Intrinsic Flame Retardant Research Articles

Erratum to: Laser-induced Janus graphene/poly(p-phenylene benzobisoxazole) fabrics with intrinsic flame retardancy as flexible sensors and breathable electrodes for fire-fighting field

Erratum to: Laser-induced Janus graphene/poly(p-phenylene benzobisoxazole) fabrics with intrinsic flame retardancy as flexible sensors and breathable electrodes for fire-fighting field

Facile preparation of magnolol-based epoxy resin with intrinsic flame retardancy, high rigidity and hydrophobicity

Facile preparation of magnolol-based epoxy resin with intrinsic flame retardancy, high rigidity and hydrophobicity

Laser-induced Janus graphene/poly(p-phenylene benzobisoxazole) fabrics with intrinsic flame retardancy as flexible sensors and breathable electrodes for fire-fighting field

Laser-induced Janus graphene/poly(p-phenylene benzobisoxazole) fabrics with intrinsic flame retardancy as flexible sensors and breathable electrodes for fire-fighting field

Hierarchical boric acid/melamine aerogel based on reversible hydrogen bonds with robust fire resistance, thermal insulation and recycling properties

A Boric acid/Melamine aerogel (BM aerogel) with robust flame retardancy and thermal insulation was fabricated by a facial green route based on fully reversible hydrogen bonds using melamine and boric acid as precursors. The resulting BM aerogel possesses a hierarchical fibril structure and exhibits both intrinsic flame retardant and thermal insulation properties. The BM aerogel cannot be ignited at an oxygen concentration of as high as 80%. The superior performance together with the simple preparation process provides some new insight into the construction of a two-component molecular aerogel that is based on hydrogen bonds. Furthermore, owning to the full hydrogen bonding between melamine and boric acid molecules, the synthesized BM aerogel demonstrates typical thermal reversibility in water, which opens the door to the recycling of aerogel.

Eco-friendly Modal/alginate knitted fabrics with intrinsic flame retardancy and wearability

Eco-friendly Modal/alginate knitted fabrics with intrinsic flame retardancy and wearability

Urea‐glutaraldehyde‐formaldehyde resin with low formaldehyde emission and high flexibility: Structure and toughening mechanism

AbstractUrea‐formaldehyde (UF) resin with excellent intrinsic flame retardancy, high strength, and low cost has been widely used as adhesives, coatings as well as molding compounds, and it is a challenge to prepare UF resin with combined properties of high toughness/strength and low formaldehyde emissions. In this work, glutaraldehyde was introduced into the synthesis system of UF resin to partially replace formaldehyde, and urea‐glutaraldehyde‐formaldehyde (UGF) copolycondensation resin was prepared. It was found that glutaraldehyde participated in additional/condensation reactions of UF resin, and the crosslinking reaction of UGF resin was hindered with higher curing activation energy than that of neat UF resin. Due to the controllable curing kinetics and introduction of long methylene chains, UGF resin presented relatively low crosslinking density, and under external force, it underwent distinct yielding before fracture and many yield folds appeared on the fractured surface, showing high toughness and strength. Compared with neat UF resin, the tensile strength, elongation at break, impact strength, and critical stress intensity factor (KIC) of UGF resin increased by 26%, 42.30%, 14.6%, and 30%, respectively. Meanwhile, the free formaldehyde emission for UGF resin decreased by 47.5%, meeting the requirement of E0 grade. Such developed eco‐friendly UGF resin exhibited promising application potentials.

Alginate Fiber-Grafted Polyetheramine-Driven High Ion-Conductive and Flame-Retardant Separator and Solid Polymer Electrolyte for Lithium Metal Batteries.

Traditional polymer-based separators and solid polymer electrolytes (SPEs) often suffer from inherent poor flame retardancy and unsatisfied ionic conductivity, which seriously affect the safety and energy storage performance of lithium metal batteries (LMBs). Inspired by the mechanism of Li+ conductivity, an alginate fiber (AF)-grafted polyetheramine (AF-PEA) separator with efficient Li+ transport and excellent flame retardancy is dedicatedly designed, which also can act as the backbone for PEO-based SPEs (PEO@AF-PEA). Based on the intrinsic flame retardancy of the AF, the AF-PEA shows self-extinguishing ability, and its Li+ transport ability (1.8 mS cm-1 at 25 °C) is enhanced by grafting the ion-conductive PEA chain segment. By simulating the transport and distribution of Li+ in the AF-PEA, the PEA with 7-segment chain lengths can uniformly fill the Li+ transport space between the alginate backbone to promote the Li+ adsorption and the utilization of Li+ anchoring points in PEA side chains, increasing the Li+ transport rate and migration capacity. The LiFePO4/Li solid-state battery assembled using PEO@AF-PEA SPEs exhibits high safety and excellent cycling performance (exceeding 100 mAh g-1 after 1500 cycles at 2 C current density and 80 °C with less than 0.016% capacity decay for each cycle).

Solvent‐free synthesis of phosphate‐containing imidazole fluid for flame retardant one‐component epoxy resin with long pot life, low curing temperature and fast curing rate

AbstractThe design of flame retardant one‐component epoxy resin (EP) with long pot life, low curing temperature and fast curing rate has been challenging in the industry. Herein, we synthesized a phosphate‐containing imidazole fluid (TA) as the thermal latent curing agent of EP. Based on simple structural design, TA endows EP with excellent curing properties, storage properties, and flame retardant properties. According to DSC results, EP/TA systems exhibit low curing temperature and fast curing rate during operation. The rotary rheometer test confirms that the viscosity curve of EP/TA system maintains long‐term stability at 40°C. The X‐ray photoelectron spectroscopy (XPS) data reveals that TA releases imidazole intermediates and phosphorous compounds during curing. The former provides conditions for fast curing of EP, while the latter gives EP intrinsic flame retardant properties. With the addition of 20 wt.% TA, EP/TA‐4 achieves UL‐94 V‐0 rating and 28.5% of LOI value. The study of flame retardant mechanism shows that the flame retardancy of TA mainly comes from the protective effect of phosphorus‐rich char layer, the dilution effect of non‐combustible gas and quenching effect of phosphorous compound. Besides, due to no solvent involved, the synthesis strategy of TA is environmentally friendly, showing a great potential of industrial application.

Superior intrinsic flame-retardant phosphorylated chitosan aerogel as fully sustainable thermal insulation bio-based material

Owing to the arising environmental pollution and energy-related challenges, the utilization of renewable polysaccharides such as chitosan (CS) in the preparation of biodegradable aerogel heat-insulation materials represents a growing interest. In this study, a simple and low-cost route was proposed to synthesize a phosphorylated chitosan (PCS) with a high substitution degree of phosphate groups in a homogeneous H3PO4/acetic acid solution, and its chemical structure was confirmed using FT–IR spectroscopy, nuclear magnetic resonance, and X–ray photoelectron spectroscopy. An outstanding intrinsic flame-retardant PCS aerogel was directly fabricated via freeze-thawing and freeze-drying process. Remarkably, limited oxygen index values of the PCS aerogels increased to above 80%, and their UL–94 test results achieved V–0 rating. The peak heat release rate and total heat release rate values of PCS-4 aerogel significantly decreased by 91.2% and 73.0% compared with those of chitosan aerogel, respectively. The bio-based PCS aerogel with superior intrinsic flame retardancy, low thermal conductivity, and excellent hydrophobicity shows promise as new sustainable flame-retardant heat-insulation material.

High-performance and fire-resistant epoxy thermosets derived from plant-derived ferulic acid

Development of epoxy thermosets derived from biomasses with intrinsic flame retardancy and high mechanical performances is of increasing demand. Here we synthesize a novel epoxy monomer (DGEFA) from ferulic acid that can be directly obtained from many plants and offers intrinsic flame retardancy due to its conjugation structure. By using 4,4’-diaminodiphenylmethane (DDM) as a curing agent, the cured epoxy resin (DGEFA-DDM) possesses a high glass transition temperature (178.5 °C). The DGEFA-DDM also exhibits high mechanical performances, i.e., tensile strength of 84.7 MPa and flexural strength of 145.1 MPa. Besides, the DGEFA-DDM presents a char yield of 40.6 % under N2, a V-1 rating of UL-94 and a limiting oxygen index of 32.8 %. The cone calorimeter test shows that the DGEFA-DDM has low heat and smoke release performances with a total heat release of 49.2 MJ/m2 and a total smoke production of 16.0 m2, indicating a high intrinsic flame retardancy. This work provides a simple way for the preparation of epoxy resins from bio-based feedstocks possessing physical properties and fire safeties.

Biomass-based epoxy resin derived from resveratrol with high temperature resistance and intrinsic flame retardant properties

Preparing biomass-based epoxy resin with high temperature resistance and flame retardancy is still an appealing yet challenging task. Now, a high-temperature resistant and flame-retardant resveratrol-based epoxy (RESEP) has been synthesized through a facile one-step method. The structure of RESEP was established using FTIR and NMR spectroscopy. RESEP and petroleum-based epoxy diglycidyl ether of bisphenol A (DGEBA) were each cured with 4,4-diaminodiphenyl methane (DDM) to prepare RESEP/DDM and DGEBA/DDM. Differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), tensile testing, thermogravimetric analysis (TGA), thermogravimetric analysis-infrared spectroscopy (TG-IR), scanning electron microscopy (SEM), limiting oxygen index (LOI) and the UL-94 vertical burning test were used to systematically evaluate the properties of RESEP and RESEP/DDM. The glass transition temperature (Tg) of RESEP/DDM is 335 ℃, which is significantly higher than that of DGEBA/DDM (168 ℃). In addition, RESEP/DDM displays good thermogravimetric performance and flame retardancy. Typically, it displays a UL-94 V-0 rating, an LOI value was as high as 31.8%, and a char yield as high as 38.6% (800 ℃). The results reported indicate the possibility of preparing biomass-based epoxy resin with high temperature resistance, flame retardancy and mechanical properties, which is potential to be utilized in the fields of electronics and aerospace.

Optical and Flame-Retardant Properties of a Series of Polyimides Containing Side Chained Bulky Phosphaphenanthrene Units.

Among the multitude of polymers with carbon-based macromolecular architectures that easily ignite in certain applications where short circuits may occur, polyimide has evolved as a class of polymers with high thermal stability while exhibiting intrinsic flame retardancy at elevated temperatures via a char-forming mechanism. However, high amounts of aromatic rings in the macromolecular backbone are required for these results, which may affect other properties such as film-forming capacity or mechanical properties; thus, much work has been done to structurally derivatize or make hybrid polyimide systems. In this respect, flexible polyimide films (PI(1-4)) containing bulky 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) units have been developed starting from commercial dianhydrides and an aromatic diamine containing two side chain bulky DOPO groups. The chemical structure of PI(1-4)) was characterized by 1H NMR, 13C NMR and 31P NMR spectroscopy. The optical properties, including absorption and luminescence spectra of these polymers, were analyzed. All polyimides containing DOPO derivatives emitted blue light with an emission maxima in the range of 340-445 nm, in solvents such as N,N-dimethylformamide, N-methyl-2-pyrrolidone, chloroform, and N,N-dimethylacetamide, while green light emission (λem = 487 nm for PI-4) was evidenced in a thin-film state. The thermal decomposition mechanism and flame-retardant behavior of the resulting materials were investigated by pyrolysis-gas-chromatography spectrometry (Py-GC), scanning electron microscopy (SEM), EDX maps and FTIR spectroscopy. The residues resulting from the TGA experiments were examined by SEM microscopy images and FTIR spectra to understand the pyrolysis mechanism.

Ternary structure design based on hydrogen bonding for transparent and flame retardant PMMA with good mechanical properties

AbstractThe synthesis of intrinsic flame retardant copolymer by copolymerization with reactive flame retardants is the most potential method to prepare transparent and flame retardant poly (methyl methacrylate) (PMMA) at present，but the main challenge of this method is that the copolymer usually has poor mechanical properties and heat resistance. In this work, the hydrogen bond enhancement strategy is adopted, and the flame retardant PMMA with excellent comprehensive properties is obtained by ternary copolymerization with methyl methacrylate (MMA) as matrix unit, diethyl (methacryloyloxymethyl) phosphonate (DEP) as flame retardant unit and methacrylamide (MAA) as hydrogen bond unit. Due to the formation of intermolecular hydrogen bond via MAA unit, the storage modulus, flexural strength and impact strength of the terpolymer containing 15 mol% MAA are 48%, 19%, and 24% higher than those of the copolymer of MMA and DEP, and its hardness, glass transition temperature and load thermal deformation temperature (increased by 7°C) are also superior. Moreover, owing to the gas‐phase dilution and charring flame retardancy of MAA unit, the terpolymer shows increased limiting oxygen index (24.3%) and UL94 rating (V‐1). This work not only provides a promising flame retardant PMMA for practical application, but also offers a new strategy to design flame retardant polymers with good mechanical properties.

Intrinsic flame retarding and non-dripping liquid crystal polyethylene terephthalate copolyesters for fire safety system

The notorious issue of high fire hazards, including the generation of considerable heat and melt dripping, is recognized as the bottleneck of extensive use of polyethylene terephthalate (PET). Although various techniques have been adopted for the fabrication of flame retardant PET, how to address the contradiction of flame retardancy and anti-dripping while maintaining its good processability in an environment-friendly method is still challenging. Hence, we design and prepare an intrinsic flame retardant copolyester based on PET and thermotropic liquid crystalline polymer (PET/TLCPx) via a simple and efficient one-step melt copolymerization to address the above challenges. On the one hand, the mesogen units not only allow copolyesters to show a typical liquid crystalline behavior with excellent processability but also constructs a highly rigid main chain to endow PET/TLCPx with outstanding thermal stability, fire resistance, and non-dripping. Furthermore, the resultant PET/TLCP3 exhibits a much lower (by 72 %) peak heat release rate than that of PET, which is attributed to the formation of a denser char layer (char yield ∼ 37 %) for excellent fire resistance. Meanwhile, the melt dripping of PET/TLCPx is suppressed with the increase of complex viscosity and the growth of molecular weight due to the post-condensation during combustion. The resultant high-performance copolyesters are highly valuable for high-end applications that have strict requirements for fire safety and thermal stability, such as fire alarm and rescue systems based on triboelectric effect and shape memory behaviors.

Effects of phenylphosphonate and aliphatic phosphonate structures on the flame retardant performance of bismaleimide

The application of bismaleimide resins (BMI) has been severely restricted due to its inherent high fire hazard and brittleness. In this work, from the perspective of molecular structure, BMI monomers constructed with phenylphosphonate and aliphatic-phosphonate structure (MPPDP and MPMPD) were synthesized to endue BMI with intrinsic flame retardant properties and improve the toughness of BMI. With 5wt% MPPDP and 1wt% MPMPD adding, the peak value of heat release rate (PHRR) of BMI/MPPDP-5 and BMI/MPMPD-1 are of 52.4% and 54.0% reductions. The UL-94 of BMI/MPPDP-5 and BMI/MPMPD-1 are both of V-0 rating. Moreover, BMI/MPPDP-5 and BMI/MPMPD-1 have 90.2% and 65.8% increase on the impact strength. Therefore, the fire safety and impact toughness of BMI can be effectively improved by the designed MPPDP and MPMPD. The effect of phenylphosphonates and aliphatic phosphonates in MPPDP and MPMPD on BMI performance was explored and proposed.

Versatile levulinic acid-derived dynamic covalent thermosets enabled by in situ generated imine and multiple hydrogen bonds

Bio-based dynamic covalent thermosets have attracted extensive attention as they are expected to break conventional thermosets' reliance on fossil resources and address the recycling issue after disposal. However, there has always been a contradiction between using bio-based feedstocks and possessing high properties, as well as a conflict between high performance and rapid recycling (reprocessing and degradation). In this work, a simple approach was developed to prepare bio-based thermosets with high performance, rapid reprocessing, high flame retardancy, and antibacterial properties enabled by in-situ generated dynamic covalent imine (Schiff base) bonds and multiple hydrogen bonds. The levulinic acid epoxy (ELA) was successfully synthesized and cured with 2-(4-aminophenyl)-1H-benzimidazol-5-amine (BIA) containing benzimidazole structures. The high concentration of Schiff bases and multiple hydrogen bonds of ELA-BIA endowed it with high glass transition temperature and mechanical properties, as well as satisfactory catalyst-free malleability, rapid reprocessing and repairing. Furthermore, due to the combined effect of the in-situ Schiff base and benzimidazole structure, ELA-BIA exhibited excellent condensed phase char formation ability, resulting in intrinsic flame retardancy with a limiting oxygen index of 33.8 % and a UL-94 V-0 rating, both of which were significantly higher than 4, 4′-diaminodiphenyl methane (DDM) cured ELA or DDM cured bisphenol A epoxy. Moreover, the Schiff bases bonded in the networks provided 100 % of the intrinsic antibacterial rates. This work provides a feasible and simple strategy for the preparation of high-performance and versatile bio-based dynamic covalent thermosets.

Dry-spun Polyimide Fibers with Excellent Thermal Stability, Intrinsic Flame Retardancy and Ultralow Smoke Release

Dry-spun Polyimide Fibers with Excellent Thermal Stability, Intrinsic Flame Retardancy and Ultralow Smoke Release

Study of the impact of epoxidized plant oil phospholipids and hydroxyl radicals on crosslinked epoxy resins

AbstractThe detrimental environmental consequences of global plastic pollution and the imperative transition, by following the key principles of sustainable development, fully tap the use of renewable feedstocks such as vegetable oil to utilize their functionalities over fossil‐based resources. The current research has developed a novel biobased additive obtained as a byproduct through aromatization of epoxidized corn oil (ECO) using diglycidyl ether aromatic compounds of epoxy resin (EP). The hybrid matrix was made with an ECO content ranging from 10% to 50%. Spectral, elemental, mechanical property, thermal, morphological, and fire hazards analyses revealed that the experimental results of the EPECO50 blend had a 34.94% hydrogen and oxygen added content, resulting in a 62% decrease in flammability when compared to a conventional petroleum‐based mix. Interestingly, the established presence of phospholipids and significant adsorption in the hydroxyl bands support the good intrinsic flame retardancy capabilities of the blend. As a result of the proposed synthesis mechanism, the covalent bonding between epoxy and ECO suggests lower toxicity, as shown by cone calorimetry, with a high reduced yield of CO2 (99%) and CO (98%) and, more importantly, the blend is a potential green flame retardant biobased additive. In practice, people die in a fire due to the lack of oxygen and inhalation of harmful smoke; hence, the reduction in total smoke production and CO2 and CO emissions clearly helps the smoke suppression of epoxy thermosets when potentially reinforced with biocomposites.

Thermal-induced self-healing bio-based vitrimers: Shape memory, recyclability, degradation, and intrinsic flame retardancy

The structure of epoxy resin determines its flammable property, non-reprocessing, unrecyclable, and nondegradable, which limits their application. Thus, a novel disulfide bond-containing dynamic covalent thiol-ene crosslinked epoxy vitrimers (TECEVs) as covalently adaptable networks were synthesized. Also, the structure-property relationship of polymeric compounds was investigated. The insoluble vitrimers networks demonstrated faster stress relaxation with 107 s at 200 °C, and obtained lower activation energy between 70.52 and 110.57 kJ·mol−1. In addition, the dynamic nature of the disulfide bond allowed the damaged TECEVs to be thermal-induced self-repairing and self-healing materials with efficiencies 100% at 160 °C. It was discovered that TECEVs can be reprocessed at 160 °C with the recovery of mechanical strength above 80% and be completely decomposed in an ethanol-acid catalyst solution. Moreover, typical TECEVs can function with excellent flame retardancy and illustrated a high limit oxygen index (LOI, 27.45–28.36%), and UL-94 V-0 rating was achieved. This work could provide an efficient strategy for the synthesis of “biobased self-repairing flame retardant” networks and contribute to the development of high-performance sustainable polymers.

Hierarchical Ti3C2Tx@BPA@PCL for flexible polyurethane foam capable of anti-compression, self-extinguishing and flame-retardant

It is of great importance to fabricate flexible polyurethane foam (FPUF) with superior mechanical properties and flame retardancy for practical applications. Herein, organosilicon and phenyl phosphorus compounds were synthesized and grafted on the surface of Ti3C2Tx (Ti3C2Tx@BPA@PCL) via in-situ polymerization. Then, the FPUF composites were fabricated, combining intrinsic flame retardancy (9,10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide-diethanolamine: DH-DOPO) (addition amount: 20 wt%) and Ti3C2Tx@BPA@PCL (addition amount: 4 wt%). Attributed to the rigid structure of Ti3C2Tx@BPA@PCL, the tensile strength and compression strength of FPUF showed 24.0% and 253% increase, respectively. In addition, anti-fatigue properties of FPUF composites during the cyclical test were dramatically enhanced. In contrast to pure FPUF, 36.1% and 44.0% reductions in peak heat release rate (pHRR) and total heat release (THR) were achieved for the FPUF containing Ti3C2Tx@BPA@PCL and DH-DOPO, the production rate of carbon dioxide (CO2) and carbon oxide (CO) also decreased by 40.3% and 52.1%, respectively. FPUF4 showed self-extinguishing behavior, and passed the vertical burning test (VBT). This work provides a facile approach to preparing high-performance FPUF with enhanced mechanical property and flame retardancy.