PP/PETA-APP system could achieve a LOI value of 30.0% and UL-94 V-0 rating after treatment in hot water for 168 h, while the LOI value of the system containing 40 wt% uncoated APP was only 19.2%, and it failed to pass the UL-94 rating. CC test results showed that the heat release rate(HRR), mass loss rate(MLR) and smoke production rate(SPR) of PP/PETAAPP system decreased significantly compared with PP/APP system, especially the peak of HRR was decreased by 51.4%. The mechanism for the improvement of flame reatardancy for PP/PETA-APP composites was discussed based on FTIR and X-ray photoelectron spectroscopy(XPS) tests. All these results illustrated that simultaneous improvement of flame retardancy and water resistance for PP/APP was achieved through coating UV-curable PETA onto APP.     

Flame retardant properties and mechanism of an efficient intumescent flame retardant PLA composites

The charring agent (CNCA‐DA) containing triazine and benzene rings was combined with ammonium polyphosphate (APP) to form intumescent flame retardant (IFR), and it was occupied to modify polylactide (PLA). The flame retardant properties and mechanism of flame retardant PLA composites were investigated by the limited oxygen index (LOI), vertical burning test (UL‐94), thermogravimetric analysis, microscale combustion calorimetry, scanning electron microscopy, laser Raman spectroscopy analysis and X‐ray photoelectron spectroscopy. The analysis from LOI and UL‐94 presented that the IFR was very effective in flame retardancy of PLA. When the weight ratio of APP to CNCA‐DA was 3:1, and the IFR loading was 30%, the IFR showed the best effect, and the LOI value reached 45.6%. It was found that when 20 wt% IFR was loaded, the flame retardancy of PLA/IFR still passed UL‐94 V‐0 rating, and its LOI value reached 32.8%. The microscale combustion calorimetry results showed that PLA/IFR had lower heat release rate, total heat release, and heat release capacity than other composites, and there was an obvious synergistic effect between APP and CNCA‐DA for PLA. IFR containing APP/CNCA‐DA had good thermal stability and char‐forming ability with the char residue 29.3% at 800°C under N₂ atmosphere. Scanning electron microscopy observation further indicated that IFR could promote forming continuous and compact intumescent char layer. The laser Raman spectroscopy analysis and X‐ray photoelectron spectroscopy analysis results indicated that an appropriate graphitization degree of the residue char was formed, and more O and N were remained to form more cross‐linking structure. Copyright © 2016 John Wiley & Sons, Ltd.     

Synergistic effects between hollow glass microsphere and ammonium polyphosphate on flame-retardant thermoplastic polyurethane

It is mainly studied that the smoke-suppression properties and synergistic flame-retardant effect of hollow glass microsphere (HM) in flame retardant thermoplastic polyurethane (TPU) composites based on ammonium polyphosphate (APP) as a flame-retardant. Also, the smoke suppression properties and flame-retardant effect were investigated by smoke density test (SDT), cone calorimeter test (CCT), limiting oxygen index, and thermogravimetric analysis, separately. The char residues left after CCT were examined by scanning electron microscopy. The data of SDT shows that HM could effectively decrease smoke production of TPU composites. The results of CCT reveal that the system of APP/HM could reduce heat release rate, smoke production rate, and total smoke release. It is shown that APP/HM is a good system with smoke-suppression and synergistic flame-retardant properties in flame-retardant TPU composites.     

协效阻燃聚丙烯的阻燃性能

本文研究了以聚磷酸铵(APP)为主阻燃剂,次磷酸铝(AHP)和三聚氰胺氰尿酸盐(MCA)为辅阻燃剂的协效阻燃体系对聚丙烯(PP)阻燃性能的影响。 采用垂直燃烧测试、极限氧指数(LOI)测试、热重分析、锥形量热仪测试、扫描电子显微镜分析等技术手段对所制备的阻燃样品进行了阻燃性能分析。 结果表明:单独添加任一质量分数30%阻燃剂,均不能使PP获得良好的阻燃性能;当阻燃剂总质量分数保持在30%,m(APP)：m(AHP)：m(MCA)=4：1：1时获得理想阻燃效果,此时阻燃PP的LOI为33%,垂直燃烧测试达到V-0级,热释放速率峰值(PHRR)从765.7 kW/m²降为122.7 kW/m²。     

Synergistic fire safety improvement between oyster shell powder and ammonium polyphosphate in TPU composites

In this article, oyster shell powder (OSP) was used as fire safety agent with ammonium polyphosphate (APP) in thermoplastic polyurethane (TPU) composites. The synergistic fire safety improvement between OSP and APP was intensively investigated using limiting oxygen index (LOI), UL‐94, smoke density test (SDT), and cone calorimeter test (CCT). There is a good synergistic effect of reducing the fire hazards when OSP was used with APP in TPU. The peak heat release rate (pHRR) of the sample with 2.0‐wt% OSP and 8.0‐wt% APP decreased to 86.8 kW/m² from 175.7 kW/m² of the sample with only 10.0‐wt% APP. The SDT results showed that the luminous flux of sample OSP2/APP8 was up to 28.9% at the end of experiment with flame, which was much higher than that of pure TPU (1.5%). The thermal stability and thermal decomposition of TPU composites were characterized by thermogravimetric analysis/Fourier infrared spectrum analysis (TG‐IR). The result revealed the inert gasses (including CO₂ and water vapor) produced by the reaction between OSP and APP. A char formed on the surface of composites, hindered the flame spread, reduced the release of combustible gas, and restricted the precursor of smoke into combustion zone.     

Hugely enhanced flame retardancy and smoke suppression properties of UHMWPE composites with silicone‐coated expandable graphite

In this paper, silicone‐coated intumescent flame retardants was prepared by an efficient and simple approach, aiming at enhancing the flame‐retardant efficiency and smoke suppression properties. The surface of expandable graphite (EG) was treated prior to the coverage of nonflammable silicone. The resultant silicone‐modified EG hybrid (SEG) was combined with ammonium polyphosphate (APP) and applied as a flame‐retardant and smoke‐suppressant for ultrahigh molecular weight polyethylene (UHMWPE). Compared with UHMWPE/APP/EG (with 15 wt% APP/EG), UHMWPE/APP/SEG (with 15 wt% APP/SEG) gives decrement by 18.5% in the peaks of the heat release rate, 6.33% in total heat release and 13.6% in total smoke release, whereas increment by 23% in tensile strength and 12.1% in elongation at break, respectively. It is suggested that the introduction of silicone on the surface of EG can improve the interfacial compatibility between EG and UHMWPE. Moreover, it can lead to forming more char residue and reducing the release of smoke particulates during combustion process of the composites.     

Metal‐organic framework MIL‐53 (Fe)@C/graphite carbon nitride hybrids with enhanced thermal stability,flame retardancy,and smoke suppression for unsaturated polyester resin

Metal‐organic framework MIL‐53 (Fe)@C/graphite carbon nitride hybrid (MFeCN), a novel flame retardant, was synthesized by hydrothermal reaction and subsequently added into unsaturated polyester resin (UPR). The structure, morphology, and thermal stability of MFeCN were characterized by Fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy‐dispersive X‐ray spectroscopy (EDS), and thermogravimetric analysis (TG). The thermal stability and flammability of the UPR composites were characterized by TG and cone calorimeter tests (CCT). The results of CCT demonstrated that the peak heat release rate (pHRR), total heat release (THR), peak smoke production rate (pSPR), and total smoke production (TSP) of UPR/MFeCN‐4 were reduced by 39.8%, 10.2%, 33.3%, and 14.5%, respectively, comparing with UPR. The results of TG and CCT indicated that MFeCN could improve the thermal stability, flame retardancy, and smoke suppression properties of the UPR composites. The residues after CCT were then characterized by laser Raman spectroscopy (LRS), XPS, and SEM. Finally, based on the above experimental results and analysis, the flame retardancy mechanism of MFeCN was proposed.     

海泡石对膨胀阻燃聚丙烯燃烧和热分解的影响

将改性后的海泡石添加到聚磷酸铵(APP)和双季戊四醇(DPER)膨胀阻燃聚丙烯(PP/IFR)体系中,采用氧指数(LOI)、热重分析(TGA)、光电子能谱(XPS)、傅里叶变换红外(FTIR)光谱、锥形量热仪(CONE)和扫描电镜(SEM)考察其对膨胀阻燃体系的催化协效作用,探讨作用机理.LOI结果表明,改性的海泡石比纳米水滑石和有机改性的蒙脱土有更好的催化协效作用.CONE数据证实,海泡石可以降低膨胀阻燃聚丙烯体系的热释放速率和总的热释放量.通过观察SEM图片发现,海泡石可以改善膨胀炭层的形貌,提高炭层的隔热隔质性能.TGA结果表明,在氮气和空气气氛下,海泡石均可以提高膨胀炭层的热稳定性,增加高温时残余物的量,其主要作用对象为APP.FTIR和XPS测试发现加热过程中海泡石可以与APP发生化学反应,形成P—O—Si键,增加了APP高温时的稳定性.     

Synergistic effects of ferric pyrophosphate (FePP) in intumescent flame‐retardant polypropylene

Ferric pyrophosphate (FePP) was added to an ammonium polyphosphate (APP)—pentaerythritol (petol) intumescent flame retardant (IFR) system in polypropylene (PP) matrix, with subsequent investigation into the synergistic effect between FePP and the IFRs. Limited oxygen index (LOI), UL‐94 test and cone calorimeter test were employed to study the flame retardance of the synthesized flame retardant PP composites. Thermogravimetric analysis (TGA) and thermogravimetric analysis‐infrared spectrometry (TG‐IR) were used to study their thermal degradation characteristics and gas products. TG‐IR results demonstrate that there is no Fe (CO)₅ produced from PP/IFR/FePP system, which implies that the flame retardant mechanism of PP/IFR/FePP system is in the condensed phase rather than in the gas phase. Real time FTIR and X‐ray photoelectron spectroscopy (XPS) were used to monitor the thermal oxidative stability and the high temperature performance of the flame retardant PP composites. The real time FTIR spectra show that all peaks around 2900 cm^?1 almost disappear at 380°C for the PP/IFR system, meaning that PP decomposes completely at this temperature. But after the addition of 2 wt%wt% FePP, the peaks still exist till 400°C. XPS shows that the aliphatic carbon atom content in PP/23 wt%wt% IFR/2 wt%wt% FePP (63.8%) is much higher than the one without FePP, and the total oxygen atom content in PP/23 wt%wt% IFR/2 wt%wt% FePP is just 19.1%, while the one in PP/25 wt% IFR is as high as 35.7%. Copyright © 2009 John Wiley & Sons, Ltd.     

Flame‐retardant performance and mechanism of epoxy thermosets modified with a novel reactive flame retardant containing phosphorus,nitrogen, and sulfur

A novel phosphorus‐containing, nitrogen‐containing, and sulfur‐containing reactive flame retardant (BPD) was successfully synthesized by 1‐pot reaction. The intrinsic flame‐retardant epoxy resins were prepared by blending different content of BPD with diglycidyl ether of bisphenol‐A (DGEBA). Thermal stability, flame‐retardant properties, and combustion behaviors of EP/BPD thermosets were investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), limited oxygen index (LOI) measurement, UL94 vertical burning test, and cone calorimeter test. The flame‐retardant mechanism of BPD was studied by TGA/infrared spectrometry (TGA‐FTIR), pyrolysis‐gas chromatography/mass spectrometry (Py‐GC/MS), morphology, and chemical component analysis of the char residues. The results demonstrated that EP/BPD thermosets not only exhibited outstanding flame retardancy but also kept high glass transition temperature. EP/BPD‐1.0 thermoset achieved LOI value of 39.1% and UL94 V‐0 rating. In comparison to pure epoxy thermoset, the average of heat release rate (av‐HRR), total heat release (THR), and total smoke release (TSR) of EP/BPD‐1.0 thermoset were decreased by 35.8%, 36.5% and 16.5%, respectively. Although the phosphorus content of EP/BPD‐0.75 thermoset was lower than that of EP/DOPO thermoset, EP/BPD‐0.75 thermoset exhibited better flame retardancy than EP/DOPO thermoset. The significant improvement of flame retardancy of EP/BPD thermosets was ascribed to the blocking effect of phosphorus‐rich intumescent char in condensed phase, and the quenching and diluting effects of abundant phosphorus‐containing free radicals and nitrogen/sulfur‐containing inert gases in gaseous phase. There was flame‐retardant synergism between phosphorus, nitrogen, and sulfur of BPD.