Intumescent Materials Research Articles

Numerical Study of the Decomposition Mechanism of Intumescent Coating

Intumescent coating represents an efficient way to increase the fire resistance of construction materials. During its degradation, intumescent materials expand and form a char layer that acts as an efficient thermal shield between the heat source and the materials.Encouraging predictions of thermal degradation and expansion of intumescent coatings in experimental conditions representative of fires were reported in the last decade by considering models involving conservation equations for mass and energy for the intumescent material coupled to approximate sub-models for describing the swelling mechanism. These degradation models used generally simplified decomposition mechanisms involving one, two or three reactions. In addition, the dehydration process that occurs in the early stage is usually ignored.The objective of this article is to assess the relevance of several multi-step reaction mechanisms to describe the mass loss and the mass loss rate of ICWB, an intumescent coating, in TGA at different heating rates in inert atmosphere. The kinetic parameters of the different reactions were optimized using the Shuffled complex evolution (SCE) technique.Results demonstrate that the drying process, which occurs up to 130°C for ICWB, cannot be neglected since the associated mass loss represents about 5%. In addition, the drying process can be described by a single reaction. The use of a simple mechanism, based on one or two reactions to model the degradation of dry intumescent coating, is insufficient and leads to significant discrepancies on both mass loss and mass loss rate. Considering three reactions improve considerably the predictions but discrepancies are still observed for temperature higher than about 420°C. Model results show that a four-step is required to capture accurately all the details of the degradation of dry intumescent coating under inert atmosphere. Simulations were run under air, showing that an additional reaction for oxidation is required to extend the four-step reaction mechanism for oxidative atmosphere, leading to a five-step reaction mechanism.

Comparative study of the thermal decomposition behaviour of different amino acids and peptides

Thirteen nitrogen-containing compounds, including 2 peptides and 11 amino acids, were analysed for their thermal decomposition behaviour using TGA/DSC coupled with MS and FTIR.Various decomposition courses have been found. Glycine, cysteine, cystine, proline, D- and L-threonine decomposed in two stages, whereas arginine, asparagine, glutamine, histidine and tryptophan decomposed in three stages. The peptides of glycine both decomposed in four decomposition steps, except for the glycylglycine under oxidative conditions, which decomposed in three stages. Proline proved to be exceptional, as it needed only one decomposition step under nitrogen to decompose (99.5% mass loss).The decomposition products of amino acids and peptides described in literature could be confirmed in this work. These were mainly carbon dioxide, water, ammonia, hydrocyanic acid and nitrogen oxides. In traces, also isocyanates and nitriles could be detected, but no clear identification of these substances could be made due to superposition of the signals. For example, in the absorption spectrum at 3000 cm−1, a superposition of the hydrocarbons and amines occurred and in the two sulphur-containing amino acids cysteine and cystine at 2100 cm−1, a superposition of the resulting sulfur compounds could be observed.It has also been shown that with increasing chain length of the peptides, in this case of glycine, the molecule becomes thermally more stable. Concerning cystine, something similar was observed for cystine, this is due to the strong sulphur bonding of the monomers. In addition, glycine and its peptides have been shown to have doubled or tripled the volume of the resulting carbon foam formed as length increased, a feature interesting for future research involving intumescent materials.

Fire resistance of circular concrete-filled steel tubular (CFST) column protected by intumescent coating

For structural components with specific requirement of fire resistance rating for safety reasons, additional fire protection is usually necessary. Intumescent fire coating (IFC) is one of the well-used materials to protect steel structures, and it has advantages such as light weight, simple construction, aesthetic appearance, easy maintenance, etc. In this study, a group of eccentrically loaded concrete-filled steel tubular (CFST) columns with and without IFC protection was tested in standard fire circumstance up to 180 min. Three types of intumescent materials were adopted and different dry film thicknesses of the fire coating were designed. Temperature field of each CFST column and the load bearing behaviour were measured and analysed. Finite element modelling of the columns was also established for heat transfer analysis and fire resisting capacity analysis. The modelling was validated by the test data. This study expands the related experimental database with large scale column specimens. The investigation results provide further evidence that CFST column protected by intumescent fire coating could achieve excellent fire resistance. A technical process to determine intumescent fire coating for CFST columns coupling with experimental verification and FE modelling analysis is presented.

Behaviour of tunnel lining material in road tunnel fire

The worldwide road tunnel linings are protected against possible fire scenarios to safeguard the structure and assist in occupant evacuation. There are various choices of active and passive protection available, passive protections includes calcium silicate boards, polypropylene fibers, vermiculite cement based sprays, and other intumescent materials. Tunnel fire is a complex phenomenon and researchers in the past has highlighted that there are various factors which affect the tunnel fires. The effect of passive protection techniques on tunnel fire is not well understood, especially for the insulation boards. It’s been understood from past research that for a heavy good vehicular (HGV) fire in the tunnel, the heat feedback effect is significant. Insulation boards may also affect the tunnel fires by altering the heat feedback effect in vehicular tunnels and hence this can affect the overall heat release rates and temperature profile inside a tunnel. This study focuses on studying the role of insulation boards in tunnel fires and evaluating its effect on overall heat release rate and tunnel temperatures.

Fire retardant device for pipeline and cable duct

The present article reviews different patented devices of heat-fire protection system of pipeline and cable duct of bulkhead having used fibrous and retardant intumescent materials. Their structures and fillers are considered, benefits and drawbacks are defined. The improved design for duct of bulkhead is offered. It is characterized by advanced equipment reliability, technological and fire retardance effectiveness. It is specially noted that breakthrough fire-fighting technology is introduced in the new device. It implies the usage of fire retardant material, providing with thixotropic properties or high viscosity. In proof of the device efficiency the article reviews the experiment conducted on the model of a fire-retardant device.

Glow-wire evaluation of polymeric materials for the electric sector: Effect of the interlayer spacing of montmorillonite

In this study the glow-wire technique was used in the evaluation of synergistic effects between organophilic montmorillonites with different basal spacings and an intumescent formulation containing ammonium polyphosphate (APP) and pentaerythritol (PER) in a poly (ethylene-co-butyl acrylate), EBA 30, polymeric matrix. The flammability of the samples was also evaluated through limiting oxygen index (LOI) analyses, UL-94 standard rating and heating microscopy. The morphology of the samples was studied by transmission electron microscopy (TEM) and X-ray diffraction (XRD). These analyses revealed that processing in a twin screw extruder led to the formation of intercalated and exfoliated nanocomposites. The influence of processing via internal mixer and twin-screw extruder was also evaluated. Glow-wire tests revealed that the addition of montmorillonites with smaller basal spacings led to a synergistic effect with the intumescent formulation, an effect which was not observed when using montmorillonites with basal spacings larger than 30Å. The intumescent materials containing montmorillonites with smaller basal spacings showed GWFI (glow-wire flammability index) as high as 960°C, which indicates that they could be used in the electrical area.

Controlled atmosphere pyrolysis apparatus II (CAPA II): A new tool for analysis of pyrolysis of charring and intumescent polymers

A new gasification apparatus has been developed to enable a comprehensive analysis of pyrolysis of charring and intumescent materials. This apparatus provides well defined boundary conditions and highly resolved measurements of mass, temperature and sample profile evolution of a disk-shaped 0.07m diameter material sample exposed to radiant heat. All measurements are collected simultaneously, in a single experiment, and recorded as a function of time. The oxygen concentration in the pyrolysis zone is controlled and can be reduced below 1vol% to ensure that the measurements are free of oxidation effects. The radiation from an external conical heater has been carefully characterized to account for changes in the sample surface position, including the surface's angular orientation. Using an empirical expression, the radiation heat flux can be predicted with less than 2% error based on the known surface position and heat flux set point. The NIST Fire Dynamics Simulator (FDS) has been utilized in the direct numerical simulation mode to investigate convective losses from the sample surfaces. The convective heat transfer coefficient computed for the top (radiation exposed) surface has been found to be dependent on the surface position; its space-averaged value has been validated against experimental measurements. The capabilities of the apparatus are demonstrated using poly(vinyl chloride). It is shown that the apparatus provides repeatable data necessary for modeling of transport processes inside pyrolyzing intumescent solids. Non-one-dimensional nature of these processes is discussed.

Measurement of kinetics and thermodynamics of the thermal degradation for flame retarded materials: Application to EVA/ATH/NC

The modelling of the behavior of a material exposed to fire is very complex and needs the coupling of fluid dynamics, combustion, heat and mass transfer, kinetics and so forth. A growing amount of studies and numerical models are reported in this field since the last decade. The aim of these models is to predict the fire behavior of wood, charring or non-charring polymers and even intumescent materials. However, these studies are seldom applied to formulated materials and especially flame retarded materials. In this study, an ethylene-vinyl acetate copolymer was formulated with a flame retardant (aluminum tri-hydroxide) and a synergist (nanoclays). A systematic approach for the characterization of the thermo-physical properties of the material as well as of its optical properties and the heat capacity of the decomposition gases is proposed and applied in this study. It is shown that it is possible to evaluate the input data required for pyrolysis modelling, even for multi decomposition steps materials. It is also shown that the diffusion of the gases inside the material had to be considered on the opposite of the classical assumption found in other studies. Indeed, using low mass diffusivity was the sole way to predict in the same time the temperature distribution and the mass loss rate of the material in a gasification experiments.

Fire-stop Wraps and Collars with Intumescent Materials – Performance Comparison

In the event of a fire in building, the places where installations penetrate may be the ones where the fire easily enters adjacent rooms. Therefore, in locations where pipes divide requiring a certain fire resistance class, their passage must be sealed in a way that provides at least the same fire resistance as barrier. The paper describes the main issues related with the fire safety of pipe penetrations sealed with use of fire-stop wraps and collars with intumescent materials. It includes fire resistance tests methodology and general principles of fire resistance classification of the elements. Moreover, the performance comparison of plastic pipes sealed with use of wraps and collars, based on the temperature rises on the unexposed surface of the elements tested in the reinforced concrete floor has been presented.

Intumescent materials for heat-shielding of constructions operating under extreme conditions

Intumescent materials for heat-shielding of constructions operating under extreme conditions

Parameter estimation approach to the thermal characterization of intumescent fire retardant paints

Intumescent paints are widely used as passive fire retardant materials in the building sector. They swell on heating to form a highly insulating char, protecting steel members. Intumescent coatings for use in buildings are typically certified according to the standard cellulosic fire resistance test. This test is expensive, often non-representative of realistic fire conditions, and not enough versatile to gather detailed performance information on the response of reactive coatings. A promising approach, that could offer a helpful tool to the engineering community involved in fire safety, is found in the modelling of the behaviour of the intumescent coating. Under this approach, the knowledge of the equivalent thermal conductivity of the intumescent material is a fundamental issue, since it represents the main parameter that allows predicting the thermal protecting capability of the layer. The purpose of this paper is to optimize an estimation procedure intended to the restoration of the equivalent thermal conductivity of intumescent layers. The thermal stress is activated by the action of a cone calorimetric apparatus, while the estimation procedure is based on the inverse heat conduction problem approach under steady state assumption, where the temperature values measured at some locations inside the layer during the expansion process are used as input known data. This procedure was successfully applied to steel samples protected with an intumescent paint; the estimated equivalent thermal conductivity of the layer results to temperature dependent while the initial thickness of the paint does not seem to have a great effect.

Functional Textiles – From Research and Development to Innovations and Industrial Uptake

Abstract Functional textiles are one of the most important fields in textile industry and textile materials science. They include breathable, heat and cold-resistant materials, ultra-strong fabrics (e.g. as reinforcement for composites), new flameretardant fabrics (e.g. intumescent materials), optimisation of textile fabrics for acoustic properties, etc. Functional textiles became more and more important materials for various applications and interest in them grew year by year; and more and more conferences are focused on functional textiles, as well as the events which are not only textile conferences but encompass various fields of Material Science. This paper presents a short overview about the European Materials Research Society 2014 Fall meeting conference Symposium M “Functional textiles - from research and development to innovations and industrial uptake” and the projects which participated as symposium co-organisers: the European Coordination Action 2BFUNTEX funded by the EC 7th Framework Programme NMP, the COST Action MP1105 on “Sustainable flame retardancy for textiles and related materials based on nanoparticles substituting conventional chemicals (FLARETEX)” and the COST Action MP1206 on “Electrospun Nano-fibres for bio inspired composite materials and innovative industrial applications”.

Rigid Polyurethane Foam Thermal Insulation Protected with Mineral Intumescent Mat

Abstract One of the biggest disadvantages of rigid polyurethane (PU) foams is its low thermal resistance, high flammability and high smoke production. Greatest advantage of this thermal insulation material is its low thermal conductivity (λ), which at 18-28 mW/(m•K) is superior to other materials. To lower the flammability of PU foams, different flame retardants (FR) are used. Usually, industrially viable are halogenated liquid FRs but recent trends in EU regulations show that they are not desirable any more. Main concern is toxicity of smoke and health hazard form volatiles in PU foam materials. Development of intumescent passive fire protection for foam materials would answer problems with flammability without using halogenated FRs. It is possible to add expandable graphite (EG) into PU foam structure but this increases the thermal conductivity greatly. Thus, the main advantage of PU foam is lost. To decrease the flammability of PU foams, three different contents 3%; 9% and 15% of EG were added to PU foam formulation. Sample with 15% of EG increased λ of PU foam from 24.0 to 30.0 mW/(m•K). This paper describes the study where PU foam developed from renewable resources is protected with thermally expandable intumescent mat from Technical Fibre Products Ltd. (TFP) as an alternative to EG added into PU material. TFP produces range of mineral fibre mats with EG that produce passive fire barrier. Two type mats were used to develop sandwich-type PU foams. Also, synergy effect of non-halogenated FR, dimethyl propyl phosphate and EG was studied. Flammability of developed materials was assessed using Cone Calorimeter equipment. Density, thermal conductivity, compression strength and modulus of elasticity were tested for developed PU foams. PU foam morphology was assessed from scanning electron microscopy images.

Thermal characterization of intumescent fire retardant paints

Intumescent coatings are now the dominant passive fire protection materials used in industrial and commercial buildings. The coatings, which usually are composed of inorganic components contained in a polymer matrix, are inert at low temperatures and at higher temperatures, they expand and degrade to provide a charred layer of low conductivity materials. The charred layer, which acts as thermal barrier, will prevent heat transfer to underlying substrate. The thermal properties of intumescent paints are often unknown and difficult to be estimated since they vary significantly during the expansion process; for this reason the fire resistance validation of a commercial coatings is based on expensive, large-scale methods where each commercial coating-beam configuration has to be tested one by one. Adopting, instead, approaches based on a thermal modelling of the intumescent paint coating could provide an helpful tool to make easier the test procedure and to support the design of fire resistant structures as well. The present investigation is focused on the assessment of a methodology intended to the restoration of the equivalent thermal conductivity of the intumescent layer produced under the action of a cone calorimetric apparatus. The estimation procedure is based on the inverse heat conduction problem approach, where the temperature values measured at some locations inside the layer during the expansion process are used as input known data. The results point out that the equivalent thermal conductivity reached by the intumescent material at the end of the expansion process significantly depends on the temperature while the initial thickness of the paint does not seem to have much effect.

Reaction‐to‐fire properties of polymer matrix composites with integrated intumescent barriers

SummaryThe integration of an intumescent barrier between the plies of prepreg based polymer matrix composite and sandwich panels is investigated in detail with regard to reaction‐to‐fire properties. Incident heat flux, panel thickness and insertion depth within the panel were varied systematically. Fire retarding effects are compared to the application of an intumescent and top coating on the surface. All tests were carried out with a commercial material: HexPly® 8552/IM7 by Hexcel. Design rules for an effective improvement of reaction‐to‐fire properties are derived. Two practical applications were identified not interfering with mechanical properties: A metal mesh as support for the intumescent material underneath a single top ply and the one‐sided integration in a sandwich with the possibility to expand into the honeycomb. Degradation mechanisms are characterized by cone calorimetry and temperature development throughout the specimens. Copyright © 2014 John Wiley & Sons, Ltd.

Study of vesiculation in intumescent material

The patterns of vesiculation in hydrosilicates are considered in the paper. The main objective is obtaining overall dependencies of vesiculation in the intumescent material based on silica to develop a strategy of production of heat-insulating materials with a structure close to optimal. General regularities of porous structure formation in foam mass with various chemical components are given. General conclusions on the influence of impurities in the initial mass on the process of material intumescence are made. It was also concluded that the change in the local moisture content does not affect the overall vesiculation process, since the rate of moisture diffusion in the material exceeds the vesiculation rate. In addition, a series of experiments on the effect of aluminium on the vesiculation of alumina material was carried out. Small additives of aluminium increase the strength characteristics and porosity in siliceous mass with small amounts of impurities.The results can be of interest to scientists and engineers dealing with the production of refractory materials.

ACOUSTICAL SOUND PROOFING MATERIAL WITH IMPROVED FIRE RESISTANCE AND METHODS FOR MANUFACTURING SAME

A material for use in building construction (partition, wall, ceiling, floor or door) that exhibits improved acoustical sound proofing and fire resistance. The material comprises a laminated structure having as an integral part thereof one or more layers of intumescent viscoelastic material which also functions as a glue, energy dissipating layer, and a fire resistive layer; and one or more constraining layers, such as gypsum, cement, metal, cellulose, wood, or petroleum-based products such as plastic, vinyl, plastic or rubber. In one embodiment, standard wallboard, typically gypsum, comprises the external surfaces of the laminated structure.

Thermal–mechanical modelling of laminates with fire protection coating

This paper presents a modelling approach to analyse the protection provided by passive and intumescent surface coatings on glass fibre reinforced laminate substrates exposed to fire. The modelling involves a multi-stage analytical approach: (i) thermal analysis of heat transfer from the fire through the surface insulation coating, which includes decomposition and expansion in the case of an intumescent material; (ii) thermal–chemical analysis of heat transfer through the fibreglass laminate substrate (beneath the fire protective coating), including decomposition of the polymer matrix; and (iii) thermal–mechanical analysis of softening and failure of the laminate under in-plane tension or compression loading. The modelling approach is validated using experimental temperature and strength data from fire structural tests performed on woven glass–vinyl ester laminates insulated with passive (ceramic fibre mat) or organic intumescent surface coatings.

A new model to predict multi-stage pyrolysis of flammable materials in standard fire tests

Test procedures to assess material flammability are focused on radiative heating of the examined material followed by ignition of volatiles produced by pyrolysis. In this work, a new model (Pyropolis) for predicting thermal degradation of polymer materials exposed to the external heat flux is presented. Composite materials of interest consist of a matrix polymer and a (glass or carbonized) fiber. If temperature is sufficiently high, the matrix polymer degrades thereby producing solid and/or gaseous components. Solid decomposition products may exhibit a considerable size change, which is a notable feature of intumescent materials also considered in this work. The model incorporates multi-step decomposition mechanism including two reactions in anaerobic conditions and four reactions in oxidative atmosphere. Kinetic data could be derived from TGA, DSC and PCFC/MCC measurements, which are processed by either simplified (peak value based) or comprehensive (non-linear optimization) approach suitable for both n-th order and autocatalytic reactions. The model is validated by comparing predictions of gasification rates for to two distinct types of non-charring (PS) and charring intumescent (PC) polymers. Reasonable agreement has been obtained with the measured mass loss rates, which are proportional to the heat release rates if volatiles are ignited.

Flame Retardant Effects of Nano-Clinoptilolite on AcrylonitrileButadiene-Styrene (ABS) Nano-Composite

In recent years, intumescent technology has found a place in polymer science as a method of providing flame retardance to polymeric materials. On heating, fire-retardant intumescent material restricts the action of the heat flux or flame. The proposed mechanism is based on charred layer acting as physical barrier, which slows down heat and mass transfer between the gas and the condensed phases. In this paper, the flammability of intumescent fire-retardant acrylonitrile-butadiene-styrene (ABS) matrix composites consisting of hydromagnesite (HMg) as an acid source and blowing agent, pentaerythritol (PER) as a carbonisation agent and natural zeolite (clinoptilolite rich, Kansar Shargh) as a synergistic agent were examined. The flammability of composites was characterized by limiting oxygen index (LOI) measurement and horizontal burning tests. A synergistic effect in flame retardancy was observed when natural zeolites were used in combination with HMg and PER.