fire behavior of regular and latent heat storage gypsum boards

FIRE AND MATERIALSFire Mater. (2014)Published online in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/fam.2246

Fire behavior of regular and latent heat storage gypsum boards

D. A. Kontogeorgos*,†, I. D. Mandilaras and M. A. Founti

National Technical University of Athens, School of Mechanical Engineering, Laboratory of Heterogeneous Mixtures andCombustion Systems, Heroon Polytechniou 9, Zografou Campus, Athens 15780, Greece

SUMMARY

This paper investigates the fire behavior of a regular and an energy storage gypsum board with latent heatstorage characteristics when exposed to fire temperatures. Gypsum board samples, with and without amicroencapsulated paraffin mixture phase change material, are studied at material and board level. At thematerial level, measurements of the physical properties, that is, mass and effective thermal conductivity,as a function of temperature, as well as differential scanning calorimetry experiments, in inert and oxidizedenvironments, are performed. At the board level, specimens are inserted into a preheated oven, and the tem-perature evolution at preselected board locations is recorded. Both experimental procedures reveal signifi-cant information concerning the evolution of the various thermochemical processes taking place insidethe gypsum boards during their heating. Results indicated the different fire behavior of the samples at differ-ent temperature ranges. At temperatures up to 300°C, the materials act as a fire retardant because of thedehydration of the free and chemically bound water contained in the gypsum boards. On the other hand,at temperatures higher than 300°C, the temperature rise within the samples is enhanced and acceleratedbecause of the oxidation of the phase change material and their external finishing. Copyright © 2014 JohnWiley & Sons, Ltd.

Received 26 July 2013; Revised 13 February 2014; Accepted 27 February 2014

KEY WORDS: gypsum board; phase change materials; fire temperatures; small-scale experiment; differentialscanning calorimetry

1. INTRODUCTION

Gypsum boards (GBs) are building materials, which are widely used as facing materials for building wallsand ceilings because of their very good mechanical and thermal properties, as well as their fire endurance.The latter is owed to the endothermic dehydration process that takes place at fire temperatures [1–4],which is capable of slowing down the fire spread through GB-based systems [5–7]. This phenomenoncan be of great importance from the fire safety point of view providing sufficient building evacuationtimes.

Conventional GBs consist of a gypsum-based core material that is covered on both sides with a thinlayer of paper or other protective material that enhances the stability and the integrity of the core. Thegypsum-based core is a porous material that consists mainly of calcium sulphate dihydrate(CaSO4 · 2H2O) (>65 wt %), which contains up to 21% by weight chemically bound water and asmall amount of absorbed free water (≤4 wt %) [5,8, 9]. In some cases, the GB core may alsocontain calcium carbonate (CaCO3) and/or magnesium carbonate (MgCO3) [10, 11].

*Correspondence to: D. A. Kontogeorgos, Laboratory of Heterogeneous Mixtures and Combustion Systems, ThermalEngineering Section, School of Mechanical Engineering, National Technical University of Athens, Heroon Polytechniou 9,Polytechnioupoli Zografou, Athens 15780, Greece.†E-mail: [email protected]

Copyright © 2014 John Wiley & Sons, Ltd.

D. A. KONTOGEORGOS, I. D. MANDILARAS AND M. A. FOUNTI

Apart from the previously mentioned ingredients and depending on the application, the GB coremay contain other additives that enhance the material with special properties. Some of them areglass fibers, fire resistant materials, and phase change materials (PCMs) that enhance themechanical, fire, and energy storage capabilities of GBs, respectively. The latter can be achieved byincorporating paraffin-mixture-based PCMs, in the form of encapsulated into PMMA microspheres(poly(methyl methacrylate)), that are incorporated into the GB core [12, 13]. The resulting incrementof its thermal mass in a specific temperature range (i.e., phase change range) can reduce significantlythe required building heating/cooling loads and consequently improve indoor thermal comfort of abuilding.

Generally, PCM technology has been investigated for more than three decades as a way ofincreasing the thermal mass of building elements [14, 15]. The technology takes advantage of thelatent heat of the PCM during its solid–liquid change of state, to stabilize the temperature of thematerial and reduce the heat losses/gains from the building to the environment [16, 17]. For thatreason, GBs containing PCM can be used instead of regular GBs in wall configurations. However,PCMs are usually mixtures of hydrocarbon molecules, which at fire temperatures evaporate. The gasmixture produced is potentially flammable and may affect the fire endurance of the material.

Building products containing PCMs are relatively new in the market, and their behavior under fireconditions has not yet been studied systematically. The paper focuses on the comparative study of thethermal behavior of two commercial GBs. A regular GB (R-GB) and a PCM-containing GB(PCM-GB) were examined at elevated temperatures, at material and board level, in order tohighlight the various thermochemical processes taking place inside the GBs. At the material level,measurements of the mass and the effective thermal conductivity as a function of temperature anddifferential scanning calorimetry (DSC) experiments, in inert and oxidized environments, wereperformed. At the board level, the two types of GBs studied were subjected to identical hightemperature environments, and the evolution of temperature at several locations of the specimenswas recorded. With R-GB serving as a reference material, it is possible to distinguish and quantitatethe effect of PCM in the PCM-GB. What is of special interest is the simultaneous presence of threecomponents: water, PCM, and external finishing material. Water acts as fire retardant, while PCMand external finishing are flammable under high temperature conditions. The instantaneous valuesand the rate of release of these components at fire temperatures provide valuable information inrelation to the performance of the examined building products under fire conditions.

2. EXPERIMENTAL EQUIPMENT/METHODOLOGY

The overall experimental procedure followed two directions: Firstly, the temperature variation of thematerials’ properties (i.e., chemical reactivity, mass, and effective thermal conductivity) wasmeasured. The experimental results were used in order to assess the impact of water dehydration, aswell as PCM and external finishing oxidation, and to figure out how these processes would affectthe fire behavior of the samples. Secondly, small-scale experiments were performed by insertingspecimens in a preheated oven. The temperature evolution inside and on the specimens’ surfaceswas recorded, quantitating the overall fire performance of the examined materials.

2.1. Material properties

As mentioned previously, commercially available regular and energy storage GBs were used. Table Isummarizes some general information about the utilized materials. The effective thermal conductivity,k0, corresponds to the respective value for the ‘as delivered’ (ambient conditions) samples. Theapparent density, ρ0, of the ‘as delivered’ samples was measured, as well as calculated according tothe mass percentages of the core and the finishing material (shown in Table I). The results revealedno significant difference. Finally, it should be mentioned that the core of each sample is covered,from both sides, by one layer of finishing material. In Table I, the thickness of each layer is tabulated.

2.1.1. Chemical reactivity. The chemical reactivity of the examined samples was defined by means ofheat flux DSC experiments in a Stare SW 8.10, Mettler Toledo apparatus. The DSC experiments were

Copyright © 2014 John Wiley & Sons, Ltd. Fire Mater. (2014)DOI: 10.1002/fam

Table I. General information about the utilized gypsum boards

MaterialThicknessd [mm]

Apparent densityρ0 [kgm

�3]Mass percentage

Y [%]Effective thermal conductivity

k0 [W�1m�1 K�1]

R-GB Core 11.5 852 95.6 0.25Finishing 0.5 448 4.4 0.25Total 12.5 820 100.0 0.25

PCM-GB Core 13 850 93.2 0.28Finishing 1 400 6.8 0.28Total 15 790 100.0 0.28

REGULAR AND LATENT HEAT STORAGE GYPSUM BOARDS

performed at the temperature range from 25 to 600°C, using a heating rate of 20°C/min, in inert(nitrogen) and oxidized (air) atmospheres with a gas flow of 200ml/min, using 40-μl pinhole lidaluminum crucibles. Before the measurements, the apparatus was calibrated at 156.6°C using indiumand at 419.6°C using zinc. Before each measurement, a blank DSC run was performed with anempty pan, using the same conditions, and the resulting blank curve was subtracted from the DSCcurve measured by having placed a sample mass in the same pan. In order to define the baseline atthe temperature range where each reaction takes place, integral tangential baselines, provided fromthe apparatus software, were used.

2.1.2. Mass loss and thermal conductivity. For the effective thermal conductivity measurements, thehot wire method was implemented. The method allows the determination of the effective thermalconductivity of homogeneous and isotropic materials, conforming to the transient method describedin ISO 8894-1 [18]. The operating principle is based on the measurement of the temperature rise ata defined distance from a linear heat source (hot wire) embedded in the test material. The “transienthot-wire” measuring device was used, which utilizes a probe containing both the heat source and thetemperature sensor in a thin laminated film (0.2mm thick) with an accuracy of ±2%. The procedurerequires the insertion of the probe between two identical samples of the material. For the mass lossmeasurements, an OHAUS® scale (TS2KV) with a precision of ±0.01 g was utilized.

Two samples of 100 × 100mm were cut off from each type of commercial board. The respectivethicknesses were 12.5mm for R-GB and 15mm for PCM-GB. The difference in the thicknessbetween the two types of boards is not expected to affect the qualitative assessment of the results.

Initially, the samples were measured as delivered (ambient conditions). Afterward, the samples wereplaced in a preheated Carbolite® natural convection oven, at 14 different predefined temperature levels(25 to 100°C with a step of 25°C and 100 to 250°C with a step of 15°C), and kept inside the oven foralmost 6 h to ensure that they obtained the predetermined temperature [19]. The samples were weighedimmediately after extracting them from the oven, sealed in a small plastic bag, and left for 24 h to cooldown to ambient temperature before the mass and the effective thermal conductivity were measured.

2.2. Small-scale experiments

Small-scale experiments were designed to account for the GB dehydration process and evaluation ofthe effects of PCM. For this purpose, a ‘special sample holder was constructed that allowed theaccurate positioning of thermocouples in prespecified positions. The holder was also used to provideadequate thermal insulation on the lateral surfaces of each specimen to ensure one-dimensional heatand mass transfer. For each experiment, two samples of the same GB, each measuring200 × 150mm (the thicknesses were 12.5 and 15mm for R-GB and PCM-GB, respectively), wereutilized. They were joined together by means of a high temperature silicon paste, to form the finaltest specimen (25- and 30-mm thickness for the R-GB and PCM-GB, respectively). The test samplewas equipped with several thermocouples and positioned into a Carbolite® natural convection oven,preheated at 300°C. The sample and the insulation were held together by a metal frame. A metallicarc was manufactured and positioned across the frame in order to support and guide thethermocouples measuring surface and air temperatures. Figure 1 illustrates the setup placed insidethe oven.


Figure 1. Photograph of the GB ‘sandwich’ fabrication located inside the oven.


The four lateral sides of the holder were thermally insulated with ceramic fiber insulation. Inaddition, the four lateral sides of the specimens were covered with a high temperature silicon pasteand 5mm thick ceramic fiber insulation (Figure 2). The reason for covering the lateral sides with thehigh temperature silicon paste and using the insulation layer was to ensure very good contactbetween the insulation and the lateral sides of the GB sample, as well as to minimize heat and masstransfer through these surfaces.

A total number of 11 thermocouples were positioned at different locations, allowing themeasurement of local temperatures at the center and two sides of the sample, as well as of thesurrounding air. Five fine thermocouples were used to measure the temperature at the interface ofthe specimen. They were positioned on the diagonal direction, at the interface between the twojoined GB samples. Two additional thermocouples were attached at two points on each side of thesample (Sf1 and Sb1 at the center and Sf2 and Sb2, 20mm from the edge of each sample’s freesurface) in order to measure the free surface temperature. Finally, two thermocouples were located50mm away from each side of the specimen (Air1 and Air2) in order to measure the air temperatureinside the oven and in the vicinity of the specimen’s surface. Figure 3 illustrates the location of thethermocouples mentioned previously. For the temperature measurements, an Agilent data acquisitionunit with accuracy of ±2% was utilized. Temperatures were recorded and stored in intervals of 2 susing the ‘LabVIEW’ software. The experiments were terminated after ca 2.5 h.

Figure 2. Photograph of the GB ‘sandwich’ fabrication indicating the insulation layers.


Figure 3. Schematic diagram of the positions of the thermocouples.


3. RESULTS AND DISCUSSION

3.1. Material properties

3.1.1. Chemical reactivity. The DSC results for the R-GB and PCM-GB samples are shown inFigure 4 (Figure 4a: R-GB and Figure 4b: PCM-GB). It should be noted that the results have beennormalized to the actual mass composition (core and finishing percentages, respectively) of eachsample (Table I).

The typical gypsum dehydration process (peaks 1A and 1B) is observed in both samples at thetemperature range 100–200°C regardless of the utilized atmosphere. Τhe calcium sulphate dihydrate(CaSO42H2O) is firstly transformed into calcium sulphate hemihydrate (CaSO40.5H2O) and then tosoluble calcium sulphate anhydrite (CaSO4-III) [3, 4]. This process is endothermic, absorbssignificant amounts of energy, and thus is capable of slowing down the fire spread through the

Figure 4. DSC results of the core and the external finishing material in inert (N2) and oxidized (air) atmo-spheres: (a) R-GB and (b) PCM-GB (heating rate: 20 C/min).



examined GB types. At temperatures near 350°C, a small exothermic peak is anticipated. This peakcorresponds to the reorganization of the GB’s crystal mesh, where the molecular structure of thesoluble crystal (CaSO4-III) irreversibly reorganizes into a lower insoluble energy state (CaSO4-II)(hexagonal to orthorhombic) [3, 4, 6, 7, 20]. The peak is clearly observed in the DSC curve ofR-GB (peak 2) but not in the case of PCM-GB, where this temperature range is dominated byPCM-related phenomena.

The influence of the R-GB covering paper is indicated in air conditions by the high energy values inthe temperature range between 300 and 550°C, a result of its oxidization (peaks 3A and 3B). The papercovering the external surfaces of R-GB is a hydrocarbon-based material, which, under fire conditions,decomposes and evaporates. Its volatiles are oxidized, producing significant amounts of energy, asshown in Figure 4a.

Phenomena associated with the PCM compounds are observed at the PCM-GB (Figure 4b), apartfrom the typical dehydration process (peaks 1A and 1B). The DSC analysis on both oxidized andinert environments revealed the effect of PCM incorporation into the GB. The combination ofparaffin and PMMA evaporation (peaks 4A and 4B) and oxidation (peaks 5A and 5B) leads to anoverall exothermic behavior under oxidized atmosphere, in the temperature range between 300 and550°C. The external surface of PCM-GB, which is an organic coating, has also an exothermicbehavior, when subjected to oxidized conditions (peaks 6A and 6B), almost in the same temperaturerange where the PCM evaporates and oxidizes (300–550°C). The exothermic behavior of bothPCM-GB core and external surface is owed to its organic synthesis, which under fire temperaturesdecomposes, evaporates, and oxidizes.

Comparing Figures 4a and 4b, it can be observed that, despite the fact that the mass percentage ofthe external surfaces of both GBs is quite low (~4.4% for R-GB and 6.8% for PCM-GB, respectively,Table I), the released energy, because of their oxidation, is quite significant in relation to the amount ofenergy released or absorbed by the other major reactions. This suggests that the external surfaces of theexamined GBs could be quite flammable, and thus, special care should be taken in case of fire events.Finally, the exothermic behavior of the PCM-GB core material suggests that the produced volatilesare flammable.

3.1.2. Mass loss and thermal conductivity. Figure 5 illustrates the mass loss (Figure 5a) and thethermal conductivity (Figure 5b) of the R-GB and PCM-GB samples as a function of theprespecified oven temperature. Thermal conductivity, mass, and mass loss values presented here aremean values obtained from the two identical samples of each GB type. Focusing on Figure 5a, itcan be stated that the dehydration process is completed at temperatures near 145°C for both GBtypes. There could be two reasons for this behavior: In the case of the R-GB, there is a significantmass loss up to ca 14.3% at the temperature range between ~80 and 145°C, while there is no

Figure 5. Scaled physical properties of the GB samples: (a) mass loss and (b) effective thermal conductivity(measured at room temperature).



significant mass reduction at temperatures higher than 145°C. The small mass reduction that isobserved at temperatures above 160°C is because of the detachment of small pieces of the samplesduring extraction from the oven, considering that after the dehydration, the samples were quitefriable. Nevertheless, the overall evaluation of the results is not affected by this issue. In the case ofthe PCM-GB, there is a significant mass reduction (~19.1%) at temperatures around 150°C. Thetotal mass loss in this case was ~34.3%, significantly higher than the expected percentage of thechemically bound water loss in any standard commercial GB (≤21%). This leads to the conclusionthat the PCM is evaporated at temperatures around 150°C, which is expected, as the PCM in theexamined sample is a mixture of paraffin with 16 to 18 carbon molecules in their chain (known tohave a flash point from 135 to 165°C). It is shown (Figure 5a) that the mass reduction as a result ofPCM evaporation takes place in two stages, where firstly, the paraffin mixture and secondly thePMMA evaporate.

Figure 5b presents the measured thermal conductivity of both samples as a function of the oven’stemperature. As it is shown, both the R-GB and PCM-GB samples exhibit similar behavior, despitetheir differences in composition. Conventional GBs consist of a solid matrix and voids, whichcontain a mixture of free moisture and air. PCMs—when included in the product recipe—aretrapped among these voids. The thermal conductivity of the air–vapor–water mixture inside thevoids depends strongly on the amount of moisture in the voids because the thermal conductivity ofwater is ca 23 times higher than the thermal conductivity of dry air [21]. During GB dehydration,the free and chemically bound water evaporates, resulting to the decrease of the moisture content, aswell as to the increase of the volume porosity. Hence, the voids are filled with the low thermalconductivity air–vapor mixture, which decreases the overall thermal conductivity. The relative localincrease of thermal conductivity above 120°C is associated with the formation of CaSO4-III fromCaSO40.5H2O. Note that the thermal conductivity of CaSO4-III is higher than the thermalconductivity of CaSO40.5H2O [22]. During the evaporation of PCM (>145°C), the porosity of thePCM-GB increases, and it results to a decrease of its thermal conductivity. Finally, the (small)reduction of the thermal conductivity observed at temperatures >200°C, where all the chemicallybound water and the PCM are evaporated, could be associated to the reshaping of the anhydritecrystal mesh.

3.2. Small-scale experiments

As shown by the DSC experiments, the external surfaces of the examined GBs, as well as the PCM-GBcore material, could be flammable under oxidized and high temperature conditions. In order to assessthe flammability of these components, small-scale experiments were performed with ‘as delivered’ and‘no finishing’ samples. In the first case, the samples composing the final specimen were used asdelivered, while in the second case, one external finishing of each sample (at the interface planeshown in Figure 3) was removed, resulting to 1-mm thickness reduction of each sample.

3.2.1. ‘As delivered’ samples. Figure 6 shows the temperature evolution on the surfaces, at theinterface and around the GB specimen as measured by the installed thermocouples for the ‘asdelivered’ samples (refer to Figure 3 for the thermocouple location). Prior to the experiment, the airtemperature inside the oven was stabilized at 300°C, but it dropped substantially when the door wasopened in order to introduce the specimen (curves Air1 and Air2 in Figures 6a and 6d, respectively).

Focusing on the temperature evolution at the interface plane of the specimen (curves C1, C14, andC4 in Figures 6c and 6f, respectively), two main dehydration stages can be observed. The first stagecorresponds to the first dehydration reaction, starting at ~122°C for both GBs, where theCaSO42H2O transforms to CaSO40.5H2O. The second stage corresponds to the second dehydrationreaction, starting at about ~174 and ~188°C for R-GB and PCM-GB, respectively, where theremaining water dissociates from the crystal lattice and the CaSO40.5H2O is transformed to CaSO4-III.The total separation of the two dehydration stages is associated to the increase of water vapor partialpressure inside the GB samples [1,3,23].

It is noted that the set point for the air temperature inside the oven was set to 300°C (oven’smaximum operating temperature). However, the recorded temperatures inside the sample (curvesC1, C14, and C4 in Figures 6c and 6f, respectively) and on the surfaces (curves Sf1, Sf2, Sb1, and


Figure 6. Temperature evolution indicated from the thermocouples in the ‘as delivered’ sample: (a) R-GB airthermocouples, (b) R-GB surface thermocouples, (c) R-GB interface thermocouples, (d) PCM-GB air

thermocouples, (e) PCM-GB surface thermocouples, and (f) PCM-GB interface thermocouples.


Sb2 in Figures 6b and 6e, respectively) exceeded that temperature. According to the DSCmeasurements (Figure 4), during the oxidation of the PCM and the external finishing of the GBsamples, a significant amount of energy is released. This energy increases the temperature within thespecimen above the temperature of air inside the oven.

In the R-GB case (Figure 6c), a short circuit was created in the C4 thermocouple cabling, and thus,the oven’s temperature was measured (air temperature), instead of the material’s temperature. The dataloss of C1 and C4 curves, at temperatures higher than 300°C, is because of failure of the utilizedthermocouple.

As shown in Figure 6f, the temperature evolution at the interface plane of the specimen at positionsC1 and C14 (curves C1 and C14, respectively) is similar to the temperature rise recorded by thethermocouple located at the edge of the specimen at position C4 (curve C4) but with somequantitative differences. The insulation used around the specimen ensured that heat transfer wouldoccur mainly in one dimension. No damage was observed at the end of the experiment in theinsulation, as shown in Figure 1 (the photo was taken at the end of the experiment), that couldjustify the discrepancy shown in Figure 6f. As the temperature increases above 122°C at theinterface plane, where the thermocouples are positioned, the produced vapor mass increasessignificantly, leading to an increase of the local vapor pressure. The ‘high’ pressure vapor migratespreferably in directions of lower resistance such as local cracks, material inhomogeneities, or theedges of the specimen. Thus, in position C4, which is near the corner of the specimen, vapormigrates through the lateral surfaces of the specimen that are not perfectly sealed and not throughthe main direction.

Finally, it should be mentioned that the observed arbitrary and unusual peaks are because of thenonperfect contact of the thermocouples with the surfaces of the specimens. Nevertheless, thequalitative and quantitative analysis of the results is not affected by this issue, and thus, these peakscan be ignored.

3.2.2. ‘No finishing’ samples. Figure 7 illustrates the temperature evolution on the surfaces, at theinterface plane, and around the GB specimen for the ‘no finishing’ samples (thermocouple locationshown in Figure 3). The dehydration process has the same characteristics as in the ‘as delivered’


Figure 7. Temperature evolution indicated from the thermocouples in the ‘no finishing’ samples: (a) R-GBair thermocouples, (b) R-GB surface thermocouples, (c) R-GB interface thermocouples, (d) PCM-GB air

thermocouples, (e) PCM-GB surface thermocouples, and (f) PCM-GB interface thermocouples.


specimen. It is again observed that the measured temperature near the edge of the sample (C4) isaffected by the lateral heat losses and water vapor mass transfer.

In the case of R-GB (Figure 7c), there is a small temperature increase above 300°C at the interfaceplane (curves C1, C2, and C3). This is owed to the GB’s crystal mesh reorganization exothermicreaction and not to paper oxidation (the external finishing at the interface plane of the specimen wasremoved). On the other hand, in the PCM-GB case (Figure 7f), the significant temperature riseleading to temperatures higher than 300°C is mainly owed to the evaporation and oxidation of thePCM-GB core material (paraffin mixture and PMMA).

Figure 8. Temperature evolution at the center for each ‘sandwich’ configuration.



3.3. Comparative assessment

Based on the DSC analysis and on the small-scale experiments, the overall fire behavior of the R-GBand PCM-GB can be discussed. Figure 8 summarizes the temperature evolution at the interface planeof the specimen for all the small-scale experiments. Results suggest that energy absorption/releasephenomena occurring within the examined specimens during high temperature exposure can belinked to two main temperature regions. The low temperature region, up to ca 300°C, is dominatedby the dehydration of the gypsum-based specimens (both R-GB and PCM-GB). In this region, theproduced water vapor acts as a fire retardant, delaying the temperature increase and fire spreadthrough the specimens. The temperature region between 300 and 550°C is dominated by theevaporation and oxidation of the PCM and of the external finishing for both the R-GB andPCM-GB specimens. The temperature increase through the specimens is enhanced and acceleratedin this temperature range.

4. CONCLUSIONS

Comparative assessment of a regular and a latent heat storage GB was undertaken using thermalanalysis techniques. DSC, thermal conductivity, and mass loss measurements, as well as asmall-scale experimental approach, were combined in order to assess the fire behavior of theexamined GB types. The results revealed the different fire behavior of the GBs at differenttemperature ranges. At temperatures up to 300°C, the dominant thermochemical process that takesplace is the dehydration of the free moisture and chemically bound water contained in the GBs. Theproduced water vapor acts as a fire retardant, delaying the temperature rise within the GBs. Attemperatures higher than 300°C, the evaporation and oxidation of the PCM and the externalfinishing enhance and accelerate the temperature rise within the GBs. Hence, special care should betaken into consideration when such materials are utilized in wall configurations, where, under fireconditions, the examined phenomena may coexist inside the assembly. Further experimental andtheoretical studies are required in order to examine and quantitate the effect and the interaction ofthese phenomena occurring in specific configurations exposed to fire conditions.

NOMENCLATURE

d

Copyright © 2014 John Wiley & Sons, Ltd.

Thickness

FirD

[m]
k Thermal conductivity [Wm�1 K�1] Y Mass fraction
Greek symbols
ρ Density [kgm�3] Subscripts 0 Ambient
Abbreviations
AVW Air vapor water DSC Differential scanning calorimetry GB Gypsum board PCM Phase change material PCM-GB Phase change material gypsum board R-GB Regular gypsum board
ACKNOWLEDGEMENT

The authors acknowledge the financial support of the Fire-Facts project within the frame of ARISTEIAaction (operational program ‘Education and Lifelong Learning’) that is cofinanced by Greece and theEuropean Union.

e Mater. (2014)OI: 10.1002/fam


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fire behavior of regular and latent heat storage gypsum boards

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