Recent advances in fire-retardant carbon-based polymeric nanocomposites through fighting free radicals

Polymeric materials are ubiquitously utilized in modern society and continuously improve quality of life. Unfortunately, most of them suffer from intrinsic flammability, significantly limiting their practical applications. Fundamentally, free-radical reaction is a critical “trigger” for their thermal pyrolysis and following combustion process regardless of the anaerobic thermal pyrolysis in the condensed phase or aerobic combustion of polymers in the gaseous phase. The addition of free radical scavengers represents a promising and effective means to enhance the fire safety of polymeric materials. This review aims to offer a state-of-the-art overview on the creation of fire-retardant polymeric nanocomposites by adding fire retardants with an ability to trap free radicals. Their specific modes of action (condensed-phase action, gaseous-phase action, and dual-phases action) and performances in some typical polymers are reviewed and discussed in detail. Following this, some key challenges associated with these free-radical capturers are discussed, and design strategies are also proposed. This review provides some insights into the modes of action of free radical capturing agents and paves the avenue for the design of advanced fire-retardant polymeric nanocomposites for expanded real-world applications in industries

Preparation and Characterization of an Invasive Plant-Derived Biochar-Supported Nano-Sized Lanthanum Composite and Its Application in Phosphate Capture from Aqueous Media

Invasive plants pose a great threat to natural ecosystems owing to their rapid propagation and spreading ability in nature. Herein, a typical invasive plant, Solidago canadensis, was chosen as a novel feedstock for the preparation of nano-sized lanthanum-loaded S. canadensis-derived biochar (SCBC-La), and its adsorption performance for phosphate removal was evaluated by batch adsorption experiment. The composite was characterized by multiple techniques. Effects of parameters, such as the initial concentration of phosphate, time, pH, coexisting ions, and ionic strength, were studied on the phosphate removal. Adsorption kinetics and isotherms showed that SCBC-La shows a faster adsorption rate at a low concentration and SCBC-La exhibits good La utilization efficiency than some of the reported La-modified adsorbents. Phosphate can be effectively removed over a relatively wide pH of 3–9 because of the high pHpzc of SCBC-La. Furthermore, the SCBC-La shows a strong anti-interference capability in terms of pH value, coexisting ions, and ionic strength, exhibiting a highly selective capacity for phosphate removal. Additionally, Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) measurements reveal that hydroxyl groups on the surface of SCBC-La were replaced by phosphate and manifest the reversible transformation between La(OH)3 and LaPO4. Considering its high adsorption capacity and excellent selectivity, SCBC-La is a promising material for preventing eutrophication. This work gives a new method of pollution control with waste treatment since the invasive plant (S. canadensis) is converted into biochar-based nanocomposite for effective removal of phosphate to mitigate eutrophication

Heterointerface engineering of polymer-based electromagnetic wave absorbing materials

Heterointerface engineering has drawn considerable interest in tuning interfacial polarization and promoting impedance matching. Therefore, it has become a key strategy for optimizing electromagnetic wave (EMW) absorption. This comprehensive review primarily focused on the EMW absorbing strategies of polymer-based materials, emphasizing the critical developments of heterointerface engineering. A possible EMW absorbing mechanism of polymer-based materials was proposed, emphasizing the synergism of multi-components, microstructure design, and heterointerface engineering. Key innovations in structural design such as porous structure, multilayered structure, and segregated structure are explored, highlighting their contributions to enhancing EMW absorption. Also, the review highlights the latest research progress of advanced conductive polymer-based and insulating polymer-based materials with desirable EMW absorption performance; their fabrication methods, structures, properties, and EMW absorption mechanisms were elucidated in detail. Key challenges on polymer-based EMW absorbing materials are presented followed by some future perspectives

Quantification of Microplastics in Agricultural Soils by total organic carbon-solid sample combustion analysis

Accurate quantification of microplastics (MPs) in soils is a significant challenge due to the complex nature of the organo-mineral matrix. Fine mineral particles and organic matter often interfere with the efficiency of extraction, identification and quantification of MPs from soils. Here, an optimized MP extraction and quantification method is proposed, using total organic carbon analyser-solid sample combustion unit (TOC-SSM) analysis. The approach entails a field survey, digestion of organic matter by Piranha solution, density separation, and quantification. This method achieves a high total recovery rate of 97.39 ± 14.25 (SE) % for particles sized between 300 and 600 µm, and 94.80 ± 13.48 (SE) % for particles less than 300 µm with spiked soil as samples. The optimised method is then applied to strawberry farm soils that use plastic mulch films to quantify MP contamination levels. Our results indicate MP concentrations of 12.24 ± 3.65 (SE) mg kg−1 (for particles of 300–2000 µm in size) and 2.62 ± 0.66 (SE) mg kg−1 (for particles smaller than 300 µm). With improved simplicity and the ability to provide the actual weight of plastics for the extraction and quantification of MPs, this work offers a potential approach for assessing low-density plastics in the northeastern Australian agricultural soils with a dominant MP contamination, specifically polyethylene (PE)

Bio-derived Schiff base vitrimer with outstanding flame retardancy, toughness, antibacterial, dielectric and recycling properties

Thermosetting resins are widely used in high-tech applications for excellent mechanical robustness and chemical resistance. With increasing attention to the environmental and usage safety issues, it is necessary to develop bio-derived, recyclable, tough, and fire-retardant thermosetting resins. Herein, a high-performance, vanillin-based vitrimer (CIP1.0) was prepared. The CIP1.0 with 1.0 wt% phosphorus passes vertical burning (UL-94) V-0 rating with a limiting oxygen index (LOI) of 27.2 %. The phosphorus-containing and Schiff base groups act synergistically in gas and condensed phases during combustion, endowing CIP1.0 with outstanding fire retardancy. The CIP1.0 shows excellent toughness with high elongation at break of 45.0 % due to the π-π stacking of numerous rigid aromatic groups and appropriate cross-linking density. The highly symmetrical structure and low polarizability of CIP1.0 result in a low dielectric constant. The CIP1.0 exhibits superior antimicrobial properties. The CIP1.0 can be reprocessed by hot-pressing at 140 °C for 10 min. The non-destructive, closed-loop recycling of carbon fibers in the carbon fiber-reinforced CIP1.0 composite can be achieved under mild conditions due to the degradable Schiff base groups of CIP1.0. In this work, a bio-derived, tough, fire-retardant, low dielectric, and antimicrobial vitrimer is prepared to provide a rational strategy for the design of advanced environmentally friendly thermosetting resins

Construction and application of flexible electromagnetic interference shielding films with multifunctionality

With the rapid development of 5G communication technology, the research on ultra-thin flexible electromagnetic interference (EMI) shielding materials has become a hot topic. The next generation of devices is moving towards miniaturization, intelligence, and high integration. Considering complex application scenarios, single function EMI shielding films no longer meet cutting-edge industrial needs. In this paper, emerging demands and applications for flexible EMI shielding films with multifunctionality, including transparency, thermal conductivity, joule heating or photothermal response, hydrophobicity and self-cleaning property, corrosion resistance, fire retardancy, pressure sensing, ultra-high mechanical properties, and excellent durability were comprehensively summarized. In addition, advanced strategies for implementing functional integrity of EMI shielding materials were proposed. The fabrication methods, structures, functions, and mechanisms of the latest research progress of multifunctional flexible EMI shielding films were elucidated in detail. Key challenges on multifunctional flexible EMI shielding films are presented followed by some future perspectives

Strong yet Tough Catalyst-Free Transesterification Vitrimer with Excellent Fire-Retardancy, Durability, and Closed-Loop Recyclability

Despite great advances in vitrimer, it remains highly challenging to achieve a property portfolio of excellent mechanical properties, desired durability, and high fire safety. Thus, a catalyst-free, closed-loop recyclable transesterification vitrimer (TPN1.50) with superior mechanical properties, durability, and fire retardancy is developed by introducing a rationally designed tertiary amine/phosphorus-containing reactive oligomer (TPN) into epoxy resin (EP). Because of strong covalent interactions between TPN and EP and its linear oligomer structure, as-prepared TPN1.50 achieves a tensile strength of 86.2 MPa and a toughness of 6.8 MJ m−3, superior to previous vitrimer counterparts. TPN1.50 containing 1.50 wt% phosphorus shows desirable fire retardancy, including a limiting oxygen index of 35.2% and a vertical burning (UL-94) V-0 classification. TPN1.50 features great durability and can maintain its structure integrity in 1 M HCl or NaOH solution for 100 days. This is because the tertiary amines are anchored within the cross-linked network and blocked by rigid P-containing groups, thus effectively suppressing the transesterification. Owing to its good chemical recovery, TPN1.50 can be used as a promising resin for creating recyclable carbon fiber-reinforced polymer composites. This work offers a promising integrated method for creating robust durable fire-safe vitrimers which facilitate the sustainable development of high-performance polymer composites

Vertically aligned cellulose nanofiber/carbon nanotube aerogel-infused epoxy nanocomposites for highly efficient solar-thermal-electric conversion

Solar-driven thermo-electric generation (STEG) emerges as a promising solution to mitigate the global energy shortage. However, the practical application of conventional photothermal materials equipped with STEG is limited due to low solar thermal conversion efficiency. Herein, we fabricated an epoxy resin (EP) nanocomposite, EP/CCA80 , with excellent photo-thermal-electric conversion properties by embedding a vertically aligned aerogel consisting of cellulose nanofibers (CNF) and carboxylated multi-walled carbon nanotubes (CMWCNTs) into a transparent EP matrix. EP/CCA80 composites possessed a broad light absorption range from 200 nm to 2500 nm and excellent photothermal properties. Under illumination of 1.0 kW m-2 , EP/CCA80 achieved a notable stable temperature of 93.2 degrees C and a photothermal conversion efficiency of up to 54.35 % with only 0.65 wt% CMWCNTs inclusion. Additionally, coupled with thermoelectric (TE) devices, the EP/CCA80 composite facilitated a significant temperature difference and voltage output of up to 25.3 degrees C and 160.29 mV (1.0 kW m-2 ), respectively, which could power a small fan to rotate at a speed of 193 min-1 . Such materials are poised to offer viable solutions for enhancing energy accessibility in remote regions, thereby contributing to the reduction of energy shortages and environmental degradation. (c) 2024 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology. This is an open access article under the CC BY license ( http://creativecommons.org/licenses/by/4.0/