Flame Retardant Coatings Research Articles

Preparation and Characterisation of UV-Curable Flame Retardant Wood Coating Containing a Phosphorus Acrylate Monomer

The application of a flame retardant coating is an effective solution to enhance the fire retardancy of wood flooring. However, finding the right balance between reducing the flame propagation and good overall coating properties while conserving wood appearance is complex. In order to answer this complex problem, transparent ultraviolet (UV)-curable flame retardant wood coatings were prepared from an acrylate oligomer, an acrylate monomer, and the addition of the tri(acryloyloxyethyl) phosphate (TAEP), a phosphorus-based monomer, at different concentrations in the formulation. The coatings’ photopolymerisation, optical transparency, hardness, water sorption and thermal stability were assessed. The fire behaviour and the adhesion of the coatings applied on the yellow birch panels were evaluated, respectively, using the cone calorimeter and pull-off tests. Scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) analyses were performed on the collected burnt residues to obtain a better understanding of the flame retardancy mechanism. Our study reveals that phosphorus monomer addition improved the coating adhesion and the fire performance of the coated wood without impacting the photopolymerisation. The conversion percentage remained close to 70% with the TAEP addition. The pull-off strength reached 1.12 MPa for the coating with the highest P-monomer content, a value significantly different from the non-flame retarded coating. For the same coating formulation, the peak of heat release rate decreased by 13% and the mass percentage of the residues increased by 37% compared to the reference. However, the flame-retarded coatings displayed a higher hygroscopy. The action in the condensed phase of the phosphorus flame retardant is highlighted in this study.

Green flame-retardant coatings based on iron alginate for polyester fabrics: Thermal stability, flame retardancy and mechanical properties

Polyester (PET) fabrics are widely used in our daily life, but they burn and drip quickly when they encounter flames, and the dripping can cause secondary damage to human bodies. In this study, flame-retardant finishing of PET fabrics was performed by preparing alginate coatings modified with Fe3+. A simple dip-coating technique was used and sodium alginate solution was employed to submerge PET fabrics, after that the coatings were complexed with Fe3+ to endow the flame retardancy of PET fabrics. The micromorphology, mechanical properties, thermal stability, flame retardancy, and burning behaviors of the coated PET fabrics were analyzed. Coated PET fabrics had a limiting oxygen index value of 29%. The vertical flame test illustrated that PET/Iron alginate-2 exhibited excellent self-extinguishing behaviors, no drips appeared. The peak heat release rate of PET/Iron alginate-2 was reduced by 70.3%. In the warp directions, compared with the control, the tensile strength of coated PET textiles increased dramatically. In a word, it is a green method to improve the flame retardancy and anti-dripping of PET fabrics.

Fabrication of an Eco-Friendly Clay-Based Coating for Enhancing Flame Retardant and Mechanical Properties of Cotton Fabrics via LbL Assembly.

An eco-friendly clay-based synergistic flame-retardant coating was established on cotton fabrics via facile layer-by-layer assembly derived from polyethyleneimine (PEI), attapulgite clay (ATP), and phytic acid (PA). The fabricated flame-retardant (FR) cotton fabrics demonstrated improved thermal stability. Compared to untreated cotton fabrics, the limiting oxygen index of Cotton-8TL was improved to 27.0%. The peak heat release rates of the prepared FR cotton fabrics were lower than that of the pristine cotton fabrics, showing a maximum reduction of 41%. The deposition coating system improved the amount of char residue effectively. The intumescent flame-retardant mechanism was proposed through the analysis of char residue and the suppression properties of volatile gases. Furthermore, compared with those of the untreated cotton fabrics, the tensile strength and elongation at break of the FR cotton fabrics in the warp direction were improved by 20% and 47% remarkably, respectively. A feasible surface modification strategy was provided for the flame-retardant treatment of cotton fabrics with the improvement of mechanical properties.

Facile synthesis of bio-based phosphorus/nitrogen compound for high efficiency flame retardant finishing of cotton fabric

Facile synthesis of bio-based phosphorus/nitrogen compound for high efficiency flame retardant finishing of cotton fabric

Water-Soluble Cyclophosphazenes as Durable Flame-Retardant Finishes for Nylon/Cotton Blend Fabrics

Water-Soluble Cyclophosphazenes as Durable Flame-Retardant Finishes for Nylon/Cotton Blend Fabrics

The effect of binder molecular weight and talc mineral filler on expansion ratio and hardness in intumescent material

AbstractIntumescent flame retardant coatings were prepared including binder (acrylic resin), solvent, TiO2, talc and flame retardant system (ammonium polyphosphate‐APP, pentaerythritol‐PEN, and melamine‐MEL). To evaluate the effect of molecular weight on the swelling process as well as the hardness of the charred layer, the acrylic resins with different molecular weights were applied. In particular, by incorporating of talc mineral, the performance of the APP‐PEN‐MEL system is significantly improved. The results showed that the highest molecular weight acrylic resin has the best expansion ratio (53.72 times) and the highest hardness of charred layer (15.5 N at the compression of 30 %). The coating with 2.5 % talc powder can be considered as an optimized content of the char layer.

Characterization of Water Repellent and Flame Retardant Finished Cotton Canvas Fabric for Bivouac Tents

Water repellency and flame retardancy have applications in many fields, such as automotive interiors, indoor decorations, upholstery, outdoor clothing and tents. Cotton, having superior qualities, is considered one of the best raw materials for tent manufacture. The study has undertaken the application of different water repellent and flame retardant chemicals on 100% cotton canvas fabric to be used as bivouac tents. The purpose was to find suitable water repellent and flame retardant chemicals that can be applied in a single bath or in a two-step process to give the desired repellency and retardancy effect. Initially, two screening sets were carried out, which aided in the identification of best-performed chemicals to be used in the combined application of water repellent and flame retardant. In the combined application, the fabric was finished using two approaches. In the first approach, both repellent and retardant chemicals were prepared in a single bath, and in the second approach, the fabric was first finished with flame retardant chemicals and then finished with water repellent chemicals. In both the approaches, the finished fabric was evaluated by a cone test, a hydrostatic pressure head test and a flammability test against locally set requirements. It is concluded that the procedure of single bath water repellent and flame retardant finishes (SBWRFR1b) showed reduced pickup percentage (60%) and resulted in better water repellency and flame retardancy properties, in comparison to other procedures and series of recipes.

Waterborne hybrid polyurethane coatings containing Casein as sustainable green flame retardant through different synthesis approaches

Waterborne polyurethane (WPU) dispersions were prepared for flame retardant coatings. Specifically, alkoxysilane-capped polycaprolactone-based WPUs were synthesized employing the acetone process, and Casein, as a green and sustainable flame retardant additive, was added by two different methods (in situ and ex situ). These two strategies made possible to evaluate the effect of the Polyurethane/Casein interaction in the final properties of the dispersions and films. FTIR and solid-state 29Si NMR, confirmed the formation of the siloxane network during film generation process. The addition of Casein during the synthesis (in situ) resulted in a covalent bonding between the polyurethane and Casein, which significantly increased the particle size. However, the incorporation after phase inversion of the WPU (ex situ), did not change the particle size. Tensile tests revealed that the covalent bond promoted an increase in the brittleness of the material compared to ex situ approach due to a better dispersion of the Casein in the system. TGA results showed that Casein increased the thermal stability of all the coatings, especially of those obtained by the ex situ route. Moreover, and according to the microscale combustion calorimeter (MCC) and vertical burning test (UL-94) measurements Casein delayed the combustion of the material. Consequently, due to their characteristics, these Casein-WPU dispersions could potentially be used as combustion retardant coatings, where good physicochemical properties are essential for effective performance.

N-substituted cyclic phosphoramides as flame-retardant and anti-dripping coatings for PET fabric

Fabric made of polyethylene terephthalate (PET) is a common textile that is widely used in daily life. Its flame retardancy has emerged as a major concern for lowering the risk of fire. As a kind of popular flame retardants, cyclic phosphoramides have been widely applied to improve the flame retardancy of various inflammable materials. To achieve more suitable and effective flame retardants for PET fabric, the fire-safety capabilities of PET fabric coated with various cyclic phosphoramides substituted by siloxane (PDPTP), hydroxyphenyl (DPHBP), and hydroxyethyl (PDNP) groups was explored in this work. All of these chemicals can successfully prevent PET fabric from melting and burning, providing it good flame retardancy and non-dripping performance. LOI values for PET fabrics coated with PDPTP, DPHBP and PDNP increased to 24.6, 25.2, and 30.3% under comparison loadings. These flame-retardant coatings enhanced the char-forming capacity for PET fabric. The residues at 700 °C increased to 26.5 and 27.4% for PDPTP and PDNP coated fabric in N2 atmosphere compared with 2.9% for pure fabric. Peak heat release rate (PHRR) and total heat release (THR) was effectively restrained by 50% and 35%, respectively. Fortunately, these flame-retardant coatings had no detrimental effects on the mechanical characteristics of PET fabric and even enhanced the weft's tensile breaking forces. Apart from DPHBP significantly reducing the fabric's whiteness, the whiteness of PDPTP and PDNP coated PET fabric hardly changed. The effect of cyclic phosphoramides with various substitutions on the flame retardancy of PET fabric is thoroughly discussed in this paper, which might be useful in the development of more effective flame retardants for PET materials.

Synergistic Effect between Piperazine Pyrophosphate and Melamine Polyphosphate in Flame Retardant Coatings for Structural Steel.

Piperazine pyrophosphate (PAPP) combined with melamine polyphosphate (MPP) was adopted to prepare a waterborne fire retardant intumescent coating (IC) for structural steel. Silicone acrylic emulsion was used as binder. In the 2-h torch test, PAPP/MPP-IC coating presented excellent fire resistance performance. The equilibrium temperature at the backside of the steel board decreased to 170 °C with protection of MPP/PAPP-IC, compared with 326 °C of APP/PER/MEL-IC. After 72-h water immersion, MPP/PAPP-IC could still provide sufficient thermal isolation, but APP/PER/MEL-IC failed the test. The water absorption of the MPP/PAPP coating was also reduced. The thermogravimetric analysis measured that the PAPP/MPP-IC had unique initial decomposition temperature of 296 °C and higher residue of 33.8 wt%, which demonstrated better thermal stability and fire retardancy in condensed phase. In addition, Scanning Electron Microscope (SEM) images illustrated that the structure of the carbon layer formed by MPP/PAPP-IC was dense, complete and consistent, indicating the improvement of mechanical strength and thermal isolation of the char. The synergistic effect between piperazine and phosphoric acid groups in MPP/PAPP contributed to the superior flame retardancy. Consequently, MPP/PAPP-IC was much more efficient than the traditional APP/PER/MEL-IC. This work provides a novel way for designing flame retardant coatings for structural steel with excellent comprehensive performance.

Flame Retardant Coatings from Bio-Derived Chitosan, Sodium Alginate, and Metal Salts for Polyamide 66 Textiles.

Bio-derived polysaccharides, namely, chitosan (CS) and sodium alginate (SA) were considered in a layer-by-layer (LbL) deposition to construct flame retardant coatings onto the polyamide 66 (PA66) fabric surfaces. The as-prepared coatings were further modified in the impregnation process with a number of inorganic salts containing boron, nickel, and iron elements. Obtained results revealed that the simultaneously LbL-assembled and metal salt-treated fabric samples exhibited superior flame retardant performance compared to the only LbL-deposited fabric samples. The limiting oxygen index (LOI) value reached up to 25.5% of the CS–SA–iron salt treated fabric sample and the dripping tendency was completely diminished only for the LbL-metal salt modified fabric samples. Among the treated fabric samples, the CS–SA—iron-salt-modified fabric sample exhibited a maximum reduction in the peak heat release rate by 34% and handed improved and higher quality char residues, indicating a possible condensed phase flame retardant mechanism of this applied finishing. Moreover, metal salt-induced cross-linking could enhance the coating stability and durable finishes against regular home laundering where an iron-salt-treated fabric sample could retain anti-dripping properties even up to 10 laundering cycles. Thus, this pairing of bio-macromolecules (i.e., charring agent) with the metal salts in a hybrid system showed efficacy in improving the fire performance of polyamide textiles via the synergistic involvement between them.

Facile synthesis and construction of renewable, waterborne and flame-retardant UV-curable coatings in wood surface

Exploring facile synthesis and organic-solvent-free of renewable flame-retardant coatings in wood surface is in line with the environmental protection and safety. In this research, acrylated epoxidized soybean oil (AESO), flame retardant FRC-6, and itaconic anhydride (IAH) were used to prepare waterborne unsaturated resins (IAESO) and monomers (IAFRC) in one pot through esterification. The waterborne coatings consisting of IAESO and IAFRC appeared favorable dispersity, and applied to prepare flame-retardant UV-curable coatings in wood surface, which presented eligible physical properties including pencil hardness, adhesion, and solvent resistance. Meanwhile, IAESO-F20-W exhibited prominent flame retardancy with UL-94 V-0 rating and the highest LOI value of 28.9 %, which improved significantly comparing with pure wood. Further, IAFRC obviously enhanced the overall carbonization and produced the dense char layer covering on the substrate surface, which hindered the transfer of heat, smoke, and combustible volatiles, thereby effectively suppressed the further combustion and pyrolysis of substrate, demonstrating that the waterborne flame-retardant UV-curable coatings ameliorated wood flammability effectively.

Surface properties and flame retardancy of polyacrylonitrile fabric modified with nitrilase and vinyl phosphate

Flame-retardant finishing is essential for polyacrylonitrile fabric because of the restriction in application caused by poor flammability. Flame-retardant polyacrylonitrile fabric treated with nitrilase and vinyl phosphate was successfully prepared in this study. X-ray photoelectron spectroscopy, thermogravimetric analysis, limiting oxygen index, KES fabric style instrument, air permeability, moisture permeability, thermal resistance, and moisture resistance tests were conducted to characterize the treated polyacrylonitrile fabrics. The results showed that carboxyl groups were introduced after nitrilase treatment, which efficiently improved the adsorption and combination of vinyl phosphate on polyacrylonitrile fibers. The sample prepared with nitrilase/vinyl phosphate treatment exhibited a high limiting oxygen index value of 27.5%. The air permeability and moisture permeability of the treated fabric decreased while moisture resistance increased.

Efficient and Durable Flame-Retardant Coatings on Wood Fabricated by Chitosan, Graphene Oxide, and Ammonium Polyphosphate Ternary Complexes via a Layer-by-Layer Self-Assembly Approach.

An efficient and durable flame-retardant coating was constructed on wood via a layer-by-layer (LBL) self-assembly approach by using a chitosan (CS), graphene oxide (GO), and ammonium polyphosphate (APP) ternary flame-retardant system. Both scanning electron microscopy (SEM) characterization and Fourier transform infrared spectroscopy (FT-IR) analysis indicated that CS-GO and APP polyelectrolytes were successfully deposited on wood, and the deposition amount was increased with the numbers of the LBLs. Thermogravimetric analysis revealed that the CS-GO-APP coating could decrease the initial and maximum thermal decomposition temperature of the coated wood while increase the char residue significantly, which may be attributed to the earlier degradation of CS and APP and effective heat barrier of the incorporated GO, thus increasing the thermal stability of the modified wood. The limited oxygen index (LOI) and cone calorimeter analysis results of the pristine and coated wood indicated that the fire resistance was significantly improved after CS-GO-APP modification; when 15 BLs were deposited on the wood, the LOI was increased from pristine 22 to 42, while the heat release rate and total heat release decreased from pristine 105.50 kW/m2 and 62.43 MJ/m2 to 57.51 kW/m2 and 34.31 MJ/m2, respectively. What is more, the 24 h immersion experiments and abrasion tests proved the excellent durability of the deposited coating. Furthermore, the SEM images of the char residues after flaming test proved that the CS-GO-APP assembly coating could promote the char layer formation on the wood surface and block the heat and flame spread, thus protecting the wood from fire attacking.

Flame Retardant Coatings: Additives, Binders, and Fillers.

This review provides an intensive overview of flame retardant coating systems. The occurrence of flame due to thermal degradation of the polymer substrate as a result of overheating is one of the major concerns. Hence, coating is the best solution to this problem as it prevents the substrate from igniting the flame. In this review, the descriptions of several classifications of coating and their relation to thermal degradation and flammability were discussed. The details of flame retardants and flame retardant coatings in terms of principles, types, mechanisms, and properties were explained as well. This overview imparted the importance of intumescent flame retardant coatings in preventing the spread of flame via the formation of a multicellular charred layer. Thus, the intended intumescence can reduce the risk of flame from inherently flammable materials used to maintain a high standard of living.

A multifunctional coating towards superhydrophobicity, flame retardancy and antibacterial performances

To meet the growing demands of multifunctional fabrics in different scenarios that require fire safety, developing flame-retardant coatings with integrated superhydrophobicity and antibacterial properties is imperative. However, how to simultaneously achieve all these features is still a big challenge. Here, a novel multifunctional coating containing polyethyleneimine (PEI), phytic acid (PA), iron ion (Fe3+) and dimethyloctadecyl [3-(trimethoxysilyl) propyl] ammonium chloride (QAS) is constructed by a facile dip-coating strategy. Attributed to the in-situ growth process of the phytic acid metal complex aggregations, the designable hierarchical micro/nano-scale protuberances can be generated. The resultant coating exhibits a good liquid repellency with water contact angles above 155°. Benefiting from the intumescent effect, the coating can produce a dense char layer, and hence to give the coated fabrics a self-extinguishing behavior in the vertical burning test with a limiting oxygen index value of ∼28.5%. Due to the presence of N+ and alkyl chain of QAS, the coating exhibits appreciable antibacterial activity and self-cleaning ability. Additionally, the multifunctional coating can endure more than 20 washing cycles and 100 abrasion cycles without losing its hydrophobicity, flame retardancy and antibacterial properties. The performance and function improvements mainly come from the well arrangements of phosphorus, nitrogen and metal elements. The multifaceted features enable promising applications of such coating in advanced functional textiles, protective clothing, transportation facility, etc.

Permanent P/N-rich polymeric coating capable of extinguishing flame on cotton fabrics

Although polyphosphazenes having attracted attention for use as flame-retardant coatings for textiles, nonetheless their add-on level is still far from ideal with regard to high-efficiency flame-retardant properties, wearing comfort and durability. Herein, for the first time, a cross-linkable phosphorus and nitrogen-rich polyphosphazene, poly(methoxy/allylphenoxy)phosphazene (PMAP), with mainly methoxy groups and an appropriate amount of unsaturated chemical bonds containing allylphenoxy side groups (ca. 8 %) was synthesized. Subsequently, the noncombustible, transparent, elastic crosslinked PMAP coating was coated on cotton fabrics through dipping and photoinduced cross-linking processes. The PMAP-coated cotton showed high-efficiency flame-retardant properties along with remarkably high durability. The intrinsic properties of cotton fabric, such as whiteness, gas permeability and bending rigidity, were highly reserved after being coated with PMAP. Interestingly, the flame-retardant properties of the 4.9 wt%-coated cotton increased, and the coated cotton obtained a self-extinguishing property and maintained >95 % of its initial mass after 60 rigorous laundry cycles. Moreover, the PMAP-coated cotton exhibited enhanced carbonization ability at lower temperatures, which was the key to the flame-retardant properties of cotton fabric. The PMAP-coated cotton also showed a lower peak heat release rate and total heat release values than the control cotton during combustion. Therefore, the comprehensive highly favorable properties of the PMAP coating make it a cutting-edge material for flame-retardant cotton fabrics and greatly expand its potential in practical applications.

Durable Flame-retardant Finishing of Cotton with a Reactive Phosphorus-based Environmental Flame Retardant

ABSTRACT A mannitol (MNT) – based reactive halogen-free flame retardant, FR-MNT, was synthesized and used for the flame-retardant finishing of cotton. FR-MNT was covalently grafted onto cotton fiber through -P = O(O−NH4 +) groups, which endowed cotton fabric superior flame retardancy. Phosphorous acid was used instead of all phosphoric acid for esterification with mannitol, which reduced the amount of the -P = O(O−NH4 +) groups, thus reducing the effect of metal ions on the flame-retardant fabric during soaping. Vertical combustion and LOI tests showed that treated cotton fabrics had excellent washing resistance. The thermal stability and combustion behavior of cotton fabric were evaluated by thermogravimetry (TG) and cone calorimetry tests. The mechanical properties of cotton fabrics changed only slightly after flame-retardant treatment.

Epoxy-modified silicone resin based N/P/Si synergistic flame-retardant coating for wood surface

Flammable wood has a negative impact on safety, however flame-retardant coatings can help to mitigate these risks. In this work, the epoxy-modified silicon (SiR) coating was formed by the condensation of dimethyldiethoxysiloxane with 3-glycidoxypropyltrimethoxysilane (KH-560), while the resin cured by nitrogen-containing phosphorus flame-retardant (PTDP) curing agent. The flame-retardant coating (PTDP/SiR) has outstanding hardness, water resistance, solvent resistance and it is appropriate for utilizing in wood surfaces. Meanwhile, PTDP/SiR-1 exhibits obvious flame retardancy. The PTDP/SiR-1-coated spline received a UL-94 V-1 rating and a 31.0% LOI, compared to 26.0% and 21.5% for the control coating and uncoated splines, respectively. Compared with the control spline, the peak heat release rate (pHRR) decreased by 23%. SEM, XPS and TGA-FTIR revealed the N/P/Si synergistic flame-retardant mechanism. The mechanism of improving the flame retardancy is due to a dense char layer, incombustible gas, and phosphorus-containing segment formed by pyrolysis. The combination of these factors improves the coatings flame retardant.

Eco-friendly and durable flame-retardant coating for cotton fabrics based on dynamic coordination of Ca2+-tannin acid

Eco-friendly durable flame-retardant coatings for cotton fabrics are urgently needed but remain a huge challenge. Here, we reported a highly durable flame-retardant coating without formaldehyde, halogen, or even phosphorus through co-coordination of biomass tannin acid (TA), tartar emetic (TE), and Ca2+. In this system, due to the dynamic replenishment of Ca2+ naturally present in tap water, the coating can maintain high durability during the long-term tap washing process. Meanwhile, Ca2+ can effectively catalyze TA and cotton fibers to form graphitized carbon residues, thereby achieving high flame retardancy. As a result, the treated cotton fabrics showed excellent durable flame retardancy. Even after 50 cycles of tap washing, the fabric can show much lower heat release and pass the horizontal flammability test, while the deionized water laundered samples largely reduced the flame retardancy due to the lack of Ca2+ supplementation. The analysis of the flame-retardant mechanism confirmed that the dense graphitized carbon layer formed in the condensed phase and abundant CO2 released in the gas phase can effectively prevent the transfer of heat and dilute the combustible gas, respectively. This work provides a new dynamic coordination strategy for the design and fabrication of flame-retardant coatings with high efficiency, environmental friendliness, and durability.