The use of fire‐retardant intumescent mats for fire and heat protection of glass fibre‐reinforced polyester composites: Thermal barrier properties

This study investigates the use of integral, hybrid intumescent thermal barriers (mats) to provide surface protection to the core fibre‐reinforced polyester composite structural integrity when exposed to a fire or heat source. Glass fibre‐reinforced composites protected by intumescent mats/fabrics containing silicate fibres, expandable graphite and in some cases borosilicate glass bounded together by an organic matrix have been evaluated for fire performance under a constant heat flux of 50kW/m². The effect of insulative fabric thickness as well as chemical composition on the flammability of the resultant hybrid composites is evaluated. Glass fibre‐reinforced polyester (GRP) composites without any surface protection have a relatively higher time‐to‐ignition and peak heat release rate values when compared with core composites protected by insulative fabrics. Thermograms representing the variation of temperature on the reverse side of the hybrid composites with time when exposed to a constant heat flux show that the inclusion of intumescent surface barriers results in retarded temperature increments within the core GRP composites. Copyright © 2009 John Wiley & Sons, Ltd.     

Modeling multi‐stage decomposition of cotton fabrics considering char oxidation in the presence of oxygen

A theoretical model, describing thermal degradation behavior of cotton fabrics that exposed to a constant radiant heat flux, is proposed in the paper. The model describes thermal and oxidative degradation of cotton fabric under the oxygen‐containing atmosphere and considers pseudo‐bi‐component separate‐stage kinetic process. Both exothermic and endothermic reactions are included in the decomposition process. At present, gas phase oxidation reactions are not included. Comparison with experimental results demonstrates that the predictions of the mass loss rate and temperature profile with these cotton fabrics are in agreement with the experiment. Effects of thermal radiation and ambient oxygen concentration on decomposition have also been investigated. The gas phase temperature is also predicted by the present numerical model. Results from numerical model will help contribute to a better understanding of the ignition mechanism of flame‐resistant cotton fabrics used for fire safety garments. Copyright © 2009 John Wiley & Sons, Ltd.     

Protective clothing: Evaluation of zirpro wool and other fabrics

Protective clothing against head and flames should be evaluated not only for flame retardance but also for protection against various heat exposure from convection (flames), conduction (molten metal splashes) and radiation sources, depending on the end use, to ensure a realistic assessment of the potential protection offered and required. Evaluations of various flame-retardant fabrics to different heat exposures showed that the fibre and the flame retardant finish should preferably form a well developed char on exposure to heat, without softening and melting. The flame retardant should act in the solid phase and the fibre should be of low thermal conductivity. For protection against convective heat (flames), a woven Zirpro wool fabric of high density over a bulky knitted Zirpro wool underwear fabric offered a significantly better protection than a single layer of a woven or knitted fabric or a double layer of a woven fabric of the same total weight. The optional multi-layer fabric approach could also decrease overall garment weight and improve wearers' comfort without adverse effect on the protection offered. Of the FR fabrics evaluated, Zirpro wool fabric assemblies showed the longest time to reach pain (first degree burn) and blister (second degree burn) thresholds, as well as the longest pain alarm time–the time available to the wearer to withdraw from the flame heat source before serious injuries occur. Zirpro wool fabric assemblies had one of the lowest residual heat transfers after al limited flame exposure to the pain threshold while some other fibres, e.g. aramid and novoloid, transferred significant residual heat, possibly causing second degree burns. For protection against conduction, such as from molten aluminium splashes, the fabric should have a smooth surface, high density and thickness, besides the other previously mentioned, basic requirements. Zirpro wool fabrics offered a significantly better protection in this case than aramid, FR cotton, glass fibre, asbestos, and other FR fibres. Aluminized fabrics are essential for adequate protection against radiant heat and the aluminization technique affects heat transfer significantly. A low density base fabric made from a fibre of low thermal conductivity, such as Zirpro wool, reduces heat transfer in this case.     

Thermal sensor performance and fire characterisation during short duration engulfment tests

A small-scale reproduction of the ISO 13506-1 thermal manikin was constructed to enable the assessment of manikin sensor performance, the partitioning of energy, and the variability of the fire generated during short duration heat and flame engulfment tests. The cylindrical test apparatus simultaneously housed four total heat flux (THF) sensors, one radiant heat flux sensor, and three manikin sensors. Calibrated manikin sensors were provided by nine laboratories and were categorised as buried thermocouple, copper-based, or surface-mounted thermocouple sensors. The test apparatus was exposed to fire generated by four propane torches for three exposure durations. All sensors presented similar profiles in net heat flux over time, which could be divided into four distinct phases: transient increase, pseudo-steady state, transient decrease, and post-exposure. Over pseudo-steady state, the mean THF over all exposure durations was 88 ± 8 kW/m², and the ratio of convective to radiant energy was approximately 50:50, but highly variable. For a 4-second exposure, manikin sensors from five laboratories had a bias in heat flux greater than ± 5% during pseudo-steady state when compared with the THF sensors. This bias can primarily be attributed to the sensitivity of the manikin sensors to convective heat or heat loss due to sensor design.     

Analysis of thermal performance of two fabrics intended for use as protective clothing

Tests were conducted on two fabrics intended for use in protective clothing: an aramid (used extensively in firefighter gear) and a modified viscose cellulosic fabric. Both were exposed to very high heat (temperatures above 400°C) and their performance as thermal insulators was assessed by the temperature transmitted through the fabric, both in their dry state and after being exposed to a water spray. Both fabrics performed satisfactorily, but the modified viscose fabric improved its thermal insulation properties when damp, while the aramid fabric remained unaffected (or perhaps negatively affected) by the water spray. Overall, the modified viscose fabric seemed a better thermal insulator than the aramid. © 1997 John Wiley & Sons, Ltd.     

Comparison of cone and OSU calorimetric techniques to assess the flammability behaviour of fabrics used for aircraft interiors

Two test methods for measuring the heat release rate, HRR have been compared on fabric composites used for aircraft interior materials as side‐wall panels. These methods are based on the principles of direct measurement of the convective and radiant heat by thermopiles using an Ohio State University (OSU) calorimeter, and oxygen consumption using a cone calorimeter. It has been observed when tested by standard procedures, cone results at 35 kW/m² incident heat flux do not correlate with OSU results at the same heat flux. This is because in the cone calorimeter, the sample is mounted horizontally whereas the OSU calorimetric method requires vertical sampling with exposure to a vertical radiant panel. A further difference between the two techniques is the ignition source—in the cone it is spark ignition, whereas in the OSU it is flame ignition; hence, samples in the OSU calorimeter ignite more easily compared to those in the cone under the same incident heat fluxes. However, in this paper we demonstrate that cone calorimetric exposure at 50 kW/m² heat flux gives similar peak heat release results as the 35 kW/m² heat flux of OSU calorimeter, but significantly different average and total heat release values over a 2 min period. The performance differences associated with these two techniques are also discussed. Moreover, the effects of structure, i.e. type of fibres used in warp/weft direction and design of fabric are also analysed with respect to heat release behaviour and their correlation discussed. Copyright © 2005 John Wiley & Sons, Ltd.     

Flammability behavior of fiber–fiber hybrid fabrics and composites

The effect of heat flux levels on burning behavior and heat transmission properties of hybrid fabrics and composites has been investigated using cone calorimeter and heat transmission techniques. The hybrid fabric structures woven out of E‐glass (warp) and polyether ether ketone (PEEK) (weft) and E‐glass (warp) and polyester (weft) have been studied at high heat flux levels keeping in view the flame retardant requirements of structural composites. The performance of the glass–PEEK fabric even at high heat flux levels of 75 kW/m² was comparable with the performance of glass–polyester fabric evaluated at 50 kW/m². The results further demonstrate that glass–PEEK hybrid fabrics exhibit low peak heat release rate, low heat release rate, low heat of combustion, suggesting an excellent combination of materials and fall under the low‐risk category and are comparable with the performance of carbon fiber‐epoxy‐based systems. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Mechanical properties of fire‐damaged glass‐reinforced phenolic composites

Changes to the mechanical and physical properties of a glass‐reinforced resole phenolic composite due to intense radiant heat and fire are investigated. Fire testing was performed using a cone calorimeter, with the composite exposed to incident heat fluxes of 25, 50, 75 or 100 kW/m² for 325 s and to a constant flux of 50 kW/m² for different times up to 1800 s. The post‐fire tensile and flexural properties were determined at room temperature, and these decreased rapidly with increasing heat flux and heat exposure time due mainly to the chemical degradation of the phenolic resin matrix. The intense radiant heat did not cause any physical damage to the composite until burning began on exposure to a high heat flux. The damage consisted of cracking and combustion of the phenolic matrix at the heat‐exposed surface, but this only caused a small reduction to the mechanical properties. The implication of the findings for the use of glass‐reinforced resole phenolic composites in load‐bearing structures for marine craft and naval ships, where fire is a potential hazard, is discussed. Copyright © 2000 John Wiley & Sons, Ltd.     

消防服用多层织物的热防护性能

研究了消防服用多层织物的热防护性能,对单层织物的热防护性能及十种多层组合织物的热防护性能分别进行了研究分析,得出以下结论:就单层纤维成分相同的阻燃面料而言,热防护系数(TPP)值与织物的厚度、面密度具有显著的正相关性;多层组合织物中,外层及防水透湿层为覆聚四氟乙烯(PTFE)膜的阻燃帆布、隔热层为芳纶1313针刺毡、舒适层为芳纶-阻燃黏胶的8#样品的防护性能最好,就阻燃防护性能方面而言,是最适合用于消防员灭火消防服的面料。     

Applicability analysis of mathematical models for the combustion characteristics in the pool fire

A pool fire characterized by high temperature and heat radiation, is a common accident in chemical industry. The important combustion characteristic parameters are the heat radiation flux, the burning rate, the flame height, etc., but the most significant one is the heat radiation flux. The calculation model of the pool fire has an important role to assess the accident. There are three types of widely used pool fire models, the Shokri and Beyler model, the Mudan model, and the point source model. The models are used to calculate the combustion parameters of three different kinds of oils in tanks of different scales. The predictions of three models are compared with the simulation results. The analysis shows that the point source model has a large error for pool fires with the diameter greater than 10 m and the thermal radiation flux smaller than 5 kW/m², and the model is more applicable to heavy crude pool fires. The scope of application of the Mudan model is broader, and this model ensures higher accuracy if the thermal radiation flux is smaller than 5 kW/m². The Shokri and Beyler model is more suitable for the case where the pool fire diameter is greater than 40 m and the thermal radiation flux is above 5 kW/m², and the results for the light crude pool fire based on this model are more reasonable.     

Heat transmission of proban®-treated fabrics subjected to a radiant heat source

The apparatus described in DIN 4842 was used to measure the heat transmission of a series of Nomex, polyester–cotton, Proban®-Treated cotton, untreated cotton and wool workwear fabrics subjected to a radiant heat source. Heat transmission was found to be dependent on the incident heat flux, fabric weight and fabric thickness. At the heat flux levels tested, 10 KJ m^?2s^?1 and 20 KJ m^?2s^?1, heat transmission was found to be largely independent of the fibre composition of the fabric when single layers of fabric were tested. The level of heat transmission was reduced by the use of multiplayer assemblies or a reflective aluminium coating, but the greatest reduction was obtained when air spaces were interposed between the fabrics. Conbinaitons of fabrics were developed which transmitted less than 205 KJ m^?2s^?1 during testing at incident heat flux levels of 10 KJ m^?2s^?1 and 20 KJ m^?2s^?1.     

Flame penetration and burn testing of fire blanket materials

Materials were evaluated in laboratory tests for a fire blocking blanket to protect stores of U.S. Army munitions from burning material and hot fragments. The objective of testing was to evaluate and rank materials' ability to resist the penetration of flame and heat and to limit flame spread. Materials in all tests were subjected to an oxyacetylene torch with temperatures in excess of 3000°C. Inorganic fiber‐based fabric, insulation and blankets evaluated in flame penetration tests were rated by their time to limit backside temperature rise to 100°C above ambient and 500°C for a given material areal mass. Carbon fiber fabric performed the best of the fabrics tested. Silica aerogel insulation was the top performing insulation material group. The blanket with carbon fiber sandwiching silica aerogel insulation performed best. Horizontal and vertical flame burn tests were conducted on several candidate blanket cover materials. Fabrics coated with polyvinyl chloride, polytetrafluoroethylene and silicone rubber coatings were all found to be immediately self‐extinguishing when the flame was removed. Burn damage was confined locally to the heated zone beneath and around the lit torch tip's flame. All flames were immediately self‐extinguishing beyond those regions, with zero flame‐out times recorded. Published in 2008 by John Wiley & Sons, Ltd.     

Burn‐through resistance of fibre/felt materials for aircraft fuselage insulation blankets

Light‐weight fire barrier materials for aircraft thermal/acoustical insulation blankets were investigated. The burn‐through test on blankets inserted with these fire‐blocking materials was performed using a small‐scale kerosene burner apparatus. The burner system generated a turbulent flame at 1000°–1100°C and a front heat‐flux at 160–180 kW/m². The rear or back‐side heat flux of blankets and their corresponding burn‐through time were monitored by a computerized data acquisition system. The blankets with ceramic or polymeric fire barrier materials provided a significantly additional burn‐through time compared with the regular blankets. Blanket samples inserted with an alumino‐silicate‐based ceramic layer were not burned‐through after 6 min. For fire resistant polymeric‐based materials, the burn‐through time varied from 2 to 6 min. The burn‐through resistance was correlated with the stable structure of SiO₂ at high temperature for the ceramic sheets and with the formation of a char layer for polymeric layers.Copyright © 2002 John Wiley & Sons, Ltd.     

Improved fire safety of composites for naval applications

This study is based on the use of integral, hybrid thermal barrier to protect the core of the composite structure. Thermal barrier treatments evaluated in this study include ceramic fabric, ceramic coating, intumescent coating, hybrid of ceramic and intumescent coating, silicone foam, and phenolic skin. The composite systems evaluated in combination with thermal barrier treatments included glass/vinyl ester, graphite/epoxy, graphite/bismaleimide, and graphite/phenolic. All configurations were tested for flammability characteristics. These included smoke density and combustion gas generation (ASTM E-662), residual flexural strength (ASTM D-790), heat release rate, and ignitability (ASTM E-1354). ASTM E-662 test method covers the determination of specific optical density of smoke generated by solid materials. ASTM D-790 test method covers the determination of flexural properties of composite materials in the form of rectangular bars. ASTM E-1354 (cone calorimeter) covers the measurement of the response of materials exposed to controlled levels of radiant heating with or without an external ignitor, and is used to determine the ignitability, heat release rates, mass loss rates, effective heat of combustion, and visible smoke development. Without any fire barrier treatments, all composite systems evaluated in this study failed to meet ignitability and peak heat release requirements of MIL-STD-2031 (SH) at radiant heat fluxes of 75 and 100 kW m^?2, respectively. Intumescent coating and a hybrid system consisting of intumescent coating over ceramic coating were the most effective fire barrier treatments for composite systems evaluated in this study. Using either of these treatments, all composite systems met the ignitability requirements of 90 and 60 at 75 and 100 kW m^?2, respectively. Except for glass/vinyl ester, all systems also met the peak and average heat release requirements of MIL-STD-2031 (SH) at radiant heat fluxes of 25, 75, and 100 kW m^?2, respectively.     

Ignition and flash-fire studies of cellulosic materials

Various celloulosic materials were evaluated for ignitability and flash-fire propensity, using screening test methods developed at the University of San Francisco. Time to ignition, using radiation from a high-temperature radiant source without a pilot flame, appeared to be primarily a function of heat flux and material density, rather than of type of wood or celloulosic board. At heat flux levels from 5.8 to 10.5 W cm^?2, time to ignition was shortest for cellulose fiberboard with a density of 0.2225 g ml^?1, followed by western red cedar at 0.314 g ml^?1, eastern white pine at 0.348 g ml^?1, southern yellow pine at 0.422 g ml^?1, Douglas fir at 0.565 g ml ^?1, and longest for hardboard at 0.878 g ml^?1. For the cotton and rayon woven-pile upholstery fabrics, time to ignition appeared to increase with increasing fabric weight. For Cellulose insulation treated with boron-containing additives, flash-fire magnitude decreased with increasing additive content. Flash-fire magnitude decreased more that could be accounted for by decreasing weight loss alone, indication reduction in the combustibility of the volatiles produced. Reduction in flash-fire propensity of cotton bating by treatment with boron-containing additives was also observed.     

A simple and efficient method for the preparation of SiO2/PI/AF aerogel composite fabrics and their thermal insulation performance

As a new type of insulation material, aerogels are characterized by a high specific surface area, high porosity, low density and low thermal conductivity, which makes them a new alternative to the use of traditional insulation materials. In this paper, a simple method for preparing aerogel insulation materials is proposed. Specifically, SiO₂/PI/AF (aramid fiber) aerogel composite fabrics were successfully obtained by combining coating technology and finishing processes to use tetraethoxysilane (TEOS) as the precursor, polyimide (PI) powder as the reinforcing agent, and nonwoven AF as the substrate. These composite fabrics were characterized using field-emission scanning electron microscopy (FESEM), tensile testing with an Instron 5967, Fourier transform infrared spectroscopy (FT-IR) and thermal infrared imaging. The results show that the composite fabrics exhibited excellent performance and could effectively block heat transfer. Moreover, the thermal conductivity of the front decreased from 4.08 to 3.91 (W/cm·°C) × 10^-4. This work provides a novel method for the structural design of thermal insulation clothing.     

Preparation,thermal properties and permeabilities of aluminum-coated fabrics destined for thermal radiation protective clothing

In this study, radiant reflective, flame retardant and water vapor permeable coatings were fabricated on aramid fabric (AF) for thermal radiation protective clothing by using a simple cost-effective coating method, which included an aluminum paste, APP-PER-MEL and a silk fibroin powder in the TPU solution system. The permeability, flame retardancy, thermal stability, radiative spectral reflectance, as well as RPP of these prepared fabrics were characterized and compared with the pure AF and aluminum-foiled AF (AF-AF). Results show that the newly developed aluminized AF had rather high permeability, and the permeable capability would be further enhanced with the additive of silk fibroin powder. The flame retardancy (FR) of the coated fabric sample was also achieved by introducing an intumescent FR system. In contrast to the pure AF, the aluminum-coated AF provided higher levels of radiation protection in RPP testing. This was further confirmed by the fact that aluminum-coated AF exhibited comparative high average reflectivities (more than 0.7) in the radiant spectral range of 1547 nm to 2500 nm. Thus, the aluminum-coated AF prepared by functional coating method exhibit great and competitive practicability in thermal protective clothing due to their excellent moisture comfort and radiant thermal protection.     

红外辐射调控原理及其在热管理应用中的材料研究进展

传统的石化能源利用率较低加剧了环境危机,低能耗的热管理材料应运而生。本文介绍了红外辐射调控技术的原理,综述了辐射选择性调控材料在建筑热管理和人体热管理领域的研究进展,并概述了两类材料红外性能的相关研究和应用进展。文中指出：辐射选择性调控材料是通过设计材料表面结构的光学特性,调节太阳辐射来实现辐射控温的。建筑热管理材料主要有透明涂层、颜料涂层和辐射冷却器等,不同的建筑围护结构对应不同的性能,如具有高太阳反射率和高红外发射率的辐射冷却器和颜料涂层大都应用在墙体和屋顶上,而窗户要为室内提供一定的照明,因此还需具有高太阳透过率;人体热管理材料主要是可穿戴织物,包括辐射散热织物、辐射保温织物和智能辐射织物,除了具有相应的辐射性能之外还应该具备普通织物所具有的柔韧性、透气性、抗菌性的特点。最后,本文从辐射调控材料的性能与实际应用相结合的角度展望了未来的研究方向。     

Fire reactions of ceramic and polymer moulding composites

Abstract

Abstract

Low cost ceramic dough moulding compounds/composites (CDMC) are composed of inorganic metal silicates and chopped fibre reinforcements. This paper investigates the fire reactions of these materials under severe thermal and heat conditions. This research is targeted to potential applications in the replacement of glass fibre reinforced polymeric insulation materials such as phenolic composites as engine heat shields which experience high temperature and heat transmission. The materials developed can provide good properties, including heat insulation with high thermal stability for engine drafts, where traditional glass/phenolic composites were used and gave a very short life cycle. This work compares the thermal properties of the glass fibre reinforced phenolic composites and metal silicate composites produced under the same processing conditions. The results show that CDMC possesses significantly better thermal stability and heat resistance in comparison with phenolic moulding composite (phenolic dough moulding composites). The indication was that under the testing condition of heat flux of 75?kW?m^?2 intended for materials used for applications in marine, transport and possibly nuclear waste immobilisation, the integration of the CDMC was kept intact and survived as a high temperature insulation material.