Flame Retardant Tests Research Articles

Superhydrophobic coatings prepared by spraying method with corrosion resistance and flame-retardant properties

In this study, aluminum tripolyphosphate (ATP) and silicon dioxide (SiO2) composites were introduced on the surface of copper sheets by spraying technique to prepare coating with flame retardant, superhydrophobic and corrosion resistant properties (ATP@SiO2). The coating not only exhibits excellent water repellency, but also has remarkable mechanical stability, with the corrosion current density reduced by an order of magnitude in electrochemical tests and the corrosion inhibition rate of 99.17 %. In flame retardant tests, the burning time of cotton fabrics coated with sprayed ATP@SiO2was extended by 38 s, with no smoldering observed. This study provides insights into the development of novel superhydrophobic materials with enhanced corrosion protection and flame-retardant properties.

Polybenzoxazine/Epoxy Copolymer Reinforced with Phosphorylated Microcrystalline Cellulose: Curing Behavior, Thermal, and Flame Retardancy Properties

This study aims to explore new flame-retardant composites based on a phosphorus-functionalized cellulose derivative and epoxy/benzoxazine thermosetting resins in order to broaden the use of natural fibers in advanced applications. The study involved the phosphorylation of microcrystalline cellulose followed by its characterization through employing various analytical methods to corroborate the accomplishment of its functionalization. The curing behavior of composites based on the polybenzoxazine/epoxy copolymer reinforced with (1 and 5 wt.%) modified microcrystalline cellulose was hereafter considered. The thermal behavior of these composites was correspondingly investigated using thermogravimetric analysis, where improved thermal stability and the limiting oxygen index were stressed. Flame retardancy tests using the vertical burning test UL 94 and heat of combustion analysis utilizing an oxygen bomb calorimeter were also carried out to deeply examine the possible flame retardancy ability of the considered composites.

Innovative Nanocomposite Coating for Aluminum Alloy in the Aircraft Manufacturing Industry with Increased Mechanical Strength, Flame Retardancy, and Corrosion Resistance

AbstractNanocomposites containing impermeable two‐dimensional materials are of significant interest for protecting metals against corrosion. Incorporating 4‐aminobutyltriethoxysilane (ABES) functionalized tantalum nitride (TaN) into a coating matrix enhances the barrier effect due to TaN's notable chemical and thermal stability. When integrated with graphitic carbon nitride (GCN) in polyurethane (PU), functionalized TaN significantly improves corrosion resistance and fire‐retardant capabilities. Electrochemical evaluations of aluminum coated with varying amounts of functionalized TaN/GCN in PU demonstrated substantial enhancements in protective behavior in chloride environments. The PU nanocomposite exhibited superior flame retardancy, with significant reductions in peak heat release rate (PHRR), total heat release (THR), and total smoke production (TSP) compared to pure PU. Flame retardancy tests demonstrated increased thermal stability, attributed to the synergistic effects between GCN and silanized TaN. Electrochemical impedance spectroscopy (EIS) measurements showed a high coating resistance of 8.89×1011 Ω cm2 for PU/functionalized TaN/GCN, even after 40 days of electrolyte exposure. Additionally, the PU/functionalized TaN/GCN coating demonstrated exceptional water repellency, indicated by a water contact angle (WCA) of 164°. Mechanical tests revealed that PU/functionalized TaN/GCN exhibited favorable adhesion strength and hardness, maintaining integrity even under prolonged immersion. These findings suggest that this nanocomposite is a promising coating component for aerospace applications. The integration of functionalized TaN/GCN within the PU matrix presents a novel approach to developing multifunctional coatings with enhanced performance across various metrics essential for aerospace materials.

S-Triazine phosphonates as flame retardants for polyurethane and polyisocyanurate rigid foams

The liquid flame retardant tris(2‑chloro-isopropyl) phosphate (TCPP) is widely used in polyurethane and polyisocyanurate rigid foams. However, TCPP is currently under assessment by the European Chemicals Agency ECHA and National Toxicology Program NTP, USA. For this reason, there is a high demand for new flame retardants with similarly good processing and application properties. This paper examines the influence of low-molecular liquid s-triazine phosphonates on the foaming behaviour and flame retardancy of polyurethane and polyisocyanurate rigid foams for building applications. The flame retardant investigations consisted of thermogravimetric analysis of the components and flame retardancy tests performed on the foams: limiting oxygen index, EN 13501 class E, and cone calorimetry. The newly developed class of s-triazine phosphonates are promising flame-retardant candidates with good processing and application properties.

Fire Properties of Paper Sheets Made of Cellulose Fibers Treated with Various Retardants.

This article presents the results of flame-retardancy tests conducted on cellulose sheets produced using a Rapid Köthen apparatus treated with retardants. The agents used were potassium carbonate (PC) K2CO3 (concentrations of 20; 33.3; and 50% wt/wt), monoammonium phosphate (MAP) NH4H2PO4 (concentrations of 35% wt/wt), diammonium phosphate (DAP) (NH4)2HPO4 (concentrations of 42.9% wt/wt), and bisguanidal phosphate (FOS) C2H10N6 (concentrations of 22.5% wt/wt). The agents were used to improve Kraft cellulose-based sheets' flame-retardant properties and compare their performances. As part of the study, the flammability of the materials was determined by the following methods: an oxygen index (OI) test, a mass loss calorimeter (MLC) test, and a mini fire tube (MFT) test. All formulations showed an increase in flame retardancy compared to the control test. All protected samples were non-flammable for OI determinations, and DAP-protected samples showed the highest OI index. For the MLC test, DAP-protected and MAP-protected samples showed the best heat-release rate (HRR), total heat release (THR), and average heat-release rate (ARHE) (samples did not ignite for 600 s). In the MFT test, all treated samples had comparably reduced weight loss. The best parameter was achieved for MAP and DAP (15% weight loss).

Preparation and properties investigation of flame‐retardant rigid polyurethane foam composites based on alkylphosphate oligomer

AbstractIn this work, FR‐PNX, an alkylphosphate oligomer was introduced into rigid polyurethane foam (RPUF) to fabricate FR‐PNX/RPUF composites. The flame retardancy, thermal stability, and combustion properties of composites were investigated by limiting oxygen index (LOI), thermogravimetric (TG), microcalorimetry (MCC), scanning electron microscopy (SEM), et al. The flame retardancy tests demonstrated that the incorporation of 50 phr of FR‐PNX yielded composites that the highest LOI of 23.6 vol% and achieved a V‐0 rating in the UL‐94 test. TG results indicated that FR‐PNX promoted the decomposition of FR‐RPUF in the process, but enhanced the high‐temperature stability of the composites. MCC analyses revealed that the addition of FR‐PNX suppressed the heat release during combustion, and FR‐PNX50/RPUF exhibited the lowest total heat release of 17.3 MJ/m2, a 35% reduction compared to the pure sample. Moreover, the peak heat release rate was decreased to 83.1 W/g, representing a 46.9% reduction compared to pure RPUF. SEM and Raman analyses of the char residue demonstrated that the incorporation of FR‐PNX facilitated the formation of a dense and continuous char layer in the FR‐RPUF, with increased graphitization degree of the char layer, thereby enhancing the composite's fire resistance through the development of a more stable fire barrier.

Modified lignin-based intumescent flame Retardant's effect on flame retardancy, mechanical and electrical properties of HDPE material for cable sheathing

High-density polyethylene (HDPE) is a commonly used material for cable sheathing, which is a flammable material. To ensure the safe transportation of electrical energy, it is necessary to enhance the flame-retardant properties of HDPE materials. In this work, ammonium polyphosphate (APP) with lignin (Lig) is used as an intumescent flame retardant, and the flame retardant properties of APP/Lig for HDPE with different ratios are analyzed. It is found that with 3/1 ratio of APP and Lig under 30 wt%, the best flame-retardant performance is achieved. To further improve its properties, chemical modification of Lig with hexachlorocyclotriphosphazene (HCCP) is conducted to introduce nitrogen and phosphorus, obtaining NP-Lig. Flame retardant, mechanical and electrical properties are tested for the prepared material. The flame retardant tests show that the LOI of HDPE is increased from 23.8 to 28.2 by the addition of APP/NP-Lig, compared to that of APP/Lig. Mechanical tests show that replacing Lig with NP-Lig slightly increases the tensile strength and elongation at break of HDPE. Electrical tests show that APP/NP-Lig flame retardant maintains the electrical properties of HDPE under the industry standards.

산불진화복 난연성능 개선방안 마련에 관한 연구

In this study, we conducted research on the evaluation criteria for the fire-retardant and flame-retardant performance of forest firefighting suits worn by firefighters. We investigated guidelines and flame-retardant test methods for the flame-retardant performance of forest firefighting suits in Korea and abroad and collected forest firefighting suit samples to compare their specifications and materials. To compare non-fire-retardant products and products with reduced flame-retardant performance before and after washing among domestic forest firefighter suit samples, we conducted a flame spread prevention test of ISO 15025. As a result of the test, non-fire-retardant and post-fire-retardant products were completely burned regardless of washing before and after, and aramid products maintained their flame-retardant performance, resulting in results that met the judgment criteria. It is expected that this study will contribute to the improvement of the material, performance, and safety of forest firefighting suits by providing directions for the material and guideline standards of firefighting suits.

Formaldehyde-free and durable phosphorus-containing cotton flame retardant with -N=P-(N)3- and reactive ammonium phosphoric acid groups

A flame retardant (FR) hexachlorocyclotriphosphazene diethylenetriamine ammonium phosphoric acid (HDAPA) was synthesized. Vertical flammability test and limiting oxygen index (LOI) results showed that cotton samples finished with HDAPA solutions (15 % and 20 %) could pass vertical flame retardancy test, and LOIs reached 30.1 % and 35.4 % even after 50 laundering cycles according to AATCC 61-2013 3A washing standard (3A), performing flame retardancy and washing durability. Meanwhile, Fourier transform infrared and X-ray photoelectron spectroscopy analyses suggested that HDAPA was grafted on cotton fibers through -P(=O)-O-C covalent bond. Total heat release (1.98 MJ/m2) and char residue (16.2 %) of HDAPA treated cotton were much lower than those (4.26 MJ/m2, 3.2 %) of untreated cotton. Thermogravimetry results showed HDAPA changed thermal decomposition pathway of cotton fabric, which was further supported by thermogravimetric-Fourier infrared spectrometer results, revealing HDAPA performed a condensed phase flame retardancy mechanism. Scanning electron microscopy implied HDAPA entered amorphous region of cotton fibers to react with cellulose. Mechanical properties of HDAPA treated cotton decreased a little. Although the synthesis process used formaldehyde but no free formaldehyde released. In consequence, the aforementioned results indicated that the introduction of -N=P-(N)3- and -P(=O)(O−NH4+)2 groups to FR was an viable method to improve flame retardancy and durability.

An experimental investigation of flame retardancy and thermal stability of treated and untreated kenaf fiber reinforced epoxy composites

Abstract Natural fiber reinforced polymeric composites perform poor in mechanical and thermal properties at elevated temperatures due to the cellulose and hemicellulose contents of natural fiber start degrading at elevated temperature. In this research work, flame retardancy and thermal stability of treated and untreated kenaf fiber reinforced epoxy composites have been experimentally investigated and reported. Two composite laminates, one with 6 % NaOH Alkali treated and another with untreated woven kenaf mats, were fabricated by hand lay-up technique followed by compression molding with 40 % fiber weight fractions. Flame retardancy test and various thermal characteristics studies such as thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), heat deflection temperature (HDT), and morphological analysis via scanning electron microscopy (SEM) tests were carried out. The results showed that alkali treated kenaf fiber composite achieved V0 fire retardancy grade. The major weight losses, 86 % and 75.5 % for untreated and treated composites respectively were recorded between 300 °C and 450 °C. 13.6 % increase in HDT was noted for treated composite with 0.25 mm deflection at 0.45 MPa pressure condition. Thus the composite laminate with 6 % NaOH alkali-treated kenaf fiber achieved the best thermal stability with less degradation which is more suitable for automobile and aerospace applications.

Evaluation of the performance properties of modacrylic-cotton blended underwear fabrics manufactured for firefighters

In this study, the mechanical, comfort and flame-retardant properties of different knitted fabric structures containing modacrylic fibers with different blend ratios were investigated. Single jersey, rib, pique, three-thread fleece and interlock fabrics were produced with modacrylic/cotton blended yarns and evaluated comparatively. In order to understand the effect of antistatic fiber content on the investigated properties, two fabrics with antistatic fiber were produced. Since modacrylic fibers have moderate abrasion resistance, pilling resistances of the fabrics are not excellent. Due to the knitted fabrics having a soft and flexible structure, their fabric stiffness and bursting strength are quite high. It has been determined that water vapor resistances of all fabrics are satisfactory and the moisture management properties of the S1 (60% modacrylic, 40% cotton) and R1 (60% modacrylic, 40% cotton) fabrics are excellent. All the fabrics passed the flame-retardancy tests and it is sufficient that the modacrylic ratio is between 50% and 60% according to the fabric structure. Results also showed that 2% antistatic fiber content had no effect on the mechanical, thermal comfort and flame-retardancy properties. Since the air permeability, water vapor resistance and moisture management properties of S1 and R1 specimens are good enough, it is recommended to use one of them according to different temperature conditions. Evaluation of modacrylic fiber blended fabrics in different knitting types in terms of mechanical strength, thermal comfort and flame resistance properties together constitutes the originality of the work. Thus, it was possible to evaluate the effect of different knitting types and contents on all tests.

A Strong, Tough and Fire-Retardant Biomimetic Multifunctional Wooden Laminate.

Mildly delignified wood showed a well-preserved wood cell wall framework, and its derived compressed materials demonstrate excellent mechanical properties and advanced functional material potential. Here, we proposed a simple yet effective approach for making strong, tough, and fire-retardant wooden laminate by a three-step process of mild delignification, infiltrating potassium nonafluoro-1-butanesulfonate (PFBS), and hot-pressing to densify the material. PFBS can be infiltrated into the micro/nano-structures of the mildly delignified wood to achieve a good flame-resistant protective barrier. Flame retardant tests showed that this strong, tough, and fire-retardant wooden laminate has a superior flame-retardant performance to natural wood. Additionally, the wooden laminate also exhibits a simultaneously enhanced tensile strength (175.6 MPa vs. 89.9 MPa for natural wood) and toughness (22.9 MJ m-3vs. 10.9 MJ m-3 for natural wood). Given these attributes, the resulting wooden laminates are identified as promising candidates for high-performance structural applications, fulfilling stringent requirements for both mechanical resilience and flame-retardant efficacy.

Innovating fire safety with recombinant hydrophobic proteins for textile fire retardancy.

Fire retardancy for textiles is important to prevent the rapid spread of fire and minimize damage to property and harm to human life. To infer fire-resistance on textile materials such as cotton or nylon, chemical coatings are often used. These chemicals are usually toxic, and economically and environmentally unsustainable, however, some naturally produced protein-based fire retardants could be an alternative. A biofilm protein from Bacillus subtilis (BslA) was identified and recombinantly expressed in Escherichia coli with a double cellulose binding domain. It was then applied to a range of natural and synthetic fabric materials. A flame retardancy test found that use of BslA reduced fire damage by up to 51% and would pass fire retardancy testing according to British standards. It is therefore a viable and sustainable alternative to current industrial fire-retardant coatings.

The synergetic effect of bis(2‐hydroxyethyl) terephthalate from glycolysis of poly(ethylene terephthalate) on the intumescent flame retardancy of waterborne polyurethane

AbstractIn light of the escalating accumulation of polymer waste in daily life, chemical recycling of polymers and value‐added utilization of products have gained considerable attention in recent years. Researchers have widely explored the potential of bis(2‐hydroxyethyl) terephthalate (BHET) derived from the glycolysis recycling of poly(ethylene terephthalate) (PET) waste in the synthesis of polymers or concrete. In this study, we synthesized BHET through glycolysis recycling of PET, and combined it with microencapsulated ammonium polyphosphate (SiO2@APP) and carboxymethyl chitosan to design a series of intumescent flame‐retardant waterborne polyurethane (IFRWPU). The synergistic effect of BHET and SiO2@APP was demonstrated, and the resulting IFRWPU with 12.5 wt% IFR and 3 wt% BHET achieved a limit oxygen index of 25.8% and a 73% reduction in the peak heat release rate in flame retardancy tests. Furthermore, the interaction of BHET and flame retardant was discussed using the analysis of char residue and pyrolytic gas. Overall, this work provides a novel strategy to construct superior flame‐retarded waterborne polyurethane with admirable bonding performance.Highlights The application of glycolysis product of PET in the flame‐retardant modification of WPU. The synergistic enhancement of flame retardancy between BHET and IFR was confirmed. The intumescent flame‐retardant was composed of SiO2@APP and CMCS.

Effect of the melt flow index of compatibilizer on the melt processing and properties of highly filled magnesium hydroxide/linear low density polyethylene composites

AbstractThe application of highly filled composites is limited by their poor processing and rheological properties due to the high loading of fillers. One possible solution to this problem is to use maleic anhydride grafted polypropylene (MAPP) with high melt index as compatibilizer and lubricant. Herein, magnesium hydroxide (MH)/linear low‐density polyethylene (LLDPE) composites with 60 wt% of MH were prepared using MAPP with three different melt flow indexes (MFI). The equilibrium torque and melt flow index tests show that the addition of MAPP with high MFI significantly improves the processability and flowability of MH/MAPP/LLDPE composites. The rheological studies show that it also leads to a substantial reduction in the viscosity and therefore MH/MAPP/LLDPE composites exhibit more solid‐like responses. The scanning electron microscopy shows that a transition layer is formed at the MH‐LLDPE interface. The flame retardancy test shows that the addition of MAPP slightly reduces the flame retardancy of the composites as evidenced by the reduced limiting oxygen index and increased total heat release. Cone calorimeter test shows that the simultaneous addition of MH and MAPP has a synergistic smoke suppression effect.

An environment-friendly, fire-resistant, thermal-insulating and mechanical-robust wood with anisotropic capacitive pressure-sensitive performance

Wood has been widely used for construction, furniture and decoration. Due to its insulating properties, it has been used as a universally renewable and eco-friendly material. Despite these appealing characteristics, wood still suffers from drawbacks such as high fire risk and insufficient mechanical strength. In this work, we fabricated high-performance and low-cost wood with enhanced thermal insulation, mechanical strength and more importantly, high fire resistance, which was prepared by infiltrating basswood with ethanolamine-modified ammonium polyphosphate (EA-APP). This wood laminate exhibited high compressive stress and tensile strength, more than seven times higher compared to the raw basswood, and also maintained stronger thermal insulation properties as tested by infrared thermography. In flame retardancy tests, the resulting flammable wood laminate exhibited excellent self-extinguishing properties and significantly reduced heat release and smoke generation, indicating that the composite possesses excellent flame resistance. Even with the EA-APP content as low as 1.7 wt%, the EA-APP dense wood still shows promising results with strong flame retardancy, thermal insulation and mechanical robustness, reaching V-0 levels in UL-94 tests even after 10 months. Due to the polyionic nature of EA-APP in the wood laminate channel, EA-APP wood exhibits certain capacitive pressure-sensing characteristics.

Thermoplastic polyurethane composite modified by piperazine pyrophosphate: Flame retardancy, thermal stability and combustion properties

In this work, flame retarded thermoplastic polyurethane (TPU) composites were fabricated by introducing a novel flame retardant piperazine pyrophosphate. The flame retardany, thermal stability and combustion performance were systematically investigated. Flame retardant tests confirmed that thermoplastic polyurethane/piperazine pyrophosphate (TPU/PAPP) composites showed LOI of 27.5 vol% without any melt dripping when only 5 wt% PAPP was added. micro-combustion calorimetry (MCC) test implied that PAPP significantly suppressed heat release of TPU/PAPP composites. 10 wt% of PAPP endow PHRR1 and THR values TPU/PAPP10 decreased by 67.0% and 35.1% compared with TPU. Thermogravimetric-Fourier transform infrared spectroscopy (TG-FTIR) showed that PAPP significantly inhibited the release of toxic and combustible gases. The char residue investigation showed that TPU/PAPP composites formed compact char residue, which was able to effectively inhibit the heat and mass transmission in combustion. Based on the investigation, the work mechanism of PAPP in TPU/PAPP composites was proposed.

Flame-retardant hybrid composite manufacturing through reinforcing lignocellulosic and carbon fibers reinforced with epoxy resin (F@LC)

Novel flame retardant hybrid composites were developed from lignocellulosic and carbon fibers reinforced with epoxy resin using hot pressing technology. The size of the lignocellulosic fibers was within 0.045 to 0.8 mm, and the carbon fibers ranged from 5 to 8 mm. The nominal thickness of the composites was 10 mm, whereas the nominal density was 730 kg/m3. The composite dimensions were 400 × 400 mm2. The developed panels were tested for internal bonding strength and flexural properties to investigate their mechanical performance. Furthermore, SEM (Scanning electron microscopy) test was conducted to examine the morphologies of the products before and after fracture and found substantial quantities of both types of fiber in the composite system. The EDX (Energy disruptive X-ray) analysis also displayed the chemical elements present in the developed products. Moreover, an FTIR (Fourier transform infrared spectroscopy) study showed strong chemical interactions among the lignocellulosic and carbon fibers with the thermosetting epoxy polymers. The flame retardancy tests of the composite materials also showed significant thermal stability, especially after loading carbon fibers in the composite system. Moreover, dimensional stability showed an improving trend with the increase of carbon fibers as the reinforcement. Overall, the composite materials developed using lignocellulosic and carbon fibers with epoxy resin are showing a novel route to develop composites with high mechanical performance and considerable flame retardancy.Graphical abstract

Enhancing flame retardancy of polyphenylene sulfide nanocomposite fibers by the synergistic effect of catalytic crosslinking and physical barrier

AbstractProtective clothing with fascinating flame‐retardant features is urgently needed to reduce the large amount of smoke and heat released from combustion during fire protection. In this study, polyphenylene sulfide (PPS) nanocomposite resin with efficient flame retardancy is obtained by mixing a low content of graphene and Fe2O3via a twin screw extruder. Followed by, the PPS/G/Fe2O3fibers are fabricated via melting spinning. The PPS/G/Fe2O3nanocomposite resin with 0.3 wt% of graphene and 1.0 wt% of Fe2O3performs the best during the flame retardant tests, giving a shorter self‐extinguishing time, lower peak heat release rate (22.3 kW/m2), total heat release (11.3 MJ/m2) and total smoke production (1.32 m2) than others. The pyrolysis analysis indicates that a large number of products with fused rings are formed in the residual char layer, which effectively inhibit the release of heat and smoke and thus improve the flame retardancy of PPS nanocomposite resin. In addition, the flame retardant textile weaved with PPS/G/Fe2O3fibers gives a high‐limiting oxygen index (40.1%), zero after‐flame time, no droppings and small damaged length (114 mm in warp and 98 mm in weft direction) during the standard flame retardancy tests provided by a third‐party independent inspection organization. The fabrication of PPS fibers with effective and enhanced synergistic flame retardancy through melting spinning is facile and scalable, providing a promising strategy for advanced protective clothing.

Improving the Heat Resistance and Flame Retardancy of Epoxy Resin Composites by Novel Multifunctional Cyclophosphazene Derivatives.

A novel multiple-ring molecule containing P and N, called HCCP-SA, was successfully prepared by the nucleophilic substitution reaction of salicylamide (SA) and hexachlorocyclotriphosphazene (HCCP). Particularly, HCCP-SA possessed the dual functions of heat resistance and flame retardancy. The molecular structure of HCCP-SA was identified by Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. HCCP-SA was bonded into the molecular chain of epoxy resin by the ring-opening curing reaction of epoxy resin, aiming to form a heat-resistant and flame-retardant composite (E-HS-x). In particular, the best-prepared E-HS-x composite with a 20 phr content of HCCP-SA (E-HS-20) presented excellent thermal stability, with an initial decomposition temperature of 267.94 °C and a max weight loss speed of only 0.95 mg·min-1. Moreover, E-HS-20 exhibited remarkable flame retardancy with a limiting oxygen index value of 27.1% and a V-2 rating in the UL94 flame retardancy test. The best-prepared E-HS-20 composite would be a suitable and potential candidate for heat-resistant and flame-retardant polymer materials.