Intumescent Fire Retardant Research Articles

Expandable Graphite as a Fire Retardant for Cellulosic Materials—A Review

A diversity of chemicals is used to produce fire retardants (FRs); some of the main group of chemicals are hazardous to the environment as well as to human life; however, expandable graphite (EG) can be a gateway to a more environmentally friendly FRs or intumescent fire retardants (IFRs). Researchers define intumescent as the swelling of a particular substance placed between a heat source and an underlying substrate when they are heated. EG is a material with extraordinary thermophysical and mechanical properties. The referred EG properties are unparalleled. EG is a low-density carbon material having a series of unique properties: developed specific surface, binder-free pressing capacity, stability to aggressive media, and low thermal conductivity. Therefore, EG is a promising material both for research work and for industrial applications. The primary goal of this literature review was to report current knowledge on the use of EG as a fire retardant for cellulose and cellulose-modified materials. EG is produced, among other methods, by thermal shock of graphite oxide under forming gas. When exposed to heat, EG will expand. The expansion mechanism was presented in this review. Equally important to this review is the knowledge related to cellulose thermal degradation and cellulose impact on the development of science and technology.

Influence of the Developed Flame Retardant System Based on Renewable Raw Materials on Epoxy Resin Fire Behavior

A novel intumescent flame retardant system based on shell (S) and histidine diphosphate (HF) was developed and introduced into the epoxy resin in order to verify its effectiveness in the inhibition of the burning process. To confirm the structure of HF, powder X-ray diffraction (XRD) was used. The influence of the flame retardant system on the burning and smoke emission of the resin was assessed based on cone calorimeter (CC) measurements. Moreover, structural evaluation of polymeric materials was carried out using scanning electron microscopy (SEM). It was found that the incorporation of the developed flame retardant system caused the formation of a protective layer in the form of char, which reduced burning process and smoke emission of the epoxy resin. The obtained results were better than those generated by commercial intumescent fire retardant.

Fireproof performance of the intumescent fire retardant coatings with layered double hydroxides additives

MgAlCO3-layered double hydroxides (LDHs) and CaAlCO3-LDHs were respectively added as a synergistic agent to intumescent fire retardant (IFR) coatings. The 2.4 wt% of MgAlCO3-LDHs and the 6.7 wt% of CaAlCO3-LDHs were found to possess the best thermal insulation according to the fire performance tests. Further characterization by a cone calorimeter shows that the MgAlCO3-LDHs are superior to decreasing the specific extinction area of IFR coating, and the CaAlCO3-LDHs are advantageous in some other properties such as heat release rate, effective heat combustion and total heat release. Moreover, the X-ray diffraction (XRD) results infer that the flame retardant of char layer is primarily dependent on the amorphous structure formed after exposure to fire, the X-ray photoelectron spectroscopy (XPS) measurements of O1s, C1s, P2p and N1s reveal that the LDHs fillers suppress the oxidation of the IFR coating, and the Fourier transform infrared spectroscopy (FTIR) tests demonstrate that the LDHs protect the bridge frame structures. It is concluded that the LDHs can prevent the degradation and improve the thermal insulation of IFR coatings.

Influence of graphene on fire protection of intumescent fire retardant coating for steel structure

Graphene (GR) was used as filler to improve the performance of fire resistance, thermal stability, smoke suppression of waterborne intumescent fire-retardant coating. The influence of graphene (GR) on the properties of the intumescent fire-retardant coating was studied by fire protection test, TGA, SEM and smoke density test. The results showed that the GR can effectively enhanced the performance of fire resistance and thermal stability of the coating. The result of SEM test indicated the coating with GR had excellent intumescent effect and enhanced foam structure. The smoke density test of the coating demonstrated the coating contain GR had excellent performance of smoke suppression.

Improving the flame retardancy of waterborne polyurethanes based on the synergistic effect of P–N flame retardants and a Schiff base

A novel reactive intumescent fire retardant hexa-[4-[(2-hydroxy-ethylimino)-methyl]-phenoxyl]-cyclotriphosphazene (HEPCP), containing both cyclotriphosphazene and Schiff base structures, is successfully prepared. The chemical structures of HEPCP and flame-retardant waterborne polyurethane (WPU) (FR-WPU) were characterized via31P, 1H NMR and FT-IR. Thermogravimetric (TG) analysis showed that HEPCP exhibited excellent thermal stability and produced rich char residue under high temperature compared with the control sample. The Schiff base and cyclotriphosphazene had a synergistic effect on the WPU. Limiting oxygen index (LOI) values of up to 26.7% were recorded; the dripping behavior was simultaneously improved and achieved a V-1 rating in the UL-94 test by incorporating 0.5 wt% phosphorus. In contrast to the pure WPU, the peak heat release rate (pHRR) of the FR-WPU/HEPCP5 decreased by 43.8%. The char residues increased from 0.63% to 6.96%, and scanning electron microscopy (SEM) showed a relatively continuous and membranous substance, with few holes. The results of TGA-FIR, Py-GC/MS and SEM indicated that HEPCP displayed a fire-retardant mechanism in the condensed-phase. In addition, the thermomechanical behaviors and the mechanical properties indicated that both mechanical properties and Tgh increased.

Casein-magnesium composite as an intumescent fire retardant coating for wood

Fire hazard associated to wood and wood-based products is a clear shortcoming of natural building materials and hence the use of fire retardants is mandated by national building codes. In this study, we have synthesized a simple and green fire retardant composite using magnesium hydroxide (Mg(OH)2) with casein protein and tested its performance as self-adhesive coating paste. The thermogravimetric analyses indicated that casein-magnesium composites are able to produce thermally stable insulating magnesium oxide (MgO) that suppresses the fire spread as a result of the synergistic combination of physical and chemical actions—the intumescent action of casein, formation of char and thermally stable MgO, and the simultaneous release of water vapor retained by the casein. The most effective performance was obtained with a sample (coating weight of 1080 g/m2) for which the ignition time of pinewood substrate was increased by 147%, while the smoke production rate and the peak heat release rate were decreased by 53% and 30%, respectively.

Improved pyrolysis behavior of ammonium polyphosphate-melamine-expandable (APP-MEL-EG) intumescent fire retardant coating system using ceria and dolomite as additives for I-beam steel application

This study describes the effects of ceria (CeO2) and dolomite [CaMg(CO3)2] additives on the pyrolysis behavior and fire resistive property of conventional intumescent flame retardant (IFR) coating system for I-beam steel substrate called ammonium polyphosphate-melamine-expandable graphite (APP-MEL-EG) system. The fire resistance of various formulations was evaluated using the standard vertical Bunsen burner fire test. Thermogravimetric analysis (TGA) was used to understand the degradation of coating formulations. Observations by scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX) demonstrated that significant amounts of additives favored the formation of homogeneous compacted char structures, which were predominantly composed of carbon (C), phosphorus (P) and oxygen (O). These three main components of the char were also found to be in various binding combinations with other lighter elements like nitrogen (N) and hydrogen (H) as illustrated by the attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy results. X-ray photoelectron spectroscopy (XPS) further suggest that polyethylene([(CH2–C2H2–CH2)n−]) free radicals were abundant on the char surface for the two best formulations and the binding energy of this radical promoted the formation of aromatic carbon chains that enhanced the char's thermal stability. This means that the selection of appropriate additives and combinations of flame-retardant ingredients could significantly change the morphology of the char layer and improve its thermal stability during fire exposure.

Intumescent fire retardant coating with recycled powder from industrial effluent optimized using response surface methodology

With the rapid development of Al electrolytic capacitors, plenty of industrial effluents are generated during the corrosion process of aluminium anode, resulting in serious environmental problems. To address such a challenging but urgent issue, we recycle powders containing lots of flame-retardant compositions from the precipitate of industrial effluents and apply them in the intumescent fire retardant coating. The formula of coating is optimized using response surface methodology based on central composite design. Under the optimum formula (APP: 60 wt%, PER: 19 wt%, MEL: 18 wt%, and the recycled powder: 9 wt%), the optimal sample is prepared and its fire resistance is investigated in our lab. During the fire resistance test, this sample displays the lowest backside temperature (only 163 °C) among all samples, indicating superior fire retardancy. In addition to fire resistance analysis, the water resistance and thermal stability of intumescent fire retardant coatings are also characterized. Our results show that the water contact angle and char yield of optimal sample reach up to 78.9° and 30.1 %, respectively. Thus, the optimal coating features superior fire retardancy, excellent water resistance and outstanding thermal stability. This work offers a practical strategy for creating a high-performance intumescent fire retardant coating based on the reuse of industrial effluent, which is favorable to environment protection and has a promising future in the industry.

Development of an SEM image analysis method to characterize intumescent fire retardant char layer

A new characterization method is proposed to investigate the microscopic morphology of intumescent fire retardant (IFR) char layer observed under a scanning electron microscope (SEM). The method consists of object segmentation extracting the object, color transformation improving the recognition of subtle details, and statistical analysis obtaining the features (area, average, and standard deviation) of the object in the SEM images. There is a descending trend in the standard deviation of the foams with the increase of CaAlCO3-LDHs (layered double hydroxides) added to the coatings. Specifically, the number of the foams in the IFR coating with 5 wt% of CaAlCO3-LDHs addition is increased from 102 (that of the char layer without CaAlCO3-LDHs) to 123. Meanwhile, the standard deviation of the foams in the char layer is decreased from 6383.6 to 4304.5, demonstrating that an appropriate addition of CaAlCO3-LDHs can improve the foam quality of the IFR coating by making it more compact and uniform, and enhance the thermal insulation of the char layer covered on the substrate surface.

Temperature rise distribution of circular concrete-filled steel tubular cross-sections with intumescent coating

Although concrete-filled steel tubular (CFST) columns exhibit exceptional fire resistance, they might not satisfy the required fire rating of 3 h without additional protection particularly when subjected to high load level. Intumescent fire retardant coating (IFC) provides an efficient way to enhance the fire safety of structural steel members. Temperature rise analysis usually acts as a preceding step when determining the mechanical performance of structures in fire. To understand the effect of IFC and the fire performance of CFST columns, the temperature rise of IFC protected CFST columns was investigated in this study. A series of IFC protected CFST columns were tested in ISO-834 standard fire for 180 min. The test parameters included the diameter of CFST cross-sections and the net dry film thickness (DFT) of IFC. The temperature data was reported and analysed. The results showed that IFC provided efficient fire protection for CFST columns and maintained its integrity throughout the 180 min of fire exposure. For tested specimen (outer diameter = 325 mm) with no coating, 1.16 mm thickness and 3.40 mm thickness of IFC, the temperature of steel surface at 180 min were 1056 °C, 592 °C and 418 °C, respectively. No crack or crumbling was observed in the expanded IFC after the tests. Physical changes and chemical reactions in intumescent coating were deemed to occur from 10 min to 90–140 min depending on thickness of IFC and cross-sectional size. The obtained equivalent thermal conductivity of the IFC attained the minimum values of 1.46 × 10−3 to 4.38 × 10−3 W/(m·oC) at temperature range of 513 to 672 °C.

Modification of intumescent coatings using multilayer carbon nanotubes: physico-technological principles and method of application on the pipeline transport facilities

Introduction. The aim of the study was to physically substantiate the principles of modification of thin-layer intu­mescent coatings by controlling their electrophysical characteristics and to develop a technique to improve the fire retardant efficiency of modern fire retardants with varying parameters of the volume fraction of functionalized multilayer carbon nanotubes (MWCNT). Materials. The materials used in fire retardant intumescent paint “Thermal barrier”, the production of NPK “OgneHimZashchita” modified by MWCNT. Experimental part. The experimental part included a study by the method of synchronous thermal analysis, the measurement of the dielectric constant, determination of adhesion and the study of electrification when ap­plied, a fire retardant metal. Results and discussion . Modification of fire retardants due to the introduction of MWCNT in concentrations of 0.1…1.25 % by vol. allows to improve the performance of nanomaterials by increasing the thermal stability of ­fire retardants at a concentration of nanoparticles up to 0.5 % by vol. In this case, the mass loss of the modified MWCNT sample occurs on average 20–30 % slower in comparison with the unmodified sample. There is an in­crease in the strength of intumescent fire retardant composition (IFRC) to 40 %. When electrophysical action ­occurs ordering MWCNT in the material, and also reduces the electric field generated by applying the modified composition on average by 40–50 %. Conclusion. Modification of MWCNT fire retardants leads to an increase in adhesive strength and increase in thermal resistance of IFRC, provided the stability of nanostructures in the material. The proposed technology of ­application of modified intumescent fire retardants at pipeline transport facilities ­should include elements of preparation of the modifying additive and its stabilization to improve the quality characteristics of the fire retardants with MWCNT.

Optimization of Fire Retardants in a Formulations of Intumescent Fire Retardant Coatings for Steel Structure via a D-optimal Mixture Design Based on Response Surface Methodology

Response surface methodology (RSM) is a very efficient tool to provide a good practical insight into developing new process and optimizing them. This methodology could help engineers to raise a mathematical model to represent the behavior of system as a convincing function of process parameters. Many experiments in research and development in the paint preparation involve mixture components. These are experiments with mixtures in which the experimental factors are the components of a mixture and the response variable depends on the relative proportion of each components, but not on the absolute amount of the mixture. Thus the mixture components cannot be varied independently. Optimizing the formulations for a preparation of intumescent fire-resistant coating requires the fire resistant effectiveness of several fire retardants combinations to be determined. We discuss the design and analysis of these types of experiments, presents a D-optimal design methodology for computer aided experimental design for fire retardant coating formulations involve mixture components, exemplifies the benefits of using design of experiments(DOE) together with statistical software package to facilitate the formulating of recipe for structural steelworks. Goal of this paper is to encourage greater utilization of information technology in paint preparation research and development.

Technology of obtaining intumescent fire retardant mastics

Technology of obtaining intumescent fire retardant mastics

Thermal Stability, Fire and Smoke Behaviour of Epoxy Composites Modified with Plant Waste Fillers.

The influence of plant fillers on the flammability and smoke emission of natural composites was investigated. Epoxy composites with 15, 25, and 35 wt % of walnut and hazelnut shell, as well as sunflower husk, were prepared and examined. The ground organic components were characterized by grain size distribution, thermogravimetric analysis (TGA) and microstructure observations (SEM). The composite materials were subjected to dynamic mechanical analysis (DMA) and structural evaluation with scanning electron microscopy. Cone calorimeter tests and TGA determined the influence of plant waste filler addition on thermal stability and flammability. Moreover, the semi-volatile and volatile compounds that evolved during the thermal decomposition of selected samples were identified using a steady state tube furnace and a gas chromatograph with a mass spectrometer. The intensity of the degradation reduced as a function of increasing filler content, while the yield of residue corresponded to the amount of lignin that is contained in the tested plants. Moreover, the incorporation of agricultural waste materials resulted in the formation of a char layer, which inhibits the burning process. The yield of char depended on the amount and type of the filler. The composites containing ground hazelnut shell formed swollen char that was shaped in multicellular layers, similar to intumescent fire retardants.

Bimetallic metal-organic frameworks and graphene oxide nano-hybrids for enhanced fire retardant epoxy composites: A novel carbonization mechanism

The fire retarded intumescent epoxy resin (EP) composites were fabricated with the incorporation of bimetallic metal-organic framework (MOF) and graphene oxide (GO) nano-hybrids (MOF@GO) with intumescent fire retardants (IFR). EP/0.5MOF@GO-9.5IFR composite exhibited a 41% decrease in peak heat release rate, 30% decrease in total smoke production compared to reference sample EP/10IFR. According to in-situ morphology observation and X-ray tomography result, we observed such a novel carbonization phenomenon forming an alternately loose and accumulated structure. The further carbonaceous char analysis indicated the formation of a reinforced structure with fewer pores and excellent insulated property. Temperature test revealed that the synergistic effect between MOF@GO and IFR promoted the construction of the insulated carbonaceous char, which can maintain its temperature at around 400 °C, thus providing sufficient time to build up the alternative reinforced char. Besides, the mechanical property of EP composite was also improved with a 11% increase in the tensile strength compared with that of EP/10IFR. In perspective, the observed carbonization phenomenon opens a window for understanding the mechanism for intumescent fire retardants.

Efficient flame-retardant and smoke-suppression properties of MgAlCO3-LDHs on the intumescent fire retardant coating for steel structures

MgAlCO3-layered double hydroxides (MgAlCO3-LDHs) were introduced in a waterborne intumescent fire retardant (IFR) with nano-coating containing ammonium polyphosphate (APP), pentaerythritol (PER), and melamine (MEL). The effects of MgAlCO3-LDHs were evaluated based on thermogravimetry (TG), differential thermal analysis (DTA), Fourier transform infrared spectroscopic analyses (FT-IR), X-ray power spectroscopy (XPS), scanning electron microscopy (SEM), fire performance test, and cone calorimetry. The 1.8 wt% of MgAlCO3-LDHs added to the IFR coating promoted the expansion of the char layer to improve its thermal insulation performance during the fire performance test. The results characterized by TG, DTA, XPS, and FT-IR revealed that MgAlCO3-LDHs enhanced the residual weight, the thermal stability and the oxidation resistance of the IFR coating. There was statistical evidence that the heat-shielding performance was reinforced by adding an appropriate amount of MgAlCO3-LDHs to the IFR coating to form uniform and compact foams in the char layer by using the digital image to process SEM images. The cone calorimetry revealed that a 46% reduction in total smoke production (or total smoke release) and a 25% decrease in the smoke production ratio were achieved in the coating with added MgAlCO3-LDHs compared with that without. It can be concluded that the addition of MgAlCO3-LDHs to IFR coating actively interacts with APP, PER, and MEL, thus improving the fire retardant properties of the coating.

Cyclodextrins and Cyclodextrin Derivatives as Green Char Promoters in Flame Retardants Formulations for Polymeric Materials. A Review.

Polymers are intrinsically flammable materials; hence, fire retardance (FR) is required in their most common applications (i.e., electronic and construction, to mention some). Recently, it has been reported that cyclodextrin (CD) and cyclodextrin derivatives are beginning to be introduced into Intumescent Fire Retardant (IFR) formulations in place of pentaerythritol, which is used in IFRs that are currently on the market. Since IFRs are of less environmental concern than their hazardous halogen containing counterparts, the use of natural origin compounds in IFRs provides a way to comply with green chemistry issues. BCD and BCD derivatives presence in IFR mixtures promotes a higher yield of blowing gases and char when polymeric materials undergo combustion. Both processes play important roles in intumescence. The key rule to obtain in insulating compact char is the good dispersion of the nanoparticles in the matrix, which can be achieved by functionalizing nanoparticles with BCD derivatives. Moreover, CD derivatives are attractive because of their nanosized structure and their ability to form inclusion complexes with many compounds used as FR components, reducing their release to the environment during their shelf life of FR items. Often, fire retardance performed by BCD and BCD derivatives accompanies other relevant properties, such as improved mechanical resistance, washability resistance, self healing ability, thermal conductivity, etc. The application of CD fire retardant additives in many polymers, such as poly(lactic acid), poly(propylene), poly(vinyl acetate), poly(methyl methacrylate), linear low density poly(ethylene), polyamides, and polyesters are comprehensively reviewed here.

Synthesis of isosorbide based flame retardants: Application for polybutylene succinate

This article deals with the improvement of flame retardancy of polybutylene succinate (PBS) using isosorbide modified by sulfur, silicon or phosphorus as fire retardants (FRs). The syntheses of these FRs are detailed, and all molecules were analyzed by liquid state nuclear magnetic resonance (NMR). Prior to be incorporated into PBS, the thermal stability of all flame-retardants was analyzed by thermogravimetric analysis (TGA). The results showed that all FRs exhibit thermal stabilities (>170 °C) suitable for the processing of PBS (140 °C). The fire properties of the PBS formulations were investigated and it was shown that i) sulfur modified FRs showed no improvement of PBS flame retardancy, ii) silicon modified FRs showed slight improvement acting as char forming agent when blending with intumescent FR, iii) performances of phosphorus modified FRs depend on the oxidation degree of phosphorus when evaluated by cone calorimetry, and at UL-94 tests these phosphorus modified FRs achieved V-0 rating with dripping without ignition of the cotton.

An emerging mineral-based composite flame retardant coating: Preparation and enhanced fireproof performance

An emerging composite flame retardant has been prepared by sodium modification of natural mineral rectorite (REC), and waterborne intumescent fire retardant coating (IFR-Na-REC) containing sodium-modified rectorite (Na-REC) was successfully fabricated. The flame retardancy, morphology, structure, chemical composition and mechanical property of the intumescent coating were in detail investigated. The results showed that Na-REC could greatly promote the heat insulation effect of waterborne intumescent coatings. The temperature of the backside of steel plate for the IFR-Na-REC coating with 10% Na-REC was recorded to be 202 °C after 60 min of fire test, 24 °C lower than that of the control coating, and the flame retardant time reached up to 119 min. The enhanced fireproof performance could be attributed to the increased adhesion of the coating to the substrate and the formation of ceramic-like protective layer between rectorite and components in intumescent coating, which acted as a fire barrier to protect the internal matrix. Our work could offer a more benign approach to the general production of composite flame retardant coatings for fire protection.

Synergistic effect of basalt fiber on the thermal properties of intumescent fire retardant coating

Abstract This research work presents the enhancement of thermal performance of intumescent fire-retardant coatings (IFRCs) to investigate the synergistic effects of novel type of fiber reinforcement (basalt fibers) towards heat shielding capability for steel structures. The coating basis consists of bisphenol-A epoxy resin (NPEL-128) cross-linked with polyamide amine (ACR Hardener (H-2310)), mixed with expandable graphite (EG), ammonium polyphosphate (APP), melamine and boric acid. Various formulations with different fiber loading were synthesized and characterized. Bunsen burner test in accordance to UL-1709 was performed to examine their fire retardant properties. Moreover, furnace test was carried out to investigate the char expansion. The results showed that 2 wt% basalt fibers (IFRC-B2) greatly enhanced the heat insulation performance, the steel plate backside temperature reaching 187°C after 1-h fire test compared to 375°C for the control formulation (CF) without fiber reinforcement. Char expansion measurements carried out after furnace test show that in the presence of basalt fibers the expansion of IFRC-B2 was twice that of CF. Char was also analyzed by Field Emission Scanning Electron Microscopy (FESEM). Micrographs revealed deep cracks on CF char surface, allowing the heat to diffuse more rapidly and explained the poor fire performances. The char of IFRC-B2 was smooth and dense, while distribution of basalt fibers and char cells were homogenous, with presence of small voids of about similar size, which limited heat transfers. Thermogravimetric analyses (TGA) in pyrolysis conditions showed that residual weight increases by 10 wt%, confirming the increase in thermal stability of the basalt containing formulation.