Microcapsule Modification Strategy Empowering Separator Multifunctionality to Enhance Safety of Lithium-Metal Batteries.

The uncontrollable growth of lithium dendrites and the flammability of electrolytes are the direct impediments to the commercial application of high-energy-density lithium metal batteries (LMBs). Herein, this study presents a novel approach that combines microencapsulation and electrospinning technologies to develop a multifunctional composite separator (P@AS) for improving the electrochemical performance and safety performance of LMBs. The P@AS separator forms a dense charcoal layer through the condensed-phase flame retardant mechanism causing the internal separator to suffocate from lack of oxygen. Furthermore, it incorporates a triple strategy promoting the uniform flow of lithium ions, facilitating the formation of a highly ion-conducting solid electrolyte interface (SEI), and encouraging flattened lithium deposition with active SiO2 seed points, considerably suppressing lithium dendrites growth. The high Coulombic efficiency of 95.27% is achieved in Li-Cu cells with additive-free carbonate electrolyte. Additionally, stable cycling performance is also maintained with a capacity retention rate of 93.56% after 300 cycles in LFP//Li cells. Importantly, utilizing P@AS separator delays the ignition of pouch batteries under continuous external heating by 138 s, causing a remarkable reduction in peak heat release rate and total heat release by 23.85% and 27.61%, respectively, substantially improving the fire safety of LMBs.

Peanut Shell Derived Carbon Combined with Nano Cobalt: An Effective Flame Retardant for Epoxy Resin.

Biomass-derived carbon has been recognised as a green, economic and promising flame retardant (FR) for polymer matrix. In this paper, it is considered that the two-dimensional (2D) structure of carbonised peanut shells (PS) can lead to a physical barrier effect on polymers. The carbonised sample was prepared by the three facile methods, and firstly adopted as flame retardants for epoxy resin. The results of thermal gravimetric analysis (TGA) and cone calorimeter tests indicate that the carbon combined with nano Cobalt provides the most outstanding thermal stability in the current study. With 3 wt.% addition of the FR, both peak heat release rate (pHRR) and peak smoke production rate (PSPR) decrease by 37.9% and 33.3%, correspondingly. The flame retardancy mechanisms of the FR are further explored by XPS and TG-FTIR. The effectiveness of carbonised PS can be mainly attributed to the physical barrier effect derived by PS's 2D structure and the catalysis effect from Cobalt, which contribute to form a dense char layer.

Air-Stable Polyphosphazene-Functionalized Few-Layer Black Phosphorene for Flame Retardancy of Epoxy Resins.

Similar to graphene, few-layer black phosphorus (BP) features thermal stability, mechanical properties, and characteristic dimension effects, which has potential as a new member of nanofillers for fabricating polymer nanocomposites. Herein, a cross-linked polyphosphazene-functionalized BP (BP-PZN) is developed with abundant -NH2 groups via a one-pot polycondensation of 4,4'-diaminodiphenyl ether and hexachlorocyclotriphosphazene on the surface of BP nanosheets. Whereafter, the resulting BP-PZN is incorporated into epoxy resin (EP) to study the flame-retardant property and smoke suppression performance. Cone results show that the introduction of 2 wt% BP-PZN distinctly improves the flame-retardant property of EP, for instance, 59.4% decrease in peak heat release rate and 63.6% reduction in total heat release. The diffusion of pyrolysis products from EP during combustion is obviously suppressed after incorporating the BP-PZN nanosheets. Meanwhile, the EP/BP-PZN nanocomposites exhibit air stability after exposure to ambient conditions for four months. The air stability of the BP nanosheets in EP matrix is assigned to surface wrapping by PZN and embedded in the polymer matrix as dual protection. As a new member of the 2D nanomaterials, BP nanosheets have potential to be a new choice for fabricating high-performance nanocomposites.

Ethanol inducing self-assembly of poly-(thioctic acid)/graphene supramolecular ionomers for healable, flame-retardant, shape-memory electronic devices.

In recent years, flexible electronic devices have great application potential in the fields of healthcare, VR virtual reality, electronic skin and intelligent robots. However, electronic devices fail during operation due to fatigue, corrosion or damage, making it difficult and expensive to maintain highly integrated portable/wearable electronic devices. In this study, highly healable, flame retardant, shape memorized supramolecular PTAZ/GO was fabricated by restricting the crosslinking of zinc ions, carboxyl graphene and poly-(thioctic acid) via self-polymerization in ethanol inducing self-assembly. The rich carboxyl groups associated with hydroxyl and disulfide groups in the system provide excellent self-healing efficiency and shape memory properties for supramolecular ionomers. The results of a microscale combustion calorimeter (MCC) test in this study showed a 65.3 % reduction in the peak heat release rate (pHRR) for ionomers compared to pure polymer, thus implying that ionic coordination cross-linking and GO nanosheets are beneficial for improving the fire safety of the materials. For the shape-memory device, the supramolecular elastomers can switch LED lights on and off by changing the shape, and the conductivity can be restored after reconnection of two damaged parts. Thus, the proposed materials have wide applications in electronic engineering.

Preparation of BMI monomers containing phosphate and phosphonate structure to enhance the flame retardant and toughness of BMI.

Aiming at enhancing the toughness and fire safety of bismaleimide (BMI), BMI monomers containing phosphate and phosphonate structure (BDTP and BDTDP) were designed and prepared. With incorporation of 5 wt% BDTP and BDTDP, the peak value of heat release rate (PHRR) of BMI/BDTP-5 and BMI/BDTDP-5 decrease by 59.4% and 52.4%, respectively. The total smoke production (TSP) of BMI/BDTP-5 and BMI/BDTDP-5 are of 8.3% and 13.1% reduction, respectively. Meanwhile, BMI/BDTP-5 and BMI/BDTDP-5 possess UL-94V-0 rating, which indicates that BMI is endowed with better flame retardant performance by modification of designed BMI monomers. Besides, the impact strength of BMI/BDTP-5 and BMI/BDTDP-5 increase by 146.3% and 90.2%, respectively. The comprehensive performance of BMI/BDTP-5 is better than that of BMI/BDTDP-5. And the effect of phenyl phosphate structure in BDTP and phenyl phosphonate structure in BDTDP on BMI performance is explored.

Covalent grafting diazotized black phosphorus with ferrocene oligomer towards smoke suppression and toxicity reduction.

In comparison with the thermal hazard of polymers, noxious smoke and gas produced by the combustion of polymers make the environment self-purification a huge challenge. As a new type of a highly effective flame retardant, black phosphorus (BP) can effectively decrease the thermal hazard of polymers, but its performances in smoke suppression and toxicity reduction are unsatisfactory. In this article, a method of covalently grafting diazotized BP with a ferrocene oligomer was applied to promote the smoke suppression and toxicity reduction efficiency of BP. In our work, the BP-NH nanomaterials with a mass of amino groups on the surface were acquired by diazotizing the BP. Then, the BP-Fe was obtained by covalently grafting the ferrocene chloride salt and nitrogen-containing heterocycles on the surface of BP. The smoke production rate (SPR) and total smoke production (TSP) values of the epoxy resin (EP) decreased by 49.8% and 52.5% with the addition of 2 wt% BP-Fe, respectively. In comparison with previous studies, this work was far more effective than the previous work in smoke suppression and flame retardant. The release of toxic gases (CO and HCN) and volatile organic compounds in the EP was also effectively inhibited at the same time. In addition, the storage modulus and tensile strength of nanocomposites increased by 35.1% and 27.2% with the addition of 1 wt% BP-Fe. This work also provides a new idea on how to simultaneously strengthen the toxic smoke suppression, mechanical properties, and flame retardant of polymer materials.

Construction of super-hydrophobic, highly effective flame retardant coating for cotton fabric with superior washability and abrasion resistance.

In order to meet the rapidly growing demand of multi-functional fabric, a super-hydrophobic flame retardant coating for cotton fabric with superior washability and abrasion resistance was prepared. Flame retardant finishing agent P, P-diphenyl-N-(3-(trithoxysilyl) propyl) phospinic amide (DPTES) and hydrophobic finishing agent polydimethylsiloxane @silicon dioxide (PDMS@SiO2) were fixed on the surface of cotton fabric by a simple sol-gel technology in combination with convenient brush-coating process. The coated cotton fabric was capable of self-extinguishing a flame, and the Limiting Oxygen Index (LOI) increased from 18.0% for the control cotton fabric to 26.0% for the treated one at weight gain of 30.3%. The water contact angle (WCA) of C3-PDMS-silica is around 154°, and the slip angle is 8°. In addition, the treated cotton fabric exhibits anti-washing and self-cleaning ability due to the superhydrophobic feature and superior friction resistance. The C3-PDMS-silica sample with excellent char-forming ability, as shown by thermogravimetric analysis (TGA), leading to outstanding flame retardancy. A composite char layer was constituted with char residues and ceramic layer during the combustion of inorganic silicon, which plays the role of heat insulation and flame retardant.

High-performance flexible polyurethane foam based on hierarchical BN@MOF-LDH@APTES structure: Enhanced adsorption, mechanical and fire safety properties.

Improving resilience, enhancing fire safety and adsorption properties were the key points for the preparation of high-performance flexible polyurethane foam (FPUF). Here, MOF-derived petal-like Co/Mg-double metal hydroxide (Co/Mg-LDH) and 3-aminopropyltriethoxysilane (APTES) were selected to modify the hydroxylated boron nitride (BNNS-OH) to obtain a hydrophobic BN@MOF-LDH@APTES. Compared with the previous work, BN@MOF-LDH@APTES demonstrated extremely high filler efficiency in reducing the heat release per unit mass (THR/TM) (18.2 % reduction) and smoke production per unit mass (TSP/TM) (19.1% reduction) of FUPF during combustion. In addition, the obtained FPUF nanocomposite exhibited high absorption capacity while achieving remarkable thermal stability and fire safety. Moreover, the FPUF nanocomposite containing 1 wt% BN@MOF-LDH@APTES achieved a 71% increase in compressive strength, indicating excellent resilience. Therefore, this work provided a new material for the preparation of high-resilience FPUF with both flame retardancy and adsorption capacity.

Revealing and modeling of fire products in gas-phase for epoxy/black phosphorus-based nanocomposites.

This work aims at revealing and optimizing the mechanism, to promote the design of phosphorus-based flame retardants (PFRs) for controlling the spread of fire risk caused by the continuous spread of polymers. Herein, we synthesized about 10 nm TiO2 grown in situ on the surface of BP through a simple hydrothermal procedure to introduce it into epoxy (EP/BP-TiO2). In the first place, EP/BP-TiO22.0 nanocomposite achieves a reduction of 58.96% and 50.35% in PHRR and THR, respectively. Secondly, the pyrolysis of BP from Pn to P4, P3 and P2 is revealed. As a guide, P4 is established as a characteristic product of the analytical model for evaluating the effects in the gas phase for BP-based hybrids. Finally, this work clarifies the enhancement path for BP-TiO2 is optimized for the capturing of OH· and H· radicals by P4(POx). Crucially, this study reveals and controls the mechanism of the BP-based hybrids at the molecular level, which is expected to provide a promising analytical model for broad market PFRs design to address the risks and challenges of casualties and ecology caused by composites fire.

Exploration on structural rules of highly efficient flame retardant unsaturated polyester resins.

Owing to the lack of research on structure-activity relationship and interaction mechanism between unsaturated polyester resins (UPR) and flame retardants, it has been a big challenge to prepare high-efficiency flame retardants for UPR in industry. In this research, to explore structural rules of high-efficiency flame retardants, several polymeric flame retardants were synthesized with varied main-chain, side-chain, phosphorus valence states and contents of flame retardant elements. The thermal stabilities of flame retardants and UPR composites were firstly assessed. It has been found the interaction existed between flame retardants and UPR, through transesterification reaction and ß scission pathway in polyester and polystyrene chains. With only 15 wt% of PCH3-S, UPR composites can reach V0 rating in UL-94. The PHRR and THR values can be maximumly decreased by 71.66 % and 77.67 %, with 20 wt% of PB-S. It has been found flame retardants with sulfone group and + 3 valence state of phosphorus in molecular backbone can release SO2 and phosphorus containing compounds in gaseous phase, which diluted fuel fragments and catalyzed H⋅ and HO⋅ radical removal. The mechanism for improved flame retardancy of UPR composites with various polymeric flame retardants were discussed in detail. Some general rules for highly efficient flame retardant UPR can be summarized: First, gaseous phase flame retardant mechanism plays the major role in improvement of flame retardant performance of UPR composites; Second, the combination of + 3 valence state of phosphorus structures, higher phosphorus contents and sulfone groups effectively improves the flame retardant efficiency of flame retardants.

Hindered phenolic antioxidant passivation of black phosphorus affords air stability and free radical quenching.

As an antioxidant, hindered phenol scavenges free radicals. Due to the oxidative degradation of black phosphorus (BP) in the presence of water and oxygen, free radical quenching of hindered phenol antioxidants can solve this issue and improve the environmental stability and flame retardant efficiency of BP. Herein, hydroxyl-modified BP (BP-OH) with active groups on the surface was obtained by hydroxylation, and then the hindered phenol antioxidant was grafted onto the surface of BP-OH through an isophorone diisocyanate bridging covalent reaction to obtain hindered phenol-modified BP (BP-HPL). The fire hazard of thermoplastic polyurethane (TPU) can be significantly reduced by introducing BP-HPL into TPU. Adding 2 wt% BP-HPL can reduce the heat release rate and total heat release values of TPU by 49.9% and 49.0%, respectively. In addition, the reductions in smoke volume and carbon monoxide production were also significant. Compared with BP-OH, the environmental stability of BP-HPL is significantly improved. This work provides a reference for the application of BP in the field of fire safety and simultaneously achieves the improvement of the environmental stability and flame retardant performance of BP.

Biodegradable L-lysine-modified amino black phosphorus/poly(l-lactide-coε-caprolactone) nanofibers with enhancements in hydrophilicity, shape recovery and osteodifferentiation properties.

Biodegradable poly-(lactide-coε-caprolactone) (PLCL) scaffolds have opened new perspectives for tissue engineering due to their nontoxic and fascinating functionality. Herein, a black phosphorus-based biodegradable material with a combination of promising enhanced hydrophilicity, shape recovery and osteodifferentiation properties was proposed. First, amino black phosphorous (BP-NH2) was prepared by a simple ball milling method. Then, L-lysine-modified black phosphorous (L-NH-BP) was formed by hydrogen bonding between L-lysine and amino BP and integrated into PLCL to form PLCL/L-NH-BP composite fibers. The scaffolds had excellent shape recovery and shape fixity properties. Moreover, based on gene expression and protein level assessment, the scaffolds could enhance the expression of alkaline phosphatase (ALP) and bone morphogenetic protein 2 (BMP2), simultaneously improving the mineralization ability of bone mesenchymal stem cells. Specifically, this new composite material was experimentally verified to be degradable under mild conditions. This strategy provided new insight into the design of multifunctional materials for diverse applications.

Construction of few-layered black phosphorus/graphite-like carbon nitride binary hybrid nanostructure for reducing the fire hazards of epoxy resin.

Black phosphorus (BP) and graphite-like carbon nitride (g-C3N4) were combined to prepare BP-CN hybrid nanostructure through a simple self-assembly method assisted by ultra-sonication, and as-obtained materials were further used as fire retardants introduced into epoxy resin to fabricate EP/BP-CNx nanocomposites. It was found that the introduction of 2 wt% BP-CNx into EP contributed to considerable decrements in peak heat release rate (up to 47.72%) and total heat release (utmost to 49.60%) of composites, and LOI value increased from 25% to 31%. SSTF results revealed that the introducing of BP-CN can distinctly reduce the production of smoke. TG-IR results demonstrated that the addition of BP-CN0.5 and BP-CN2.0 into EP matrix exert different influences on the decomposition of resin. Analyses of residual chars further validated through adjusting the proportion of BP and CN can achieve different fire performances of matrix. This work illustrates that BP can reduce the fire hazards of EP, and the hybridization of CN can achieve better flame retarded efficiency, which provides a new strategy for black phosphorus to be used as a flame retardant.

Facilely produced highly adhered, low thermal conductivity and non-combustible coatings for fire safety.

Fire resistant coatings have been proven as an efficient way to improve fire safety in three aspects: reducing the Heat Release Rate (HRR), delaying the ignition time and preventing heat transfer. Herein, a SiO2 based polymeric composite coating with a lower thermal conductivity and brilliant fire resistance was developed. Isocyanate and sodium silicate could form the final Si-O-Si network structure by polymerization. Compared to the wood without coating, the coated wood shows a significantly increase in limit oxygen index (LOI), has reached 48.0 vol% in the test. As for the cone calorimetry test, coated wood shows a 55.3% decrease in the first peak Heat Release Rate (pHRR) and the Total Heat Release (THR) obtains fire-resistant standard. After exposed to butane flame for 30 mins, the coated wood could still maintain its structural integrity with only 180℃ on the non-exposed side. The commercial standard test of the coating was also investigated. To better understand what role does the polyurea play in the system, a theoretical calculation was done during the research to discuss the interaction between the silica and polyurea. As a fast brush-formed coating, it exhibits a great potential in the field of fire-resistant materials, and may broaden the application prospects of wood.

Supramolecular wrapped sandwich like SW-Si3N4 hybrid sheets as advanced filler toward reducing fire risks and enhancing thermal conductivity of thermoplastic polyurethanes.

A sandwich-like melamine/phytic acid/silicon nitride hybrid (SW-Si3N4) sheets were prepared by supramolecular wrapping as the hybrid flame retardants for thermoplastic polyurethane (TPU). The introduction of Si3N4 sheets as a template could not only induce the generation of two-dimensional phytic/melamine (PAMA) capping layers, but also produce the synergistic flame-retardant effect on TPU composites. Cone test showed that heat release rate (HRR), smoke production rate (SPR) and total smoke production (TSP) values of TPU were decreased obviously by adding SW-Si3N4. TG-IR test indicated the dramatic inhibition of aromatic compound, hydrocarbons, CO and HCN release. Besides, the thermal conductivity of composites was obviously improved by adding SW-Si3N4. This work may provide better reference for developing multi-functional TPU composites for diverse application.

Polypyrrole-Coated Mesoporous TiO2 Nanocomposites Simultaneously Loading DOX and Aspirin Prodrugs for a Synergistic Theranostic and Anti-Inflammatory Effect.

Although a number of therapeutic strategies have been applied in cancer therapy, treatment for cancer metastasis is challenging due to unsatisfactory cure rate and easy cancer recurrence. In our work, nanocomposites (NCs) based on polypyrrole-coated mesoporous TiO2 with a suitable size are prepared through a modified soft-templating strategy, which integrates double prodrugs (doxorubicin (DOX) prodrug and aspirin prodrug) with superior drug loading capacity. Under external stimulation of near-infrared (NIR) and ultrasound (US), the prepared nanocomposites have an excellent photothermal conversion efficiency (over 50.8%) and a satisfactory sonodynamic therapeutic effect, and simultaneous prodrug activation and drug release occur rapidly under external stimulation. Through intravenous injection, the tumor area can be clearly seen through thermal imaging, benefiting from the enhanced permeability and retention (EPR) effect. Through synergistic therapy, cancer cell toxicity and the tumor inhibition effect are significantly enhanced. Moreover, downregulated inflammatory factors also reduce the risk of cancer recurrence. In general, the designed NCs provide a potential alternative for synergistic therapy as well as downregulation of inflammatory cytokines.

Nacre-Inspired Black Phosphorus/Nanofibrillar Cellulose Composite Film with Enhanced Mechanical Properties and Superior Fire Resistance.

Natural nacre offers an optimized guiding principle for the assembly of lightweight and high-strength nanocomposites with excellent mechanical properties. Inspired by the "brick-and-mortar" layered structure of natural nacre, we present a cohort of bioinspired nanocomposites consisting of nanofibrillar cellulose (NFC) and few-layer hydroxyl functionalized black phosphorus (BP-OH) via a vacuum-assisted filtration self-assembly procedure. Owing to the well dispersed two-dimensional (2D) BP-OH in one-dimensional (1D) NFC and strong interfacial hydrogen bonding between them, these novel nacre-like BP-OHx/NFC composite films show excellent mechanical performance with tensile strength up to 214.0 MPa, 300% increase compared to pure NFC and tensile fracture strain up to 23.8%, 1.8 times higher than that of pure NFC. Moreover, these nacre-like composite films bare good fire resistance and high thermal stability. This nacre-inspired approach demonstrates a promising strategy for designing high-performance BP-OHx/NFC composite film, and the obtained bioinspired material could be a potential candidate in the application of flexible construction materials and flame retarded insulation materials.

Construction of graphite oxide modified black phosphorus through covalent linkage: An efficient strategy for smoke toxicity and fire hazard suppression of epoxy resin.

The black phosphorus (BP) can be compounded with other two-dimensional materials with flame retardant effect to achieve better synergistic effect. Herein, the multifunctional BP-RGO nanohybrids was fabricated by solvothermal strategy to improve the dispersion state of BP in epoxy resin (EP) and enhance its fire safety performance, where the reduced graphene oxide (RGO) was attached on the surface of BP via PC and POC bonds. With the incorporation of 2.0 wt% BP-RGO into EP matrix, 54.4 % reduction in total heat release (THR) was achieved along with 55.2 % decrease in peak heat release rate (PHRR) compared with neat EP. As a similar trend, the toxic CO and aromatic compounds were significantly inhibited, and the maximum decrease (28.5 %) in total smoke production (TSP) was achieved, indicating the enhanced fire safety performance of EP nanocomposites. These positive results is attributed to the synergistic effect of physical nano-barrier, free radicals trapping and char formation between BP and RGO components. Meanwhile, the EP/BP-RGO2.0 nanocomposites exhibited satisfying air stability even after being immersed in water for a month. This work enriches the strategies for enhancing the air stability of BP, and confirms its potential for smoke toxicity and fire hazard suppression in polymer nanocomposites.

Combination of black phosphorus nanosheets and MCNTs via phosphoruscarbon bonds for reducing the flammability of air stable epoxy resin nanocomposites.

As a rising star of two-dimensional material, black phosphorus (BP) has attracted tremendous attention in applications of photovoltaics, transistors and batteries due to its unique characteristics. Inspiring, we developed a simple strategy to fabricate BP-MCNTs as highly promising inorganic phosphorus-based flame retardant. After incorporation 2 wt% BP-MCNTs11(the mass ratio of BP:MCNTs=1:1) nanohybrid, the peak of heat release rate and total heat release of EP nanocomposites reduced by 55.81% and 41.17% at a phosphorus content of only 1 wt%, and the comprehensive index FGI for evaluating the flame retardant of materials decreased from 17.35 to 6.97. In addition, the typical flammable volatile are suppressed significantly, and the first stage of carbon monoxide release is disappeared. The improvement of fire safety and inhibition of smoke toxicity could be attributed to the the synergistic effects of nano-barrier, catalytic charring and radicals trapping of BP-MCNTs nanohybrid. More importantly, BP hybrid with MCNTs and wrapped in EP matrix which formed effective isolation protection against the ambient degradation. Raman spectra and SEM results confirmed that EP/BP-MCNTs performed enhanced ambient stability than EP/BP-BS nanocomposites after three months. This study demonstrates its great potential for preparation of air-stable BP based nanocomposites with enhanced fire safety.

Bi2Se3 decorated recyclable liquid-exfoliated MoS2 nanosheets: Towards suppress smoke emission and improve mechanical properties of epoxy resin.

Bimetallic compounds have been proved superior suppression effect on smoke emission during combustion of polymers. In this work, MoS2/Bi2Se3 (MB) hybrids were prepared by a facile wet chemical method and showed superior performance on smoke suppression of EP matrix during combustion. N-vinyl pyrrolidone (NVP) was employed to exfoliate molybdenum disulfide (MoS2) nanosheets in a recyclable method, which showed high efficiency and was recyclable. Exfoliated MoS2 exhibited large surface area and used as carriers to synthesize MB hybrids. Considering the catalytic effect of bismuth and molybdenum, the hybrids had a great influence on the smoke emission behaviors of EP composites. The smoke production was obviously suppressed during the flaming combustion (more than 22% and 23% decrease obtained from cone calorimeter and steady state tube furnace, respectively) or smolder processes (more than 23% decrease obtained from smoke chamber) at only 1 wt% content of MB hybrids. What's more, due to superior dispersion state, the addition of MB hybrids also enhanced the mechanical properties of EP matrix, including wear resistance and tensile property. This work provided a safe and green exfoliation method of MoS2 to prepare polymers/MoS2 composites and also constructed a novel binary hybrids for enhancing combination performances of polymers.