Good Flame Retardancy Research Articles

Synthesis of a novel flame retardant with phosphaphenanthrene and phosphazene double functional groups and flame retardancy of poly (lactic acid) composites

A novel flame retardant hexa (4- (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10 -sulfide)-hydroxymethylphenoxy) cyclotriphosphazene (HAP-DOPS) with double functional groups was synthesized, and poly (lactic acid) (PLA) composites were prepared by melt extrusion. The flame retardancy and thermal degradation behavior of flame retardant PLA composites were studied by limiting oxygen index (LOI), vertical burning test (UL-94), cone calorimeter test (CCT), and thermogravimetric-infrared spectroscopy analysis (TG-IR). The experimental results showed that HAP-DOPS had a good flame-retardant effect on PLA. At flame retardant content of 5 wt%, the PLA/HAP-DOPS composite achieved a V-0 rating (UL-94, 3.2 mm) and a LOI value of 26.6%. The heat release rate (HRR) and total heat release (THR) of PLA composites were decreased by adding HAP-DOPS. The flame retardancy index (FRI) of PLA/HAP-DOPS-7.5 wt% was 1.0257, which showed good flame retardancy. The results of TG-IR showed that HAP-DOPS mainly had a gas-phase flame-retardant effect in PLA.

Scalable Manufacturing Process and Multifunctional Performance of Cotton Fibre-Reinforced Poly(Lactic Acid) (PLA) Bio-Composites Coated by Graphene Oxide.

Natural fibre biopolymer composites with both fibres and matrix being derived from biomaterials are increasingly used in demanding applications, such as sensing, packaging, building, and transport, and require good electrical, thermal, and flame retardant properties. Herein, an investigation of the effectiveness of functionalising nonwoven cotton/poly(lactic acid) (PLA) fibre mats with graphene oxide nanosheets has been reported by using a facile dip-coating method followed by thermal reduction for enhancing the electric, thermal, and abrasion-resistance properties. The manufacturing processes for preparing biocomposites and introducing functionality are readily scalable. Experimental results reveal that with the addition of less than 0.5 wt% graphene nanoplatelets, the biocomposites showed significant improvements in abrasion resistance, electrical conductivity, thermal conductivity, and diffusivity. Furthermore, the composite shows excellent piezo-resistivity to act as strain sensors with a gauge factor of 2.59 at strains up to 1%.

Cyclotriphophazene-Centered Six-Arm Eugenol-Linked Low-Dielectric Materials with High Thermostability and Transparency

Two silicon-containing eugenol-based benzocyclobutene monomers were prepared by a simple solvent-free hydrosilylation reaction. After heat treatment, a series of materials were obtained by a free radical addition reaction, [4 + 4] cycloaddition, or [4 + 2] Diels–Alder cycloaddition. All polymers displayed high thermostability with a 5% weight loss temperature (T5d) of over 410 °C and a glass transition temperature (Tg) of up to 216 °C as well as a good transmittance of 90% varying from 500 to 800 nm. In particular, all polymers also exhibited good hydrophobicity with contact angles exceeding 100° and water absorption as low as 8‰ after immersing in boiling water for 72 h. It should be noted that P3 showed excellent dielectric properties with a dielectric constant (Dk) of 2.48 and a dielectric loss (Df) of 6.38 × 10–3 at a high frequency of 2 GHz as well as good flame retardancy due to the high content of cyclotriphophazene compared with those of P1, P2, and previously reported biobased materials. The above advantages indicate that eugenol-based low-dielectric materials have great potential for application in encapsulation resins in the field of microelectronics.

A vanillin‐derived flame retardant based on 2‐aminopyrimidine for enhanced flame retardancy and mechanical properties of epoxy resin

AbstractIn order to give epoxy resin good flame retardance, a novel bio‐based flame retardant based on 2‐aminopyrimidine (referred to as VAD) was synthesized from renewable vanillin as one of the starting materials. Its structure was confirmed by NMR and mass spectra. The epoxy resins containing VAD were prepared by utilizing 4,4‐diaminodiphenylmethane (DDM) as a co‐curing agent, and their flame‐retardant, mechanical and thermal properties and corresponding mechanisms were studied. VAD accelerated the cross‐linking reaction of DDM and E51 (diglycidyl ether of bisphenol A). 12.5 wt% VAD made the epoxy resin achieve UL‐94 V‐0 rating and its limited oxygen index (LOI) value increase from 22.4% to 32.3%. The cone calorimetric testing results revealed the decline in the values of total heat release (THR) and peak of heat release rate (pk‐HRR) and the obvious enhancement of residue yield. A certain amount of VAD enhanced the flame inhibition, charring and barrier effects, resulting in good flame retardance of the epoxy resin. Furthermore, the tensile strength, flexural strength and flexural modulus of the epoxy resin with 12.5 wt% loading of VAD were 6.5%, 14.9%, 15.2% higher than those of EP, indicating the strengthening effect of VAD. This work guarantees VAD to be a promising flame retardant for enhancing the fire retardancy of epoxy resin without compromising its mechanical properties.

CNT film supported MXene/Co3O4 composite interlayers for high performance Li–S batteries

Adding a functionalized interlayer is one of the effective means to solve the problem of capacity attenuation caused by the shuttle of polysulfides in lithium–sulfur (Li–S) batteries. Moreover, the interlayer has the potential to take on more roles, such as having good mechanical flexibility to ensure high safety and flame-retardant property to improve the high temperature performance of the battery. Thus, in this work, an MXene/Co3O4–CNT film interlayer that is capable of dual chemisorption to polysulfides with good mechanical strength and flame retardancy has been investigated. The resultant Li–S battery assembled with this interlayer exhibits a high discharge capacity of 1569.5 mA h g−1, an excellent charge–discharge stability over 600 cycles, and a high temperature stability of the electrochemical performance.

Preparation and enhanced flame retardancy of co‐polybenzoxazines containing diacetal structure

AbstractA comparative study on the flame retardancy of two polybenzoxazines with and without a diacetal structure, p(A) and p(B), is firstly carried out by microscale combustion calorimeter (MCC). It is proved that the presence of the diacetal structure can endow p(A) with good flame retardancy with a low heat release capacity (HRC). Then, the monomer of this diacetal containing p(A), A‐boz, is used to modify a typical diamine type benzoxazine (M‐boz) to improve its flame retardancy. The effects of A‐boz with different ratios on curing behavior, heat resistance and thermal stability of the co‐polybenzoxazines of M‐boz and A‐boz, p(M/A)s, are analyzed by differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy, dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA). Furthermore, the flame retardancy of p(M/A)s is investigated by UL‐94 test, limiting oxygen index (LOI) and MCC, and the degradation and flame retardant mechanisms are investigated by scanning electronic microscopy (SEM), Raman spectra and TGA‐FTIR. When the addition amount of A is 20 wt%, the LOI value of p(M/A) is as high as 39.5% and its flame retardant rating reaches UL‐94 V‐0. In addition, the mechanical properties of p(M/A)s are tested. The results suggest that the Tg and char yield at 800°C in N2 of p(M/A)s increase from 210 to 243°C and 45% to 51%, respectively. This work suggests that the incorporation of the diacetal structure is an effective strategy to improve the flame retardancy of resins.

Core-shell structured ZnO nanorods enable flame-retardant, smoke suppressed and mechanically reinforced epoxy resin composites

The engagement of bio-based materials in the manufacture of flame-retardant has gained particular popularity in the past few years due to the raising environmental concerns. In this paper, a multifunctional nanoparticle (ZnO@TPB) that can confer flame-retardancy, mechanical enhancement and smoke suppression to epoxy resin (EP) is designed by constructing a shell layer containing bio-based materials (tannic acid) on the surface of zinc oxide (ZnO) nanorods. It is found that 10 wt% of ZnO@TPB can impart good flame-retardancy (UL-94 V-0 grade, LOI = 31% and 26.1% reduction in total smoke production (TSP)) and good mechanical properties (Young's modulus increased by 22.86%, hardness increased by 50.0% and storage modulus increased by 92.29%) to the modified EP. These desirable properties come from the multiple synergistic effects between ZnO and TPB. This research offered a viable tactic for the manufacture of EP with a low fire hazard.

A biomimetic durable superhydrophobic 3D porous composite with flame retardant for multi-environment adsorption emulsion separation

Selective adsorption materials with durability and flame retardancy have always been a research hotspot. To endow the melamine sponge with the ability of selective adsorption, it is necessary to endow the sponge with superhydrophobic properties. Here, using the means of mussel biomimetic chemistry, durable flame-retardant selective adsorbents were prepared by growing PPy, PDA, and SiO2 on the surface, and modified by siloxane to achieve superhydrophobicity. The material has good adsorption capacity for organic solutions and oils. Each gram of sponge can absorb 18–39 g of organic solvents and can also stably and efficiently separate a variety of oil-in-water emulsions, with a maximum separation efficiency of 99.78%. More importantly, the sponge has good mechanical and chemical stability, which can stably purify water pollution in harsh environments. At the same time, it has good thermal stability and flame retardancy to ensure safe work in high temperature environments. Compared with other superhydrophobic fabrics, SPC has good chemical, mechanical stability and durability, and more importantly, SPC has flame retardancy, which can be used more safely in complex marine pollution environments.

Development of trilayered multifunctional superhydrophobic cotton fabric using biogenic materials

PurposeThis study aims to develop multifunctional, namely, superhydrophobic, flame-retardant and antibacterial, coatings over cotton fabric, using casein as green-based flame-retardant and silver nanoparticles as antibacterial agent by solution immersion method.Design/methodology/approachThe cotton fabric is first coated with casein to make it flame-retardant. AgNPs synthesized using Cinnamomum zeylanicum bark extract is coated over the casein layer. Finally, stearic acid is used to coat the cotton to make it superhydrophobic. X-ray diffraction, transmission electron microscopy analysis and ultraviolet-visible spectroscopy are used to investigate the produced AgNPs. The as-prepared multifunctional cotton is characterized by scanning electron microscopy, energy dispersive X-ray analysis and attenuated total reflection-infrared studies. Flame test, limiting oxygen index test and thermogravimetric analyzer studies have also been performed to study the flame-retardant ability and thermal stability of treated fabric, respectively. The antibacterial effect of the coatings is evaluated by disc-diffusion technique. Water contact angle is determined to confirm the superhydrophobic nature of cotton fabric.FindingsThe outcomes of this study showed that the prepared multifunctional cotton fabric had maximum contact angle of greater than 150° with good flame retardancy, high thermal stability, greater washing durability and high antibacterial activity against the growth of Pseudomonas aeruginosa and Acinetobacter indicus. Additionally, the as-prepared superhydrophobic cotton showed an excellent oil–water separation efficiency.Research limitations/implicationsThe trilayered multifunctional cotton fabric has limiting washing durability up to 20 washing cycles. Treated functional fabric can be used as an antibacterial, therapeutic, water repellent and experimental protective clothing for medical, health care, home curtains and industrial and laboratory purposes.Originality/valueThe study brings out the robustness of this method in the development of multifunctional cotton fabrics.

Superhydrophobic and flame retardant polydimethylsiloxane coatings with layered double hydroxide and ammonium polyphosphate

The development of coatings with flame retardancy and superhydrophobicity is of great importance in practical application. Herein, a fluorine-free superhydrophobic and halogen-free flame retardant coating was constructed via simple dip-coating and efficient ultraviolet (UV) curing methods, using heavy cross-linking polydimethylsiloxane networks (HCPDMS) as low-surface-energy materials and hierarchical-structured layered double hydroxide-ammonium polyphosphate (LDH-APP) as organic-inorganic composite flame retardants. Owing to the such combination of hierarchical structure and low surface energy, these prepared coatings show striking repellency to various liquids, great self-cleaning and antifouling ability. Besides, they can resist the abrasion test by sandpaper for 30 cycles, the tape-peeling test for 200 cycles, and repeatedly kneading test. Meanwhile, these coatings offer good thermal stability and flame retardant, exhibiting an enhanced limiting oxygen index (LOI) from 18.0 % to 29.0 %. Moreover, a high oil/water separation efficiency of these coatings is over 95 % even after 16 separation cycles. Equipped with harmless to environment, facile preparation process, and excellent comprehensive performances, these coatings will have the potential for widespread application.

Preparation of boron nitride hybrid containing phosphorus and silicon and its effect on flame retardant, smoke suppression, and thermal conductivity properties of styrene‐butadiene rubber

AbstractIn this study, a nanofiller (M‐DOPO‐BN) was synthesized by surface modification of hexagonal boron nitride with vinyltrimethoxysilane (KH‐171) and 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO), and compounded with aluminum diethyl phosphinate (ADP) to study their effects on flame retardant, smoke suppression and thermal conductivity properties of styrene‐butadiene rubber (SBR). The results showed that the composites with an ADP content of 20 parts per hundred of rubber (phr) have good flame retardant properties, but the total smoke production increased significantly. The flame retardant properties of SBR composites compounded with 3 phr M‐DOPO‐BN and 17 phr ADP were not only further improved, but also the peak carbon monoxide production rate (pCOP) and peak carbon dioxide production rate (pCO2P) were reduced by 37.0% and 67.5%, respectively, compared with pure samples, showing a good smoke inhibition effect. In addition, the thermal conductivity of the composites have also been improved to a certain extent. The variable temperature infrared and residual char analysis of SBR composites showed that the reasons for its flame retardancy and smoke suppression are that M‐DOPO‐BN can catalyze the formation of carbon, and the silica and boron nitride generated by decomposition during combustion can improve the density of residual char.

Synthesis of a novel composite component inhibitor and its flame retardant effect on coal

In order to solve the problem of coal spontaneous combustion in the goaf, this paper used multi-component polymers as materials, and determined the optimal concentration of polyethylene glycol, carbonate and sodium polyacrylate was 13.7 wt%, 14.1 wt%, 0.03 wt% by response surface method. The water loss rate and surface tension of PAS-W were tested. The effect of PAS-W on functional groups was analyzed by infrared experiments. Thermogravimetric experiment was used to test the thermodynamic properties of PAS-W. The research showed that PAS-W had good applicability and stability. After treated with PAS-W, the content of aliphatic hydrocarbon and aromatic hydrocarbon in coal decreased by 49.5% and 39.7%, respectively. The oxidation rate of coal slowed down, and the ignition temperature also increased significantly. By analyzing the flame retardant mechanism of PAS-W, it was found that PAS-W had good flame retardant effect in physical and chemical properties.

Thermal degradation behavior and gas phase flame-retardant mechanism of diamine-based polybenzoxazine/polyhexahydrotriazine interpenetrating polymer network

It is an important research direction to improve the flame retardant properties of polymers. Benzoxazine resins have attracted a great deal of interest due to their good thermal property, but the brittleness hindered their further application. A high-toughness diamine-based polybenzoxazine/polyhexahydrotriazine interpenetrating polymer network (poly(PH-ddm)/PHT IPN) have been prepared successfully in our group. In this paper, the flame-retardant mechanism of the poly(PH-ddm)/PHT IPN was discussed. Its flammability property and the thermal decomposition mechanism were measured and analyzed with Cone Calorimeter, Thermogravimetric Analysis-Fourier Transform Infrared Spectroscopy (TGA-FTIR), and Pyrolysis-Gas Chromatography/Mass Spectrometry (Py-GC/MS). The results illustrated that little heat was released during the ignition process of the cured resin. The main gas including NH3 and CO2 were generated during the thermal decomposition. With the release of these self-extinguishing gas that insulate the materials from oxygen and take away the burning heat, the poly(PH-ddm)/PHT IPN with the hexahydrotriazine structure exhibits good gas phase flame retardance.

Ultrastrong and flame-retardant microfibers via microfluidic wet spinning of phosphorylated cellulose nanofibrils

Translation of the high mechanical properties of cellulose nanofibrils (CNFs) to macroscopic fibers represents a great challenge due to difficulties in the assembly of CNFs into well-ordered structures. In this study, we report the ultrastrong and flame-retardant microfibers via the microfluidic wet spinning of phosphorylated cellulose nanofibrils (PCNFs) with high charge content. The macroscopic stress is effectively transferred to the individual PCNFs and results in a Young's modulus of 29 GPa and a tensile strength of 654 MPa. The as-prepared microfibers retain >85 % strength in the wet hydration state, exceeding most natural or synthetic microfibers. Furthermore, glycerol and egg yolk were introduced to the microfibers for enhancing the modulus (31 GPa), strength (865 MPa) and the strain to failure (10.95 %). In addition, the PCNFs microfibers have good flame retardancy. This study expands the potential applications of nanocellulose microfibers in biomedical and flame-retardant materials.

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.

Research on preparation and flame retardancy of melamine-modified flame retardant loofah composites

As a natural plant material with unique porous structure, loofah is used in many fields, but there are still defects in fire safety performance in that its flammability. The melamine-modified flame retardant loofah composites (M-FR-PL) were prepared by impregnation baking method. The experimental synthesis conditions were optimized by L9 (34) orthogonal design. The flame retardancy, heat release rate (HRR), thermal stability and smoke density of the composites were analyzed. M-FR-PL6 prepared under the optimum experimental conditions had good properties: the adsorption rate of flame retardant (AR, %) was 6.8%, the limiting oxygen index (LOI, %) reached 27.5%, the vertical combustion level reached V-0, and the amount of residual char was 17.2% higher than that of loofah. The flame retardant mechanism of M-FR-PL6 was thoroughly discussed by various characterization methods. The peak of the HRR curve of M-FR-PL6 declined compared with loofah, indicating the loofah after melamine flame-retardant treatment has good flame retardancy and smoke suppression properties.

The synergistic effect of lamellar cobalt phosphate and sodium metaborate hydrate improves the flame retardancy of epoxy resin

The aim of this paper is to probe the synergistic effect of cobalt phosphate (Co-Pi) and sodium metaborate hydrate (SMB) on the flame retardancy of aqueous epoxy resins. In situ growth of sodium metaborate on cobalt phosphate surfaces by co-precipitation to form a multi-functional flame retardant material and the prepared mixture was added to a waterborne epoxy resin to improve the inflaming retarding of the resin. Finally, water-based epoxy resin with flame retardant was applied to the wood for performance testing. After experimental comparison, the Co-Pi@SMB3%/EP shows the best results in maximum decomposition temperature (374.3 ℃), the residual carbon (26.6 %), the limiting oxygen index (26 %), time to ignition (26 s) peak heat release rate (173.9 kW/m2), total heat release (41.35 MJ/m2), peak smoke release rate (0.060 m2/s), total smoke release (5.6 m2), peak CO release (0.035 g/g), and peak CO2 release (0.613 g/g), possessing the optimum flame retardant effect. The residual char after the limiting oxygen index test was characterized, and it was confirmed that the Co-Pi@SMB composites have good flame retardant feature.

Effect of Mg(OH)2/silica composite aerogel filler on the glass transition temperature and flame retardancy of detachable polymer coatings

Polymer-based detachable coatings are used to protect industrial products and military equipment from surface damage and contamination during manufacturing and transportation. To expand their application to various industrial fields, it is essential to simultaneously implement diverse characteristics, such as low glass transition temperature, high detachability and uniformity, and high flame retardancy. In this study, we prepared Mg(OH)2/silica composite aerogel, which was used to prepare a detachable poly(vinyl butyral) coating solution to improve the flame retardancy and reduce the glass transition temperature of the coating. Furthermore, we investigated the effect of the addition of a surfactant for achieving a detachable coating with good uniformity and flame retardancy. The coating prepared using the Mg(OH)2/silica composite aerogel and nonionic surfactant exhibited a surface area of 496 m2/g. In addition, the coating maintained its flexibility even at sub-zero temperature (−7 °C) and exhibited significantly improved flame retardancy as it withstood fire for more than 15 s before igniting compared to the original coating.

An efficient method to recycle and reuse meta-aramid from used dust filter bags

The annual replacement of a large number of used dust filter bags generated as industrial waste has seriously polluted the environment and caused waste of resources. The meta-aramid filter media is a typical representative of them. In this work, a complete and efficient process for the recovery and reuse of meta-aramid filter bag was proposed, which mainly included three stages, i.e., pretreatment, dissolution recovery and reuse. Firstly, the feasibility of recycling the pretreated used meta-aramid filter media was demonstrated by FT-IR, XRD and SEM characterization. Then the optimum dissolution method was selected for the recovery of used filter materials. The effects of dissolving temperature, type and concentration of solubilizer on dissolution time, solubility and dissolution products were systematically investigated. 110 °C, 4 wt% LiCl as solubilizer and DMAc as solvent were selected as the preferred conditions. The method was successfully used to achieve 100% dissolution recovery of used meta-aramid material with a concentration of 25 wt%, and the whole recovery process was environmentally friendly. Moreover, the recovered meta-aramid solution was used to prepare meta-aramid films by phase inversion method. The performance tests and characterization confirmed that the obtained films had good thermal stability, mechanical properties, flame retardancy and insulation properties. The whole recycling process not only alleviated the threat of waste filter bags to the environment, but also achieved high quality reuse of meta-aramid filter material and had great application prospects.

Combustion and Thermal Properties of Flame Retardant Polyurethane Foam With Ammonium Polyphosphate Synergized by Phosphomolybdic Acid

Phosphomolybdic acid (PMA) as a synergist was added into polyurethane (PU) rigid foam with ammonium polyphosphate (APP) to improve its flame retardancy and thermal stability. The combustion performance of PU was studied by limiting oxygen index (LOI), UL-94, and a cone calorimeter. The thermal degradation behavior of PU was determined by thermogravimetric analysis (TG) and thermogravimetric infrared spectroscopy (TG-IR). Experimental results showed that the introduction of PMA could further improve the flame retardant performance of PU/APP composites and significantly increase the amount of carbon residue at high temperatures. Adding 3wt% PMA to PU containing 12wt% APP could make the foam pass UL-94 V-0, increase the carbon residue at 800°C by 69.16% in the air atmosphere, and decrease the THR by 24.62% compared to those of PU/15APP. TG-IR results showed that the presence of PMA reduced the production of small-molecule gas-phase products. As for the mechanical properties of PU composites, the addition of PMA influences their density and compressive strength obviously. The results suggest that PMA and APP have good synergistic flame retardancy on PU and can reduce its fire risk.