Strong, tough and environment-tolerant organohydrogels for flaw-insensitive strain sensing.

Conductive organohydrogels are promising for strain sensing, while their weak mechanical properties, poor crack propagation resistance and unstable sensing signals during long-term use have seriously limited their applications as high-performance strain sensors. Here, we propose a facile method, i.e., solvent exchange assisted hot-pressing, to prepare strong yet tough, transparent and anti-fatigue ionically conductive organohydrogels (ICOHs). The densified polymeric network and improved crystallinity endow ICOHs with excellent mechanical properties. The tensile strength, toughness, fracture energy and fatigue threshold of ICOHs can reach 36.12 ± 4.15 MPa, 54.57 ± 2.89 MJ m-3, 43.44 ± 8.54 kJ m-2 and 1212.86 ± 57.20 J m-2, respectively, with a satisfactory fracture strain of 266 ± 33%. In addition, ICOH strain sensors with freezing and drying resistance exhibit excellent cycling stability (10 000 cycles). More importantly, the fatigue resistance allows the notched strain sensor to work normally with no crack propagation and output stable and reliable sensing signals. Overall, the unique flaw-insensitive strain sensing makes ICOHs promising in the field of wearable and durable electronics.

Spatial Confinement Engineered Gel Composite Evaporators for Efficient Solar Steam Generation.

Recently, solar-driven interfacial evaporation (SDIE) has been developed quickly for low-cost and sustainable seawater desalination, but addressing the conflict between a high evaporation rate and salt rejection during SDIE is still challenging. Here, a spatial confinement strategy is proposed to prepare the gel composite solar evaporator (SCE) by loading one thin hydrogel layer onto the skeleton of a carbon aerogel. The SCE retains the hierarchically porous structure of carbon aerogels with an optimized water supply induced by dual-driven forces (capillary effects and osmotic pressure) and takes advantage of both aerogels and hydrogels, which can gain energy from air and reduce water enthalpy. The SCE has a high evaporation rate (up to 4.23 kg m-2 h-1 under one sun) and excellent salt rejection performance and can maintain structural integrity after long-term evaporation even at high salinities. The SDIE behavior, including heat distribution, water transport, and salt ion distribution, is investigated by combining theoretical simulations and experimental results. This work provides new inspiration and a theoretical basis for the development of high-performance interfacial evaporators.

Fluorine-Free Amphiphobic SBS/PAN Micro/Nanofiber Membrane by Integrating Click Reaction with Electrospinning for Efficient and Recyclable Air Filtration.

The membrane fouling derived from the accumulated dust pollutants and highly viscous oily particles causes irreversible damage to the filtration performance of air filters and results in a significant reduction in their service life. However, it is still challenging to construct high-efficiency and antifouling air filtration membranes with recyclable regeneration. Herein, the fluorine-free amphiphobic micro/nanofiber composite membrane was controllably constructed by integrating click chemistry reaction and electrospinning technique. Low-surface-energy fibers were constructed by a thiol-ene click chemical reaction between mercaptosilane and vinyl groups of polystyrene-butadiene-styrene (SBS), combined with hydroxyl-terminated poly(dimethylsiloxane) during the electrospinning process. The functional air filter is then prepared by the two-layer composite strategy. Because of the advantages of liquid-like fibrous surface and micro/nanofibrous porous structure, SBS/PAN composite membrane simultaneously shows superior antifouling performances of pollutants and filtration efficiency of over 97% PM0.3 removal. More importantly, the antifouling fibrous membrane still presents a stable and efficient filtration efficiency after multiple washes. Its service life in dust filtration environments is approximately 1.7 times longer than that of the substrate membrane. This work may provide a significant reference for the design of antifouling fiber membranes and high-efficiency air filters with long life spans and reusability.

Construction of Fire Safe Thermoplastic Polyurethane/Reduced Graphene Oxide Hierarchical Composites with Electromagnetic Interference Shielding.

Incorporating outstanding flame retardancy and electromagnetic interference shielding effectiveness (EMI SE) into polymers is a pressing requirement for practical utilization. In this study, we first employed the principles of microencapsulation and electrostatic interaction-driven self-assembly to encapsulate polyethyleneimine (PEI) molecules and Ti3C2Tx nanosheets on the surface of ammonium polyphosphate (APP), forming a double-layer-encapsulated structure of ammonium polyphosphate (APP@PEI@Ti3C2Tx). Subsequently, flame-retardant thermoplastic polyurethane (TPU) composites were fabricated by melting the flame-retardant agent with TPU. Afterwards, by using air-assisted thermocompression technology, we combined a reduced graphene oxide (rGO) film with flame-retardant TPU composites to fabricate hierarchical TPU/APP@PEI@Ti3C2Tx/rGO composites. We systematically studied the combustion behavior, flame retardancy, and smoke-suppression performance of these composite materials, as well as the flame-retardant mechanism of the expansion system. The results indicated a significant improvement in the interface interaction between APP@PEI@Ti3C2Tx and the TPU matrix. Compared to pure TPU, the TPU/10APP@PEI@1TC composite exhibited reductions of 84.1%, 43.2%, 62.4%, and 85.2% in peak heat release rate, total heat release, total smoke release, and total carbon dioxide yield, respectively. The averaged EMI SE of hierarchical TPU/5APP@PEI@1TC/rGO also reached 15.53 dB in the X-band.

Engineering Sulfur-Containing Polymeric Fire-Retardant Coatings for Fire-Safe Rigid Polyurethane Foam.

With the advantages of lightweight and low thermal conductivity properties, polymeric foams are widely employed as thermal insulation materials for energy-saving buildings but suffer from inherent flammability. Flame-retardant coatings hold great promise for improving the fire safety of these foams without deteriorating the mechanical-physical properties of the foam. In this work, four kinds of sulfur-based flame-retardant copolymers are synthesized via a facile radical copolymerization. The sulfur-containing monomers serve as flame-retardant agents including vinyl sulfonic acid sodium (SPS), ethylene sulfonic acid sodium (VS), and sodium p-styrene sulfonate (VSS). Additionally, 2-hydroxyethyl acrylate (HEA) and 4-hydroxybutyl acrylate are employed to enable a strong interface adhesion with polymeric foams through interfacial H-bonding. By using as-synthesized waterborne flame-retardant polymeric coating with a thickness of 600 µm, the coated polyurethane foam (PUF) can achieve a desired V-0 rating during the vertical burning test with a high limiting oxygen index (LOI) of >31.5 vol%. By comparing these sulfur-containing polymeric fire-retardant coatings, poly(VS-co-HEA) coated PUF demonstrates the best interface adhesion capability and flame-retardant performance, with the lowest peak heat release rate of 166 kW m-2 and the highest LOI of 36.4 vol%. This work provides new avenues for the design and performance optimization of advanced fire-retardant polymeric coatings.

Large-Scale, Mechanically Robust, Solvent-Resistant, and Antioxidant MXene-Based Composites for Reliable Long-Term Infrared Stealth.

MXene-based thermal camouflage materials have gained increasing attention due to their low emissivity, however, the poor anti-oxidation restricts their potential applications under complex environments. Various modification methods and strategies, e.g., the addition of antioxidant molecules and fillers have been developed to overcome this, but the realization of long-term, reliable thermal camouflage using MXene network (coating) with excellent comprehensive performance remains a great challenge. Here, a MXene-based hybrid network comodified with hyaluronic acid (HA) and hyperbranched polysiloxane (HSi) molecules is designed and fabricated. Notably, the presence of appreciated HA molecules restricts the oxidation of MXene sheets without altering infrared stealth performance, superior to other water-soluble polymers; while the HSi molecules can act as efficient cross-linking agents to generate strong interactions between MXene sheets and HA molecules. The optimized MXene/HA/HSi composites exhibit excellent mechanical flexibility (folded into crane structure), good water/solvent resistance, and long-term stable thermal camouflage capability (with low infrared emissivity of ≈0.29). The long-term thermal camouflage reliability (≈8 months) under various outdoor weathers and the scalable coating capability of the MXene-coated textile enable them to disguise the IR signal of various targets in complex environments, indicating the great promise of achieved material for thermal camouflage, IR stealth, and counter surveillance.

Water vapor assisted aramid nanofiber reinforcement for strong, tough and ionically conductive organohydrogels as high-performance strain sensors.

Conductive organohydrogels have gained increasing attention in wearable sensors, flexible batteries, and soft robots due to their exceptional environment adaptability and controllable conductivity. However, it is still difficult for conductive organohydrogels to achieve simultaneous improvement in mechanical and electrical properties. Here, we propose a novel "water vapor assisted aramid nanofiber (ANF) reinforcement" strategy to prepare robust and ionically conductive organohydrogels. Water vapor diffusion can induce the pre-gelation of the polymer solution and ensure the uniform dispersion of ANFs in organohydrogels. ANF reinforced organohydrogels have remarkable mechanical properties with a tensile strength, stretchability and toughness of up to 1.88 ± 0.04 MPa, 633 ± 30%, and 6.75 ± 0.38 MJ m-3, respectively. Furthermore, the organohydrogels exhibit great crack propagation resistance with the fracture energy and fatigue threshold as high as 3793 ± 167 J m-2 and ∼328 J m-2, respectively. As strain sensors, the conductive organohydrogel demonstrates a short response time of 112 ms, a large working strain and superior cycling stability (1200 cycles at 40% strain), enabling effective monitoring of a wide range of complex human motions. This study provides a new yet effective design strategy for high performance and multi-functional nanofiller reinforced organohydrogels.

Hydrosilylation Adducts to Produce Wide-Temperature Flexible Polysiloxane Aerogel under Ambient Temperature and Pressure Drying.

Despite incorporation of organic groups into silica-based aerogels to enhance their mechanical flexibility, the wide temperature reliability of the modified silicone aerogel is inevitably degraded. Therefore, facile synthesis of soft silicone aerogels with wide-temperature stability remains challenging. Herein, novel silicone aerogels containing a high content of Si are reported by using polydimethylvinylsiloxane (PDMVS), a hydrosilylation adduct with water-repellent groups, as a "flexible chain segment" embedded within the aerogel network. The poly(2-dimethoxymethylsilyl)ethylmethylvinylsiloxane (PDEMSEMVS) aerogel is fabricated through a cost-effective ambient temperature/pressure drying process. The optimized aerogel exhibits exceptional performance, such as ultra-low density (50 mg cm-3), wide-temperature mechanical flexibility, and super-hydrophobicity, in comparison to the previous polysiloxane aerogels. A significant reduction in the density of these aerogels is achieved while maintaining a high crosslinking density by synthesizing gel networks with well-defined macromolecules through hydrolytic polycondensation crosslinking of PDEMSEMVS. Notably, the pore/nanoparticle size of aerogels can be fine-tuned by optimizing the gel solvent type. The as-prepared silicone aerogels demonstrate selective absorption, efficient oil-water separation, and excellent thermal insulation properties, showing promising applications in oil/water separation and thermal protection.

Tunable construction of fire safe and mechanically strong hierarchical composites towards electromagnetic interference shielding.

Cotton fabric composites were designed to be protected by fire safe thermoplastic polyurethane (TPU) composites for developing electromagnetic interference (EMI) shielding polymer composites with superior mechanical properties. Herein, the as-prepared MXene was coated onto the fiber surface of cotton and then thermally compressed with TPU composites, which were filled with the sodium dodecyl sulfate modified layered double hydroxides functionalized the short carbon fiber hybrids through melt blending method. Then, a series of highly fire safe cotton/TPU hierarchical composites were constructed by a designed thermal compression technique. For instance, the obtained cotton/TPU hierarchical sample showed greatly reduced peak of heat release rate, peak of carbon monoxide production rate and peak of carbon dioxide production rate of TPU by 50.1%, 52.1% and 55.4%, respectively. Furthermore, the cotton/TPU hierarchical composites possessed the EMI shielding effectiveness of 40.0 dB in the X band and 54.6 dB in the K band. The mechanical property of the cotton/TPU hierarchical composites was also reinforced, where the elongation at break and toughness values of the TPU/SCF/mLDH1/C2 hierarchical composite were 21.47 and 18.30 times higher than those of pure TPU, respectively. These mechanically strong hierarchical composites have brought a promising attempt to broaden their practical application, removing the fire hazards and electromagnetic waves radiation from the environment.

A facile strategy for constructing lightweight, fire safety and compression resistance poly(vinylalcohol) aerogels with highly-efficient expansible graphene oxide/layered double hydroxides hybrid synergistic flame retardant.

Poly(vinyl alcohol) (PVA) aerogels with excellent environmentally friendly properties have been considered to replace undegradable polymer foams. However, due to highly flammable, hydrophilic, and worse compression resistance performance, PVA aerogels have always been excluded from practical. Herein, a fire safety and compression resistance PVA/expansible graphene oxide (EGO)/Layered double hydroxides (LDHs) (PGL) aerogel was prepared via the freeze-drying method and electrostatic adsorption of flame retardant. The ice crystals from aerogels were sublimated and left a mass of tree-like pore tunnel structures. Meantime, the compound of EGO and LDHs rendered PGL aerogels high compressive strength of 6.0917 MPa (at 80% of strains), a high specific modulus of 19.16 m2/s2, and an ultra-low density of 0.059 g/cm3. Especially, the as-prepared PGL aerogels showed heat release reduced by 55.4%, smoke release reduced by 54.3%, and the limiting oxygen index reaching up to 31%. Moreover, LDHs also enhanced the interface with PVA/EGO resulting in hydrophobic performance improvement. The proposed enhancements mechanism suggested that (i) chemical reactions between EGO and PVA matrix; (ii) a mass of negative potential sites from the interface of PVA/EGO composites made LDHs sheets easily adsorbing; (iii) oxygen-containing groups from EGO and LDHs absorbed mass of heat during combustion; (iv) the compact char residues on the surface of aerogels acting as barriers suppressed smoke and prevented PVA matrix from further combustion. Therefore, electrostatic adsorption as a facile production process was paved for meeting the compression resistance, flame-retardant, heat-insulating, and smoke-suppressed requirements of PVA aerogels in this work.

Nanofiber Composite Reinforced Organohydrogels for Multifunctional and Wearable Electronics.

Composite organohydrogels have been widely used in wearable electronics. However, it remains a great challenge to develop mechanically robust and multifunctional composite organohydrogels with good dispersion of nanofillers and strong interfacial interactions. Here, multifunctional nanofiber composite reinforced organohydrogels (NCROs) are prepared. The NCRO with a sandwich-like structure possesses excellent multi-level interfacial bonding. Simultaneously, the synergistic strengthening and toughening mechanism at three different length scales endow the NCRO with outstanding mechanical properties with a tensile strength (up to 7.38 ± 0.24 MPa), fracture strain (up to 941 ± 17%), toughness (up to 31.59 ± 1.53 MJ m-3) and fracture energy (up to 5.41 ± 0.63 kJ m-2). Moreover, the NCRO can be used for high performance electromagnetic interference shielding and strain sensing due to its high conductivity and excellent environmental tolerance such as anti-freezing performance. Remarkably, owing to the organohydrogel stabilized conductive network, the NCRO exhibits superior long-term sensing stability and durability compared to the nanofiber composite itself. This work provides new ideas for the design of high-strength, tough, stretchable, anti-freezing and conductive organohydrogels with potential applications in multifunctional and wearable electronics.

Intelligent cyclic fire warning sensor based on hybrid PBO nanofiber and montmorillonite nanocomposite papers decorated with phenyltriethoxysilane.

An abundance of early warning graphene-based nano-materials and sensors have been developed to avoid and prevent the critical fire risk of combustible materials. However, there are still some limitations that should be addressed, such as the black color, high-cost and single fire warning response of graphene-based fire warning materials. Herein, we report an unexpected montmorillonite (MMT)-based intelligent fire warning materials that have excellent fire cyclic warning performance and reliable flame retardancy. Combining phenyltriethoxysilane (PTES) molecules, poly(p-phenylene benzobisoxazole) nanofiber (PBONF), and layers of MMT to form a silane crosslinked 3D nanonetwork system, the homologous PTES decorated MMT-PBONF nanocomposites are designed and fabricated via a sol-gel process and low temperature self-assembly method. The optimized nanocomposite paper shows good mechanical flexibility (good recovery after kneading or bending process), high tensile strength of âˆ¼81 MPa and good water resistance. Furthermore, the nanocomposite paper exhibits high-temperature flame resistance (almost unchanged structure and size after 120 s combustion), sensitive flame alarm response (∼0.3 s response once exposure onto a flame), cyclic fire warning performance (>40 cycles), and adaptability to complex fire situations (several fire attack and evacuation scenarios), showing promising applications for monitoring the critical fire risk of combustible materials. Therefore, this work paves a rational way for design and fabrication of MMT-based smart fire warning materials that combine excellent flame shielding and sensitive fire alarm functions.

Effects of Ammonium Polyphosphate and Organic Modified Montmorillonite on Flame Retardancy of Polyethylene Glycol/Wood-Flour-Based Phase Change Composites.

With the depletion of fossil fuel energy and both the slow development and low utilization rate of new eco-friendly energy, finding new ways to efficiently store energy has become a research hotspot. Presently, polyethylene glycol (PEG) is an excellent heat storage material, but it is a typical solid-liquid phase change material (PCM) with a risk of leakage during phase transition. A combination of wood flour (WF) and PEG can effectively eliminate the risk of leakage after the melting of PEG. However, WF and PEG are both flammable materials, which impedes their application. Therefore, it is of great significance to expand their application by forming composites from among PEG, supporting mediums, and flame-retardant additives. This will improve both their flame retardancy and phase change energy storage performance, and will also lead to the preparation of excellent flame-retardant phase change composite materials with solid-solid phase change characteristics. To address this issue, ammonium polyphosphate (APP), organic modified montmorillonite (OMMT), and WF were blended into PEG in specific proportions to prepare a series of PEG/WF-based composites. Both thermal cycling tests and thermogravimetric analysis results demonstrated that the as-prepared composites had good thermal reliability and chemical stability. In addition, during differential scanning calorimetry tests, the PEG/WF/8.0APP@2.0OMMT composite presented the highest melting latent heat (176.6 J/g), and its enthalpy efficiency reached more than 98.3%. The PEG/WF/8.0APP@2.0OMMT composite also exhibited superior thermal insulation performance when compared to the pure PEG/WF composite. Furthermore, the PEG/WF/8.0APP@2.0OMMT composite exhibited a significant 50% reduction in peak heat release rate as a result of the synergistic effect between OMMT and APP in the gas and condensed phases. This work offers a useful strategy for the fabrication of multifunctional phase-change material, which is expected to broaden its industrial applications.

Stretchable, durable and asymmetrically wettable nanofiber composites with unidirectional water transportation capability for temperature sensing.

The one-way transportation of liquids plays an important role in smart and wearable electronics. Here, we report an asymmetric nanofibrous membrane (ANM) with unidirectional water transport (UWT) capability by integrating one superhydrophilic MXene/Chitosan/Polyurethane (PU) nanofiber membrane (MCPNM) and one ultrathin hydrophobic PU/Polyvinylpyrrolidone (PVP) layer with a "bead-on-string" structure. The UWT performance shows long-term stability and can be well maintained during the cyclic stretching, abrasion and ultrasonic washing tests. The ANM exhibits negative temperature coefficient and is served as a temperature sensor to monitor the temperature variation of the environment, which can provide efficient alarm signals in a hot or cold condition. When attached on person's skin, the ANM displays a unique anti-gravity UWT behavior. The stretchable, wearable and multi-functional nanofibrous composite membrane with an asymmetric wettability shows potential applications in flexible and wearable electronics, health monitoring, etc.

Fabrication of covalent organic frameworks modified nanofibrous membrane for efficiently enriching and detecting the trace polychlorinated biphenyls in water.

Enriching and detecting the trace pollutants in actual matrices are critical to evaluating the water quality. Herein, a novel nanofibrous membrane, named PAN-SiO2@TpPa, was prepared by in situ growing ß-ketoenamine-linked covalent organic frameworks (COF-TpPa) on the aminated polyacrylonitrile (PAN) nanofibers, and adopted for enriching the trace polychlorinated biphenyls (PCBs) in various natural water body (river, lake and sea water) through the solid-phase micro-extraction (SPME) process. The resulted nanofibrous membrane owned abundant functional groups (-NH-, -OH and aromatic groups), outstandingly thermal and chemical stability, and excellent ability in extracting PCBs congeners. Based on the SPME process, the PCBs congeners could be quantitatively analyzed by the traditional gas chromatography (GC) method, with the satisfactory linear relationship (R2>0.99), low detection limit (LODs, 0.1∼5 ng L-1), high enrichment factors (EFs, 2714∼3949) and multiple recycling (>150 runs). Meanwhile, when PAN-SiO2@TpPa was adopted in the real water samples, the low matrix effects on the enrichment of PCBs at both 5 and 50 ng L-1 over PAN-SiO2@TpPa membrane firmly revealed the feasibility of enriching the trace PCBs in real water. Besides, the related mechanism of extracting PCBs on PAN-SiO2@TpPa mainly involved the synergistic effect of hydrophobic effect, π-π stacking and hydrogen bonding.

Architecting fire safe hierarchical polymer nanocomposite films with excellent electromagnetic interference shielding via interface engineering.

Integrating high flame retardancy and excellent electromagnetic interference (EMI) shielding into polymetric materials is extremely necessary, and well dispersing conductive fillers into polymeric materials is still a great challenge because of incompatible interfacial polarity between polymer matrix and conductive fillers. Therefore, under the premise of maintaining integral conductive films in the process of hot compression, constructing a novel EMI shielding polymer nanocomposites where conductive films closely adhere to polymer nanocmposites layers should be a fascinating stratety. In this work, salicylaldehyde-modified chitosan decorated titanium carbide nanohybrid (Ti3C2Tx-SCS) was combined with piperazine-modified ammonium polyphosphate (PA-APP) to fabricate thermoplastic polyurethane (TPU) nanocomposites, which were used for construction of hierarchical nanocomposite films by inserting reduced graphene oxide (rGO) films into TPU/PA-APP/Ti3C2Tx-SCS nanocomposite layers through our self-developed air assisted hot pressing technique. The total heat release, total smoke release and total carbon monoxide yield for TPU nanocomposite containing 4.0 wt% Ti3C2Tx-SCS nanohybrid were 58.0%, 58.4% and 75.8% lower than those of pristine TPU, respectively. Besides, the hierarchical TPU nanocomposite film containing 1.0 wt% Ti3C2Tx-SCS presented an averaged EMI shielding effectiveness of 21.3 dB in X band. This work provides a promising strategy for fabricating fire safe and EMI shielding polymer nanocomposites.

Synergistic Function between Phosphorus-Containing Flame Retardant and Multi-Walled Carbon Nanotubes towards Fire Safe Polystyrene Composites with Enhanced Electromagnetic Interference Shielding.

As a universal polymer material, polystyrene (PS) is widely applied in electrical devices and construction. Thus, it is necessary to improve the flame retardancy and electromagnetic shielding properties of PS material. In this work, PS/silicon-wrapped ammonium polyphosphate/Inorganic acid-treated multi-walled carbon nanotubes composites (PS/SiAPP/aMWCNT, abbreviated as PAC) were prepared via methods of filtration-induced assembly and hot-pressing. Morphology and structure characterization demonstrated that SiAPP and aMWCNT had good dispersion in PS and excellent compatibility with the PS matrix. Thermogravimetric analysis revealed that the addition of aMWCNT to PS improved its thermal stability and carbon-forming characteristics. The peak heat release rate, the peak carbon monoxide production rate, and the peak smoke production rate of the PAC10 composite decreased by 53.7%, 41.9%, and 45.5%, respectively, while its electromagnetic shielding effectiveness reached 12 dB. These enhancements were attributed to the reason that SiAPP and aMWCNT synergistically catalyzed the char generation and SiAPP produced free radical scavengers and numbers of incombustible gases, which could decrease the oxygen concentration and retard the combustion reaction. Therefore, the assembled PS/SiAPP/aMWCNT system provides a new pathway to improve the flame retardant and electromagnetic shielding properties of PS.

Fire Intumescent, High-Temperature Resistant, Mechanically Flexible Graphene Oxide Network for Exceptional Fire Shielding and Ultra-Fast Fire Warning.

Smart fire alarm sensor (FAS) materials with mechanically robust, excellent flame retardancy as well as ultra-sensitive temperature-responsive capability are highly attractive platforms for fire safety application. However, most reported FAS materials can hardly provide sensitive, continuous and reliable alarm signal output due to their undesirable temperature-responsive, flame-resistant and mechanical performances. To overcome these hurdles, herein, we utilize the multi-amino molecule, named HCPA, that can serve as triple-roles including cross-linker, fire retardant and reducing agent for decorating graphene oxide (GO) sheets and obtaining the GO/HCPA hybrid networks. Benefiting from the formation of multi-interactions in hybrid network, the optimized GO/HCPA network exhibits significant increment in mechanical strength, e.g., tensile strength and toughness increase of ~ 2.3 and ~ 5.7 times, respectively, compared to the control one. More importantly, based on P and N doping and promoting thermal reduction effect on GO network, the excellent flame retardancy (withstanding ~ 1200 °C flame attack), ultra-fast fire alarm response time (~ 0.6 s) and ultra-long alarming period (> 600 s) are obtained, representing the best comprehensive performance of GO-based FAS counterparts. Furthermore, based on GO/HCPA network, the fireproof coating is constructed and applied in polymer foam and exhibited exceptional fire shielding performance. This work provides a new idea for designing and fabricating desirable FAS materials and fireproof coatings.

Constructing segregated polystyrene composites for excellent fire resistance and electromagnetic wave shielding.

Electroconductive polystyrene (PS) composites with ideal flame-retardant properties are considered as potential electromagnetic interference (EMI) shielding materials. In this work, PS/silicon wrapped ammonium polyphosphate/multi-wall carbon nanotubes (PS/SiAPP/MWCNT) composites with segregated structure were synthesized via the methods of balling mill and hot-pressing. The obtained results revealed that the SiAPP and MWCNT were successfully introduced onto PS spheres and showed uniform distribution on the PS surface. The thermogravimetric analysis showed that PS/SiAPP/MWCNT containing 7 wt% MWCNT exhibited excellent thermal stability. Furthermore, the results of cone calorimeter test indicated that the heat release rate and total heat release of the PS/SiAPP/MWCNT containing a loading of 7 wt% MWCNT were reduced by 60.5% and 33.9%, respectively. In addition, the EMI shielding performance could reach 11 dB. Above results implied that the synergistic effect between the MWCNT and SiAPP effectively enhanced the flame retardant performance of the PS by promoting the generation of dense and continuous char layer to protect the PS from burning. The multiple reflection and adsorption are responsible for improved EMI shielding effectiveness. Therefore, segregated PS/SiAPP/MWCNT hybrid is an up-and-coming candidate for satisfactory EMI shielding materials with exceptional fire retardancy for electronic devices.

Efficient extraction of trace organochlorine pesticides from environmental samples by a polyacrylonitrile electrospun nanofiber membrane modified with covalent organic framework.

Detecting and analyzing of the trace organochlorine pesticides (OCPs) in the real water has become a big challenge. In this work, a novel functional electrospun nanofiber membrane (PAN@COFs) was synthesized through the in situ growth of covalent organic frameworks (COFs) on a polyacrylonitrile electrospun nanofiber membranes under room temperature and used in the solid-phase micro-extraction (SPME) to enrich trace organochlorine pesticides (OCPs) in water. The resulted PAN@COFs composite consisted of numerous nanofibers coated ample porous COFs spheres (~ 500 nm) and owned stable crystal structure, abundant functional groups, good stability. In addition, the enrichment experiments clearly revealed that PAN@COFs exhibited rather outstanding performance on adsorbing the trace OCPs (as low as 10 ng L-1) with the enrichment of 482-2686 times. Besides, PAN@COFs displayed good reusability and could be reused 100 times. Notably, in the real water samples (sea water and river water), the high enrichment factors and recovery rates strongly confirmed the feasibility of PAN@COFs for detecting the trace OCPs. Furthermore, due to the synergy of π-π stacking interaction and hydrophobic interaction between the OCPs molecules and PAN@COFs, the OCPs could be efficiently adsorbed on PAN@COFs, even under the extremely low driving force.