Flame retarded polymer nanocomposites: Development, trend and future perspective

Heterostructured Graphene@Silica@Iron Phenylphosphinate for Fire-Retardant, Strong, Thermally Conductive Yet Electrically Insulated Epoxy Nanocomposites

The portfolio of extraordinary fire retardancy, mechanical properties, dielectric/electric insulating performances, and thermal conductivity (λ) is essential for the practical applications of epoxy resin (EP) in high-end industries. To date, it remains a great challenge to achieve such a performanceportfolio in EP due to their different and even mutually exclusive governing mechanisms. Herein, a multifunctional additive (G@SiO2@FeHP) is fabricated by in situ immobilization of silica (SiO2) and iron phenylphosphinate (FeHP) onto the graphene (G) surface. Benefiting from the synergistic effect of G, SiO2 and FeHP, the addition of 1.0 wt% G@SiO2@FeHP enables EP to achieve a vertical burning (UL-94) V-0 rating and a limiting oxygen index (LOI) of 30.5%. Besides, both heat release and smoke generation of as-prepared EP nanocomposite are significantly suppressed due to the condensed-phase function of G@SiO2@FeHP. Adding 1.0 wt% G@SiO2@FeHP also brings about 44.5%, 61.1%, and 42.3% enhancements in the tensile strength, tensile modulus, and impact strength of EP nanocomposite. Moreover, the EP nanocomposite exhibits well-preserved dielectric and electric insulating properties and significantly enhanced λ. This work provides an integrated strategy for the development of multifunctional EP materials, thus facilitating their high-performance applications.

Empowering the flame retardancy and adhesion for various substrates using renewable feedstock

Developing biobased flame retardant adhesives using a green and simple strategy has recently gained significant attention. Therefore, in this study, we have orange peel waste (OPW) and Acacia gum (AG) phosphorylated at 140 °C to synthesize biomass-derived flame retardant adhesive. OPW is a biomass material readily available in large quantities, which. Has been utilized to produce an eco-friendly, efficient adhesive. Functionalized polysaccharides were used as a binder rather than volatile, poisonous, and unsustainable petroleum-based aldehydes. The P@OPW/AG green adhesive exhibited a higher tensile strength of 11.25 MPa when applied to cotton cloth and demonstrated versatility across various substrates such as glass, cardboard, plastic, wood, and textiles. Additionally, this bio-based robust adhesive displayed remarkable flame-retardant properties. To optimize its flame retardancy, three tests were employed: the spirit lamp flame test, the vertical flammability test (VFT), and the limiting oxygen index (LOI) test. The P@OPW/AG-coated cotton fabric achieved an impressive LOI result of 42 %, while the VFT yielded a char length of only 4 cm. Additionally, during the flame test, P@OPW/AG coated cloth endured more than 845 s of continuous flame illumination. This work offers a sustainable and fire-safe method for creating environmentally friendly high-performance composites using a recyclable bio-based flame-retardant OPW/AG glue.

Preparation and properties of flame retardant and hydrophobic cotton fabrics based on poly-(dimethylsiloxane-co-diphenylsiloxane, dihydroxy terminated)/ammonia phytate

Applications for cotton fabrics with multifunctional qualities, such as flame retardancy, hydrophobicity, and anti-ultraviolet properties, are increasingly common and growing daily. The primary objective of this study is to investigate the preparation of flame retardant, hydrophobic, and ultraviolet (UV) protection cotton fabrics through the utilization of Poly-dimethylsiloxane-co-diphenylsiloxane, dihydroxy terminated (HTDMS) and ammonia phytate (AP). The flame retardancy, thermal stability, mechanical properties, anti-UV properties, air permeability and the hydrophobicity properties of coated cotton fabrics were evaluated. The results indicated that the HTDMS/AP coating was successfully deposited on the surface of cotton fabrics. The damaged length of Cotton/HTDMS/AP was 4.7 cm, and the limiting oxygen index reached 31.5 %. The thermogravimetric analysis revealed that the char residues in the high-temperature range were increased. Furthermore, cone calorimetry results indicated that after the HTDMS/AP coating, the peak heat release rate, total heat release, and total smoke production values decreased by 88.7 %, 51.2 %, and 98.4 %, respectively. Moreover, the deposition of HTDMS/AP provided cotton fabrics with hydrophobicity with a water contact angle of over 130°, while Cotton/HTDMS/AP maintained their air permeability, and enhanced the breaking force compared with those of Cotton/AP. Such desirable qualities make HTDMS/AP a meaningful coating for producing multifunctional cotton fabrics.

Recent remediation strategies for flame retardancy via nanoparticles

This review article delves into the application of nanoparticles (NPs) in fire prevention, aiming to elucidate their specific contribution within the broader context of various fire prevention methods. While acknowledging established approaches such as fire safety principles, fire suppression systems, fire alarm systems, and the use of fire-retardant chemicals and safety equipment, this review focuses on the distinctive properties of NPs. The findings underscore the remarkable potential of NPs in controlling and mitigating fire propagation within both architectural structures and vehicles. Specifically, the primary emphasis lies in the impact of NPs on reducing oxygen levels, as assessed through the limiting oxygen index , a subject explored by various researchers. Furthermore, this review delves into the examination of combustion reduction rates facilitated by NPs, utilizing assessments of ignition time, heat release rate (HRR), and flammability tests (UL-94) on plastic materials. Beyond these aspects, the review evaluates the multifaceted role of NPs in achieving weight reduction and establishing fire-retardant properties. Additionally, it discusses the reduction of smoke, a significant contributor to environmental pollution and health risks. Among the nanoparticles investigated in this study, SiO2, MgAl, and nano hydrotalcite have demonstrated the best results in weight reduction, smoke reduction, and HRR, respectively. Meanwhile, Al2O3 has been identified as one of the least effective treated nanoparticles. Collectively, these findings significantly contribute to improving safety measures and reducing fire risks across a range of industries.

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.

Precise Control of a Yolk-Double Shell Metal-Organic Framework-Based Nanostructure Provides Enhanced Fire Safety for Epoxy Nanocomposites

Nanomaterials derived from metal-organic frameworks (MOFs) are highly promising as future flame retardants for polymeric materials. The precise control of the interface for polymer nanocomposites is taking scientific research by storm, whereas such investigations for MOF-based nanofillers are rare. Herein, a novel yolk-double shell nanostructure (ZIF-67@layered double hydroxides@polyphophazenes, ZIF@LDH@PZS) was subtly designed and introduced into epoxy resin (EP) as a flame retardant to fill the vacancy of yolk/shell construction in the field. Meanwhile, the interface of the polymer nanocomposites can be further accurately tailored by the outermost layer of the nanofillers from PZS to Ni(OH)₂ (NH), by which hollow nanocages with treble shells (LDH@PZS@NH) were obtained. It is remarkably interesting that LDH@PZS@NH endows the EP with the lowest peak of heat release rate in the cone calorimeter test, but the total heat and smoke releases (THR and TSP) of the nanocomposites are even higher than those of the neat polymer. In contrast, EP blended with ZIF@LDH@PZS shows outstanding comprehensive performance: with 2 wt.%, the limiting oxygen index is increased to 29.5%, and the peak heat release rate is reduced by 26.0%. The impact and flexural strengths are slightly lowered, while the storage modulus is enhanced remarkably compared with that for neat EP. The flame retardant mechanism is systematically explored focusing on the interfacial interactions of different hybrids within the epoxy matrix, ushering in a new stage of study of nanostructural design-guided interface manipulation in MOF-based polymer nanocomposites.

High-Performance TPE-S Modified by a Flame-Retardant System Based on Black Phosphorus Nanosheets

Few-layer black phosphorus nanosheets (BPs) combined with melamine cyanurate and poly(phenylene oxide) were used to prepare a flame-retardant thermoplastic elastomer based on polystyrene (TPE-S) for the first time. Compared with neat TPE-S, BP-modified TPE-S with a phosphorus content of 7.98% (TPE-S/BP-7.98) passed the UL-94 vertical burning V-0 rating, and the limiting oxygen index value increased to 24.0%. The peak heat release rate (PHRR), total heat release, and the average combustion effective heat of TPE-S/BP-7.98 were decreased by 61.8, 26.0, and 35.3%, respectively. The time to PHRR was increased from 90 s (neat TPE-S) to 170 s. Scanning electron microscopy of frozen fracture sections showed favorable compatibility and dispersibility of BPs in TPE-S. In addition, the introduction of BPs showed the most negligible effect on the mechanical properties of TPE-S compared with other flame retardants (aluminum hypophosphite and red phosphorus).

Research on Fabrication of Flame Retardant Nanocomposite Coating to Protect Steel Structures on Epikote 240 Epoxy Resin Base with the Synergy of MWCNTs and Fly Ash

The use of industrial wastes such as thermal power plant fly ash can reduce the environmental risk. The fly ash properties are useful and can contribute to organic coatings. This paper examines a new strategy for coatings that protect steel structures from the effects of fire while enhancing mechanical properties. The aim of this study was to show that the fly ash additive can be a partial replacement for other conventional additives while also having a flame retardant effect. To study the effectiveness of the use of fly ash additives, we have sought to combine them with nanoadditives. Specifically, we study the synergy of fly ash with multi-wall carbon nanotube additives to reinforce the coating on the system: epoxy Epikote 240/ammonium polyphosphate (APP)/pentaerythritol (PER), and melamine. Content of fly ash was studied: 10 wt.% with 0.5, 1, and 1.5 wt.% of multi-wall carbon nanotubes (MWCNTs). The results prove that the synergies between fly ash and multi-wall carbon nanotubes increase the fire resistance to increase the protection of steel structures of the building. When using 10 wt.% fly ash and 1 wt.% MWCNTS, the coating can be considered as a flame retardant material with UL 94V-0 fire resistance and the limiting oxygen index of 27.2%..

Surface Charges Control the Structure and Properties of Layered Nanocomposite of Cellulose Nanofibrils and Clay Platelets

The interfacial bonding and structure at the nanoscale in the polymer-clay nanocomposites are essential for obtaining desirable material and structure properties. Layered nanocomposite films of cellulose nanofibrils (CNFs)/montmorillonite (MTM) were prepared from the water suspensions of either CNFs bearing quaternary ammonium cations (Q-CNF) or CNFs bearing carboxylate groups (TO-CNF) with MTM nanoplatelets carrying net surface negative charges by using vacuum filtration followed by compressive drying. The effect of the ionic interaction between cationic or anionic charged CNFs and MTM nanoplatelets on the structure, mechanical properties, and flame retardant performance of the TO-CNF/MTM and Q-CNF/MTM nanocomposite films were studied and compared. The MTM nanoplatelets were well dispersed in the network of TO-CNFs in the form of nanoscale tactoids with the MTM content in the range of 5-70 wt %, while an intercalated structure was observed in the Q-CNF/MTM nanocomposites. The resulting TO-CNF/MTM nanocomposite films had a better flame retardant performance as compared to the Q-CNF/MTM films with the same MTM content. In addition, the effective modulus of MTM for the TO-CNF/MTM nanocomposites was as high as 129.9 GPa, 3.5 times higher than that for Q-CNF/MTM (37.1 GPa). On the other hand, the Q-CNF/MTM nanocomposites showed a synergistic enhancement in the modulus and tensile strength together with strain-to-failure and demonstrated a much better toughness as compared to the TO-CNF/MTM nanocomposites.

Flame Retardation of Natural Rubber: Strategy and Recent Progress

Natural rubber (NR) as a kind of commercial polymer or engineering elastomer is widely used in tires, dampers, suspension elements, etc., because of its unique overall performance. For some NR products, their work environment is extremely harsh, facing a serious fire safety challenge. Accordingly, it is important and necessary to endow NR with flame retardancy via different strategies. Until now, different methods have been used to improve the flame retardancy of NR, mainly including intrinsic flame retardation through the incorporation of some flame-retarding units into polymer chains and additive-type flame retardation via adding some halogen or halogen-free flame retardants into NR matrix. For them, the synergistic flame-retarding action is usually applied to simultaneously enhance flame retardancy and mechanical properties, in which some synergistic flame retardants such as organo-montmorillonite (OMMT), carbon materials, halloysite nanotube (HNT), etc., are utilized to achieve the above-mentioned aim. The used flame-retarding units in polymer chains for intrinsic flame retardation mainly include phosphorus-containing small molecules, an unsaturated chemical bonds-containing structure, a cross-linking structure, etc.; flame retardants in additive-type flame retardation contain organic and inorganic flame retardants, such as magnesium hydroxide, aluminum hydroxide, ammonium polyphosphate, and so on. Concerning the flame retardation of NR, great progress has been made in the past work. To achieve the comprehensive understanding for the strategy and recent progress in the flame retardation of NR, we thoroughly analyze and discuss the past and current flame-retardant strategies and the obtained progress in the flame-retarding NR field in this review, and a brief prospect for the flame retardation of NR is also presented.

Preparation of carbon-based hybrid particles and their application in microcellular foaming and flame-retardant materials

Polymeric microcellular foams with high strength and light weight are very important for industrial applications. However, regulating their cell structure and their weak flame retardancy are problematic. We designed single-arm POSS-based ionic liquids ([bel-POSS][PF₆]), and constructed hybrid composites based on physical interaction between ionic liquids and carbon-based materials in PS microcellular foaming. Ionization of bel-POSS could result in a quaternary ammonium reaction and ion-exchange reaction, and the carbon materials exhibit good dispersion through blending. The prepared hybrid composites showed high CO₂ adsorption. Conical calorimeter tests showed that PS composite materials could reduce the heat release rate, total heat release, toxic gases (CO₂ and CO) release, and amount of smoke generated. These carbon materials could affect PS micropore structure, including the cell diameter and density. Upon addition of 5 wt% of carbon materials, the hole diameter decreased by >50%, and the hole density increased nearly ten folds.

Influence of Carbon Fillers on Thermal Properties and Flammability of Polymeric Nanocomposites

Undesirable features of polymeric materials include insufficient thermal stability under specified exploitation conditions and too high flammability. These features depend on the chemical structure of polymer macromolecules, and composition of polymeric composites. Polymeric materials with increased thermal stability and improved resistance to the action of fire are produced with the use of various types of fillers with nanometric dimensions. Among numerous nanofillers, carbon-based nanofillers such as graphite nanoplatelets, carbon nanotubes and graphenes (graphene oxide, reduced graphene oxide and modified graphene) play an essential role. The aim of this report is to highlight the latest findings concerning the effect of carbon fillers, mainly graphene and carbon nanotubes on the thermal properties and flammability of polymer nanocomposites.

Gaseous-phase flame retardant behavior of a multi-phosphaphenanthrene compound in a polycarbonate composite

The gaseous-phase dominating mechanism of the multi-phosphaphenanthrene compound TDBA suppressed the combustion of PC materials with excellent anti-ignition and self-extinguishing abilities.

Highly transparent and flame-retardant epoxy composites based on a hybrid multi-element containing POSS derivative

Epoxy resin modified with ODMAS comprising a POSS core and sixteen DOPO groups possess high transparency, excellent flame retardant property and enhanced mechanical strength.

Flame-retardant effect of a novel phosphaphenanthrene/triazine-trione bi-group compound on an epoxy thermoset and its pyrolysis behaviour

A novel phosphaphenanthrene/triazine-trione bi-group flame retardant TOD, containing two different chemical bridge bonds (aliphatic and aromatic) between flame-retarding groups, was synthesized to prepare satisfactory flame-retardant epoxy thermoset.

Effect of graphene nanosheets and layered double hydroxides on the flame retardancy and thermal degradation of epoxy resin

Graphene nanosheets and layered double hydroxides showed a synergistic effect on improving the flame retardancy of epoxy resin.

Investigations of the Montmorillonite and Aluminium Trihydrate Addition Effects on the Ignitability and Thermal Stability of Asphalt

By means of limiting oxygen index (LOI), cone calorimeter, and TG-DSC tests, this paper investigated the effect of unmodified montmorillonite (MMT), organically modified montmorillonite (OMMT), and aluminium trihydrate (ATH) additions on the flame retardancy for asphalt combustion. Experimental results showed that adding a small amount of montmorillonite did not significantly increase the oxygen index of the asphalt but reduced the heat release rate during asphalt combustion. TGA tests had indicated that the montmorillonite (MMT and OMMT) could suppress the release of flammable volatiles and form more asphaltenes, which hence postponed the burnout time of asphalt. Furthermore, the combination of montmorillonite (MMT and OMMT) and ATH had yielded a synergistic effect, which had further reduced the heat release rate and also increased the oxygen index of asphalt. In particular, after further addition of OMMT, the barrier layer showed less crack, leading to a significant decrease in the heat release rate as compared to the adding of ATH alone.

A DFT study on the initial stage of thermal degradation of Poly(methyl methacrylate)/carbon nanotube system

DFT calculations, with VWN exchange correlation functional and double numeric basis set, were used to evaluate the energies required for the scission reactions taking place in the initial stage of the thermal degradation of Poly(methyl methacrylate) (PMMA) in the presence of a carbon nanotube (CNT). Side group and main chain scissions were investigated. The results averaged from five configurations of pure PMMA (DP=5) were used as references and compared to the results obtained for the five same configurations of PMMA grafted on three carbon nanotubes of similar diameter (1.49 nm). The bond dissociation energies (BDE) of main chain scission evaluated for grafted PMMA was 4 % less endothermic than for pure PMMA. These results seemed independent of the tested chirality (11,11); (12,10) and (16,5) of the carbon nanotubes. Comparisons with the BDE of the weakest bonds due to intrinsic defaults (head to head and unsaturated end chain) were performed.