Flame Retardancy Of Polyurethane Foam Research Articles

Current commercial reactive and polymeric flame retardants in polyurethane foams

Polyurethane foams encompass a wide range of materials which, depending on the foam structure, chemical composition, and presence of flame retardants, can be very combustible or fire resistant. The first commercial flame retardants for polyurethane foams were developed 60 years ago with a focus on fire retardant efficiency. These legacy flame retardants are relatively small volatile molecules that can migrate from the foam to the environment. Now the flame retardant industry has been changing with a focus on reactive or polymeric flame retardants. This article gives a short overview of these new commercial flame retardants.

Fabrication of a 2D/2D g-C3N4@ZnTDA nanosheets catalyst for highly efficient degradation of 2,4-dibromophenol and improved flame retardancy of polyurethane foam

High charge separation and transfer efficiency are considered as key factors of photocatalysts in wastewater treatment applications. In this work, a high performance photocatalyst g-C3N4@ZnTDA was designed and applied through a facile solvothermal strategy. The microstructural, morphological, physicochemical, and photoelectrochemical properties of g-C3N4@ZnTDA were fully characterized. The photocatalytic activity of g-C3N4@ZnTDA nanoparticles under visible light source in degrading the 2,4-dibromophenol(2,4-dB) contaminants was also successfully studied. Additionally, the g-C3N4@ZnTDA composite demonstrates easy operation and good regeneration ability, making it highly promising for the efficient removal of phenolic pollutants from wastewater. Besides, a novel reutilization method for used catalyst as flame retardant and for PU foams was successfully testified. The MCN-3 as a fire-safety coating could reduce the heat release and improve flame retardancy of PU composites. This work opens a new window for valuable inspiration and structural design of reutilized MOF composites.

Phosphorus and nitrogen-containing soybean oil polyols: Effect on the mechanical properties and flame retardancy of polyurethane foam.

In recent years, there has been an increasing interest in producing new materials that use renewable resources and halogen-free flame retardants with nonleaching properties. This research focuses on designing and synthesizing phosphorus-nitrogen-based biopolyols for use in polyurethane (PU) foam production. Polyol (ESBO-DYM) with dual functionalities, renewability, and nonflammability is synthesized through the epoxy ring-opening reaction of epoxidized soybean oil with phosphorus and nitrogen-containing tetraol products (DYM). The mechanical and flame retardant properties of PU foams with the addition of an ESBO-DYM were investigated. Increasing the amount of phosphorus in the PU foams increased the thermal stability properties. Using 100% ESBO-DYM as a polyol in the foam formulation increased the limiting oxygen index (LOI) value to 22.9% and resulted in the highest char yield according to the thermal gravimetric analysis (17% at 600 °C). Additionally, the introduction of ESBO-DYM polyol into the formulation resulted in a decrease in the compression strength of the foams. The foam density decreased as the amount of ESBO-DYM polyol in the formulation increased. The foam with the highest amount of ESBO-DYM had a foam density of 29.1 kg/m3. The morphology of the foams was characterized using a scanning electron microscope (SEM). As a result of this study, flame retardant polyurethane foams were formulated using a renewable source, polyol, along with commercial compounds.

Enhancing Flame Retardancy of Polyurethane Foam with Montmorillonite-Based Nanocoatings

Enhancing Flame Retardancy of Polyurethane Foam with Montmorillonite-Based Nanocoatings

Effect of flame‐retardant melamine and dispersants on the mechanical, thermal, and foaming properties of flexible polyurethane foam

AbstractThe objective of this study was to investigate the effect of adding flame‐retardant melamine and five different dispersants on the precipitation, foaming, mechanical, and thermal properties of flexible polyurethane foam (FPUF). Precipitation experiments were conducted to analyze the effect of dispersant on the separation of flame retardant and polyol, and the foaming characteristics of polyurethane (PU) foam after adding dispersant were analyzed. The effect of adding a dispersant on mechanical strength was characterized by measuring tensile strength, tearing strength, and hardness, and scanning electron microscopy analysis was performed to analyze morphological characteristics. Thermogravimetric analysis (TGA) was performed to analyze the thermal properties of PU foam. A horizontal flame test, limiting oxygen index test, and cone calorimeter tests were conducted to examine the flame retardancy of PU foam with flame retardant melamine and dispersant added. The dispersant ANTI‐TERRA‐U is a solution of a salt of unsaturated polyamine amides and low‐molecular acidic polyesters. And, the dispersant BYK‐220S is a solution of a low molecular weight, unsaturated acidic polycarboxylic acid polyester with a polysiloxane copolymer. The dispersants ANTI‐TERRA‐U and BYK‐220S improved the density, tensile strength, tear strength, and hardness of FPUF. TGA of the top and bottom portions of the foam showed less weight difference for samples containing dispersants, indicating better homogeneity due to improved dispersibility. Therefore, we conclude that dispersants are beneficial additives to improve the mechanical properties and dispersibility of PU foam.

INVESTIGATES THE INFLUENCE PHOSPHORUS-NITROGEN-CONTAINING ANTIPYRENES ON THERMAL STABILITY AND FLAME RETARDANCY OF POLYURETHANE FOAM

The paper investigates the influence of melamine and ammonium polyphosphates on thermal degradation and flame retardancy of polyurethane foams (PUFs) composites, based on phosphorus-containing polyol. The limiting oxygen index of PUF was increased from 27,5 to 31,5 vol. % as compared to PUF composites based on phosphorus-containing polyol. The TGA of polyurethane foams demonstrated an increase of the thermal stability. Synthesized polyurethane foams have the highest category of combustion resistance.

Flame retardancy of polyurethane foams prepared from green polyols with flame retardants

AbstractPolyurethane foams (PUFs) were synthesized using bis(2‐hydroxyethylene terephthalate) (BHET), 1,4‐cyclohexanedimethanol (CHDM), and polycaprolactone diol (PCLD), and their flame retardancies were investigated. BHET and CHDM are eco‐friendly chemicals derived from waste polyethylene terephthalate, and PCLD is a precursor monomer used for synthesizing biodegradable polymers. Expandable graphite (EG) and tris(1‐chloro‐2‐isopropyl) phosphate (TCPP) were used as flame retardants. For conventional PUFs prepared with an aliphatic polyol, thermal stability was significantly enhanced with EG and TCPP through thermogravimetric analysis (TGA) and micro‐combustion calorimetry (MCC). PUFs prepared with BHET and CHDM exhibited higher thermal stability than conventional PUFs. This is attributed to the alicyclic and aromatic ring structures, which contribute to thermally stable char formation during pyrolysis. PCLD was introduced as an additional polyol, as well as a possible flame retardant, without the addition of EG and TCPP. PUFs were successfully prepared and exhibited improved resilience to burning up to 300°C due to the intrinsic thermal stability of PCLD. The limiting oxygen index (LOI) indicated that PUFs containing BHET moiety exhibited higher LOI values, whereas PUFs prepared with PCLD showed the lowest LOI value. PCLD can be used as a polyol; however, additional flame retardants are needed to obtain high flame retardancy for PUFs.

Vermiculite Filler Modified with Casein, Chitosan, and Potato Protein as a Flame Retardant for Polyurethane Foams.

In this study, polyurethane (PU) composite foams were modified with 2 wt.% of vermiculite fillers, which were themselves modified with casein, chitosan, and potato protein. The impact of the fillers on selected properties of the obtained composites, including their rheological (foaming behavior, dynamic viscosity), thermal (temperature of thermal decomposition stages), flame-retardant (e.g., limiting oxygen index, ignition time, heat peak release), and mechanical properties (toughness, compressive strength (parallel and perpendicular), flexural strength) were investigated. Among all the modified polyurethane composites, the greatest improvement was noticed in the PU foams filled with vermiculite modified with casein and chitosan. For example, after the addition of modified vermiculite fillers, the foams’ compressive strength was enhanced by ~6–18%, their flexural strength by ~2–10%, and their toughness by ~1–5%. Most importantly, the polyurethane composites filled with vermiculite filler and modified vermiculite fillers exhibited improved flame resistance characteristics (the value of total smoke release was reduced by ~34%, the value of peak heat release was reduced by ~25%).

Facile deposition of environmentally benign organic-inorganic flame retardant coatings to protect flammable foam

The combination of clay and intumescent, also termed hybrid organic−inorganic coating is an attractive strategy to improve the flame retardancy of polyurethane foam (PUF). However, the fabrication of such flame retardants remains challenging as it requires the deposition of many layers to achieve the desired level of the intumescing effect. Herein, we describe a facile route to fabricate a hybrid clay−intumescent coating comprising a OnePot−deposited chitosan (CH)−phytic acid (PA) polyelectrolyte complex (PEC) intumescent stacked on top of a layer-by−layer self−assembled clay trilayer (TL) of poly−d −lysine, CH, and alginate-stabilized montmorillonite. Combustibility tests using cone calorimetry revealed that a PUF coating of CH−PA PEC intumescent on a 5 TL clay nanobrick wall (CH−PA@5 TL@PUF) can reduce the peak heat release rate (a critical flammability metric), peak rate of smoke release, and peak CO2 production rate of neat PUF by 73%, 33%, and 65%, respectively. Additionally, this hybrid coating imparted UL−94 horizontal burning rating by avoiding melt dripping and flashover, while the neat foam was completely consumed during the UL−94 flammabilty test. The proposed method is adaptable for the facile construction of other multifunctional surfaces in various application fields.

Improvement of Flame Retardancy of Polyurethane Foam Using DOPO-Immobilized Silica Aerogel

In this work, silica aerogel was modified by 9,10-dihydro-9-oxa-10-phosphaphenanthrene-1-oxide (DOPO). Then DOPO-immobilized silica aerogel nanoparticles were used as a flame retardant to prepare flame-retardant polyurethane foams. Microscale combustion calorimeter and cone calorimeter tests were employed to evaluate the flame retardancy of polyurethane foams. It was found that both the heat release rate and the total heat release of the composites were reduced with the incorporation of DOPO immobilized silica aerogel. It is speculated that the DOPO-immobilized silica aerogel nanoparticles can inhibit the degradation of polyurethane and catalyze the formation of carbonaceous carbon on the surface.

The Impact of Hemp Shives Impregnated with Selected Plant Oils on Mechanical, Thermal, and Insulating Properties of Polyurethane Composite Foams.

Polyurethane (PUR) foams reinforced with 2 wt.% hemp shives (HS) fillers were successfully synthesized. Three different types of HS fillers were evaluated—non-treated HS, HS impregnated with sunflower oil (SO) and HS impregnated with tung oil (TO). The impact of each type of HS fillers on cellular morphology, mechanical performances, thermal stability, and flame retardancy was evaluated. It has been shown that the addition of HS fillers improved the mechanical characteristics of PUR foams. Among all modified series, the greatest improvement was observed after the incorporation of non-treated HS filler—when compared with neat foams, the value of compressive strength increased by ~13%. Moreover, the incorporation of impregnated HS fillers resulted in the improvement of thermal stability and flame retardancy of PUR foams. For example, the addition of both types of impregnated HS fillers significantly decreased the value of heat peak release (pHRR), total smoke release (TSR), and limiting oxygen index (LOI). Moreover, the PUR foams containing impregnated fillers were characterized by improved hydrophobicity and limited water uptake. The obtained results confirmed that the modification of PUR foams with non-treated and impregnated HS fillers may be a successful approach in producing polymeric composites with improved properties.

Melamine-based polyol containing phosphonate and alkynyl groups and its application in rigid polyurethane foam

The rapid depletion of energy resources is the most serious challenge facing humanity today. Energy consumption by buildings is the largest component of energy consumption, and most of it is in the form of heat loss. Therefore, many buildings use rigid polyurethane foam (PUF) as thermal insulation material to effectively reduce heat loss. However, the greatest disadvantage of PUF is its high flammability. In this work, to reduce the risk of fire caused by PUF, melamine-based polyol containing phosphonate and alkynyl groups (MF3.5 and MB3F3) is synthesized and used to improve the flame retardancy of PUF by replacing common polyether polyol. The effects of MF3.5 and MB3F3 on the physical and mechanical properties, cell morphology, thermal stability and flame retardancy of PUF are systematically studied. The research results show that the flame-retardant polyols have no effect on the thermal insulation properties of PUF, but result in a slight decrease in compressive strength. Thermogravimetric analysis proves that MF3.5 and MB3F3 can increase the temperature of the maximum mass loss rate and reduce the maximum mass loss rate, and significantly increase the char yield at 800 °C. The limiting oxygen index (LOI) value is increased to 24.3%. Cone calorimetry experiments show that MB3F3 reduces the peak heat release rate and total heat release by 28.2% and 30.5%, respectively. Vertical combustion tests show that the average burning rate of the flame-retardant PUF is much slower, and melt-dripping behavior is eliminated. The flame retardancy of PUF is improved mainly through a condensed phase mechanism.

Melamine, silica, and ionic liquid as a novel flame retardant for rigid polyurethane foams with enhanced flame retardancy and mechanical properties

Rigid polyurethane (PU) foams were successfully filled with different weight ratios of melamine (1 wt%, 5 wt%, 10 wt%), silica (0.1 wt%) and ionic liquid, 1-Ethyl-3-methylimidazolium chloride, [EMIM]Cl (0.3 wt%). The aim of this study was to improve the flame retardancy of PU foams and to develop the synergistic effect between melamine, silica and ionic liquid on the flame-retardant PU foams. The influence of different loadings of the fillers was examined. The results showed that in comparison with unfilled foam, all modified compositions are characterized by higher density (41–46 kg m−3), greater compression strength (134–148 kPa), and comparable thermal conductivity (0.023–0.026 W m−1 K−1). Moreover, the reaction to fire of the PU composites has been investigated by the cone calorimeter test. The results showed that the fire resistance of PU foams containing as little as 1 wt% of melamine is significantly improved. For example, the results from the cone calorimeter test showed that the incorporation of the melamine, silica and ionic liquid significantly reduced the peak of heat release rate (pHRR) by ca. 84% compared with that of unmodified PU foam. SEM results showed that incorporated fillers can form an intumescent char layer during combustion which improves the reaction to fire of the composite foams.

Two in One: Modified Polyurethane Foams by Dip‐Coating of Halloysite Nanotubes with Acceptable Flame Retardancy and Absorbency

AbstractPoor flame retardancy of polyurethane foam (PUF) limits its practical application in many fields. Here, flame‐retardant performance of PUF is improved by a simple dip‐coating method. Halloysite nanotube (HNT) coating can be uniformly bonded to PUF surfaces via hydrogen‐bonding interactions, which is confirmed by element mapping and X‐ray photoelectron spectra. Density and mechanical properties of PUF increase with the concentration of HNT suspension, while porosity of the foam decreases with HNT loading. Weight ratio of HNTs to PUF in the composite can be achieved as high as 65.2%. Surfaces of PUF transfer from hydrophobic to super‐hydrophilic after HNT coating, and the water contact angle decreases from 116° to 0° after HNT coating. As a result, methylene blue adsorption capacity of HNTs‐coated PUF increases from 0.02 to 0.15 mg g−1, and adsorption efficiency can reach 98% after 10 s. HNT coating can prevent PUF from burning and dripping, which suggests that flame‐retardant performance of PUF is significantly improved by HNTs. This work establishes a general procedure for improving flame retardancy and dye absorbency of polymer materials by simple dip‐coating of environmental‐friendly clay nanotubes, which shows great potential in high‐performance polymer and functional composite materials.

Bi-phase fire-resistant polyethylenimine/graphene oxide/melanin coatings using layer by layer assembly technique: Smoke suppression and thermal stability of flexible polyurethane foams

In an effort to achieve a high-efficient fire-resistant coating for the flexible polyurethane (PU) foams, a layer-by-layer assembly technique of polyethylenimine (PEI), graphene oxide (GO) and synthetic melanin nanoparticles (SMNPs) was constructed on the surface of PU foams. The preeminent radical scavenging capacity and high-temperature thermal stability of SMNPs enable it to be applied as a flame retardant for the subsequent coating process. Scanning electron microscope (SEM) images indicate that the as-fabricated PEI/GO/SMNPs coatings are uniformly deposited on the PU foam along the cell walls. In contrast with pure and bilayer-coated (BL-coated) PU foams, thermogravimetric analysis (TGA) reveals that the trilayer-coated (TL-coated) foam exhibits a better thermos-oxidative stability and a lower pyrolysis rate with the deposition of PEI/GO/SMNPs nanocoating. In the torch burn test, the flame of PU-1TL foam coated with only one-trilayer PEI/GO/SMNPs is able to self-extinguish and the original shape of the entire foam is intactly preserved. Cone colorimeter tests indicate that the release amount of heat and smoke can be effectively suppressed in the coated foam, and the formation of the highly graphitized char is beneficial to the improvement of the fire-resistant performance. In addition, thermogravimetric analysis/infrared spectrometry (TG-IR) results demonstrate that the volatilization of organic and toxic gases in gas phase are effectively restrained, which can be attributed to the lamellar shield of GO and radical trapping effect of SMNPs. These results illustrate that synthetic melanin material is one of the promising candidates as efficient additive in fire-resistant polymers, and the PEI/GO/SMNPs coatings play a part in gas-solid phase to improve the flame retardancy of PU foams.

Synthesis of a novel phosphorus and nitrogen-containing bio-based polyol and its application in flame retardant polyurethane foam

A novel, castor oil (CO)-based, flame-retardant polyol containing phosphorus and nitrogen was successfully synthesized. The novel polyol was characterized by Fourier transform infrared (FTIR), proton nuclear magnetic resonance (1H NMR), and carbon-13 nuclear magnetic resonance (13C NMR) spectroscopies. Flame-retardant polyurethane foams (FRPUF) were prepared by curing flame retardant polyols (FRPE) and flame retardant dihydric alcohol (BHAPE) with polyisocyanate (PM-200). The flame retardant properties and thermal decomposition of FRPUF were investigated using the limiting oxygen index (LOI), cone calorimeter testing, and thermogravimetric analysis (TGA). The FRPE and BHAPE composites were found to enhance the thermal stability and flame retardancy of polyurethane foams (PUF) without the use of other flame retardants. Insight was gained into the gaseous degradation products of FRPUF using thermogravimetric analysis-infrared spectrometry (TG-IR) and thermogravimetric analysis-mass spectrometry (TG-MS). The character of polyurethane foams was explored using FTIR, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Gas-phase pyrolysis products were investigated by TG-IR and TG-MS. Good flame retardancy was observed in FRPUF, which was attributed to the flame retardant FRPE and BHAPE.

Comprehensive characteristic and potential application of POSS-coated MgO-SiO2 binary oxide system

This study concerns the possibility of functionalization of a binary oxide system with an organic agent in order to change its physicochemical properties and surface activity. The binary oxide material – MgO-SiO2–was obtained via a sol-gel route using organic precursors of magnesium oxide and silica, ammonia as catalyst and methanol as a solvent. The powder material prepared according to the proposed method of synthesis was functionalized with a commercial POSS compound – AminoethylaminopropylIsobutyl POSS®. The efficiency of immobilization of the modifying agent onto MgO-SiO2 material was evaluated by the FTIR, 29Si and 13C CP MAS NMR methods. Moreover, detailed physicochemical and structural characteristics of the resulting materials, including morphology, parameters of the porous structure, hydrophobic/hydrophilic nature and thermal stability, were determined. As a result of this functionalization, a novel group of oxide systems with defined physicochemical properties dedicated to specific applications was created. The functionalized form of the synthesized MgO-SiO2 material was successfully applied as a bond/stabilizer in polyol mixtures and as a flame retardant for polyurethane foams.

Flame retardant polyurethane foam prepared from compatible blends of soybean oil‐based polyol and phosphorus containing polyol

ABSTRACTA phosphorus containing polyether polyol (THPO‐PO) was synthesized by polymerization between tris(hydroxymethyl) phosphine oxide (THPO) and propylene oxide (PO). A soybean oil‐based polyol(SBP) was synthesized from epoxidized soybean oil by ring‐opening reaction with lactic acid. The corresponding polyurethane foams (PUFs) were prepared by mixing SBP with THPO‐PO. The density of these foams decreased as the content of THPO‐PO increased. The yield strength of PUFs was observed to be decreased firstly and then increased with the addition of THPO‐PO. Microphotographs of PUFs were examined by scanning electron microscope which displayed the cells as spherical or polyhedral. The thermal degradation and fire behavior of PUFs were investigated by thermogravimetric analysis, limiting oxygen index (LOI), and UL‐94 test. Although the thermal stability of PUFs were decreased with increasing THPO‐PO percentage, the flame retardancy of PUFs were improved. The LOI value increased to 27.5 with 40% THPO‐PO. THPO‐PO in sequence worked in inhibiting flame and forming phosphorus‐rich char layer, thus endowing PUFs with the increased flame‐retardant performance. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45779.

Environmentally Benign Halloysite Nanotube Multilayer Assembly Significantly Reduces Polyurethane Flammability

AbstractIn an effort to develop a more environmentally benign flame retardant for polyurethane foam (PUF), layers of halloysite clay nanotubes (HNT) stabilized by branched polyethylenimine (BPEI) or poly(acrylic acid) (PAA) are deposited from aqueous suspensions to create multilayered nanocomposite coatings. PUF is very flammable and widely used in upholstered furniture throughout the world. Foam treated with five BPEI‐HNT/PAA‐HNT bilayers, deposited using layer‐by‐layer assembly, is rendered self‐extinguishing in open flame testing. Cone calorimetry reveals that this coating reduces the peak heat release rate (pkHRR) by 62%. Due to the tubular morphology of HNT, small volatile gasses given off during combustion are trapped, so total smoke release (TSR) is reduced by 60%. Infrared spectroscopy suggests this multilayer film survives during combustion, forming an HNT‐rich barrier that prevents mass and energy transfer during open flame testing and calorimetry. The significant reductions in pkHRR and TSR, along with the self‐extinguishing behavior, indicate that these halloysite‐based multilayer films have the potential to greatly improve PUF fire safety. The low cost and natural abundance of HNT makes this technology especially amenable to widespread use.

Melamine Polyphosphate - the Reactive and Additive Flame Retardant for Polyurethane Foams.

Melamine polyphosphate, MPP was applied as reactive and additive flame retardant for thermally resistant polyurethane foams. MPP was hydroxyalkylated with ethylene and propylene carbonates to get oligoetherols with 1,3,5-triazine ring and phosphorus. The structure and physical properties of the products were studied. The polyurethane foams, PUFs obtained from this oligoetherols were self-distinguishing. The addition of powdered MPP into foaming mixture resulted in further decrease of flammability modified PUFs. The MPP-modified PUFs were characterized by physical methods adequate to thermal resistance and flammability of the PUFs. The best MPP-modified PUF showed oxygen index 24.6. All the modified PUFs were remarkably thermally resistant; they could stand long lasting thermal exposure even at 200 °C.