Intumescent Materials Research Articles

Polyurethane foams based local montmorillonite (magnite) as intumescent materials

Polyurethane foams based local montmorillonite (magnite) as intumescent materials

Preparation and characterization of bis-phosphonated polycarbohydrates.

A simple, cost-effective, one-pot method was proposed to introduce bis-phosphonic groups onto alginic acid and carboxymethyl cellulose (CMC). New derivatives were characterized by means of nuclear magnetic resonance, X-ray photoelectron, and attenuated total reflectance Fourier transform infrared spectroscopy. These analyses confirmed the successful transformation of carboxylic groups present in alginic acid and CMC into bis-phosphonic groups. Additionally, thermogravimetric analysis coupled with differential scanning calorimetry was employed to investigate the thermal properties of the bis-phosphonic derivatives of alginate and CMC. The results clearly demonstrate the char-forming ability of both studied bis-phosphonated polycarbohydrates, suggesting their potential as intumescent materials.

Flame‐Retardant Properties and Characterization of Nylon/Tannic Acid Electrospun Fibers

Incorporating flame‐retardant compounds into polymeric composites is a key area of materials research. Halogenated flame‐retardants are most widely used; however, they are under scrutiny due to health and environmental concerns which increases interest in eco‐friendly alternatives. Tannic acid (TA) is a naturally occurring polyphenol with flame‐retardant properties. To overcome current challenges incorporating TA into polymer composites at high concentrations, nonwoven mats of nylon/TA composite nanofibers are fabricated using electrospinning. TA is incorporated at concentrations up to 50 wt% while maintaining uniform fiber morphology. Thermogravimetric analysis (TGA) shows TA within the nanofibers degrades at 230 °C and nylon degrades at 400 °C, irrespective of the initial TA concentration. Char yield increases with the concentration of TA, resulting in a maximum of 25% for fibers containing 50 wt% TA. Flame resistance is characterized using microscale combustion calorimetry (MCC) which shows composite fibers have reduced heat capacity and total heat release (THR) indicating flame resistance at ≥75 rel. wt%. Finally, ignition tests and condensed phase analysis show that TA acts as an intumescent material when embedded within the polymer matrix which produces an insulating foam‐like char under direct heat that eliminates flaming melt dripping and results in self‐extinguishing nanofibers.

Modelling of the swelling behaviour of a fire retarded material under a cone calorimeter

Modelling the swelling behaviour of intumescent materials is an important and challenging issue because this phenomenon influences their pyrolysis process. It must be therefore considered to improve the predictability of pyrolysis models. The objective of this work was to implement a swelling model in the pyrolysis code Gpyro in order to predict the behaviour of a sample of ethylene vinyl acetate containing aluminium trihydroxide (EVA/ATH) polymer studied by cone calorimetry. This polymer is used for making the external sheath of electrical cables. Unlike existing works in the literature, the model implemented here, and adapted to EVA/ATH, does not require information on the densities of the initial and final materials, which makes it more predictive. To characterize the swelling, experiments were carried out to measure the evolution of the sample thickness as a function of time. The mass loss and the back surface temperature of the sample were also measured. This was done under different operating conditions. These measurements are compared with the swelling predicted by the model and the results were found to be in good agreement. The model can be extended easily to other materials.

Impact of Accelerated Weathering on Fire Resistance Performance of Intumescent Materials

The fire resistance performance of intumescent fireproofing materials for steel structure changes with time, as a result of exposure to environmental conditions especially temperature. The objective of this study is to investigate the impact of environmental conditions on fire protection properties (fire performance and char formation) of intumescent coating materials by using accelerated weathering technique. In this study a group of eight steel plates were coated with intumescent fireproofing of the same dry film thickness (DFT), the prepared samples were devided into two supgroups in which every supgroup of four specimens was exposed to ultraviolet radiation (UV) of wavelength (340 nm) for 0, 3, 6 and 9 years. The all intumescent coated samples were exposed to fire resistance tests in accordance with International test standard to evaluate their fire resistance performance. The formed char layers were characterized by using scanning electron microscopy (SEM). The results revealed insignificant change in the fire resistance for the 3 years aged samples. Increasing the accelerating aging over 3 years led to remarkable degradation of fire resistance. The SEM analysis revealed various foaming efficiencies as function of the exposure time.

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.

Compressible battery foams to prevent cascading thermal runaway in Li-ion pouch batteries

Lithium-ion battery packs require thermal management to achieve optimum life and safety. This is becoming crucial for battery packs composed of high-energy-density cells. Pouch cells themselves achieve highest packaging efficiency but require additional structural support and thermal management when grouped into modules, especially under abusive conditions such as thermal runaway. Novel foam battery pads have demonstrated to cushion volume changes of pouch cells and are reengineered in this study to mitigate cell-to-cell thermal runaway propagation. The compressible pads are made of polyurethane foams incorporating flame-retardant additives or coatings, including intumescent and fire wall materials. Their performances were evaluated by conducting nail penetration tests on modules composed of pouch cells at 100% state of charge (SOC), with the foams placed in between the cells. Experimental results show cascading thermal runaway was considerably delayed by polyurethane foams incorporating flame-retardant additives or coatings. Complete prevention of cascading failure was achieved with dense polyurethane foams with multilayered coatings of both fire wall and intumescent materials.

Intumescent Silicate Coatings with the Addition of Alkali-Activated Materials.

Fireproof inorganic coatings based on sodium silicate solution with intumescent additions were prepared and tested to assess their ability to limit the negative effect of a fire. The intumescent materials were obtained by the alkali activation of waste glass powder (obtained by the grinding of recycled soda-lime culet) and slag (waste resulting from the metallurgical industry). The replacement of talc (used as filler in paint formulation) with the intumescent materials obtained by the alkaline activation of waste glass powder (WGP), determined an increase in the intumescence coefficient (up to 65%) and decreased the activation temperature of this process. To evaluate these coatings’ abilities to prevent or delay the temperature increase in metal structures, the paints were applied on steel plates and tested in direct contact with the flame of a butane burner for 60 min. The coatings prevented the increase in the steel substrate temperature over one considered critical (500°C) for steel mechanical properties; the combination of two coatings, with different intumescence activation temperatures, correlated with the increase in the coating’s thickness, sensibly reduced the rate of temperature increase (up to 75%) in the steel substrate.

Synthesis of intumescent materials by alkali activation of glass waste using intercalated graphite additions

Abstract Intumescent materials are defined as the ability to swell when they are subjected to fire or thermal treatment. This paper presents the preparation of geopolymer pastes from glass waste powder without/with intercalated graphite (IG) powder (0.1, 0.2 and 0.3) wt.% additions by 5 M NaOH solution alkali activation. The Intercalated Graphite (IG) was prepared by mixing graphite powder (G) with Nitric Acid and Potassium permanganate in weight ratio (1:2:1) for 3 min. A thermal treatment was subjected to the hardened pastes between 400 °C and 800 °C, for 60 min to achieve a favorable porous microstructure. The result values of compressive strength were between 10 and 25 MPa. During the thermal treatment, a mass loss for all prepared paste specimens, ranging from 5.69 − 10.2% for the TG-N5 sample and between 8.27 and 9.4%, 7.06–11.02%, 8.12–9.97% for the (TGIG1-N5, TGIG2-N5 and TGIG3-N5) samples respectively the intercalated graphite additions recorded a decrease in the initial temperature of swelling at 500 °C (i.e. determined the swelling at temperature below 100 °C) as compared with the composition without addition, lightweight and volume increase of the specimens as well as the porosity (closed pores with various shapes and sizes) due to the intumescence process. Consequently, this type of materials could be used for fire protection in buildings, providing thermal and acoustic insulations or sealing the penetrations in walls preventing fire extension to adjacent rooms.

Влияние средств огнезащиты на интенсивность прогрева и особенности обугливания деревянных конструкций

Introduction. Over the past decades, the sphere of wooden house construction has been undergoing revolutionary changes in relation to the development of large-scale construction using wood-based structures. In this regard, one of the first places is the direction associated with ensuring the fire-safe use of such structures in the construction of buildings and structures of various functional purposes. An important sector of this direction is various types and methods of fire protection for wood, materials and structures based on it. The lack of systematic research on these issues hinders the development of effective technical solutions for fire protection of wooden structures. Goals and objectives. Identification of priority areas for research in the field of fire protection of wood, materials and structures based on it. Development of effective flame retardants that can have an impact on reducing fire danger and increasing the fire resistance of wooden structures. Determination of the influence of various flame retardants on the intensity of the process of heating and charring of elements of wooden structures in conditions of fire exposure (fire). Methods. A standard muffle furnace of the SNOL type was used as a test installation with the possibility of one-sided radiation thermal effect on the sample surface and a uniform temperature increase in the furnace up to 1200 С. The muffle furnace was upgraded taking into account the horizontal fixing of the sample on the outer panel of the furnace. To measure the temperature by the thickness of the sample, a set of thermoelectric converters of type K (chromel-kopel) with a junction diameter of 0,8 mm was used. Results and their discussion. Based on the results of theoretical and experimental studies, the main directions of research on the possibility of using various methods and types of fire protection to achieve the required fire hazard characteristics and fire resistance of wooden structures were determined. During the study, the analysis of such characteristics of charring as the rate of charring, the thickness of the charred layer was carried out. Conclusion. The research results show the possibility of certain classes of flame retardants, intumescent and heat-protective materials not only to influence the intensity of the process of charring wood, but also to affect the properties and structure of the charred layer, as well as the intensity of heating of the inner layers of wooden structures. Key words: fire resistance, fire resistance limit, fire hazard, charring, heating intensity, flame retardant efficiency, wood, wooden structures, flame retardant coatings, flame retardants.

Experimental characterization and modeling of boundary conditions and flame spread dynamics observed in the UL-94V test

Abstract To characterize the UL-94 vertical burning test (UL-94 V), temperature, oxygen content, and heat flux of the burner flame were measured using an R-type thermocouple, oxygen analyzer, and water-cooled Schmidt–Boelter gage, respectively. To account for sample geometry, mock samples from Kaowool PM insulation board were used during the burner measurements. Temperature and heat flux measurements were used to express the heat flux of the burner as a linear, piecewise function of burner flame temperature and a constant convective heat transfer coefficient. UL-94 V tests were conducted using 0.27 cm thick poly(methyl methacrylate) (PMMA) samples with and without insulated sides to investigate edge effects. All UL-94 V tests were recorded on video using a 900-nm narrow-band filter to focus on emissions from soot for tracking flame length over time. In some of these tests, a heat flux gage was embedded into the sample to measure PMMA flame heat flux to verify a previously developed laminar wall flame heat feedback submodel. PMMA flame heat fluxes of insulated samples confirmed the wall flame submodel, while non-insulated samples had significantly greater heat fluxes; the flame submodel was scaled accordingly. The burner and wall flame heat flux submodels were combined with an independently developed pyrolysis model of PMMA to conduct two-dimensional, time-resolved simulations of the UL-94 V test. Burner flame oxygen content was measured to be about 5 vol% and was found to enhance PMMA decomposition. Inclusion of the oxygen effect was essential to predict ignition. The simulation predicted flame length and spread on insulated UL-94 V samples reasonably well, validating the submodels. However, the simulation underpredicted flame length on the non-insulated samples; discrepancies were attributed to burning and spread on the edges which were not modeled explicitly. The developed model can be applied to non-charring polymeric solids with no to moderate amount of dripping. Its applicability for charring and intumescent materials will be explored in the future.

Development of an ABS Nanocomposite Material and Its Application to a Fire-Resistant Glazing System - Part I: Development of an ABS Nanocomposite Material

This study is focused on the development of a curtain-wall-type fire-resistant glazing system to contribute to both energy efficiency and fire safety of a building. The weakness of the aluminum frame on thermal insulation was supplemented by an ABS nanocomposite material with a superior thermal insulation performance. It contained (i) a maleic-anhydride-grafted ABS to improve the dispersion of clay, (ii) nanoscale clay, and (iii) intumescent material to retard the combustion on the exposed surface of the polymer. A series of X-ray diffraction, transmission electron microscopy, differential scanning calorimetry, LFA, and cone calorimetry tests were carried out to analyze the degree of improvement in flame retardancy and optimize the compound ratio. In Part II (the authors’ companion paper), the ABS nanocomposite material based on the optimized compound ratio was scaled up for application to a fire-resistant glazing system in industries. Bench- and full-scale tests were performed to confirm the system’s performances in terms of both thermal resistance and insulation.

Fire performance of sandwich composites with intumescent mat protection: Evolving thermal insulation, post-fire performance and rail industry testing

In this study, a novel approach to improving the fire performance of sandwich composites without effect on intrinsic composite structure was explored. The intumescent mat M10 and M20 with expansion ratio 10:1 and 20:1, respectively, were used to protect sandwich composite with evaluation for thermal insulation, heat release rate, smoke density, smoke toxicity, and post-fire performance. Due to char layer formed with expanded graphite when intumescent mat exposed to fire, significant reduction in the maximum average rate of heat emission (MARHE), specific optical density and Valeur Obscurcissement Fumée values in the initial 4 min (VOF4) were observed for sandwich composite with intumescent mat protection, which also improved mechanical properties retention following exposure to flame. According to the EN 45545 standard, all composites passed HL3 hazard level of smoke toxicity. However, due to higher expansion ratio, sandwich composites with M20 mat passed HL3 hazard level of MARHE and HL2 for specific optical density. As such, the M20 mat with excellent flame retardant performance and mechanical properties retention could be potentially used for rail industry applications.

Ramie fabric Elium® composites with flame retardant coating: Flammability, smoke, viscoelastic and mechanical properties

This investigation studied the utilization of intumescent thermal resistive mats to provide surface protection to the core natural fibre-reinforced Elium® composite structural integrity. The intumescent mats contained flame retardant (FR) i.e. expandable graphite (EG) with four different expansion ratios and alumina trihydrate (ATH). All natural fibre thermoplastic composites were fabricated using a resin infusion technique. The impact of char thickness and chemical compositions on the flammability and smoke properties was investigated. It was found that surface protection significantly reduced the peak heat release rate, total smoke release, smoke extinction area and CO2 yield, and substantially enhanced UL-94 rating, time to ignition and residual char network, depending on the EG exfoliation ratio, ATH and mineral wool fibre. The glass transition temperature increased for the FR composites containing EG with lower expansion ratio. Inclusion of intumescent mats increased the strength of the composites while it had a negative effect on the modulus.

Study of intumescent coatings in operation using x-ray phase and thermal analysis and IR spectroscopy

The problem of increasing the fire resistance of buildings and structures is still relevant. Nowadays, fireproof intumescent and other materials with a limited service life are used to ensure fire safety of infrastructure and social facilities. Among these, fire-proofing of metal structures is one of the vital problems. The results of studying samples of fire-retardant intumescent coatings based on ammonium polyphosphate-melamine-pentaerythritol and subjected to artificial climatic aging (3, 6, and 9 years) and thermal exposure (heating to 300 and 500°C) are presented. The methods of X-ray diffraction and thermal analyzes, optical and IR spectroscopy are used to study the phase and structural composition of materials. It was found that the intumescence of the samples significantly decreases during service life of the coating. This leads to a decrease in the fire resistance of the protected object. Moreover, a sharp change in the phase composition of materials occurs as a result of aging and heating, accompanied by a decrease in the degree of crystallinity. Since the composition of fire-retardant coatings plays a key role in ensuring the fire safety of buildings and structures, the results of the study can be used for timely detection of violations in the quality of coatings and forecasting their service life.

Passive Mitigation of Thermal Runaway Propagation in Dense 18650 Lithium Ion Cell Assemblies

The dynamics, heating rates, gaseous emissions and energetics of thermally-induced thermal runaway propagation in dense arrays consisting of 12–15 fully charged 18650 lithium ion cells have been quantified to determine the effectiveness of several passive mitigation strategies. These strategies include implementing 5 mm gaps between select rows and columns in the array, and inserting physical barriers, such as double-layer stainless steel, intumescent material or ceramic fiber board into the gaps. All experiments were performed in a wind tunnel facility that allows tracking of thermal runaway propagation through the arrays with well-defined experimental conditions. None of the tested mitigation strategies completely prevented propagation. However, the physical barriers were found to be effective in slowing the propagation speed. Among the barriers, ceramic fiber board was found to be the most effective slowing down the propagation by more than a factor of 30. Additionally, contributions of different heat transfer processes driving the propagation were quantified. In air experiments on the arrays without gaps or barriers, 50% of heat flow to downstream (non-failed) cells was associated with flaming combustion of ejected battery materials, 20% was associated with direct cell-to-cell conduction and the rest was associated with convective and radiative heat transfer between cells.

Comparative analysis of pyrolysis and combustion of bisphenol A polycarbonate and poly(ether ether ketone) using two-dimensional modeling: A relation between thermal transport and the physical structure of the intumescent char

A quantitative understanding of the thermal transport within a growing intumescent char layer remains largely unsolved. The development of improved techniques to analyze charring and intumescent materials is necessary to investigate the physics of heat transfer within the char. To aid in this endeavor, a systematic methodology to parameterize comprehensive pyrolysis models for charring and intumescent materials is presented. Thermogravimetric analysis, differential scanning calorimetry and microscale combustion calorimetry were conducted on 4–7 mg samples to analyze the kinetics and thermodynamics of thermal decomposition and determine heats of complete combustion of gaseous pyrolyzates. A multi-step reaction mechanism, consisting of sequential first-order reactions, was constructed to capture the physical transformations and chemical reactions observed in the milligram-scale experiments. 0.07 m diameter disk-shaped samples were gasified in the Controlled Atmosphere Pyrolysis Apparatus II to characterize the thermal transport within the condensed phase material and evolving char layer. ThermaKin2Ds was employed to interpret the experimental data using inverse analysis techniques. Bisphenol A polycarbonate and poly(ether ether ketone), widely used intumescent materials, were analyzed within this study. The resulting two-dimensional models of bisphenol A polycarbonate and poly(ether ether ketone) were capable of predicting the experimental gasification mass loss rates with a mean error of 17.8% and 16.9%, respectively. An analysis of the char pore structure was also conducted from which quantitative relationships were subsequently developed between relevant thermal transport quantities and physical descriptors of the char's physical structure. Two prominent linear correlations were discovered: the char's effective thermal conductivity increased as a function of increasing volume-weighted mean pore diameter and the product of density and thermal conductivity increased with an increasing char porosity based on image analysis. Finally, a brief sensitivity analysis of the polycarbonate and poly(ether ether ketone) burning rates was conducted to determine which key material properties were responsible for the observed differences in flammability.

Intumescent polypropylene: Interactions between physical and chemical expansion

SummaryTo decrease the reaction to fire of a highly flammable plastic, polypropylene (PP), the concept of intumescence was applied. Two intumescent systems were designed on the basis of different mechanisms: physical expansion with expandable graphite (EG) and chemical expansion with modified ammonium polyphosphate (AP). Fire behavior of PP containing EG, AP, or an AP/EG mixture with a total loading of 10 wt% was evaluated by cone calorimetry at 35 kW·m−2. Thermocouples allowed measuring the temperature at the backside or inside samples over time and evaluating the thermal barrier of these intumescent materials. Two grades of AP (difference in composition) and several grades of EG (difference in expansion characteristics) were compared. Mixing AP and EG does not create a synergistic effect in studied conditions. Contrarily, the incorporation of small amount of EG in PP‐AP modifies heat transfer in the coating, creating a strong anisotropy. Graphite worms are trapped vertically into the expanded AP, which increases the transverse heat conductivity (lower efficiency of the thermal barrier) and decreases the fire performance. This phenomenon disappears in thicker specimens. While a higher expansion volume of graphite worms improves fire performances of PP with only small amount of EG (1 wt%), this effect is not noticeable with AP/EG mixtures.

The effect of intumescent mat on post-fire performance of carbon fibre reinforced composites

This study investigated the effect of intumescent mats (M1 and M2) with different compositions on the post-fire performance of carbon fibre reinforced composites. The sandwich structure was designed for composites where M1 (carbon fibre reinforced composite-M1) or M2 (carbon fibre reinforced composite-M2) mats were covered on the composite surface. A significant reduction in the peak heat release rate and total heat release was observed from the cone calorimetric data, and carbon fibre reinforced composite-M1 showed the lowest value of 148 kW/m2 and 29 MJ/m2 for peak heat release rate and total heat release, respectively. In addition, a minor influence on mechanical properties was observed due to the variation of composite thickness and resin volume in the composite. The post-fire properties of composite were characterised, and the M1 mat presented better retention of flexural strength and modulus. The feasibility of two-layer model was confirmed to predict the post-fire performance of composites and reduce the reliance on the large amounts of empirical data.

Characterization of pyrolysis and combustion of rigid poly(vinyl chloride) using two-dimensional modeling

A quantitative understanding of an intumescent material’s reaction to fire is largely an unsolved challenge in the field of fire science. To advance fire modeling, a systematic methodology to fully parameterize a comprehensive pyrolysis model for charring and intumescent materials is presented. Thermogravimetric analysis, differential scanning calorimetry and microscale combustion calorimetry were employed to characterize the kinetics and thermodynamics of thermal decomposition and heats of complete combustion of gaseous pyrolyzates. A multi-step reaction mechanism, consisting of sequential steps, was constructed to capture the physical transformations and chemical reactions observed in all milligram-scale experiments. Controlled Atmosphere Pyrolysis Apparatus II gasification experiments were conducted on 0.07 m diameter disk-shaped samples to parameterize the thermal transport within the undecomposed material and developing char layer. A recently expanded fully verified and validated numerical framework, ThermaKin2Ds, was employed to inversely model the gasification experimental results. The model accounted for spatially non-uniform swelling of the sample and associated changes in the radiant heat exposure. Rigid poly(vinyl chloride), a widely used intumescent material, was analyzed in this work. The resulting two-dimensional model was shown to reproduce the gasification experimental unexposed surface temperatures and mass loss rates with a mean error of 3.9% and 12.6%, respectively. A preliminary analysis of the char pore structure was also conducted to determine the pore size distribution and char porosity. The resulting porosity based on the density of graphite and the porosity based on image analysis (including only the pores that are greater than 1 × 10−4 m in diameter) was found to be 0.96 and 0.53, respectively.