Excellent Flame Retardant Properties Research Articles

Investigation of the Flame Retardant Properties of High-Strength Microcellular Flame Retardant/Polyurethane Composite Elastomers.

Flame retardants (FRs) often reduce the mechanical properties of polymer materials, and FR/microcellular polyurethane elastomer (MPUE) composite materials have not been systemically studied. Hence, we conducted this study on FR/MPUE composites by using multiple liquid FRs and/or expandable graphite (EG). Compared with liquid flame retardants, the LOI of an expandable graphite/dimethyl methylphosphonate (EG/DMMP) (3:1) combination was significantly increased (~36.1%), and the vertical combustion grade reached V-0 without a dripping phenomenon. However, the corresponding tensile strength was decreased by 17.5%. With the incorporation of EG alone, although the corresponding LOI was not a match with that of DMMP/EG, there was no droplet phenomenon. In addition, even with 15 wt% of EG, there was no significant decline in the tensile strength. Cone calorimeter test results showed that PHRR, THR, PSPR, and TSR were significantly reduced, compared to the neat MPUE, when the EG content surpassed 10 wt%. The combustion process became more stable and thus the fire risk was highly reduced. It was found that flame retardancy and mechanical properties could be well balanced by adding EG alone. Our proposed strategy for synthesizing FR/MPUE composites with excellent flame retardancy and mechanical properties was easy, effective, low-cost and universal, which could have great practical significance in expanding the potential application fields of MPUEs.

A top-down strategy for the preparation of flame retardant, robust, and transparent wood-derived films

Transparent wood is a promising material with many advantages, including high optical transmittance, adjustable optical haze, and excellent mechanical properties. However, the manufacture of transparent wood always requires polymer filling, which affects its sustainability; the flammability of transparent wood also limits its development and application in more fields. Herein, a flame retardant transparent wood film (FR-TWF) was prepared by a top-down chemical treatment. Delignification and TEMPO-mediated oxidation can effectively remove lignin from natural wood and introduce carboxyl groups into the cellulose for further chelation with Al ions. Then, FR-TWF was obtained through self-densification by forming fully collapsed wood cell walls and elastic lumen after drying. The obtained FR-TWF had high optical transmittance (∼76.1%) and haze (∼75.2%); its tensile strength reached 354.3 MPa, exceeding most existing plastic films. Compared with natural wood, the peak of heat release rate and total heat release of FR-TWF decreased by 91.4% and 77.1%, respectively. The excellent flame retardant property of FR-TWF is attributed to the generation of graphitized carbon layers during combustion and the release of more water vapor at high temperatures. Furthermore, the FR-TWF merits being price moderate, sustainable, and biodegradable, which can be widely used in flexible device substrates or optical management devices.

Improving the controlled-release effects of composite flame retardant by loading on porous attapulgite and coating

The attapulgite (ATP) is one of important raw materials of ceramics and often used as a loading carrier. To control the release rate of composite flame retardant (CFR) when exposed to a fire, and to meet the multi-stage flame retarding requirements, the vacuum negative pressure method was adopted to load four kinds of monomer flame retardants on porous ATP as a carrier after activating pretreatment, respectively. Then CFR nanoparticles with controlled-release effects were prepared by the in-situ polymerization reaction on the surface of monomer flame retardants. After that, zinc hydroxyl stannate, styrene, melamine formaldehyde resin and silicon dioxide with high thermal stability and excellent flame retarding properties were selected as the coating layer of four kinds of monomer flame retardants on ATP carrier. Test results of environmental scanning electron microscope and energy dispersive spectrometer show the satisfactory loading and coating results of CFR nanoparticles. Test results of X-ray photoelectron spectroscopy further confirm the excellent loading conditions and coating film formation on ATP carrier. The thermogravimetry-differential thermal scanning calorimetry tests indicate that the flame retarding duration of both loaded and coated CFR nanoparticles on ATP carrier is prolonged and has a satisfactory controlled-release effect.

Fabrication of Flame Retarded Cellulose Aerogel with Hydrophobicity via MF/MTMS Double Cross-Linking

ABSTRACT In order to overcome the disadvantage of highly flammable and poor mechanical performance of cellulose aerogel, herein, cellulose nanofibrils (CNF) were cross-linked by melamine formaldehyde (MF), and further cross-linked and surface decorated by methyltrimethoxysilane (MTMS) to obtain flame retarded compound aerogels. FT-IR spectra confirmed that cross-linking reaction occurred between MF/MTMS and CNF matrix. The morphological analysis demonstrated that the pore size shrinked, whereas the pore amount of compound aerogels increased after cross-linking, thereby resulting in the improvement of mechanical performance. Via double cross-linking, the compound aerogels also exhibited excellent hydrophobicity (contact angle up to 132.3°) and flame retardant properties. The limited oxygen index (LOI) value of double cross-linked specimen (Si-CNF/MF) increased from 19.5% to 37.1%, and the vertical combustion test (UL-94) reached V-0 grade. Microcalorimetry measurement showed that the peak heat release rate (pHRR) and total heat release (THR) of Si-CNF/MF decreased by 50.6% and 64.3% in comparison with pure CNF aerogel, respectively. The analysis results of char residue showed that both condensed phase and gas phase flame retardant mechanisms occurred during combustion, and synergistic effect existed between MF and MTMS. Moreover, the very low thermal conductivity of compound aerogels permitted their application as heat preservation materials.

Enhancing flame retardant property of graphene oxide via phosphorus and nitrogen co-doping

A simple and versatile method has been developed to efficiently enhance the flame retardant of graphene oxide (GO) by adding ammonium phosphate (AP) into GO. The as-made GO/AP exhibits excellent flame retardant properties, which emits some smoke at the beginning without catching any fire and any observable shrinkage. In contrast, the GO catches fire within several seconds and completely burns out. The improvement of flame retardancy can be attributed to the formation of CP and CN bonds with heat. This simple and effective technique of the introduction of P and N can be adopted for inexpensive mass production of GO/AP for many practical applications such as sensors, energy-storing materials, and nanomaterial electronics.

Cyclotriphosphazene-based epoxy resins with excellent mechanical and flame retardant properties

The design, synthesis, and characterization of a novel epoxy monomer, CP-EP, which consists of nontoxic eugenol and nonflammable cyclotriphosphazene has been carried out in this work. Chemical structure of CP-EP was confirmed by nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS). Using 4,4′-diaminodiphenylmethane + diethyltoluenediamine (DDM + DETDA), succinic anhydride (SA), or methylhexahydrophthalic anhydride (MeHHPA) as curing agent, three cyclotriphosphazene-based thermosets (CPTs) were produced, and non-isothermal curing behaviors were investigated by using dynamic differential scanning calorimetry. In comparison to the bisphenol-A epoxy resin, CPTs exhibit higher glass transition temperature, enhanced tensile/flexural strengths, and significantly improved nonflammability. UL-94 rating and limiting oxygen index (LOI) for CPTs were V-0 and 28% respectively. These observations suggest an effective approach for the preparation of a halogen-free epoxy thermosetting system. This approach may be used for the generation of high-performance fire-safe epoxy thermosets. Both environment and human health can benefit from the use of such materials.

Organohydrogel based on cellulose-stabilized emulsion for electromagnetic shielding, flame retardant, and strain sensing

In the past, electromagnetic interference (EMI) shielding materials have achieved great breakthroughs, however, they still suffer from high reflectivity and poor environmental stability, resulting in detrimental secondary pollution and weak adaptability. Herein, an organohydrogel-based EMI shielding material was prepared through cellulose nanofibril-based Pickering emulsion, composed of an MXene network for electron conduction, encapsulated paraffin wax microspheres with MXene-Fe3O4 shells for multiple scattering of the incident wave, and MXene-CNF-Fe3O4-polyacrylamide hybrid interfaces for dielectric polarization. The EMI shielding performance of our organohydrogel shows an absorption-dominated feature. It can effectively shield 99.625 % electromagnetic wave, satisfying the requirement of commercial EMI shielding materials. Moreover, the organohydrogel possesses excellent flame retardancy properties and long-time environment properties to improve safety and reliability; and it also demonstrates sensitive deformation responses as an on-skin sensor. Therefore, our organohydrogel can simultaneously detect human motion and protect human from EMI radiation and accidental burn.

Low carbon footprint preparation of MXene incorporated lignocellulosic fibers for high thermal conductivity applications

New wood-based composite materials with thermal conductivity are greatly desired in the fields of packaging materials for electronic components. In this study, a new multifunctional composite material (M@FC) is prepared by simply blending clay-like Ti3C2Tx MXene and delignified wood fibers together, and then followed by an infusing epoxy resin with environmentally friendly vacuum assisted resin transfer molding (VARTM) process. The resulting M@FC (0.92 W m−1 K−1) possesses superior thermal conductivity as compared to natural wood (0.099 W m−1 K−1) and most polymers. Furthermore, after the VARTM process, the structure of the M@FC is tighter, and thus showing excellent mechanical properties (tensile strength of 93.0 MPa and flexural strength of 172.7 MPa). In addition, good water resistance and excellent flame retardant property are observed for M@FC. The improvement of thermal conductivity provides the possibility for its application for packaging materials in electronic components. This study using waste wood as the important component provides a new idea for carbon cycling and recycling of natural resources.

Synthesis and properties of a new halogen-free flame-retardant epoxy resin flame retardant

PurposeThis paper aims to study a new halogen-free fame-retardant curing agent 1-aminoethylidenediphosphonate (AAEDP).Design/methodology/approachThe AAEDP was synthesized by phosphoric acid, acetonitrile and ammonia. The chemical structures of AAEDP were characterized by proton nuclear magnetic resonance, mass spectrometry and Fourier transform infrared spectrometer. Thermal gravimetric analysis (TGA) and scanning electron microscope (SEM) would study the thermal properties and the char residues of AAEDP/EP. The thermal stability, mechanical and flame properties and morphology for the char layer of composite materials were separately investigated using TGA, tensile and charpy impact tests, limiting oxygen index (LOI), UL-94 HB flammability standard (UL-94) and SEM.FindingsThe results showed that the AAEDP had been prepared successfully. When the intumescent flame retardant was added into the EP, the LOI of composite material was improved.Research limitations/implicationsThe AAEDP can be prepared successfully and can improve the flame resistance of composite material.Practical implicationsThe AAEDP has excellent flame-retardant properties and produce no toxic fumes when burnt in case of fire.Originality/valueThe results showed that the phosphorus content of AAEDP was 2.958 Wt.%; the impact and tensile strength of the composite material were 6.417 kJ m−2 and 38.0 MPa, respectively; and the LOI and UL-94 were 29.7% and V-0 ranking, respectively. The TGA results indicated that the carbon residue ratio can be increased by 1000°C in air. The denser and more uniform structure of residual carbon prevents heat transfer and diffusion, restricts the production of combustible gas and reduces the rate of heat release.

Cross-linkable phosphorus/nitrogen-containing aromatic ethylenediamine endowing epoxy resin with excellent flame retardancy and mechanical properties

Endowing epoxy resins (EPs) with enhanced flame retardancy without losing its mechanical properties is a considerable challenge for applications in wide areas. Herein, a phosphorus/nitrogen-containing aromatic ethylenediamine (BSEA) was synthesised by a simple addition reaction between N, N’-bis(salicylidene)ethylenediamine (NEA) and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), and utilised as a reactive flame retardant for EP/biscitraconimide resin (BCI) system. With only 0.35 wt% of phosphorus, EP/BCI/BSEA-4 showed excellent flame retardancy with an increased LOI of 32.1 %; a UL-94V-0 rating; and lower peak of heat release rate, total heat release, fire growth rate index and average effective heat combustion than pure EP. The flame-retardant mechanism of BSEA was revealed to be in gas and condensed phase. Additionally, modified EP possessed increased storage modulus and good mechanical properties in room and cryogenic temperatures. All these results verified that the BSEA was a high-efficiency flame retardant for EP matrix and have a broad application prospect.

Boosting both flame retardancy and mechanical properties of carbon fiber/epoxy composites via polycyclic phosphorus-nitrogen imidazole derivative

As a huge challenge to improve the mechanical properties while improving flame retardant performance in carbon fiber/epoxy resin composites. Hence, a novel flame retardant, polyaromatic ring phosphor-nitrogen imidazole derivative (PNB), was designed and used to prepare carbon fiber/epoxy composites (CF/EP-PNB). The optimal flame-retardant CF/EP-PNB composites exhibit excellent flame retardancy (the LOI of CF/EP-PNB composites with 10 % PNB could reach 33.8 % and pass V-0 grade in the UL-94 test and the residual chars could be as high as 70.7 %) and remarkable mechanical properties (the bending and impact strength of the CF/EP-PNB composites had increased by 41.5 % and 38.2 %, respectively).

Durable flame retardant and dip-resistant coating of polyester fabrics by plasma surface treatment and UV-curing

Polyester fabric is ubiquitously applied for clothing, furniture and transportation, whereas its flammability with severe dripping often causes secondary hazards. Herein, it is highly imperative to impart excellent flame retardant to polyester fabric. In this work, a coating for polyester fabrics was prepared through a continuous dipping and ultraviolet (UV) curing process, which exhibited high-efficiency flame-retardant, anti-dripping and washing resistance. Firstly, the surface of polyester fabric was pretreated with plasma for providing more grafting sites of polyester fabric. Then, the flame retardant 6-((((2-(acryloyloxy) ethoxy) (oxo)(phenyl)phosphonio) oxy) methyl) dibenzo[c,e][1,2]oxaphosphinine 6-oxide (DPEA) and Tri(acryloyloxyethyl) phosphate (TAEP) were successfully synthesized and applied to the coating by UV-curing. In vertical burn test, the damage length of polyester with DPEA and TAEP (PET-D3/T4.5) was reduced from 300 mm of pristine PET to 100 mm with no dripping. In the Thermogravimetric Analysis (TGA) test, the char residue of PET-D3/T4.5 in nitrogen increased to 26.7 % compared with 9.7 % of pristine polyester. More specifically, the Peak Heat Release Rate (PHRR) and Total Heat Rate (THR) of PET-D3/T4.5 decreased 43.3 % and 22.2 % in the Micro-scale Combustion Calorimetry (MCC) test, which reflected excellent thermal stability and flame retardant properties. In addition, the Limiting Oxygen Index (LOI) of PET-D3/T4.5 only dripped from 24 % to 23.5 % after ten standard laundering cycles, indicating prominent water resistance. Remarkably, Thermogravimetric Analysis-Fourier transform infrared (TG-IR), Scanning Electron Microscope (SEM) and X-ray Photoelectron Spectroscopy (XPS) have been performed for investigating the mechanism of flame retardant. Thus, a strategy with convenience and economics is proposed, which is of gargantuan significance to the improvement of coating durability through plasma surface treatment and UV-curing.

Highly dispersed red phosphorus produced by mechanical milling for enhanced flame retardancy of polyurethane-based foam

To improve the exothermic temperature and flammability of polyurethane foam (PUF), red phosphorus (RP) and diatomite (D) from mechanical milling were chosen as the flame retardants to be incorporated into the polyurethane/waterglass foam (PUHF). The maximum exothermic temperature and temperature distribution of PUF and PUHF were measured using an infrared thermal camera. The morphology and chemical structure of the flame retardants as well as the chemical structure, morphology, compressive strength, thermal stability and flame retardancy of different PUFs were comprehensively investigated by scanning electron microscope, energy dispersive spectrometer, Fourier transform infrared spectroscopy, X-ray diffraction, compression test, thermogravimetric analysis, limiting oxygen index, vertical burning combustion test, cone calorimetry and X-ray photoelectron spectroscopy. The obtained results showed that the maximum exothermic temperature and temperature distribution of PUHF were lower and more uniform than those of PUF. The addition of D increased the dispersion of RP in PUHF, and the uniform and closed pore structures and compressive property were well-retained. Moreover, RP/D/PUHF exhibited excellent thermal stability and flame retardant properties. In addition, a possible flame retardant mechanism of RP/D/PUHF was proposed.

Facile construction of three-dimensional porous netlike reduced graphene oxide/zinc oxide composite aerogels as the lightweight, flame retardant, compression resilience and high-performance electromagnetic wave absorbers

In this work, reduced graphene oxide/zinc oxide (RGO/ZnO) composite aerogels were constructed through a one-pot hydrothermal route. Results manifested that the composite aerogels had the extremely low density and a unique three-dimensional porous network structure, and lots of ZnO particles were almost homogeneously loaded on the rippled surfaces of lamellar RGO. Moreover, the micromorphology and electromagnetic absorbing properties of composite aerogels were facilely regulated by changing the additive amounts of sodium citrate. Notably, the optimal minimum reflection loss reached −79.1 dB at a matching thickness of 2.49 mm and maximum effective absorption bandwidth achieved 7.7 GHz under a thickness of 1.97 mm and filling ratio of 20.0 wt%. Furthermore, the attained composite aerogels presented excellent flame retardant and compression resilience properties. Additionally, the possible electromagnetic dissipation mechanism was proposed. This work provided a reference for the design and preparation of RGO-based dielectric composites as the multifunctional electromagnetic wave absorbers.

Chitosan/clay aerogel: Microstructural evolution, flame resistance and sound absorption

Different porous structures of biomass-based aerogels were regulated by adjusting the ratios of carboxymethyl chitosan (CCS) and montmorillonite (Mt). The hierarchically porous structures were obtained via a directional freeze method and the freeze-drying process. The diverse microstructures and flame retardant and sound absorption properties of as-prepared CCS/Mt. aerogels were studied. The results revealed that the incorporation of Mt. could dramatically improve the flame retardancy of the resultant aerogel, with the limiting oxygen index reaching up to 85%, attaining the nonflammable level. And the CCS/Mt. aerogels exhibit a super low density (33.85–38.27 mg/cm3) and high porosity (98.20%). The honeycomb-like structure of the aerogel could apparently improve the sound adsorption properties at low-frequency. Overall, this work provides a novel approach to develop bio-composites featured with excellent flame retardant and sound-adsorption properties that would find a broad range of potential applications as building material.

Creating multilayer-structured polystyrene composites for enhanced fire safety and electromagnetic shielding

Two-dimensional (2D) titanium carbide (Ti3C2Tx) with high electrical conductivity and large active surfaces has attracted extensive attention in recent years. Here, in order to address the fire safety and poor electromagnetic shielding performance of polystyrene (PS), a highly effective cetyltrimethyl ammonium bromide-multi-wall carbon nanotubes@Ti3C2Tx (C-MWCNT@Ti3C2Tx) bilayer was deposited on PS sphere to achieve PS@C-MWCNT@Ti3C2Tx (PCT) composites for improving its fire safety and electromagnetic shielding performances. In addition, Ti3C2Tx and γ-propyl-trimethoxysilane (KH550) were adopted to modify silicon wrapped ammonium polyphosphate (SiAPP-NH2@Ti3C2Tx) via the microencapsulation strategy. Finally, the SiAPP-NH2@Ti3C2Tx was incorporated into PCT composites to fabricate excellent fire-resistant PS composites, i.e. PCTS. The obtained results demonstrated that Ti3C2Tx not only promoted the thermal stability and fire safety but also enhanced the electromagnetic shielding performance of PS. For instance, the PS composite with three number of C-MWCNT@Ti3C2Tx bilayers (PCTS3) exhibited dramatically lowest the peak of heat release rate (528 kW/m2) and highest electromagnetic shielding effectiveness value (11 dB), indicative of the excellent flame retardant and considerable electromagnetic shielding properties. This work sheds light on the design of multifunctional multi-layer structured polymer composites.

Ma Lao-like structural fireproof aramid nanofiber@Ag nanocomposite film enhanced with MXene for advanced thermal management applications

Here, inspired by the traditional Chinese cuisine Ma Lao, aramid nanofiber (ANF) decorated by silver nanoparticles (ANF@Ag) is prepared via in-situ depositing process of Ag ions on the surface of ANF based on dopamine chemistry reduction method. MXene/ANF@Ag nanocomposite films with various MXene concentrations are further prepared via a vacuum-assisted self-assembly strategy. ANF@Ag is designed as the organic-inorganic hybrid thermal conductive chains, while Ag nanoparticles not only play a role in heat transfer, but also catalyze the carbonization process and form massive inert gas during the combustion. Surprisingly revealing that toxic gases effectively catalyzing into friendly non-toxic carbon dioxide (CO2) and forming the CO2 molecular fire extinguisher-like effect, which are suitable for the development of ecological sustainability. The 5-MXene/ANF@Ag nanocomposite film shows excellent flame retardant properties, and the total heat release (THR) is only 0.1 kJg−1. Meanwhile, the high in-plane thermal conductivity of 5-MXene/ANF@Ag is 18.56 W·m−1·K−1, which is enhanced about 4.97 times higher than pure ANF film. It can be ascribed to the hydrogen bonding interactions and synergistic bridging effects from the MXene nanosheets and thermal conductive chains of rigid ANF@Ag. Therefore, this work displays a novel tactic to provide favorable interfacial interactions for the uninflammable thermal management materials.

Robust composite aerogels with excellent flame retardant and thermal insulation properties based on modified hollow glass microspheres

The development of high-performance flame-retardant materials with better thermal insulation properties is of great significance to modern building energy conservation. In this study, we report the facile and scalable fabrication of novel aerogels (SA-HGM-APP) based on the building blocks of ammonium polyphosphate (APP) coated hollow glass microspheres (HGM) and matrix material sodium alginate (SA) by freeze drying method. The as-prepared composite aerogel exhibits better thermal stability (decomposition temperature over 210°C). In addition, SA-HGM-APP composite aerogels have good thermal insulation properties and low thermal conductivity, which is 0.035 W m−1 K−1. More importantly, the peak heat release rate (pHRR) is 14.14 kW m−2, the limiting oxygen index (LOI) value is as high as 100%, and the aerogel composite material can reach UL-94 V-0 grade, so it shows excellent flame retardancy. These results attributed to a synergistic effect, which combines the rich porous structure derived from HGM, so that SA and APP have better thermal insulation and excellent non flammability, thus providing excellent flame retardancy. SA-HGM-APP aerogel composite has many advantages, such as simple preparation method and high mechanical strength. It has great potential in future thermal insulation and flame retardancy applications.

Assembled hybrid films based on sepiolite, phytic acid, polyaspartic acid and Fe3+ for flame-retardant cotton fabric

Abstract To impart durable flame retardant property to cotton fabric, a kind of multilayered hybrid film based on environmentally friendly phytic acid, sepiolite, polyaspartic acid, and Fe3+ were deposited on the surface of cotton fabric by layer-by-layer and spraying method to form a dense protective layer. Compared with cotton fabric, hybrid film coated cotton showed excellent flame retardant property and low fire hazard, which can be demonstrated by vertical flame test, limiting oxygen index (LOI) and cone calorimeter test. After-flame time and after-glow time of hybrid film coated cotton is 1 s and 1 s, respectively. LOI value of hybrid film coated cotton increased by 44.4% compared with control sample. Cone calorimeter test revealed a total heat release rate reduction of 52.6% and peak heat release rate reduction of 73.6% for hybrid film coated cotton fabric. This work demonstrates that the hybrid film composed of phytic acid, sepiolite, polyaspartic acid, and Fe3+ could improve the durable flame retardant property of cotton fabric.

Biodegradable epoxy resin from vanillin with excellent flame-retardant and outstanding mechanical properties

In this work, the sustainable and biodegradable flame retardant epoxy resin was designed and prepared to replace resource-limited petrochemicals, especially, bisphenol A type epoxy resin (DGEBA). A renewable chemical, vanillin was condensation to produce Schiff-based compound (MAV) employing the novel epoxy resin (MVE) through the epoxidation reaction. The epoxy equivalent of MVE was approximately 217 g/eq and used non-isothermal differential scanning calorimetry (DSC) to study the curing kinetics of MVE/DDM (4,4′-Diaminodiphenylmethane). After curing by DDM, they exhibit outstanding mechanical property and a residual char rate as high as 41.77%, excellent inherent flame retardancy and limited oxygen index (LOI) value higher than 34%, far superior to DGEBA. The total heat release (THR) and smoke release rate (SPR) of MVE/DDM decreased by 67.44% and 64.69% compared with DGEBA/DDM, respectively. The mechanisms for the enhancement of flame retardancy by intrinsic flame retardant epoxy resin were investigated. Moreover, the sustainable epoxy crosslinking could degrade completely benefited from the structure of the Schiff base in the moderate conditions (THF: H2O = 6: 4, 50 °C) within few hours. Overall, this work contributes a multifunctional vanillin-based epoxy monomer and environmentally friendly thermosets with high mechanical property and enhanced flame retardancy.