MPHPB was prepared from melamine,phenylphosphonic acid and boric acid,and its flame retardant effect in PE was investigated.Compared to the intermediate product(melamine phenyl hypophosphite(MPHP)),the residual char i...MPHPB was prepared from melamine,phenylphosphonic acid and boric acid,and its flame retardant effect in PE was investigated.Compared to the intermediate product(melamine phenyl hypophosphite(MPHP)),the residual char increased from 17.9% of MPHP to 41.2% of MPHPB at 800℃.The limiting oxygen index(LOI)of PE/20%MPHPB is 23.6%,which reaches V-0 rating.After the addition of 20%MPHPB,the total heat release(THR),peak heat release rate(pK-HRR),and average effective thermal combustion rates(av-EHC)of PE decreased.Additionally,characterizations including the pyrolysis gas chromatography-mass spectrometry(Py-GC-MS),scanning electron microscopy(SEM),raman spectroscopy test(LRS)and fourier transform infrared(FT-IR)were taken to investigate the flame retardant mechanism,and the results show that MPHPB plays roles in both gas and condensed phases.展开更多
By combining the merits of radiative cooling(RC)and evaporation cooling(EC),radiative coupled evaporative cooling(REC)has attracted considerable attention for sub-ambient cooling purposes.However,for outdoor devices,t...By combining the merits of radiative cooling(RC)and evaporation cooling(EC),radiative coupled evaporative cooling(REC)has attracted considerable attention for sub-ambient cooling purposes.However,for outdoor devices,the interior heating power would increase the working temperature and fire risk,which would suppress their above-ambient heat dissipation capabilities and passive water cycle properties.In this work,we introduced a REC design based on an all-in-one photonic hydrogel for above-ambient heat dissipation and flame retardancy.Unlike conventional design RC film for heat dissipation with limited cooling power and fire risk,REC hydrogel can greatly improve the heat dissipation performance in the daytime with a high workload,indicating a 12.0℃lower temperature than the RC film under the same conditions in the outdoor experiment.In the nighttime with a low workload,RC-assisted adsorption can improve atmospheric water harvesting to ensure EC in the daytime.In addition,our REC hydrogel significantly enhanced flame retardancy by absorbing heat without a corresponding temperature rise,thus mitigating fire risks.Thus,our design shows a promising solution for the thermal management of outdoor devices,delivering outstanding performance in both heat dissipation and flame retardancy.展开更多
Bio-based 2,5-furandicarboxylic acid polyesters offer significant promise for reducing energy and environmental crises.However,their intrinsic flammability remains a critical limitation,and conventional flame-retardan...Bio-based 2,5-furandicarboxylic acid polyesters offer significant promise for reducing energy and environmental crises.However,their intrinsic flammability remains a critical limitation,and conventional flame-retardant strategies often compromise their mechanical properties,hindering their practical applications.Herein,a 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide(DOPO)-based comonomer(DDP)was used to synthesize flame-retardant poly(ethylene furandicarboxylate-co-phosphaphenanthrene)(PEFDn).The covalent integration of DDP confers intrinsic flame retardancy,avoiding the plasticization and migration issues associated with additive-type systems.Upon thermal decomposition,the DOPO-derived moieties release phosphoric acid and radical scavengers,promoting char formation and suppressing flame propagation.Furthermore,density functional theory(DFT)calculations combined with non-covalent interaction(NCI)analysis revealed that DOPO dimer molecules adopt a stable parallel-displaced π-π stacking configu ration,potentially facilitating microphase separation and enhancing the energy dissipation capability.PEFD_(10)achieves a UL-94 V-0 rating while simultaneously increasing impact toughness from 1.5 kJ/m^(2) to 14.7 kJ/m^(2).Im portantly,PEFDn maintained acceptable oxygen-barrier properties.PEFD10 also exhibited high transparency and UV-shielding performance.The combination of intrinsic flame safety,im pact-toughness resistance,UV shielding,and an oxygen barrier ensures reliable protection of electrical components and long-term operational stability.The integration of multiple critical properties within a single bio-based material represents a novel approach fo r enabling sustainable polymer solutions for high-pe rformance electrical applications.展开更多
The Lean Blowout(LBO)limit is crucial for the aircraft engines.The semi-empirical(such as Lefebvre’s LBO model and Flame Volume(FV)model),numerical and hybrid methods are widely utilized for the LBO limit quick predi...The Lean Blowout(LBO)limit is crucial for the aircraft engines.The semi-empirical(such as Lefebvre’s LBO model and Flame Volume(FV)model),numerical and hybrid methods are widely utilized for the LBO limit quick prediction.An innovative hybrid method based on the FV concept is proposed.This method can be classified as a semi-empirical/physical based hybrid prediction method.In this hybrid method,it is assumed that the flame volume varies nearly linearly with the fuel/air ratio near the LBO.The flame volume is obtained directly by the numerical simulation using the threshold value of the visible flame boundary as 900 K.Then the final LBO limits is determined by the FV model.On the premise of keeping the good generality of prediction,the hybrid method based on the FV concept can further improve the prediction accuracy.The comparison with the prediction of the existing available methods on fifteen combustors shows that the hybrid method based on the FV concept achieves better prediction accuracy.The prediction uncertainties between the experimental results and the predicted values by the hybrid method based on the FV concept are within about±10%.展开更多
Asymptotic analysis is conducted for outwardly propagating spherical flames with large activation energy. The spherical flame structure consists of the preheat zone, reaction zone, and equilibrium zone. Analytical sol...Asymptotic analysis is conducted for outwardly propagating spherical flames with large activation energy. The spherical flame structure consists of the preheat zone, reaction zone, and equilibrium zone. Analytical solutions are separately obtained in these three zones and then asymp- totically matched. In the asymptotic analysis, we derive a correlation describing the spherical flame temperature and propagation speed changing with the flame radius. This cor- relation is compared with previous results derived in the limit of infinite value of activation energy. Based on this correla- tion, the properties of spherical flame propagation are inves- tigated and the effects of Lewis number on spherical flame propagation speed and extinction stretch rate are assessed. Moreover, the accuracy and performance of different mod- els used in the spherical flame method are examined. It is found that in order to get accurate laminar flame speed and Markstein length, non-linear models should be used.展开更多
An aliphatic epoxy monomer＂polypropyleneglycol-diglycidylether（PPGDGE,YF878）＂is loaded in the epoxy resins（EP）to evaluate the influence of epoxy structure on the blowing-out effect,which is caused by 9,10-dihydr...An aliphatic epoxy monomer＂polypropyleneglycol-diglycidylether（PPGDGE,YF878）＂is loaded in the epoxy resins（EP）to evaluate the influence of epoxy structure on the blowing-out effect,which is caused by 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide（DOPO）and octaphenyl silsesquioxane（OPS）.The flame retarding properties of these EP composites were tested using the LOI and UL-94 procedures.The pyrolytic gases produced and the thermal stability of the EP composites with different flame retardants were detected by TGA-FTIR in air.The negative effect of YF878 was detected from the TTI,HRR,and p-HRR results after the cone calorimeter test.The char produced by the EP composites after the cone calorimeter test was investigated by FTIR.It is proposed that the aliphatic chain of the YF878 is easy to break down and produce combustible gases,so it does not easily form a crosslinked structure in the condensed phase.These results are very helpful for investigation of the conditions under which the blowing-out effect in epoxy resins can be caused by synergy of phosphorous and silicon.展开更多
Lean Blow Out(LBO)poses a significant safety hazard when occurring in aero-engines.Understanding the lower stability limits of gas turbine combustors and the characteristics of spray flame close to LBO are imperative ...Lean Blow Out(LBO)poses a significant safety hazard when occurring in aero-engines.Understanding the lower stability limits of gas turbine combustors and the characteristics of spray flame close to LBO are imperative for safe operation.The objective of this work is to evaluate the effects of fuel decreasing rates and pressure drops of the injector on LBO performances in a multiswirl staged combustor equipped with an airblast injector.A set of hardware and control system was developed to realize a user-defined fuel supply law.High-speed imaging was applied to record complete LBO processes under the conditions of linear fuel reduction and stable airflow.Partical Image Velocimetry(PIV)and Planar Mie(PMie)scattering were used to acquire the flow fields and spray fields under non-reacting conditions.Experimental results have shown that LBO limits extend to leaner conditions as the pressure drop of the injector increases.With an increase of the fuel decreasing rate,the exhaust temperature before flame extinction increases,and the LBO Fuel-to-Air-Ratio(FAR)decreases.The time evolution of the integral CH*intensity conforms to a linear function during the LBO process.Proper Orthogonal Decomposition(POD)was used to analyze the dynamic characteristics of lean-burn flames.Under different fuel decreasing rates and pressure drops of the injector,flames close to LBO present similar modal spatial distributions,alternately appearing axial,radial,high-order axial,and high-order radial oscillations.展开更多
The microstructure design for thermal conduction pathways in polymeric electrical encapsulation materials is essential to meet the stringent requirements for efficient thermal management and thermal runaway safety in ...The microstructure design for thermal conduction pathways in polymeric electrical encapsulation materials is essential to meet the stringent requirements for efficient thermal management and thermal runaway safety in modern electronic devices.Hence,a composite with three-dimensional network(Ho/U-BNNS/WPU)is developed by simultaneously incorporating magnetically modified boron nitride nanosheets(M@BNNS)and non-magnetic organo-grafted BNNS(U-BNNS)into waterborne polyurethane(WPU)to synchronous molding under a horizontal magnetic field.The results indicate that the continuous in-plane pathways formed by M@BNNS aligned along the magnetic field direction,combined with the bridging structure established by U-BNNS,enable Ho/U-BNNS/WPU to exhibit exceptional in-plane(λ//)and through-plane thermal conductivities(λ_(⊥)).In particular,with the addition of 30 wt%M@BNNS and 5 wt%U-BNNS,theλ//andλ_(⊥)of composites reach 11.47 and 2.88 W m^(-1) K^(-1),respectively,which representing a 194.2%improvement inλ_(⊥)compared to the composites with a single orientation of M@BNNS.Meanwhile,Ho/U-BNNS/WPU exhibits distinguished thermal management capabilities as thermal interface materials for LED and chips.The composites also demonstrate excellent flame retardancy,with a peak heat release and total heat release reduced by 58.9%and 36.9%,respectively,compared to WPU.Thus,this work offers new insights into the thermally conductive structural design and efficient flame-retardant systems of polymer composites,presenting broad application potential in electronic packaging fields.展开更多
The construction of hierarchical thermoplastic polyurethane(TPU)composites with superior flame retardant and electromagnetic shielding capabilities hold significant practical importance.In this work,TPU composites loa...The construction of hierarchical thermoplastic polyurethane(TPU)composites with superior flame retardant and electromagnetic shielding capabilities hold significant practical importance.In this work,TPU composites loaded with a multilayer core-shell flame retardant(APP@CoAl-LDH@Si)and a modified conductive nanofiller(MWCNT-NH_(2)-PA)were firstly prepared through the melt blending method,acting as surface layer.Additionally,multilayered MXene films functionalized by bacterial cellulose(BC)and dopamine hydrochloride(DA)were fabricated via a facile and efficient vacuum filtration approach.Finally,a PBM film was utilized as an intermediate layer to construct hierarchical TPU composites.The results indicated that the introduction of 10 wt%APP@CoAl-LDH@Si hybrid,the peak heat release rate,total heat release,peak smoke production rate,and total smoke release of the TPU composites were decreased by 83.0%,61.3%,48.5%and 66.9%,respectively,compared with those of pure TPU due to the free radicals capture effect of APP,and the flame-retardant functions of LDH and silane.Moreover,the hierarchical TPU/APP@CoAl-LDH@Si/CP1-PBM exhibited excellent electromagnetic shielding performance,achieving 43.6 dB in the X-band because of multiple reflection losses,interface polarization losses,and charge carrier movement-induced thermal dissipation.Extraordinarily,the A and R coefficients were reversed in the X and K bands.This phenomenon was attributed to the different degrees of confinement of the multilayer structure to electromagnetic waves with different wavelengths.This work presents a novel model for the design and preparation of high-performance polymer composites with multiple properties and regulation mechanism.展开更多
Silicone rubber(SR)exhibits superior breathability and high-temperature resistance.However,SR is prone to degradation under extreme heat or combustion,limiting its effectiveness in mitigating secondary hazards.In this...Silicone rubber(SR)exhibits superior breathability and high-temperature resistance.However,SR is prone to degradation under extreme heat or combustion,limiting its effectiveness in mitigating secondary hazards.In this study,phosphate glass powder was used to calcinate zinc borate,lanthanum oxide,and cerium oxide.Methylphenyl polysiloxane was then grafted onto the surface of the glass powder,resulting in the modified pow-ders designated as Methylphenyl polysiloxane-grafted zinc borate-modified phosphate glass powder(GF-ZnBM),Methylphenyl polysiloxane-grafted lanthanum oxide-modified phosphate glass powder(GF-LaM),and Methylphenyl polysiloxane-grafted cerium oxide-modified phosphate glass powder(GF-CeM).The modified powders were sub-sequently incorporated into silicone rubber composites to enhance the ceramicization capability of silicone rubber at high temperatures.Specifically,GF-CeM and GF-LaM significantly increased the limiting oxygen index(LOI)to 33%and reduced the tendency for combustion propagation.Additionally,GF-CeM notably contributed to enhancing ceramicization strength.The presence of cerium oxide helps in the melting of the glass powder and enhances its adhesion to the silicone rubber matrix.SR/ZnB-GF exhibited the lowest activation energy among the tested composites,along with the best protective capability.The inclusion of modified glass powder has a minor impact on the rheological properties,indicating that the composite retains its ability to flow and deform under stress.This confirms that the material remains flexible under normal conditions and forms a ceramic structure when heated,thereby exhibiting self-supporting properties.This study provides a practical methodology for the targeted modification of glass powders,thereby further enhancing the fire safety of silicone-based composites.展开更多
Sodium-ion batteries hold great promise as next-generation energy storage systems.However,the high instability of the electrode/electrolyte interphase during cycling has seriously hindered the development of SIBs.In p...Sodium-ion batteries hold great promise as next-generation energy storage systems.However,the high instability of the electrode/electrolyte interphase during cycling has seriously hindered the development of SIBs.In particular,an unstable cathode–electrolyte interphase(CEI)leads to successive electrolyte side reactions,transition metal leaching and rapid capacity decay,which tends to be exacerbated under high-voltage conditions.Therefore,constructing dense and stable CEIs are crucial for high-performance SIBs.This work reports localized high-concentration electrolyte by incorporating a highly oxidation-resistant sulfolane solvent with non-solvent diluent 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether,which exhibited excellent oxidative stability and was able to form thin,dense and homogeneous CEI.The excellent CEI enabled the O3-type layered oxide cathode NaNi_(1/3)Mn_(1/3)Fe_(1/3)O_(2)(NaNMF)to achieve stable cycling,with a capacity retention of 79.48%after 300 cycles at 1 C and 81.15%after 400 cycles at 2 C with a high charging voltage of 4.2 V.In addition,its nonflammable nature enhances the safety of SIBs.This work provides a viable pathway for the application of sulfolane-based electrolytes on SIBs and the design of next-generation high-voltage electrolytes.展开更多
In this study, the concentration of alkylphenol ethoxylates (APEs) and brominated flame retardants (BFRs) were determined in fish samples, Labeo umbratus and Carp, collected from the Vaal River in South Africa. Ultras...In this study, the concentration of alkylphenol ethoxylates (APEs) and brominated flame retardants (BFRs) were determined in fish samples, Labeo umbratus and Carp, collected from the Vaal River in South Africa. Ultrasonic-assisted extraction technique was used to extract the organic contaminants from fish samples, and the resulting extract was purified by sulphuric acid lipid removal followed by Strata X-cartridge SPE clean-up. The APEs and BFRs were derivatized using heptafluorobutyric anhydride before analysis with GC-MS. In both types of fish samples, lower oligomers of APEs were more abundant than the higher oligomers, while HBCD, BDE99 and PBB101 were the dominant BFRs. The concentrations of these pollutants ranged from 1.061 ng/g lipids (t-BP) in Labeo umbratus to 11.860 ng/g lipids (HBCD) in Carp.展开更多
The oxidation behavior and mechanism of Mg-Ca alloys in air and under flame exposure were studied.Results show that for the oxidation in air,the Mg-Ca-O oxide film with Ca accumulation and low Mg vapor pressure on the...The oxidation behavior and mechanism of Mg-Ca alloys in air and under flame exposure were studied.Results show that for the oxidation in air,the Mg-Ca-O oxide film with Ca accumulation and low Mg vapor pressure on the surface of Mg-Ca alloys with high Ca content shows good protective effect.However,the falling off phenomenon of the oxide film on Mg_(2)Ca results in the further oxidation.Hence,the Mg-Ca alloys with high Ca content only show good protective effect.For the oxidation in flame,the molten alloys release the Ca atoms to diffuse outward.The Mg-Ca-O oxide film with high Ca accumulation layer forms in Mg-Ca alloys with high Ca content.Despite the high Mg vapor pressure in the molten alloy,the Mg-Ca-O oxide film with high Ca accumulation layer shows excellent protective effect.展开更多
To further expand the application of Mg alloys at high temperatures,the oxidation resistance of Mg-0.3Ca and Mg-3.6Ca alloys with protective coating under flame exposure was studied.Results show that the oxidation res...To further expand the application of Mg alloys at high temperatures,the oxidation resistance of Mg-0.3Ca and Mg-3.6Ca alloys with protective coating under flame exposure was studied.Results show that the oxidation resistance of Mg-Ca alloys under flame exposure is significantly improved by the protective coating,and Mg-3.6Ca alloy shows better oxidation resistance performance.The surface temperature of Mg-Ca alloys is reduced by the coating,therefore improving the oxidation resistance under flame exposure.However,the thermal insulation effect of the coating on Mg-3.6Ca alloy is better,which can be attributed to the Ca accumulation on the surface film.In addition,the surface film with Ca accumulation layer plays a crucial role in protecting the alloy.No obvious Ca accumulation layer exists on the Mg-0.3Ca alloy surface,presenting a restricted protective effect.Nevertheless,the surface film containing Ca accumulation layer is formed on Mg-3.6 Ca alloy,which shows an excellent protective effect.展开更多
Developing polymer materials combining high strength,toughness,multifunctionality,and environmental sustainability remains a major challenge.Herein,high-performance PVA-PCSx composite films were successfully fabricate...Developing polymer materials combining high strength,toughness,multifunctionality,and environmental sustainability remains a major challenge.Herein,high-performance PVA-PCSx composite films were successfully fabricated by incorporating H_(3)PO_(3)-protonated chitosan(PCS)into the PVA matrix as both a bio-based multi-hydrogen-bonding crosslinking agent and a macromolecular flame retardant.Specifically,a comprehensive investigation was conducted on the hydrogen bonding interactions,microstructure,mechanical properties,antibacterial performance,and flame retardancy of the PVA-PCSx films.Strong hydrogen bonds between PCS and PVA enabled excellent compatibility and formed a unique mechanical interlocking interface architecture.This further resulted in superior transparency and synchronous reinforcement and toughening effects in the composites films.Compared with pure PVA,the PVA-PCSx films showed a 23%-51%increase in tensile strength and an 80%-108%improvement in fracture toughness.Moreover,PVA-PCSx films exhibited superior fire safety performance,achieving an LOI value of 31.3%,attaining UL-94 V-0 rating,and reducing the heat release rate by up to 73.1%.Additionally,PVA-PCSx films demonstrated 99.99%antibacterial efficacy against both Escherichia coli and Staphylococcus aureus.Collectively,this study presents a simple yet effective strategy for fabricating high-strength,high-toughness,multifunctional composites using biopolysaccharides as additives.展开更多
In this manuscript,we conveniently prepared a series of polyester-polycarbonate copolymer(PPC-P)/polybutylene adipate terephthalate(PBAT)blends that exhibit both flame-retardant properties and toughness.Piperazine pyr...In this manuscript,we conveniently prepared a series of polyester-polycarbonate copolymer(PPC-P)/polybutylene adipate terephthalate(PBAT)blends that exhibit both flame-retardant properties and toughness.Piperazine pyrophosphate(PAPP),melamine phosphate(MPP)and ZnO were used as synergistic flame retardants for PPC-P/PBAT blends.The effects of synergistic flame retardants on thermal stability,combustion behavior and flame retardancy of PPC-P/PBAT blends were investigated.The results showed that when the ratio of PAPP/MPP/ZnO was 18.4:9.2:2.4,the LOI of PPC-P/PBAT composite was 42.8%,and UL-94 reached V-0 level.The results of cone calorimetry showed that the mass loss rate(MLR),the peak value of the biggest smoke production rate(pSPR)and total smoke production(TSP)of the material decreased,and a continuously expanded carbon layer with a compact structure was formed after combustion.The carbon layer formed after surface combustion protects the material from decomposition over a long temperature range.In terms of mechanical properties,compared with the composites with only PAPP and MPP,PAPP/MPP/ZnO composites can improve the mechanical properties.After adding 2.4 wt% ZnO,the tensile strength and impact strength of the polymer increased to 34.2 MPa and 28.5 kJ/m^(2),respectively.The results showed that the use of non-toxic,environmentally friendly,halogen-free flame retardants to enhance the flame retardant properties of biodegradable polymer composites is a promising direction in the future.展开更多
Generally,gaining fundamental insights into chain processes during the combustion of flame-retardant polymers relies on the qualitative and quantitative characterization of key chain carriers.However,polymer combustio...Generally,gaining fundamental insights into chain processes during the combustion of flame-retardant polymers relies on the qualitative and quantitative characterization of key chain carriers.However,polymer combustion processes based on conventional solid-fuel combustion strategies,due to the high coupling of pyrolysis,combustion,soot formation and oxidation,exhibit relatively high complexity and poor flame stability,and lead to a huge obstacle to the use of optical diagnostics.Herein,a spatial-confinement combustion strategy,which can produce a special staged flame with multi-jets secondary wave,is devised to provide a highly decoupled combustion environment.Glowing soot particles are therefore decoupled from main chemiluminescence region and confined to the flame tip to provide a well-controlled,opticalthin test environment for combustion diagnostic.Based on this strategy,a multi-nozzle-separation(MNS)burner is designed and fabricated,and the combustion processes associated with four model compounds,PVC,PS,PP/TBBA blends and PP/RP blends are investigated by spontaneous spectral diagnosis,and the chemiluminescence fingerprint of key diatomic/triatomic intermediates(such as OH,CH,C_(2),ClO,Br_(2),and PHO)are clearly observed.This encouraging result means that the strategy of spatial-confinement combustion we proposed shows promising prospect in many subjects associated with combustion chain regulation,such as efficient design of flame retardants.展开更多
A novel eco-friendly charring agent(L-OH)was successfully synthesized by combining pentaerythritol(PER)with lignin through a simple two-step reaction.The structure of L-OH was characterized using Fourier transform inf...A novel eco-friendly charring agent(L-OH)was successfully synthesized by combining pentaerythritol(PER)with lignin through a simple two-step reaction.The structure of L-OH was characterized using Fourier transform infrared(FTIR),X-ray diffraction(XRD),scanning electron microscopy(SEM)and EDS.In addition,L-OH was introduced into polypropylene(PP)together with melamine(MEL)and ammonium polyphosphate(APP)as an intumescent flame retardant(IFRR).The flame retardancy of PP/IFRR composites were investigated using limited oxygen index(LOI),UL-94,thermogravimetric analysis(TGA)and cone calorimeter(CC)test.The experimental results indicate that the PP/IFRR composites pass the V-0 grade of the UL-94 test when the addition amount of IFRR is no less than 20%,and the LOI value of the composite reaches 32.2%at 30%IFRR addition.The peak heat release rate(PHRR)and peak smoke production rate(PSPR)of the composite decrease by 72.8%and 70.4%compared with pure PP,respectively.The flame retardancy mechanism was investigated by TGA,TG-FTIR and residual carbon analysis.These analyses indicate that L-OH can form a more continuous and dense carbon layer during the combustion process,which is the main factor contributing to the improved flame retardancy of PP.展开更多
Although lightweight aramid paper honeycombs are highly desirable for microwave absorption owing to their dual functions of both load-bearing and microwave-absorbing,unsatisfactory microwave absorption,inferior mechan...Although lightweight aramid paper honeycombs are highly desirable for microwave absorption owing to their dual functions of both load-bearing and microwave-absorbing,unsatisfactory microwave absorption,inferior mechanical and inadequate thermal properties present significant challenges for practical applications in diverse complex scenarios.Herein,lightweight,high-strength and flame-retardant aramid nanofibers-based honeycombs(MANHs)for integrated microwave absorption and thermal insulation are successfully fabricated via the hydrogen bonding assembly,mold forming and aerogel filling strategy using aramid waste as raw material.The dense network structure formed by the interwoven aramid nanofibers(ANFs)in the honeycomb body acts as a framework endows the MANH with impressive mechanical performance,and the specific strength and toughness of MANH reach 153.6 MPa g^(−1) cm^(−3) and 13.9 MJ m^(−3),respectively,which are 3.5 and 19 times higher than those of commercial microwave absorption honeycombs(CMAH).The ultralight MXene/ANFs aerogels(a density of 25 mg cm^(−3))with multiscale pore structure filled in the honeycomb apertures give the honeycomb outstanding microwave absorption performance,with a minimum reflection loss of−62.5 dB,and can cover the entire X-band with a thickness of only 3.5 mm.Meanwhile,compared with CMAH,the thermal insulation and flame-retardant performance of MANH are also significantly improved.Notably,MANH also demonstrates favorable sound absorption performance at high-frequency bands.The MANH is considered to be a promising candidate for aerospace and military stealth applications as a result of its lightweight,high strength,exceptional microwave absorption,and remarkable thermal insulation performance.展开更多
We aimed to enhance the flame retardancy of epoxy resin(EP)by synthesizing a novel,halogen-free flame retardant through a one-pot method.The synthesis utilized 9,10-dihydro-9-oxa-10-phospha-phenanthrene-10-oxide(DOPO)...We aimed to enhance the flame retardancy of epoxy resin(EP)by synthesizing a novel,halogen-free flame retardant through a one-pot method.The synthesis utilized 9,10-dihydro-9-oxa-10-phospha-phenanthrene-10-oxide(DOPO),furfurylamine(FA),and benzene propionaldehyde(BPA)as raw materials.We conducted differential scanning calorimetry(DSC)analysis to investigate the effects of FPD on the curing process and thermal properties of EP.Our findings reveal that incorporating FPD into EP can facilitate a faster curing process and increase the carbon residue post-combustion.Specifically,the FPD/EP-7 composite demonstrates a limiting oxygen index(LOI)of 34.9%and achieves a UL-94V-0 rating with a phosphorus content of 0.91wt%.These results indicate that FPD significantly enhances the thermal stability and charring rate of EP,thereby improving its flame retardancy.Although the addition of FPD slightly reduces the mechanical properties of EP,the composite material maintains excellent performance.展开更多
基金Funded by the Natural Science Foundation of Guangdong(Nos.2014A030313241,2014B090901068,and 2016A010103003)。
文摘MPHPB was prepared from melamine,phenylphosphonic acid and boric acid,and its flame retardant effect in PE was investigated.Compared to the intermediate product(melamine phenyl hypophosphite(MPHP)),the residual char increased from 17.9% of MPHP to 41.2% of MPHPB at 800℃.The limiting oxygen index(LOI)of PE/20%MPHPB is 23.6%,which reaches V-0 rating.After the addition of 20%MPHPB,the total heat release(THR),peak heat release rate(pK-HRR),and average effective thermal combustion rates(av-EHC)of PE decreased.Additionally,characterizations including the pyrolysis gas chromatography-mass spectrometry(Py-GC-MS),scanning electron microscopy(SEM),raman spectroscopy test(LRS)and fourier transform infrared(FT-IR)were taken to investigate the flame retardant mechanism,and the results show that MPHPB plays roles in both gas and condensed phases.
基金financially supported by the Science and Technology Innovation Program of Hunan Province(2024RC3003)the Central South University Innovation-Driven Research Programme(2023CXQD012)the Initiative for Sustainable Energy for its financial support。
文摘By combining the merits of radiative cooling(RC)and evaporation cooling(EC),radiative coupled evaporative cooling(REC)has attracted considerable attention for sub-ambient cooling purposes.However,for outdoor devices,the interior heating power would increase the working temperature and fire risk,which would suppress their above-ambient heat dissipation capabilities and passive water cycle properties.In this work,we introduced a REC design based on an all-in-one photonic hydrogel for above-ambient heat dissipation and flame retardancy.Unlike conventional design RC film for heat dissipation with limited cooling power and fire risk,REC hydrogel can greatly improve the heat dissipation performance in the daytime with a high workload,indicating a 12.0℃lower temperature than the RC film under the same conditions in the outdoor experiment.In the nighttime with a low workload,RC-assisted adsorption can improve atmospheric water harvesting to ensure EC in the daytime.In addition,our REC hydrogel significantly enhanced flame retardancy by absorbing heat without a corresponding temperature rise,thus mitigating fire risks.Thus,our design shows a promising solution for the thermal management of outdoor devices,delivering outstanding performance in both heat dissipation and flame retardancy.
基金financially supported by the National Key Research and Development Program of China(No.2021YFB3700300)the National Natural Science Foundation of China(Nos.52573017 and U21B2093)+1 种基金Key Research and Development Program of Ningbo(No.2022Z200)the Zhejiang Provincial Natural Science Foundation(No.LY23E030005)。
文摘Bio-based 2,5-furandicarboxylic acid polyesters offer significant promise for reducing energy and environmental crises.However,their intrinsic flammability remains a critical limitation,and conventional flame-retardant strategies often compromise their mechanical properties,hindering their practical applications.Herein,a 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide(DOPO)-based comonomer(DDP)was used to synthesize flame-retardant poly(ethylene furandicarboxylate-co-phosphaphenanthrene)(PEFDn).The covalent integration of DDP confers intrinsic flame retardancy,avoiding the plasticization and migration issues associated with additive-type systems.Upon thermal decomposition,the DOPO-derived moieties release phosphoric acid and radical scavengers,promoting char formation and suppressing flame propagation.Furthermore,density functional theory(DFT)calculations combined with non-covalent interaction(NCI)analysis revealed that DOPO dimer molecules adopt a stable parallel-displaced π-π stacking configu ration,potentially facilitating microphase separation and enhancing the energy dissipation capability.PEFD_(10)achieves a UL-94 V-0 rating while simultaneously increasing impact toughness from 1.5 kJ/m^(2) to 14.7 kJ/m^(2).Im portantly,PEFDn maintained acceptable oxygen-barrier properties.PEFD10 also exhibited high transparency and UV-shielding performance.The combination of intrinsic flame safety,im pact-toughness resistance,UV shielding,and an oxygen barrier ensures reliable protection of electrical components and long-term operational stability.The integration of multiple critical properties within a single bio-based material represents a novel approach fo r enabling sustainable polymer solutions for high-pe rformance electrical applications.
基金co-supported by National Science and Technology Major Project(No.2017-III-0007-0032)Key Laboratory Fund(No.6142702180306)。
文摘The Lean Blowout(LBO)limit is crucial for the aircraft engines.The semi-empirical(such as Lefebvre’s LBO model and Flame Volume(FV)model),numerical and hybrid methods are widely utilized for the LBO limit quick prediction.An innovative hybrid method based on the FV concept is proposed.This method can be classified as a semi-empirical/physical based hybrid prediction method.In this hybrid method,it is assumed that the flame volume varies nearly linearly with the fuel/air ratio near the LBO.The flame volume is obtained directly by the numerical simulation using the threshold value of the visible flame boundary as 900 K.Then the final LBO limits is determined by the FV model.On the premise of keeping the good generality of prediction,the hybrid method based on the FV concept can further improve the prediction accuracy.The comparison with the prediction of the existing available methods on fifteen combustors shows that the hybrid method based on the FV concept achieves better prediction accuracy.The prediction uncertainties between the experimental results and the predicted values by the hybrid method based on the FV concept are within about±10%.
基金supported by the National Natural Science Foundation of China (50976003,51136005)Doctoral Fund of Ministry of Education of China (20100001120003)
文摘Asymptotic analysis is conducted for outwardly propagating spherical flames with large activation energy. The spherical flame structure consists of the preheat zone, reaction zone, and equilibrium zone. Analytical solutions are separately obtained in these three zones and then asymp- totically matched. In the asymptotic analysis, we derive a correlation describing the spherical flame temperature and propagation speed changing with the flame radius. This cor- relation is compared with previous results derived in the limit of infinite value of activation energy. Based on this correla- tion, the properties of spherical flame propagation are inves- tigated and the effects of Lewis number on spherical flame propagation speed and extinction stretch rate are assessed. Moreover, the accuracy and performance of different mod- els used in the spherical flame method are examined. It is found that in order to get accurate laminar flame speed and Markstein length, non-linear models should be used.
基金Supported by the National Natural Science Foundation of China(51273023)China Postdoctoral Science Foundation(2014M550023)
文摘An aliphatic epoxy monomer＂polypropyleneglycol-diglycidylether（PPGDGE,YF878）＂is loaded in the epoxy resins（EP）to evaluate the influence of epoxy structure on the blowing-out effect,which is caused by 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide（DOPO）and octaphenyl silsesquioxane（OPS）.The flame retarding properties of these EP composites were tested using the LOI and UL-94 procedures.The pyrolytic gases produced and the thermal stability of the EP composites with different flame retardants were detected by TGA-FTIR in air.The negative effect of YF878 was detected from the TTI,HRR,and p-HRR results after the cone calorimeter test.The char produced by the EP composites after the cone calorimeter test was investigated by FTIR.It is proposed that the aliphatic chain of the YF878 is easy to break down and produce combustible gases,so it does not easily form a crosslinked structure in the condensed phase.These results are very helpful for investigation of the conditions under which the blowing-out effect in epoxy resins can be caused by synergy of phosphorous and silicon.
基金supported by National Science and Technology Major Project (Nos. 2017-Ⅲ-0007-0032 and J2019-Ⅲ-00020045)
文摘Lean Blow Out(LBO)poses a significant safety hazard when occurring in aero-engines.Understanding the lower stability limits of gas turbine combustors and the characteristics of spray flame close to LBO are imperative for safe operation.The objective of this work is to evaluate the effects of fuel decreasing rates and pressure drops of the injector on LBO performances in a multiswirl staged combustor equipped with an airblast injector.A set of hardware and control system was developed to realize a user-defined fuel supply law.High-speed imaging was applied to record complete LBO processes under the conditions of linear fuel reduction and stable airflow.Partical Image Velocimetry(PIV)and Planar Mie(PMie)scattering were used to acquire the flow fields and spray fields under non-reacting conditions.Experimental results have shown that LBO limits extend to leaner conditions as the pressure drop of the injector increases.With an increase of the fuel decreasing rate,the exhaust temperature before flame extinction increases,and the LBO Fuel-to-Air-Ratio(FAR)decreases.The time evolution of the integral CH*intensity conforms to a linear function during the LBO process.Proper Orthogonal Decomposition(POD)was used to analyze the dynamic characteristics of lean-burn flames.Under different fuel decreasing rates and pressure drops of the injector,flames close to LBO present similar modal spatial distributions,alternately appearing axial,radial,high-order axial,and high-order radial oscillations.
基金support from the National Natural Science Foundation of China(22268025,52473083,and 22475176)Key Research and Development Program of Yunnan Province(202403AP140036)+2 种基金Natural Science Basic Research Program of Shaanxi(2024JC-TBZC-04)Applied Basic Research Program of Yunnan Province(202201AT070115 and 202201BE070001-031)supported by the Innovation Capability Support Program of Shaanxi(2024RS-CXTD-57).
文摘The microstructure design for thermal conduction pathways in polymeric electrical encapsulation materials is essential to meet the stringent requirements for efficient thermal management and thermal runaway safety in modern electronic devices.Hence,a composite with three-dimensional network(Ho/U-BNNS/WPU)is developed by simultaneously incorporating magnetically modified boron nitride nanosheets(M@BNNS)and non-magnetic organo-grafted BNNS(U-BNNS)into waterborne polyurethane(WPU)to synchronous molding under a horizontal magnetic field.The results indicate that the continuous in-plane pathways formed by M@BNNS aligned along the magnetic field direction,combined with the bridging structure established by U-BNNS,enable Ho/U-BNNS/WPU to exhibit exceptional in-plane(λ//)and through-plane thermal conductivities(λ_(⊥)).In particular,with the addition of 30 wt%M@BNNS and 5 wt%U-BNNS,theλ//andλ_(⊥)of composites reach 11.47 and 2.88 W m^(-1) K^(-1),respectively,which representing a 194.2%improvement inλ_(⊥)compared to the composites with a single orientation of M@BNNS.Meanwhile,Ho/U-BNNS/WPU exhibits distinguished thermal management capabilities as thermal interface materials for LED and chips.The composites also demonstrate excellent flame retardancy,with a peak heat release and total heat release reduced by 58.9%and 36.9%,respectively,compared to WPU.Thus,this work offers new insights into the thermally conductive structural design and efficient flame-retardant systems of polymer composites,presenting broad application potential in electronic packaging fields.
基金financially supported by the National Natural Science Foundation of China(No.52173070)the Key research and development projects of Baoying County(No.BY202205).
文摘The construction of hierarchical thermoplastic polyurethane(TPU)composites with superior flame retardant and electromagnetic shielding capabilities hold significant practical importance.In this work,TPU composites loaded with a multilayer core-shell flame retardant(APP@CoAl-LDH@Si)and a modified conductive nanofiller(MWCNT-NH_(2)-PA)were firstly prepared through the melt blending method,acting as surface layer.Additionally,multilayered MXene films functionalized by bacterial cellulose(BC)and dopamine hydrochloride(DA)were fabricated via a facile and efficient vacuum filtration approach.Finally,a PBM film was utilized as an intermediate layer to construct hierarchical TPU composites.The results indicated that the introduction of 10 wt%APP@CoAl-LDH@Si hybrid,the peak heat release rate,total heat release,peak smoke production rate,and total smoke release of the TPU composites were decreased by 83.0%,61.3%,48.5%and 66.9%,respectively,compared with those of pure TPU due to the free radicals capture effect of APP,and the flame-retardant functions of LDH and silane.Moreover,the hierarchical TPU/APP@CoAl-LDH@Si/CP1-PBM exhibited excellent electromagnetic shielding performance,achieving 43.6 dB in the X-band because of multiple reflection losses,interface polarization losses,and charge carrier movement-induced thermal dissipation.Extraordinarily,the A and R coefficients were reversed in the X and K bands.This phenomenon was attributed to the different degrees of confinement of the multilayer structure to electromagnetic waves with different wavelengths.This work presents a novel model for the design and preparation of high-performance polymer composites with multiple properties and regulation mechanism.
基金supported by National Natural Science Foundation of China(51991352 and 51874266).
文摘Silicone rubber(SR)exhibits superior breathability and high-temperature resistance.However,SR is prone to degradation under extreme heat or combustion,limiting its effectiveness in mitigating secondary hazards.In this study,phosphate glass powder was used to calcinate zinc borate,lanthanum oxide,and cerium oxide.Methylphenyl polysiloxane was then grafted onto the surface of the glass powder,resulting in the modified pow-ders designated as Methylphenyl polysiloxane-grafted zinc borate-modified phosphate glass powder(GF-ZnBM),Methylphenyl polysiloxane-grafted lanthanum oxide-modified phosphate glass powder(GF-LaM),and Methylphenyl polysiloxane-grafted cerium oxide-modified phosphate glass powder(GF-CeM).The modified powders were sub-sequently incorporated into silicone rubber composites to enhance the ceramicization capability of silicone rubber at high temperatures.Specifically,GF-CeM and GF-LaM significantly increased the limiting oxygen index(LOI)to 33%and reduced the tendency for combustion propagation.Additionally,GF-CeM notably contributed to enhancing ceramicization strength.The presence of cerium oxide helps in the melting of the glass powder and enhances its adhesion to the silicone rubber matrix.SR/ZnB-GF exhibited the lowest activation energy among the tested composites,along with the best protective capability.The inclusion of modified glass powder has a minor impact on the rheological properties,indicating that the composite retains its ability to flow and deform under stress.This confirms that the material remains flexible under normal conditions and forms a ceramic structure when heated,thereby exhibiting self-supporting properties.This study provides a practical methodology for the targeted modification of glass powders,thereby further enhancing the fire safety of silicone-based composites.
基金financial support by National Natural Science Foundation(NNSF)of China(Nos.52202269,52002248,U23B2069,22309162)Shenzhen Science and Technology program(No.20220810155330003)+1 种基金Shenzhen Basic Research Project(No.JCYJ20190808163005631)Xiangjiang Lab(22XJ01007).
文摘Sodium-ion batteries hold great promise as next-generation energy storage systems.However,the high instability of the electrode/electrolyte interphase during cycling has seriously hindered the development of SIBs.In particular,an unstable cathode–electrolyte interphase(CEI)leads to successive electrolyte side reactions,transition metal leaching and rapid capacity decay,which tends to be exacerbated under high-voltage conditions.Therefore,constructing dense and stable CEIs are crucial for high-performance SIBs.This work reports localized high-concentration electrolyte by incorporating a highly oxidation-resistant sulfolane solvent with non-solvent diluent 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether,which exhibited excellent oxidative stability and was able to form thin,dense and homogeneous CEI.The excellent CEI enabled the O3-type layered oxide cathode NaNi_(1/3)Mn_(1/3)Fe_(1/3)O_(2)(NaNMF)to achieve stable cycling,with a capacity retention of 79.48%after 300 cycles at 1 C and 81.15%after 400 cycles at 2 C with a high charging voltage of 4.2 V.In addition,its nonflammable nature enhances the safety of SIBs.This work provides a viable pathway for the application of sulfolane-based electrolytes on SIBs and the design of next-generation high-voltage electrolytes.
基金The authors are indebted to Rand Water for providing the technical environment and funding for this project which is part of Mr.Chokwe’s doctoral degree and Tshwane University of Technology for support
文摘In this study, the concentration of alkylphenol ethoxylates (APEs) and brominated flame retardants (BFRs) were determined in fish samples, Labeo umbratus and Carp, collected from the Vaal River in South Africa. Ultrasonic-assisted extraction technique was used to extract the organic contaminants from fish samples, and the resulting extract was purified by sulphuric acid lipid removal followed by Strata X-cartridge SPE clean-up. The APEs and BFRs were derivatized using heptafluorobutyric anhydride before analysis with GC-MS. In both types of fish samples, lower oligomers of APEs were more abundant than the higher oligomers, while HBCD, BDE99 and PBB101 were the dominant BFRs. The concentrations of these pollutants ranged from 1.061 ng/g lipids (t-BP) in Labeo umbratus to 11.860 ng/g lipids (HBCD) in Carp.
基金National Natural Science Foundation of China(52405425)Project of Natural Science Research in Higher Education Institutions in Jiangsu Province(23KJB430039)+1 种基金Major Natural Science Research Project of Higher Education Institutions in Jiangsu Province(21KJA460007)333 High Level Talent Training Project in Jiangsu Province(2022-3-12-182)。
文摘The oxidation behavior and mechanism of Mg-Ca alloys in air and under flame exposure were studied.Results show that for the oxidation in air,the Mg-Ca-O oxide film with Ca accumulation and low Mg vapor pressure on the surface of Mg-Ca alloys with high Ca content shows good protective effect.However,the falling off phenomenon of the oxide film on Mg_(2)Ca results in the further oxidation.Hence,the Mg-Ca alloys with high Ca content only show good protective effect.For the oxidation in flame,the molten alloys release the Ca atoms to diffuse outward.The Mg-Ca-O oxide film with high Ca accumulation layer forms in Mg-Ca alloys with high Ca content.Despite the high Mg vapor pressure in the molten alloy,the Mg-Ca-O oxide film with high Ca accumulation layer shows excellent protective effect.
基金General Project of Natural Science Research in Higher Education Institutions in Jiangsu Province(23KJB430039)Major Natural Science Research Project of Higher Education Institutions in Jiangsu Province(21KJA460007)National Natural Science Foundation of China(51905462)。
文摘To further expand the application of Mg alloys at high temperatures,the oxidation resistance of Mg-0.3Ca and Mg-3.6Ca alloys with protective coating under flame exposure was studied.Results show that the oxidation resistance of Mg-Ca alloys under flame exposure is significantly improved by the protective coating,and Mg-3.6Ca alloy shows better oxidation resistance performance.The surface temperature of Mg-Ca alloys is reduced by the coating,therefore improving the oxidation resistance under flame exposure.However,the thermal insulation effect of the coating on Mg-3.6Ca alloy is better,which can be attributed to the Ca accumulation on the surface film.In addition,the surface film with Ca accumulation layer plays a crucial role in protecting the alloy.No obvious Ca accumulation layer exists on the Mg-0.3Ca alloy surface,presenting a restricted protective effect.Nevertheless,the surface film containing Ca accumulation layer is formed on Mg-3.6 Ca alloy,which shows an excellent protective effect.
基金financially supported by the National Natural Science Foundation of China(Nos.51991351,52173100)the Taishan Scholars Program(No.tsqn202312176)the Youth Innovation Team Project of Shandong Province(No.2022KJ304)。
文摘Developing polymer materials combining high strength,toughness,multifunctionality,and environmental sustainability remains a major challenge.Herein,high-performance PVA-PCSx composite films were successfully fabricated by incorporating H_(3)PO_(3)-protonated chitosan(PCS)into the PVA matrix as both a bio-based multi-hydrogen-bonding crosslinking agent and a macromolecular flame retardant.Specifically,a comprehensive investigation was conducted on the hydrogen bonding interactions,microstructure,mechanical properties,antibacterial performance,and flame retardancy of the PVA-PCSx films.Strong hydrogen bonds between PCS and PVA enabled excellent compatibility and formed a unique mechanical interlocking interface architecture.This further resulted in superior transparency and synchronous reinforcement and toughening effects in the composites films.Compared with pure PVA,the PVA-PCSx films showed a 23%-51%increase in tensile strength and an 80%-108%improvement in fracture toughness.Moreover,PVA-PCSx films exhibited superior fire safety performance,achieving an LOI value of 31.3%,attaining UL-94 V-0 rating,and reducing the heat release rate by up to 73.1%.Additionally,PVA-PCSx films demonstrated 99.99%antibacterial efficacy against both Escherichia coli and Staphylococcus aureus.Collectively,this study presents a simple yet effective strategy for fabricating high-strength,high-toughness,multifunctional composites using biopolysaccharides as additives.
基金Financial support from National Natural Science Foundation of China(Grant No.22075298)National Key R&D Program of China(2022YFD2301204)is gratefully acknowledged.
文摘In this manuscript,we conveniently prepared a series of polyester-polycarbonate copolymer(PPC-P)/polybutylene adipate terephthalate(PBAT)blends that exhibit both flame-retardant properties and toughness.Piperazine pyrophosphate(PAPP),melamine phosphate(MPP)and ZnO were used as synergistic flame retardants for PPC-P/PBAT blends.The effects of synergistic flame retardants on thermal stability,combustion behavior and flame retardancy of PPC-P/PBAT blends were investigated.The results showed that when the ratio of PAPP/MPP/ZnO was 18.4:9.2:2.4,the LOI of PPC-P/PBAT composite was 42.8%,and UL-94 reached V-0 level.The results of cone calorimetry showed that the mass loss rate(MLR),the peak value of the biggest smoke production rate(pSPR)and total smoke production(TSP)of the material decreased,and a continuously expanded carbon layer with a compact structure was formed after combustion.The carbon layer formed after surface combustion protects the material from decomposition over a long temperature range.In terms of mechanical properties,compared with the composites with only PAPP and MPP,PAPP/MPP/ZnO composites can improve the mechanical properties.After adding 2.4 wt% ZnO,the tensile strength and impact strength of the polymer increased to 34.2 MPa and 28.5 kJ/m^(2),respectively.The results showed that the use of non-toxic,environmentally friendly,halogen-free flame retardants to enhance the flame retardant properties of biodegradable polymer composites is a promising direction in the future.
基金supported by the National Natural Science Foundation of China(No.51827803)the Fundamental Research Funds for the Central Universities,111 Center(No.B20001)Institutional Research Fund from Sichuan University(No.2021SCUNL201).
文摘Generally,gaining fundamental insights into chain processes during the combustion of flame-retardant polymers relies on the qualitative and quantitative characterization of key chain carriers.However,polymer combustion processes based on conventional solid-fuel combustion strategies,due to the high coupling of pyrolysis,combustion,soot formation and oxidation,exhibit relatively high complexity and poor flame stability,and lead to a huge obstacle to the use of optical diagnostics.Herein,a spatial-confinement combustion strategy,which can produce a special staged flame with multi-jets secondary wave,is devised to provide a highly decoupled combustion environment.Glowing soot particles are therefore decoupled from main chemiluminescence region and confined to the flame tip to provide a well-controlled,opticalthin test environment for combustion diagnostic.Based on this strategy,a multi-nozzle-separation(MNS)burner is designed and fabricated,and the combustion processes associated with four model compounds,PVC,PS,PP/TBBA blends and PP/RP blends are investigated by spontaneous spectral diagnosis,and the chemiluminescence fingerprint of key diatomic/triatomic intermediates(such as OH,CH,C_(2),ClO,Br_(2),and PHO)are clearly observed.This encouraging result means that the strategy of spatial-confinement combustion we proposed shows promising prospect in many subjects associated with combustion chain regulation,such as efficient design of flame retardants.
基金the equipment support of Sharing Platform of Scientific Equipments,Ministry of Education's Research Center for Comprehensive Utilization and Clean Process Engineering of Phosphrous Resources,Sichuan University。
文摘A novel eco-friendly charring agent(L-OH)was successfully synthesized by combining pentaerythritol(PER)with lignin through a simple two-step reaction.The structure of L-OH was characterized using Fourier transform infrared(FTIR),X-ray diffraction(XRD),scanning electron microscopy(SEM)and EDS.In addition,L-OH was introduced into polypropylene(PP)together with melamine(MEL)and ammonium polyphosphate(APP)as an intumescent flame retardant(IFRR).The flame retardancy of PP/IFRR composites were investigated using limited oxygen index(LOI),UL-94,thermogravimetric analysis(TGA)and cone calorimeter(CC)test.The experimental results indicate that the PP/IFRR composites pass the V-0 grade of the UL-94 test when the addition amount of IFRR is no less than 20%,and the LOI value of the composite reaches 32.2%at 30%IFRR addition.The peak heat release rate(PHRR)and peak smoke production rate(PSPR)of the composite decrease by 72.8%and 70.4%compared with pure PP,respectively.The flame retardancy mechanism was investigated by TGA,TG-FTIR and residual carbon analysis.These analyses indicate that L-OH can form a more continuous and dense carbon layer during the combustion process,which is the main factor contributing to the improved flame retardancy of PP.
基金supported by the Key Research and Development Project of Shaanxi Province(No.2024GX-YBXM-331)the Scientific Research Plan Projects of Shaanxi Education Department(Program No.24JC009)the National Natural Science Foundation of China(No.22278260).
文摘Although lightweight aramid paper honeycombs are highly desirable for microwave absorption owing to their dual functions of both load-bearing and microwave-absorbing,unsatisfactory microwave absorption,inferior mechanical and inadequate thermal properties present significant challenges for practical applications in diverse complex scenarios.Herein,lightweight,high-strength and flame-retardant aramid nanofibers-based honeycombs(MANHs)for integrated microwave absorption and thermal insulation are successfully fabricated via the hydrogen bonding assembly,mold forming and aerogel filling strategy using aramid waste as raw material.The dense network structure formed by the interwoven aramid nanofibers(ANFs)in the honeycomb body acts as a framework endows the MANH with impressive mechanical performance,and the specific strength and toughness of MANH reach 153.6 MPa g^(−1) cm^(−3) and 13.9 MJ m^(−3),respectively,which are 3.5 and 19 times higher than those of commercial microwave absorption honeycombs(CMAH).The ultralight MXene/ANFs aerogels(a density of 25 mg cm^(−3))with multiscale pore structure filled in the honeycomb apertures give the honeycomb outstanding microwave absorption performance,with a minimum reflection loss of−62.5 dB,and can cover the entire X-band with a thickness of only 3.5 mm.Meanwhile,compared with CMAH,the thermal insulation and flame-retardant performance of MANH are also significantly improved.Notably,MANH also demonstrates favorable sound absorption performance at high-frequency bands.The MANH is considered to be a promising candidate for aerospace and military stealth applications as a result of its lightweight,high strength,exceptional microwave absorption,and remarkable thermal insulation performance.
基金Funded by the Fundamental Research Funds for the Central Universities(WUT:2023III012JL)。
文摘We aimed to enhance the flame retardancy of epoxy resin(EP)by synthesizing a novel,halogen-free flame retardant through a one-pot method.The synthesis utilized 9,10-dihydro-9-oxa-10-phospha-phenanthrene-10-oxide(DOPO),furfurylamine(FA),and benzene propionaldehyde(BPA)as raw materials.We conducted differential scanning calorimetry(DSC)analysis to investigate the effects of FPD on the curing process and thermal properties of EP.Our findings reveal that incorporating FPD into EP can facilitate a faster curing process and increase the carbon residue post-combustion.Specifically,the FPD/EP-7 composite demonstrates a limiting oxygen index(LOI)of 34.9%and achieves a UL-94V-0 rating with a phosphorus content of 0.91wt%.These results indicate that FPD significantly enhances the thermal stability and charring rate of EP,thereby improving its flame retardancy.Although the addition of FPD slightly reduces the mechanical properties of EP,the composite material maintains excellent performance.
