Fire Retardant Research Articles

Layered double hydroxides bundled Agar-g-PAN/Ag nanocomposite films: A strategy to improve thermal, barrier and antibacterial properties

With an aim of designing a biodegradable packaging material with considerable stability, herein, layered double hydroxides (LDH) bundled agar grafted polyacrylonitrile nanocomposites (Agar-g-PAN/Ag/LDH) incorporated with silver nanoparticles (Ag Nps) have been synthesized using surfactant free in situ polymerization method. The LDH platelets form a laminating structure around the Agar-g-PAN copolymeric network while the Ag Nps are dispersed throughout the material. The prepared nanocomposite films exhibit high thermal stability because of the sandwiching of polymeric chains in between the LDH platelets which also evidences the improvement in fire retardancy. The comparative analysis of limiting oxygen indices of Agar-g-PAN/Ag/LDH nanocomposites with PAN and Agar-g-PAN clearly indicates the fire-repellent nature of the materials. Proper exfoliation and partial intercalation of the LDH platelets as well as presence of Ag Nps result in almost five-fold enhancement in oxygen barrier properties of Agar-g-PAN/Ag/LDH nanocomposite films as compared to the copolymeric matrix. The combination of LDH with Ag Nps shows a synergistic effect in improving the biodegradability and chemical resistance of the nanocomposite films. The antibacterial studies indicate remarkable antibacterial properties of the Agar-g-PAN/Ag/LDH nanocomposites which are more pronounced for gram negative bacterial strains. The synthesized nanocomposite films are biodegradable and chemically inert with enhancement in thermal, barrier and antibacterial properties, making them suitable candidates for packaging applications.

From Bioresources to Thermal Insulation Materials: Synthesis and Properties of Two-Component Open-Cell Spray Polyurethane Foams Based on Bio-Polyols from Used Cooking Oil.

Open-cell spray polyurethane foams are widely used as highly efficient thermal insulation materials with vapor permeability and soundproofing properties. Unfortunately, for the production of commercial foams, mainly non-renewable petrochemical raw materials are used. The aim of this study was to determine the possibility of completely replacing petrochemical polyols (the main raw material used in the synthesis of polyurethanes, alongside isocyanates) with bio-polyols obtained from used cooking oils, classified as waste materials. The research consisted of three stages: the synthesis of bio-polyols, the development of polyurethane foam systems under laboratory conditions, and the testing of developed polyurethane spray systems under industrial conditions. The synthesis of the bio-polyols was carried out by using two different methods: a one-step transesterification process using triethanolamine and a two-step process of epoxidation and opening oxirane rings with diethylene glycol. The obtained bio-polyols were analyzed using gel chromatography and nuclear magnetic resonance spectroscopy. The developed polyurethane foam formulations included two types of fire retardants: halogenated tris(1-chloro-2-propyl) phosphate (TCPP) and halogen-free triethyl phosphate (TEP). In the formulations of polyurethane systems, reactive amine catalysts were employed, which become incorporated into the polymer matrix during foaming, significantly reducing their emission after application. The foams were manufactured on both a laboratory and industrial scale using high-pressure spray machines under conditions recommended by commercial system manufacturers: spray pressure 80-100 bar, component temperature 45-52 °C, and component volumetric ratio 1:1. The open-cell foams had apparent densities 14-21.5 kg/m3, thermal conductivity coefficients 35-38 mW/m∙K, closed-cell contents <5%, water vapor diffusion resistance factors (μ) <6, and limiting oxygen indexes 21.3-21.5%. The properties of the obtained foams were comparable to commercial materials. The developed polyurethane spray systems can be used as thermal insulation materials for insulating interior walls, attics, and ceilings.

Recycling construction wastes to fabricate particle boards with admirable flame retardancy, smoke suppression and mechanical performance

Construction wastes (CWs) were utilized in this work as the feedstock for manufacturing wasted-based particle boards (WPBs). Results revealed that phytic acid (PA), as a natural and sustainable fire retardant, imparts the WPBs excellent flame retardancy and smoke suppression. The hydrogen bonds network formed among PA, waste particles, and adhesive improves the stress transferring of WPBs when subjected to load, thus elevating the modulus of elasticity and inner bonding strength of PA-treated WPBs. We believe that the as-proposed recycling methods promote the value-added utilization of CWs, and it is also beneficial for realizing the recycling of timber architectures.

Influence of Protic Ionic Liquid-Based Flame Retardant on the Flammability and Water Sorption of Alkalized Hemp Fiber-Reinforced PLA Composites.

This article investigates the effects of combining a novel protic ionic liquid-based fire retardant (FR) with alkalized hemp fiber. A pivotal importance of this study refers to the hydrophilic properties and limits regarding poor thermal resistance of green composites where standard guidelines for fire risks are crucial. Although it is well-studied that alkalization is essential for green composite's moisture and mechanical durability, research on the flammability of such a combined treatment for natural fiber-reinforced biopolymer composites is lacking. The alkaline treatment used in the current study follows a process already studied as optimal, particularly for the selected hemp fiber. The fire performance was examined using a bench scale approach based on self and piloted ignition from cone calorimeter tests. The result from the Fourier-transform infrared analysis of the hemp fiber confirms phosphorylation following the fire-retardant treatment, which was visible from the morphological examination with scanning electron microscope. The presence of FR in the composites led to impactful moisture sorption. However, the FR composites demonstrated an enhanced response to fire, indicating potential use as a Class B standard for building construction, and hazard level 3 (HL3) classification as an interior material in vehicles, provided the problem of high emission of smoke is mitigated.

Improvement of thermal stability and flame retardancy of beech wood fibers using steam explosion and phosphorylation reaction

An environmentally friendly approach was studied for improving the fire retardancy of beech wood using a steam explosion process coupled with a phosphorylation reaction. Raw beech, steam-exploded, or bleached wood was subjected to phosphorylation employing etidronic acid (HEDP) and urea, and the resulting chemical composition and thermal behavior were analyzed using techniques such as elemental analysis, Fourier transform infrared spectroscopy, ionic chromatography, and pyrolysis combustion flow calorimetry. The thermal performance of beech wood underwent significant enhancements after the steam explosion treatment combined with soda impregnation. It resulted in a striking reduction in heat release rates (HRR), especially its peak (pHRR) and time-to-pHRR (TpHRR) values (from 139.5 W/g and 365 °C to 40 W/g and 247 °C) and an increase in residue from 10.5% to 41.3%. The results demonstrate that the process created a self-extinguishing and non-flammable material that exhibited noteworthy flame retardancy improvement.

Flexural strength and flammability of pineapple leaf fiber (PALF)/fire retardants reinforced polymer composites

The use of natural fibers as reinforcement in composite materials, such as pineapple leaf fiber (PALF), has been extensively studied. However, it is important to note that natural fiber-reinforced polymer composites are often associated with high flammability. The aim of this paper is to investigate the mechanical properties and fire retardancy of Pineapple Leaf Fiber (PALF) reinforced polymer composites treated with various flame retardants. The PALF composites were treated with different fire-retardant additives, including ammonium polyphosphate (APP), aluminum hydroxide (ALH), and magnesium hydroxide (MH), at varying ratios (10 wt%, 20 wt%, and 30 wt%). The flexural properties of the PALF composites were assessed using a Universal Testing Machine (UTM) in accordance with ASTM D7264. The flammability testing was conducted following the Underwriters Laboratories 94 (UL-94) using standard ASTM D635 and ASTM D3801. The results of flexural tests indicated that PALF-reinforced polymer composites containing 10% MH as fire retardant exhibited the highest flexural strength (102.96 MPa). Scanning Electron Microscopy (SEM) was employed to analyze the fracture behavior of PALF-reinforced polymer composites with different fire-retardant additives. The SEM analysis revealed various characteristics including fiber pull-out, fiber breakage, inhomogeneous structural distribution (in cases of APP, MH, ALH), presence of undesired bubbles, and fiber–matrix cracking. In terms of fire retardancy, the most promising results were obtained with the addition of 20% and 30% APP. These compositions achieved V-1 and V-0 ratings respectively, in the vertical UL-94 flammability test. Notably, the horizontal test demonstrated that the composites containing 30% APP did not sustain burning and exhibited no burning rate. Similarly, the composite with 20% APP self-extinguished before the first mark without any observable burning rate.

Mechanical properties and flammability of pineapple leaf fiber (PALF) reinforced polymer composite with hybridized fire retardants

Mechanical properties and flammability of pineapple leaf fiber (PALF) reinforced polymer composite with hybridized fire retardants

Fire-Resistant Coatings, Obtained by Layer-by-Layer Assembly, in the System of Silicic Acid Gel – Diammonium Hydrogen Phosphate – Urea

The paper discusses the influence of flame retardant compositions obtained in the system of silicic acid sol (SiO2 sol) – flame retardants on the fire retardant properties of thin dense cotton fabrics and low density voluminous tapestry fabrics. The need to develop the optimal composition of a fire-retardant composition for a specific fabric, or to unify it for two main groups of fabric: thin and bulky low-density ones, is substantiated. Experimental coatings were obtained by applying SiO2 sol, which was obtained by the reaction between liquid glass and acetic acid, followed by application of flame retardant solutions (diammonium hydrogen phosphate (DAHP) and urea) by spraying or by the bath method. As a result of the optimization, using the central composite uniform rotatable plan of the second order, it was established that the main effect of the flame retardant is exerted by diammonium hydrogen phosphate (DAHP). The content or concentration of urea depends on the concentration of DAHP used: if diluted DAHP solutions (9–10 %) are used, trace amounts of urea (0–0.5 %) must be added. In the case of using a concentrated DAHP solution (18–20 %), the concentration of the urea solution should also be increased to 8–10 %.

Synergistic fire retardancy of melamine resin modified with pentaerythritol and ammonium polyphosphate in PP

AbstractThe synergistic fire retardancy of modified melamine resin with pentaerythritol (MF‐PER, a novel green and effective triazine charring agent), and ammonium polyphosphate (APP) in polypropylene was investigated by UL‐94 test, LOI measurement, and cone calorimetry test. It is found that the synergism of MF‐PER is obviously better than pentaerythritol (PER). MF‐PER/APP imparts a fire retardancy mainly by the following mode: in burning process, MF‐PER, and APP are first pyrolyzed respectively into polyols and polyphosphoric acid, which is esterified to form phosphoric ester, and the inert gases make the molten residues foaming; When the temperature increases, and polyphosphoric acid is dehydrated to polymetaphosphoric acid, which dehydrates phosphoric ester to form an intumescent char layer, inducing a fire retardant effect by barrier effect. The graphitization degree of the cone calorimetry test residues of the FR‐PP with MF‐PER is higher than that with PER, which leads to a better synergism.Highlights Melamine formaldehyde resins modified with pentaerythritol (MF‐PER) as a novel triazine charring agent was designed and synthesized. MF‐PER is synthesized by solid phase method and using hexahydroxymethyl melamine (HMM) instead of cyanuric chloride as raw material, so the emission of three wastes in its synthesis process is very little, only a small amount of formaldehyde and water are produced. MF‐PER has excellent synergistic fire retardancy with APP in polypropylene. The highly efficient and environmentally benign charring agent show great potential for developing more efficient and eco‐friendly IFR.

Effect of Magnesium Hydroxide and Aluminum Hydroxide as Thermal Barriers on the Flame-Retardant Behavior of Acrylic-Based Coating

In the effort to improve fire safety in residential, industrial, or naval structures, the study of flame-retardant coatings has become increasingly interesting. Flame-retardant additives are definitely the most traveled route; however, often these additives are halogenated compounds that increase the amount of smoke and toxic decomposition of the products during polymer combustion. It is necessary to develop new fire retardant (FR) agents that respect the environment and are safe for human health. This work aims to study two completely harmless hydroxides, Mg(OH)2 and Al(OH)3, added in low percentages (2 wt.%) to an already marketed acrylic polymer emulsion (79.2 wt.% of solid content, 37.3 wt.% and 41.8 wt.%, respectively, for polymer and fillers contents) in order to decrease the dangerous effects of these additives on the physical integrity and durability of the coatings. The hydroxides content was added in 6.2 wt.% and 5.6 wt.%, respectively, to polymer and total solids present in the emulsion. Flame exposure tests are conducted at different times (15 s and 30 s) to verify the flame stability and thermal insulation exerted by the investigated coatings. Furthermore, through a precise analysis of the areas damaged by the combustion process, it is possible to link the flame-retardant properties to the FR choice and its particle size, finding a promising solution in the sample based on small Mg(OH)2 particles for fire protection in naval applications.

Hydrophobicity, transparency, mechanically excellent and fire safety multifunctional epoxy resin based on a novel DOPO derivative with cyano group

A novel derivative of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) bearing cyano groups, referred to as PDPO, was successfully synthesized and applied as an additive for epoxy resin (E-44, with epoxide equivalent weights ranging from 201 to 240 g/epoxide), along with the curing agent 4,4′-diaminodiphenylmethane (DDM). Comprehensive characterization techniques, including Fourier transform infrared (FTIR) spectroscopy, 1H and 31P nuclear magnetic resonance (NMR) spectroscopy, and elemental analysis (EA), were employed to confirm the chemical structure of PDPO. Thermogravimetric analysis (TGA) revealed remarkable thermal stability for PDPO, with a substantial char residue of 43.1 wt% at 800 °C. Introducing 5 wt% PDPO into the EP formulation resulted in a notable enhancement of fire retardancy, as evident from the increased Limiting Oxygen Index (LOI) value of 32.2 % and the attainment of UL-94 V-0 rating for the EP/PDPO-5. The efficacy of fire retardancy was further underscored by cone calorimeter (CC) testing, which showcased a reduction in heat release rate and smoke production. An in-depth analysis of pyrolysis behavior and char formation demonstrated that PDPO exhibited multifaceted roles in both the gas and condensed phases, contributing to the fire retardant properties of the material. Additionally, the incorporation of PDPO at a concentration of 1 wt% led to notable enhancements in the tensile and flexural strength of EP/PDPO-1 by 15.2 % and 10.4 %, respectively, compared to neat EP. Remarkably, the transparency of EP/PDPO-1 was preserved at 95.6 %, while the water contact angle was elevated to 115.5°, indicating improved hydrophobicity. These results collectively highlight the potential of PDPO as a fire-retardant additive, demonstrating its ability to simultaneously stay transparency and enhance mechanical properties and hydrophobic characteristics in the EP/PDPO systems.

Research Progress in Boron-Modified Phenolic Resin and Its Composites.

As one of the most successful modified phenolic resins, boron-modified phenolic resin (BPF) has excellent heat resistance and ablative resistance, good mechanical and wear resistance, and flame retardancy. BPF and its composites can be widely used in areas such as aerospace, weapons and equipment, automobile brakes, and fire retardants. In this review, the current state of development of BPF and its composites is presented and discussed. After introducing various methods to synthesize BPF, functionalization of BPF is briefly summarized. Particular emphasis is placed on general methods used to fabricate BPF-based composites and the heat resistance, ablative resistance, mechanical property, wear resistance, flame retardancy, and water resistance of BPF-based composites. Finally, the challenges of this research area are summarized and its future outlook is prospected.

Fast Lithium Ion Transport Pathways Constructed by Two-Dimensional Boron Nitride Nanoflakes in Quasi-Solid-State Polymer Electrolyte.

Quasi-solid-state electrolytes (QSSEs) are gaining huge popularity because of their significantly improved safety performance over nonaqueous liquid electrolytes and superior process adaptability over all-solid-state electrolytes. However, because of the existence of liquid molecules, QSSEs typically have low lithium ion transference numbers and compromised thermal stability. In this work, we present the fabrication of a well-rounded QSSE by introducing hexagonal boron nitride nanoflakes (BNNFs) as an inorganic filler in a poly(vinylene carbonate) matrix. BNNFs, in contrast to most inorganic fillers used as anion trappers, are used to build fast lithium ion transport pathways directly on their two-dimensional surfaces. We confirm the attractive coupling between lithium ions and BNNFs, and we confirm that with the help of BNNFs, lithium ions can migrate with less damping and a lower transport energy barrier. As a result, the designed electrolyte exhibits good ion transportability, promoted fire retardancy, and good compatibility with lithium metal anodes and commercial cathodes.

Circuit Integrity Assessment of Fire-Resistant Cables

In the electrical industry, fire accidents may happen due to overheating of electrical equipment, short circuit faults and any external source of fire. Polymeric Electrical Cables are prone to spread fire along the cable run as the insulation and sheathing materials are of flammable nature. Hence various flame retardants and low-smoke polymers are being used so that the flame spread and toxic gas release can be controlled. There are some special application cables called Fire Resistant cables which need to maintain the circuit integrity of the cable even during fire conditions. The construction of these fire-resistant cables requires fire-resistant insulation to achieve the fire-resistance property. They are such as Glass- Mica tape, Silicone Rubber, mineral insulation, metal insulation and fire retardant coating. There is various International and National standard assessing methods to assess these special cables. In this paper, the fire-resistant insulating materials and their performance during the assessment in achieving the required fire-resistant property are discussed.

Hydrogen bonding induced polyphosphazene/MXenes 2D/2D structure loaded with MOFs enabling fire-safe epoxy composite

High thermal runway hazard has been the blocking stone on the way of extended usage of epoxy resin (EP). In such context, the method of preparing fire retardant EP composite with inorganic filler has been adapted, and the shining star of transition metal carbides (MXenes, denoted as MX) has evoked the ardent concern. Nevertheless, the inferior flame retardation efficiency, severe agglomeration, surface scarcity of organic groups have collectively appealed to design MX based flame retardant (FR) with high efficiency. Here, the hydrogen bonding induced strategy and in-situ growth method are utilized to gain FR of P-MX@UIO. Under 2.0 wt% loading, the reductions on peak heat release rate and total heat release reach 48.9% and 45.4%. Meanwhile, the decreases in peak smoke production and total smoke production approach 48.6% and 43.6%. Also, the peak CO production rate is impaired by 48.3%. Such strengths both in suppressing heat and toxicants emissions, are vividly validated via comparison with previous works. Ulteriorly, the inhibited releases of NO and HCN are detected. Peculiarly, the storage modulus is promoted by 75.6% after incorporating P-MX@UIO. This work may inspire the judicious design of MX based FR and fire-safe polymer composites.

Harvesting value from agricultural waste: Dimensionally stable fiberboards and particleboards with enhanced mechanical performance and fire retardancy through the use of lignocellulosic nanofibers

The present work provides a comprehensive study on the utilization of rapeseed stalks, an agricultural waste, as a raw material for the production of resin-free fiberboards and particleboards, using LCNFs as binder. The rapeseed stalks underwent appropriate crushing and fibrillation and were combined with a novel class of lignocellulosic nanofibers (LCNFs) derived from date palm waste, another agricultural residue. The incorporation of LCNFs in both fiberboards and particleboards resulted in increased density and enhanced mechanical properties, dimensional stability, and fire resistance. These positive effects can be attributed to several factors. Firstly, the incorporation of LCNFs led to a reduction in porosity, positively impacting the modulus of rupture, modulus of elasticity, and internal bonding of the produced fiberboards and particleboards. Notably, fiberboards containing 15 wt% LCNF exhibited superior specific properties compared to our commercial reference. Additionally, this densification effect mitigated moisture absorption and thickness swelling, as even a 2 wt% incorporation of LCNF in fiberboards showed reduced values for both properties. Secondly, the high lignin content of the LCNFs contributed to decreased hydrophilicity in the fiberboards and particleboards, leading to significant improvements in water contact angle, water absorption, and thickness swelling. Lastly, the increased density of the fiberboards and particleboards resulted in improved fire resistance, with flame propagation time being higher for all boards containing LCNFs, even at low content (2 wt%), compared to the commercial fiberboard. Notably, fiberboards demonstrated superior performance compared to particleboards, attributed to factors such as low cohesion, particle heterogeneity, and excessive porosity. Overall, this study demonstrates the feasibility of utilizing agricultural waste as a raw material for board production, eliminating the need for urea-formaldehyde resins and paraffin waxes commonly found in commercial fiberboards.

Radionuclide surrogate aerosolization, resuspension and suppression in hazardous situations

Radioactive fire following nuclear accidents causes resuspension of radioactive contamination that can spread over large areas. Although many papers focus on particle deposition and resuspension, a limited number of studies model its suppression. Even less data is available for the comparison of emissions across particle size, surface, and mode of resuspension. In this study, cerium dioxide surrogate for internal hazards such as radionuclide particle matter was aerosolized into a large chamber and subsequently resuspended after sedimentation. Resuspension was induced by common modes of human movement including walking, wind, and driving on common surfaces including polyvinyl chloride (PVC), artificial grass (turf), and concrete in a 5.8 m long, 3.7 m wide and 3 m high tent. The resuspension was experimentally measured for two particle sizes (1 and 10 μm) at three different heights (0.3 m, 1.2 m, and 2.4 m) and compared across size, surface, and mode of resuspension. Particle size distribution was measured using an aerodynamic particle sizer and the resuspended particles were collected with the wetted wall cyclone aerosol collector and quantitated using inductively coupled plasma mass spectrometry. The testing was repeated with the F-500 fire retardant application to study its effect on resuspension. In this study, artificial grass flooring was found to generate the most resuspension, with walking on turf for the 1 μm particle testing yielding the highest factor overall. Concrete had the lowest resuspension, showing variations in the size distribution of aerosol as a function of height from the source resuspension factors. The application of fire retardant was found to significantly reduce surrogate resuspension, regardless of resuspension method or testing surface.The results provide impactful information regarding the different modes of resuspension including human transport (walking and driving) and wind for the resuspension of radionuclide surrogate particles deposited onto common surfaces and the effect of fire retardant application on their resuspension, leading to higher levels of safety for nuclear energy plants and facilities.

Producing safer, more environmentally friendly fire-resistant fabrics

Novel finishing method employs anchor peptides to adhere bio-hybrid fire retardants.

Flammability and burning behaviour of fire protected timber

Decarbonization has driven the construction industry to rediscover biobased, but inherently combustible, materials like timber. To avoid compromising fire safety, reaction to fire of timber can be effectively reduced by fire retardant surface coatings or impregnation treatments. Using a combination of simultaneous thermal analysis, microscale combustion calorimetry and cone calorimetry, vacuum-pressure impregnated (boron free, phosphorus-based) plywood was tested against plywood coated with a thin layer of water-based fire retardant intumescent coating (melamine free, phosphorus-based). Comparing the peak heat release rate (pHRR) and total heat release (THR) of the three plywood samples, the impregnated was lowest, and the coated was lower (pHRR −34% and −20%, THR -45% and −21% respectively) relative to the untreated plywood. In contrast, the coating layer postponed sustained flaming for longer than impregnated wood and delayed burnthrough, effects critical to the growth rate of a developing fire. Better understanding of the assessment of flammability of fire protected timber has been obtained using cone calorimeter data supported by microscale analyses. The results challenge the simple flammability ranking based on total heat release, and highlight the need for further development of a methodology for comparing different fire protection strategies for timber.

Preparation of Graphene Quantum Dots Decorated Montmorillonite to Reinforce Fire Retardancy of Polystyrene

Preparation of Graphene Quantum Dots Decorated Montmorillonite to Reinforce Fire Retardancy of Polystyrene