Superior Flame Retardancy Research Articles

Facile construction of lamellar-like phosphorus-based triazole-zinc complex for high-performance epoxy resins

Epoxy resins (EP) possessing superior flame retardancy, mechanical properties and glass transition temperature are urgently needed to meet the ever-increasing requirement of high performance for the practical application of EP. Herein, lamellar-like phosphorus-based triazole-zinc complex (Zn-PT) was firstly constructed through coordination reaction in a facile condition to address the above issue. The results revealed that Zn-PT was well dispersed in epoxy matrix, and with 3 wt% Zn-PT, the tensile strength, flexural strength and modulus of epoxy composites were remarkably increased from 71, 112 and 2982 MPa of neat epoxy resin (EP) to 80, 162 and 3482 MPa respectively. The glass transition temperature was higher than EP. Besides, the limiting oxygen index (LOI) increased to 28.3%, and UL-94V-1 level was available. Meanwhile, the cone calorimeter test (CCT) results showed that epoxy composites displayed less heat release and smoke production. Generally, this work provides a feasible strategy to prepare high-performance epoxy composites, which has the potential to satisfy the requirement of epoxy in the practical application.

Synthesis and performance characteristics of organic-inorganic hybrid fire prevention and extinguishing gel based on phytoextraction-medical stone

This study is aimed at lowering material costs and meanwhile achieving cleaner production by making full use of peanut shells, a kind of agricultural waste. To this end, cellulose nanofibrils (CNF) extracted from peanut shells were mixed with 2-acrylamide-2-methylpropanesulfonic acid (AMPS), medical stone (MDS) and acrylic acid (AA) for preparing biodegradable AA-AMPS-CNF/MDS gel for fire prevention and extinguishing (FPE). The experimental results show that the optimal water absorption rate and salt resistance performance of the prepared AA-AMPS-CNF/MDS FPE gel are achieved under the CNF: AMPS: MDS: AA ratio of 2: 1: 0.3: 14, the crosslinking agent amount of 1.8% and the initiator amount of 2.5%. The infrared spectroscopy and X-ray diffraction analysis results suggest that MDS, AA, AMPS and CNF have experienced copolymerization which leads to the formation of an amorphous structure. The scanning electron microscopy analysis results demonstrate that the product has an orderly three-dimensional structure containing voids on the whole, and elements in it are highly uniformly and densely distributed. Relevant test experiments show that the product has high water absorption and salt resistance. Through Hartmann tube test and inhibition performance test, as well as the combustion HRR curve of coal samples, the proposed FPE gel and mixed products, it is proved that the product has superior flame retardant effect. In addition, the effect and mechanism between the proposed FPE gel and coal is rarely reported in related researches. In this study, the proposed FPE mechanism and wetting effect of AA-AMPS-CNF/MDS are explained by means of molecular dynamic simulation (MS) simulation, which agrees with the above experimental results. The proposed FPE gel can effectively inhibit coal oxidation and lower coal temperature, thus protecting the physical and mental health of coal workers. In general, this research is of crucial economic and social benefits.

Fully recyclable, flame-retardant and high-performance carbon fiber composites based on vanillin-terminated cyclophosphazene polyimine thermosets

Carbon fiber reinforced polymer composites (CFRPs) have been widely applied in various high-tech fields because of their superior performance. However, with the increasing consumptions of CFRPs, the nondestructive recycling of expensive carbon fibers (CFs) and the reduction of fire-hazards are highly desirable for the sustainable and safe utilization of CFRPs. Herein, a fully recyclable CFRPs with high flame retardance was newly designed by incorporating the vanillin-terminated phosphazene monomer (HVP) into the polyimine binder material. The six-functional HVP monomer makes the polyimine thermosets have a high crosslinking density and high P/N content, thereby ensuring the excellent flame retardancy and mechanical performances of the resulted composites. And the preparation of this kind of composites just need simple hot-pressing at lower temperature and shorter time, which is more energy-saving and efficient. Owing to the degradable imine bonds, the nondestructive closed-loop recycling of CFs and HVP monomers from the composites are achieved under mild conditions, which is extremely vital to preserve the structure of virgin CFs and HVP functional monomer. The regenerated CFRPs displayed same performance with that of fresh ones, and it also could be reprocessed and repaired within few minutes at elevated temperatures. More importantly, due to the rational combination of cyclophosphazene and imine bond, the excellent synergistic effect of gas phase and condensed phase during combustion endows the composites with superior flame retardancy. This work prepared bio-based recyclable, flame-retardant CFRPs, offering a green, sustainable and fire-safe strategy for designing eco-friendly high-performance composites. ● A vanillin terminated cyclophosphazene (HVP) was synthesized through a facile one-step reaction ● Dynamic polyimine resin for CFRP was prepared by HVP and D230 without catalyst. ● High recyclability and flame retardance are simultaneously attained in this CFRP. ● The comprehensive properties of recycled CFs are same with that of virgin ones. ● Near total flame-retardant monomer HVP could be retrieved.

Structure Stability, Flame Retardancy, and Antimicrobial Properties of Polyurethane Composite Nanofibers Containing Tannic Acid and Boron‐Doped Carbon Nanotubes

AbstractA polyurethane (PU) composite nanofiber with superior flame retardancy and antimicrobial property is developed through the simultaneous incorporation of boron‐doped carbon nanotubes (CNTs) and tannic acid (TA), resulting in excellent thermal, mechanical, and eco‐friendly flame‐retardant properties. The tensile strength and peak heat‐release rate of the composite nanofiber increase with increasing filler content, with the optimal performance (7.38 ± 1.04 MPa and 254 W g−1) being achieved at 3 wt% filler. Using a series of analytical techniques, it is demonstrated that the nanostructure of the neat PU completely collapses upon heating, transforming into a film‐like structure; in contrast, a higher loading of nanofiller leads to a higher heat‐shielding capability, thereby facilitating preservation of the composite nanofiber structure. Finally, the antibacterial activity is shown to increase as a result of the synergic effect of the boron‐doped CNTs and TA.

Flame-retardant, transparent, mechanically-strong and tough epoxy resin enabled by high-efficiency multifunctional boron-based polyphosphonamide

It is of great significance to develop high-performance epoxy resins (EPs) combining superior flame retardancy, smoke suppression, thermal oxidation stability, transparency and mechanical properties. However, current flame retardant design strategy usually realizes satisfied flame retardancy at the expense of other properties. Herein, a novel multifunctional high-efficiency boron-containing polyphosphonamide (PB) is synthesized, and its impacts on integrated properties of EP are studied thoroughly. As expected, the well-designed PB features high flame retardant efficiency due to the combination of phosphorus, boron and nitrogen elements, only 3 wt% of which increases the limiting oxygen index (LOI) and UL-94 classification of EP thermoset to 32.2% and V-0, with a ~32.2% decrease in the peak smoke production rate (PSPR). Compared with the unmodified EP sample, the tensile strength, elongation at break and impact strength of EP sample with 3 wt% PB are elevated by ~29.8%, ~37.7% and ~50.2%, respectively. Meanwhile, high glass transmission temperature and transparency are maintained. Hence, this work offers an integrated strategy to develop highly efficient multifunctional polyphosphonamides for the preparation of high-performance flame-retardant and smoke-suppressive EPs combining high mechanical strength and toughness, thermal resistance and transparency, which are expected to meet the increasingly rigorous industrial requirements.

Synergy between piperazine pyrophosphate and aluminum diethylphosphinate in flame retarded acrylonitrile-butadiene-styrene copolymer

Acrylonitrile-butadiene-styrene (ABS) copolymer was combined with piperazine pyrophosphate (PAPP) and aluminum diethylphosphinate (AlPi) to prepare the flame retarded ABS (FRABS) composites by melt blending method. The PAPP/AlPi mixture with a mass ratio of 4:1 achieved an optimum synergy at a 25 wt.% flame retardant loading. The relevant composite (FRABS-3) reached the UL-94 V-0 rating (3.2 mm) and got a limiting oxygen index (LOI) of 30.8%. The synergistic flame retardancy mechanism of PAPP and AlPi was investigated using thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analyzer coupled with an FTIR spectrometer (TG-FTIR), cone calorimeter test (CCT), scanning electron microscope (SEM), and X-ray photoelectron spectroscopy (XPS). The synergism is based primarily on the Lewis acid-base interactions between PAPP and AlPi. The interactions lead to the formation of a cohesive, uniform, and thermally stable char layer before ABS starts to decompose. The barrier effect of the high-quality char layer plays a dominant role in reducing the flammability of FRABS-3. Furthermore, fuel dilution and flame inhibition effects of the evolved gases also contribute to the superior flame retardancy of FRABS-3 to some extent.

Experimental and numerical perspective on the fire performance of MXene/Chitosan/Phytic acid coated flexible polyurethane foam

Recent discoveries of two-dimensional transitional metal based materials have emerged as an excellent candidate for fabricating nanostructured flame-retardants. Herein, we report an eco-friendly flame-retardant for flexible polyurethane foam (PUF), which is synthesised by hybridising MXene (Ti_3hbox {C}_2) with biomass materials including phytic acid (PA), casein, pectin, and chitosan (CH). Results show that coating PUFs with 3 layers of CH/PA/Ti_3hbox {C}_2 via layer-by-layer approach reduces the peak heat release and total smoke release by 51.1% and 84.8%, respectively. These exceptional improvements exceed those achieved by a CH/Ti_3hbox {C}_2 coating. To further understand the fundamental flame and smoke reduction phenomena, a pyrolysis model with surface regression was developed to simulate the flame propagation and char layer. A genetic algorithm was utilised to determine optimum parameters describing the thermal degradation rate. The superior flame-retardancy of CH/PA/Ti_3hbox {C}_2 was originated from the shielding and charring effects of the hybrid MXene with biomass materials containing aromatic rings, phenolic and phosphorous compounds.

Superior flame retardancy of glass fiber-reinforced polyamide 6T composites by synergism between DOPO-based derivative and carbon nanotube

How to create high-performance flame-retardant semi-aromatic polyamide with minimum flame retardant loading remain a major challenge. Herein, glass fiber-reinforced polyamide 6T (GFPA6T) composites with superior flame retardancy were obtained by synergism between DOPO-based derivative (PN-DOPO) and carbon nanotube (CNT). The introduction of 9 mass% PN-DOPO and 1 mass% CNT into GFPA6T, which is significantly lower than the loading reported (15 mass%), leads to superior flame retardancy with V-0 rating during UL-94 test and a higher limiting oxygen index (LOI) value of 28.5%. Thermogravimetry, cone calorimeter and char residue analysis suggest that the addition of CNT can enhance the thermal stability and promote the formation of stable char layers, effectively protecting the matrix from fire. By quantitative analysis, the flame retardancy mechanism of the resulting GFPA6T composites includes three aspects: 14.3% flame inhibition, 8.5% charring effect and 34.7% protective-barrier effect. Besides, the introduction of CNTs can compensate the loss of mechanical properties due to the incorporation of flame-retardant PN-DOPO.

Bio-inspired and dual interaction-based layer-by-layer assembled coatings for superior flame retardancy and hydrophilicity of polyamide 6.6 textiles

A dual interaction-based (i.e., ionic/covalent) deposition of carbohydrate polymers, namely chitosan (CS) and oxidized sodium alginate (OSA) along with a plant-derived phosphorus-rich compound like phytic acid (PA) and a nitrogen rich compound like melamine (ME) was considered onto the phosphorylated chitosan (PCS) modified polyamide 6.6 (PA6.6) fabric surfaces in order to impart durable flame retardancy along with super-hydrophilicity of the same. Firstly, the pure PA6.6 textile surfaces were modified by PCS via UV-induced grafting and subsequently, the above-mentioned polyelectrolytes were assembled onto the fabric surfaces in a quadralayer fashion [i.e., (CS/ME-OSA-CS/ME-PA) n; “n” represents the number of quadralayers (QLs)]. Here, the amino groups of CS/ME and the aldehyde groups of the OSA were stabilized via covalent interaction and the deposition of positively charged CS/ME and negatively charged phytic acid (PA) formed ionic interaction. In the vertical burning (UL-94) test, both the only PCS grafted and the simultaneously PCS-grafted along with LbL assembled fabrics could completely stop the melt dripping tendency and attained a V-1 rating. In the meantime, the limiting oxygen index (LOI) value received a moderate increase from 18.5 % of pure PA6.6 to 23.5 % for the PCS grafted and 8-QLs deposited fabric sample (i.e., PA6.6-g-PCS-8QL). Moreover, the PA6.6-g-PCS-8QL fabric sample exhibited a dramatic decrease in the peak heat release rate (pHRR) and total heat release (THR) by about 45 % and 24.7 % respectively alongside enhanced thermal stability. Apart from the appreciable flame retardancy, this fabric sample (i.e., PA6.6-g-PCS-8QL) could boost up the hydrophilicity to attain a water contact angle of 0°. Finally, this dual interaction-based deposition of bio-inspired polyelectrolytes posed a positive impact in enhancing the coating stability in laundering and imparting durable flame retardancy to sustain even up to 20 laundering cycles.

Synergistic effect between piperazine pyrophosphate and melamine polyphosphate in flame retarded glass fiber reinforced polypropylene

Piperazine pyrophosphate (PAPP) combined with melamine polyphosphate(MPP) was adopted to prepare the flame retarded glass fiber reinforced polypropylene (FRGFPP) composites. The PAPP/MPP mixture with a 2:1 mass ratio achieved an optimum synergistic effect. The corresponding system (FRGFPP-4) passed the UL-94 V-0 classification (1.6 mm) and had an LOI value of 39.9%. Series of characterizations involving cone calorimeter test (CCT), thermogravimetric analysis (TGA), scanning electron microscope (SEM), Fourier transform infrared (FTIR) spectra, and thermogravimetric analyzer coupled with FTIR (TG-FTIR) were performed to investigate the synergistic mechanism. The synergism depends mainly on the strong interaction between PAPP and MPP. The interaction accelerates the formation of the high-quality char layer, which plays a dominant role in improving the flame retardancy and the thermal stability of FRGFPP-4. Additionally, flame inhibition and fuel dilution effects in the gas phase also contribute to the superior flame retardancy of FRGFPP-4.

Exceptionally flame-retardant flexible polyurethane foam composites: synergistic effect of the silicone resin/graphene oxide coating

A facile strategy was developed to fabricate flexible polyurethane (PU) foam composites with exceptional flame retardancy. The approach involves the incorporation of graphene oxide (GO) into a silicone resin (SiR) solution, which is then deposited onto a PU foam surface via the dip-coating technique and cured. Fourier-transform infrared spectroscopy, scanning electron microscopy, and Raman spectroscopy measurements demonstrated that the SiR and GO were successfully coated onto the PU skeleton and the intrinsic porous structure of the PU foam remained intact. The effects of SiR and GO on the mechanical and thermal stability and flame retardancy of PU composites were evaluated through compression tests, thermogravimetric analysis, vertical combustion tests, and the limiting oxygen index. The measurement results revealed that the composites (PU@SiR-GO) showed superior flame retardancy and thermal and mechanical stability compared to pristine PU or PU coated with SiR alone. The mechanical and thermal stability and the flame-retardant properties of the PU composites were enhanced significantly with increasing GO content. Based on the composition, microstructure, and surface morphology of PU@SiR-GO composites before and after combustion tests, a possible flameretardance mechanism is proposed. This work provides a simple and effective strategy for fabricating flame-retardant composites with improved mechanical performance.

A Novel Silicon/Phosphorus Co-Flame Retardant Polymer Electrolyte for High-Safety All-Solid-State Lithium Ion Batteries.

Developing a solid polymer electrolyte with superior flame retardancy and lithium-ion transportation properties is still a challenge. Herein, an intrinsic silicon/phosphorus co-flame retardant polymer solid electrolyte was prepared by using polyethylene glycol (PEG) co-polymerized with silicon and phosphorus-containing monomers. Due to the synergistic flame-retardant effect of silicon and phosphorus elements, this polymer electrolyte exhibits excellent thermal stability and flame resistance. Moreover, the ionic conductivity of the electrolyte at 25 °C is as high as 2.98 × 10−5 S/cm when the mass ratio of LiN(SO2CF3)2 (LiTFSI) and the prepared polymer electrolyte is 10:1. What is more, the LiFePO4/Li all-solid-state battery assembled with this solid electrolyte can work stably at a high temperature of 60 °C and exhibits a specific capacity of 129.2 mAh/g at 0.2 C after 100 cycles, providing a promising application prospect for high-safety lithium-ion batteries.

Synthesis of a novel organic–inorganic hybrid flame retardant based on Ca(H2PO4)2 and hexachlorocyclotriphosphazene and its performance in polyvinyl alcohol

AbstractTo optimize the poor thermal stability and flammable of polyvinyl alcohol (PVA), a novel environmental‐friendly organic–inorganic hybrid flame retardant Ca(H2PO4)2@HCCP was successfully designed and synthesized via surface treatment technology and used to advance the flame retardancy of PVA. The thermogravimetric analysis implied that Ca(H2PO4)2@HCCP can enhance significantly the thermal stability and char forming ability of PVA. Combustion results demonstrate that Ca(H2PO4)2@HCCP could effectively suppress the melt dripping of PVA in the process of combustion. The presence of Ca(H2PO4)2@HCCP can sharply reduce peak heat release rate and the total heat release up to 75% and 22.9%, respectively, in the microscale combustion calorimeter measurement. The results manifested that Ca(H2PO4)2@HCCP could endow PVA with superior flame retardancy. Moreover, char residues analysis explained the flame retardant mechanism in condensed and gas phase, which is mainly attributed to the strong catalytic char formation, free radical trapping, and gas barrier effect. Therefore, the green flame retardant has great applications prospect in fire safety.

Highly flame-retardant epoxy-based thermal conductive composites with functionalized boron nitride nanosheets exfoliated by one-step ball milling

Boron nitride nanosheet (BNNS) reveals a huge potential in preparing highly flame-retardant polymer-based thermal conductive composite, but is limited by its difficult exfoliation and functionalization. Here, hexagonal boron nitride (hBN) was simultaneously exfoliated and flame-retardant functionalized into BNNS via one-step ball milling process based on the synergetic effect of mechanical shear and chemical peeling of ammonium phosphate and sodium hydroxide. Then the epoxy (EP)-based composites containing hBN or BNNS were prepared by solution blending and program-controlled curing. The possible mechanochemical reaction mechanisms were proposed according to the incorporation of density functional theory (DFT) calculations and chemical structure characteristics. As one of potential applications, the obtained flame-retardant functionalized BNNS (BNNS1 and BNNS2) were used as multifunctional additives for fabricating high-performance EP-based thermal conductive composites with excellent flame retardancy. As expected, the obtained EP-based composites containing only 5 wt% BNNS exhibited a superior flame retardancy with a dramatic decrease in the values of peak heat release rate (PHRR), the total heat release (THR), the smoke production rate (SPR) and the total smoke production (TSP) corresponding to 60.9%, 35.7%, 44.3% and 38.8% reductions, respectively, compared to neat EP. The dramatical enhancement in flame retardancy was mainly attributed to the catalytic charring effect and physical barrier action of flame-retardant functionalized BNNS, led to the formation of a compact and robust char layer during combustion to protect the underlying polymer. Simultaneously, due to uniform dispersion and strong interfacial adhesion, the incorporation of BNNS not only increased the thermal conduction paths by increasing specific surface area, but also reduced the interfacial thermal resistance (Rb) caused by phonon scattering, leading to an enhancement (312.4% and 397.0%) in the TC of EP/BNNS composites at 30 wt% BNNS1 and BNNS2, respectively.

Novel alkynyl-containing phosphonate ester oligomer with high charring capability as flame retardant additive for thermoplastic polyurethane

Phosphonate esters may be used as flame retardants for flammable polymers, but always face low flame-retardant efficiency and melt dripping. Until now, no remarkable progress was made in solving the above two defects, thus tremendously affecting their applications as flame retardants. In current work, from the chemistry viewpoint, we designed and synthesized poly(2-butyne-1,4-diol phenylphosphonate) (PPBP) containing alkynyl group to break through above-mentioned defects. Compared with the corresponding control sample poly(1,4-butanediol phenylphosphonate) (PPBOP) without alkynyl, thermal analysis revealed that residual char of the PPBP with CC bonds increased to 45.0%, much higher than 1.6% for the PPBOP without CC bonds, and greatly increased by 27 folds. Various measurements and kinetic analysis were used to investigate the underlying cause for the leap in charring. It turns out that PPBP was involved in a unique decomposing and crosslinking process upon heating, which played a vital role in the leap in charring for PPBP. The leap in charring might afford polymers better flame retardancy through condensed phase. After incorporation of the PPBP into thermoplastic polyurethane (TPU), burning tests illustrated that PPBP not only endowed TPU with excellent flame retardancy and anti-melt dripping performance, but also resulted in extremely low heat release rate and smoke production rate, correspondingly decreased by 70.7% and 53.9% compared with those of TPU. Various measurements further confirmed that the charring caused by PPBP itself and the enhanced charring of TPU induced by PPBP played a crucial role in the remarkable superior flame retardancy of TPU/PPBP.

Corrosion Behavior of Diecast Mg–Al–Mn–Ca–Si Magnesium Alloy

The corrosion behavior of diecast Mg–Al–Mn–Ca–Si (AMXS6020) magnesium alloy with superior flame-retardance and heat-resistance was systematically investigated and compared to diecast AZ91D magnesium alloy and ADC12 aluminum alloy by salt spray test, cyclic corrosion test, electrochemical experiment, scanning electron microscopy and energy dispersive X-ray spectroscopy. The results showed that AMXS6020 alloy had a higher corrosion resistance than AZ91D and ADC12 alloys. The superior corrosion resistance of AMXS6020 alloy was attributed to netlike eutectic structure consisting of (Al, Mg)2Ca and α-Mg, which could hinder the corrosion growth. The barrier effect of netlike (Al, Mg)2Ca phase structure on corrosion growth was also confirmed by potentiodynamic polarization.

Strategy for constructing electromagnetic interference shielding and flame retarding synergistic network in poly (butylene succinate) and thermoplastic polyurethane multilayered composites

Fabricating electromagnetic interference (EMI) shielding materials with excellent flame retarding properties is significant to attenuate undesirable electromagnetic waves caused by electronic devices and simultaneously improve the flame safety of the electronic components. Herein, a novel EMI shielding composite with multilayered structure was fabricated at a low particle loading via layer-multiplying coextrusion technology. Especially, within the multilayered composites, poly (butylene succinate) (PBS) filled with carbon nanotubes (CNTs) was used to construct conducting layer while thermoplastic polyurethane (TPU) filled with intumescent flame retardants (IFRs) and CNTs was used to construct synergistic flame-retarding layer. The content of CNTs and IFRs in the whole system were below 4 wt% and 20 wt%, respectively. Morphological observation demonstrated the alternating multilayered structure and the selective distribution of IFRs and CNTs. Besides, by tailoring the layer numbers, the composites showed tunable EMI shielding and flame retarding performances. With regard to EMI shielding performance, the absorption-dominated average EMI shielding effectiveness (SE) values of both 8- and 16-layer specimens exceeded 30 dB in the range of 8.2–12.4 GHz. Furthermore, superior flame retardancy with prompt self-extinguishment and anti-dripping was achieved in these specimens owning to the production of continuous and foaming carbonaceous structure among layers. Especially the 8-layer specimen, the UL-94 rating was categorized in V-0. Consequently, this work provided a promising and facile route to fabricate polymeric composites simultaneously possessing excellent EMI shielding and flame-retarding properties to fulfill the stringent requirements in practical application.

Flame-retardant concentrated electrolyte enabling a LiF-rich solid electrolyte interface to improve cycle performance of wide-temperature lithium–sulfur batteries

Abstract Lithium–sulfur batteries have been regarded as the most promising high-energy electrochemical energy storage device owing to the high energy density, low cost and environmental friendliness. However, traditional lithium–sulfur batteries using ether-based electrolytes often suffer from severe safety risks (i.e. combustion). Herein, we demonstrated a novel kind of flame-retardant concentrated electrolyte (6.5 M lithium bis(trifluoromethylsulphonyl)imide/fluoroethylene carbonate) for highly-safe and wide-temperature lithium–sulfur batteries. It was found that such concentrated electrolyte showed superior flame retardancy, high lithium-ion transference number (0.69) and steady lithium plating/stripping behavior (2.5 mAh cm−2 over 3000 h). Moreover, lithium–sulfur batteries using this flame-retardant concentrated electrolyte delivered outstanding cycle performance in a wide range of temperatures (−10 °C, 25 °C and 90 °C). This superior battery performance is mainly attributed to the LiF-rich solid electrolyte interphase formed on lithium metal anode, which can effectively suppress the continuous growth of lithium dendrites. Above-mentioned fascinating characteristics would endow this flame-retardant concentrated electrolyte a very promising candidate for highly-safe and wide-temperature lithium–sulfur batteries.

Application of Chitosan and DOPO derivatives in fire protection of polyamide 66 textiles: Towards a combined gas phase and condensed phase activity

A DOPO-based phosphorus compound (DOPA) was synthesized and applied onto the pure and chitosan (CS) modified polyamide 66 (PA66) fabric surfaces via a simple pad-dry-cure method to improve the flame retardant properties of the same. The pure and chitosan modified fabric samples treated with DOPA at different content % degraded in a different way as the char residue formation and releasing of volatile and non-volatile gas species were dissimilar which were evident from the thermogravimatric and thermogravimetric-gas chromatography-mass spectroscopy (TG-GC-MS) test analysis. Obtained results also showed that no dripping occurred in the vertical burning test and a sharp increase in limiting oxygen index (LOI) values was noticed for all the treated fabric samples. CS modified PA66 fabric sample treated with a 10 wt % of DOPA exhibited a greater reduction in pHRR by 40% and showed superior flame retardant performance compared to the only DOPA treated pure fabric sample. The superb flame retardant properties of CS modified fabrics were due to the co-presence of DOPA and CS; where a synchronized gas phase and a condensed phase flame retardant mechanism was realized as DOPA showed a quenching effect in a gas phase mechanism and simultaneously, catalyzed the charring of CS in a condensed phase activity which was also justified from the TG-GC-MS analysis, TGA and FTIR analysis of char residues. However, this kind of facile application showed poor wash durability and deteriorated the physical properties of the fabric materials specifically treated with a higher DOPA content.

A DOPO-based phosphorus-nitrogen flame retardant bio-based epoxy resin from diphenolic acid: Synthesis, flame-retardant behavior and mechanism

Searching a renewable and flame-retardant alternative to bisphenol A epoxy resins is a necessary development trend. Diphenolic acid, a plant derivative, has been proven to be one of the sustainable alternatives to bisphenol A. However, how to impart the flame-retardant property to diphenolic acid thermosets is still a challenge to synthesize high performance intrinsic flame-retardant bio-based epoxy resins. A flame-retardant bio-based epoxy resin (TEBA) was designed and synthesized via a three-step synthetic pathway from 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO)、diethanolamine and diphenolic acid (DPA). The chemical structures of the intermediate and final products were confirmed by 1HNMR and FTIR spectroscopy. TEBA cured with 4,4′-diaminodiphenylmethane (DDM) curing agent was compared with a standard bisphenol A epoxy resin (DGEBA). Due to the combination of phosphorus and nitrogen in the main chain, the TEBA-DDM shows superior flame retardancy. Compared with DGEBA-DDM, LOI of TEBA-DDM increased from 25.8% to 42.3%, UL-94 test rating from no rating to V-0 rating, self-extinguishing within 3s. The peak heat release rate (PHRR) in the cone calorimetry test decreased by 67%. total heat release (THR) and total smoke generation (TSP) decreased by 27% and 35%, respectively. In addition, the flame retardant mechanism of TEBA epoxy thermosets was researched by FTIR, residual char photograph, SEM, TG-IR analysis and Raman spectroscopy. Meanwhile, TEBA-DDM and DGEBA-DDM have comparable mechanical properties.