Ammonium polyphosphate-based nanocoating for melamine foam towards high flame retardancy and anti-shrinkage in fire

Epoxy/melamine polyphosphate modified silicon carbide composites: Thermal conductivity and flame retardancy analyses

Silicon carbide (SiC) was modified by melamine polyphosphate (MPP)-modified silicone to form SiC-MPP, then incorporated into epoxy resin (EP) for developing thermally resistant composites, which showed thermal conductivity and flame retardancy performance. The EP/SiC-MPP composites were prepared by blending and cured under 60°C for 2 h and 150°C for 8 h. The grafting degree of SiC-MPP was analyzed using Fourier transform Infrared, scanning electron microscope, and thermogravimetric measurements. The flame retardancy of the EP/SiC-MPP composites was studied by UL-94 vertical combustion and cone calorimetry test. The results showed that for EP/SiC-MPP containing 20 wt%, the UL-94 was case V1. Also compared to pure epoxy, the peak heat release rate (PHRR) of composites was reduced from 800 to 304 kW·m−2. The thermal conductivity of EP/SiC-M20 composites was 0.53 W·m−1·K−1, almost 2.5-fold higher than pure epoxy (0.21 W·m−1·K−1). The as-prepared EP/SiC-MPP composites exhibited enhanced flame retardancy and thermal conductivity. Based on analyses performed, these composites took credit-related applications.

Improvement the Flame Retardancy and Thermal Conductivity of Epoxy Composites via Melamine Polyphosphate-Modified Carbon Nanotubes

Surface chemical modification of carbon nanotubes can enhance the compatibility with polymers and improve flame retardancy performances. In this work, the double bond active sites were constructed on the surface of carbon nanotubes modified by the γ-methacryloyloxypropyl trimethoxysilane (KH570). Glycidyl methacrylate (GMA) was further grafted onto the surface of carbon nanotubes via free radical polymerization. Finally, the flame retardant melamine polyphosphate (MPP) was bonded to the surface of carbon nanotubes by the ring-opening reaction. This modification process was proved to be achieved by infrared spectroscopy and thermogravimetric test. The carbon nanotubes modified by flame retardant were added into the epoxy matrix and cured to prepare flame retardant and thermal conductive composites. The flame retardancy of composites were studied by cone calorimetry, UL94 vertical combustion test and limiting oxygen index. The thermal conductivity of composites was characterized by laser thermal conductivity instrument. The results showed that when the addition amount of flame retardant MPP-modified carbon nanotubes in composites was 10 wt%, the flame retardant level of UL94 reached to V2, the limiting oxygen index increased from 25.1 of pure epoxy resin to 28.3, the PHRR of pure epoxy resin was reduced from 800 kW/m² to 645 kW/m² of composites and thermal conductivity of composites was enhanced from 0.21 W/m·K⁻¹ of pure epoxy resin to 0.42 W/m·K⁻¹ of the composites.

Cobalt nanoparticles embedded into nitrogen-doped graphene with abundant macropores as a bifunctional electrocatalyst for rechargeable zinc-air batteries

Nitrogen doped carbon materials containing transition metal nanoparticles have attracted much attention as bifunctional oxygen electrocatalysts. In this paper, the template etching method is used to obtain the nitrogen-doped graphene with abundant macropores embedded with cobalt nanoparticles (Co@N-C). The prepared Co@NC-800 catalyst has a half-wave potential (E 1/2= 0.835V) close to Pt/C and good stability in excess of Pt/C for oxygen reduction reaction (ORR). At the same time, the catalyst has good oxygen evolution reaction (OER) performance. In addition, zinc-air batteries (ZABs) based on the Co@NC-800 catalyst show good cycle stability of up to 200000 s and high power density of 73.5 mW cm -2 . The synergistic effect of the integrated component between nitrogen-doped graphene and cobalt nanoparticles as well as the macroporous structure endow Co@NC-800 with abundant exposed active sites and mass/electron transfer capacity, thus leading to the high electrocatalytic activity. This work shows potential for practical applications in electrochemistry.

Synergetic integration of thermal conductivity and flame resistance in nacre-like nanocellulose composites

Highly thermally conductive and flame resistant nanocellulose-based composites can synchronously achieve efficient thermal dissipation and low fire hazards of electronic devices, which shows great promise in next-generation green and flexible electronics. However, it has long been intractable to optimize the high thermal conductivity (TC) and flame resistance simultaneously. Herein, synergetic integration of high TC and flame resistance in nacre-like nanocellulose composites has been successfully achieved by the vacuum-assisted filtration of cellulose nanofibers (CNFs) and functionalized boron nitride nanosheets (BNNS-p-APP). Benefiting from the highly oriented hierarchical microstructure, strong hydrogen-bonding interaction, and successful immobilization of ammonium polyphosphate (APP), the as-obtained CNFs/BNNS-p-APP composite film achieves a high in-plane TC of 9.1 W m^-1 K^-1 and outstanding flame resistance. Meantime, this eco-friendly nanocellulose-based composite also exhibits remarkable flexibility, folding endurance, and mechanical robustness, robustness, which may open up a new opportunity for the thermal management of flexible electronics.

Flame-responsive aryl ether nitrile structure towards multiple fire hazards suppression of thermoplastic polyester

Multiple fire hazards (heat, smoke, dripping) caused by thermoplastic polymers pose integrated risks. Halogen or phosphorus flame-retardants tend to increase toxic, smoke or dripping hazards due to their flame-retardant mechanism. The physical blending flame-retardants into matrixes also presents a migration dilemma with causing potential environmental threats. Herein, we propose a novel multi-hazards inhibition strategy by chemical-incorporating aryl ether nitrile structures into poly(ethylene terephthalate)(PET), which is a typical thermoplastic polymer and a major contributor of multiple fire hazards. Through flame-responsive cyclotrimerization and aliphatic fragment capture, the flammability risks and multi-hazards (heat, smoke, toxicity, dripping) are significantly suppressed. The limiting oxygen index of the modified PET increases from 21.0 to 31.0. The peak of heat release, total smoke release, and carbon monoxide production decrease by 49.0 %, 31.1 %, and 52.6 %, respectively. The dripping hazards are eliminated, and the UL-94 rating reaches to V-0 level with no dripping production. Hence, this state-of-art strategy supplies a new approach for the fire hazards suppression of thermoplastic polymers.

Fire behavior of innovative alginate foams

A new biosourced composite foam (AF, associating foamed alginate matrix and orange peel filler) is successfully tested for fire-retardant properties. This material having similar thermal insulating properties and density than fire-retardant polyurethane foam (FR-PUF, a commercial product) shows promising enhanced properties for flame retardancy, as assessed by different methods such as thermogravimetric analysis (TGA), pyrolysis combustion flow calorimetry (PCFC) and a newly designed apparatus called RAPACES for investigating large-scale samples. All these methods confirm the promising properties of this alternative material in terms of fire protection (pHRR, THR, EHC, time-to-ignition, flame duration or production of residue), especially for heat flux not exceeding 50 kW m^-2. At higher heat flux (i.e., 75 kW m^-2), flame retardant properties tend to decrease but maintain at a higher level than FR-PUF. The investigation of the effect of AF thickness shows that the critical thickness (CT) is close to 1.5-1.7 cm: heat diffusion and material combustion are limited to the CT layer that protects the underlying layers from combustion. A multiplicity of factors can explain this behavior, such as: (a) negligible heat conduction, (b) low heat of combustion, (c) charring formation, and (d) water release. Water being released from underlying layers, dilutes the gases emitted during the combustion of superficial layers and promotes the flame extinction.

Polybenzoxazine Resins with Polyphosphazene Microspheres: Synthesis, Flame Retardancy, Mechanisms, and Applications

Polyphosphazene microspheres were fabricated by ultrasonic-assisted precipitation polymerization using 4,4'-(hexafluoroisopropylidene)diphenol, 4,4'-sulfonyldiphenol, 4,4-(9-fluorenylidene)diphenol, and phenolphthalein to obtain poly[4,4'-(hexafluoroisopropylidene)diphenol]phosphazene (PZAF), poly(4,4'- sulfonyldiphenol)phosphazene (PZS), poly[4,4'-(9-fluorenylidene)diphenol]phosphazene, and poly(phenolphthalein)phosphazene (PZPT) and were incorporated into polybenzoxazines (PBa) to obtain corresponding PZAF/PBa, PZS/PBa, fluorenyl polyphosphazene (PZFP)/PBa, and PZPT/PBa composites. Addition of 5 wt % of PZAF, PZS, PZFP, and PZPT microspheres improved the thermal stability and fire retardancy of PBa resin significantly. Notably, addition of PBa with 5% PZAF led to a 62.5% decrease in the peak heat release rate and 49.3% reduction in total heat release. The role of microspheres in the gas-phase flame-retardancy mechanism in the PBa matrix was studied. Dynamic mechanical analysis results demonstrated that the T _g of PBa flame-retardant composites was still around 210 °C compared to 221 °C of pure PBa. Hence, the synthesized PBa composites had potential applications as high flame-retardancy materials.

Nitrogen/phosphorus synergistic flame retardant-filled flexible polyurethane foams: microstructure, compressive stress, sound absorption, and combustion resistance

Compared with a rigid polyurethane foam, a flexible polyurethane foam (FPUF) has more diversified applications including filtration, sound absorption, vibration-proofing, decoration, packaging, and heat insulation. However, its most potential hazard is flammability. Therefore, in this study, we focused on improving its flame retardation and then tested its sound absorption with the addition of nitrogen/phosphorus synergistic flame retardants. The influence of phosphorus-based flame retardants (TCPP, TDCP, and V6) and a nitrogen/phosphorus synergistic flame retardant (melamine-TDCP) on its microstructure, compressive stress, sound absorption, thermal stability, and flame retardation was systematically explored. The presence of phosphorus flame retardants improved the sound absorption but considerably decreased the mechanical properties. The melamine-TDCP compound flame retardant delivered smaller cells and thus increased the compression property of the resulting foam. Moreover, with a higher content of melamine, the initial mass-loss temperature also increased. In particular, on using TDCP and 5 wt% of melamine as flame retardants, the compressive stress increased by 3.4 times, the average sound absorption coefficient was 0.45, and LOI reached 25.5, which met the requirements of industrial flame retardant/sound absorbent materials. This resultant flame retardant/sound absorbent flexible polyurethane foam can serve as a mattress and furniture pad material, vehicle seat cushion material, and liner for laminated composites in the future.