Synthesis and thermal behavior of inorganic–organic hybrid geopolymer composites

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Synthesis and Thermal Behavior of InorganicOrganicHybrid Geopolymer CompositesM.Hussain,1 R. Varely,2 Y. B.Cheng,1 Z.Mathys,3 G. P.Simon11School of Physics and Materials Engineering, Monash University, Wellington Rd, Clayton, Vic-3168, Australia2CSIRO, Molecular Science, Clayton, Vic-3168, Australia3DSTO, Platform Laboratory, Melbourne, AustraliaReceived 18 November 2003; accepted 1 August 2004DOI 10.1002/app.21413Published online 26 January 2005 in Wiley InterScience (www.interscience.wiley.com).ABSTRACT: Inorganic geopolymer potassium alumino-silicate was prepared at room temperature by the reaction ofkaolin, potassium silicate, and potassium hydroxide solu-tion and was dispersed in situ into an epoxy matrix byvarious proportions to fabricate novel inorganicorganichybrid geopolymer composites. The formation of inorganicgeopolymer with respect to time was monitored by X-raydiffraction and FT-IR analysis and conrmed that 30 min isrequired to complete the geopolymerization. When geopoly-mers were properly mixed at different ratios with organicpolymers such as epoxy and cured, these hybrid polymersexhibit signicant thermal stability. Pure kaolin was alsoincorporated into the epoxy matrix to compare the change inchemical and thermal properties. Cone calorimetry resultsshowed about 27% decreased in rate of heat release (RHR)on addition of 20% pure kaolin. However, about 57% ofRHR was decreased on addition of only 20% geopolymer.Evaluation of CO2 and CO were found to be minimum 2.0and 0.7 kg/kg, respectively, for hybrid geopolymer compos-ites compared to very high yield for epoxy at 3.5 kg/kg after200 s of ignition. The current study shows that due to thehigh thermal stability of hybrid geopolymer composites, thenovel hybrid geopolymer composites have the ability to bepotential candidates to use in practical application wherere is of great concern. 2005 Wiley Periodicals, Inc. J ApplPolym Sci 96: 112121, 2005Key words: geopolymer; thermal properties; epoxy; hybridcalorimetry; cone calorimetryINTRODUCTIONMany advanced polymer composites consist of an or-ganic phase of highly crosslinked resins, often fromthe epoxy family. The fusible, soluble starting materi-als can incorporate various llers, such as glass, liquidcrystal polymer (Kevlar) bers, carbon bers, ceramicparticulates, and clays, in a variety of ways to improvethe nal physical, mechanical, and thermal properties.However, the ammability of the virgin polymer ma-trix or additive modied polymer limits the use ofthese materials in many applications, such as marineplatforms and ships, automobiles, and military andcommercial spacecrafts, where re hazard is an im-portant design consideration13 since most of the or-ganic polymers soften and ignite at temperatures of200500C, which are characteristic of fuel re expo-sure conditions. Carbon bers and glass bers areinherently re resistant, and signicant progress hasbeen made in recent years to develop new, high-tem-perature, thermo-oxidatively stable bers from boron,silicon carbide, and ceramics.4 However, these arecomplex and costly to make. Moreover, the presenceof the organic phase in ber-reinforced compositeswill collapse or degrade at higher temperature, de-stroying the total structure.Various methods have been proposed for forminginorganic protective layers on the surface of burningpolymers, but their positive effect is mostly accompa-nied by certain disadvantages. Inorganic ller parti-cles act through a dilution effect and reduced heatfeedback. Silica additives of high surface area are mostefcient as these particles accumulate on the surfaceinstead of sinking into the polymer melt.5 The physicalnetwork formed by such additives in the polymer meltmay reduce dripping but, on the other hand, the sameeffect signicantly restricts the processability of suchsystems. Similar problems may occur when porousllers like zeolites are used in higher concentration,which allows the polymer chains to penetrate. Atlower concentration, zeolites can be combined advan-tageously with intumescent ame retardant addi-tives.6A current area of much interest involves polymer-clay (layered silica) nanocomposites, which, when in-troduced in intercalated or exfoliated (delaminate)within the matrix, upon burning, may accumulate onthe surface of the polymer during burning and form abarrier layer to either outgoing degradation productsor incoming gases. Their effect is clearly indicated bythe reduced rate of heat release of horizontal samplesCorrespondence to: M. Hussain.Journal of Applied Polymer Science, Vol. 96, 112121 (2005) 2005 Wiley Periodicals, Inc.in the cone calorimeter.7 Recent work also suggeststhat even very low levels (14%) of nano-clay lowerthe peak heat release rate in a cone-calorimeter byabout 30%.In addition, other strategies, such as the use of poly-mer precursors, which lead to formation of a protec-tive ceramic coating in the presence of re, have beenproposed by Anna,8 and are able to improve the ther-mal stability and re performance. Although such sys-tems have been examined in a number of studies, theoptimization of the composition and the mechanismhas not been completed.9Looking at the broader picture, it has been thoughtthat new inorganic materials may increasingly replaceconventional plastics. This has been proposed to leadto the reduction of world pollution resulting fromby-products of plastics manufacturers as well as theuse and disposal cycle of these materials. In particular,a family of new materials called geopolymers (polysi-lates) has emerged during the last decade as one of themost promising replacement candidates for plastics incertain applications, and even ceramics, since theyhave appropriate physical properties of the latter ma-terials class.1013 The manufacture of polysilates doesnot create CO2 emissions, they can be made fromrecycled mineral wastes or naturally occurring geolog-ical materials, and they provide excellent acid and reresistant and mechanical properties. Although similarto zeolites in chemical composition, they have anamorphous microstructure. The term geopolymerwas rst used by Davidovits1113 to describe a familyof mineral binders closely related to articial zeolites.Most waste materials, such as y ash, slag of blastfurnaces, and mine tailing, contain sufcient amountsof reactive alumina and silica that can be used assource materials for in situ geopolymerization reac-tions. The most attractive geopolymers (polysilates)are inorganic polymers made from aluminosilicatessince they can be synthesized at low temperatures andhave useful properties, such as high compressivestrength, and are stable at temperatures up to 13001400C. By changing the Si/Al ratio, it is possible toproduce products with very high re resistant prop-erties. Polysilates are readily synthesized from naturalaluminosilicates, such as kaolinite, a very abundantsource of alumina and silica. The formation ofgeopolymeric materials follows the same route as thatfor most zeolites. Geopolymers are formed by thecopolymerization of alumino and silicate species,which originate from the dissolution of silicon andaluminum-containing source materials at a high pH,in the presence of soluble alkali metal silicates. Thecurrent commercial use of geopolymers, compared toplastics, for example, is limited because of the com-plexity of processing on a large scale, high density,and problems with machining and molding, and mostimportantly, their brittleness.Geopolymers are linear poly(metasilicate) with tet-ra-coordinate aluminate crosslinks. The geopolymer-ization involves the chemical reaction of aluminosili-cate oxides (Al3 in iv-fold coordination) with alkalipolysilicates, yielding polymeric Si-O-Al bonds; theamorphous to semicrystalline three dimensionalsilico-aluminate structures are of the poly(silate) type(-Si-O-Al-O-), the poly(silate-siloxo) type(-Si-O-Al-O-Si-O-), and the poly(Silate-disiloxo) type (-Si-O-Al-O-Si-O-Si-O-). The atomic ratio Si : Al in the poly(silate)structure determines the properties and applicationareas for which they are relevant. A low ratio Si : Al (1,2, or 3) initiates a three-dimensional network that isvery rigid. A ratio of 3 creates a two-dimensionalstructure, which is exible. However, Si : Al ratioshigher than 15 result in a material with a linear poly-meric nature.13This article focuses on a different approach involv-ing geopolymers, the use of their re retardant phaseto incorporate them into crosslinked polymeric struc-ture systems. In so doing, we make use of the process-ability and properties of the crosslinked polymers(such as epoxy resins), in combination with thegeopolymers, to get polymeric characters with hightoughness, strength, and re resistant materials. Therst system reported involves choice of a standard,bi-functional epoxy resin diglycidyl ether of bisphenolA (DEGEBA) to be incorporated with the geopoly-mers. The results will be compared with physicallyblended kaolin (the primary source of the geopoly-mer) with epoxy resins to investigate the ability ofgeopolymers within epoxy resins to act as the reretardant component. Incorporation of geopolymersinto organic polymer systems has been demonstratedfor the rst time and has not been reported yet.EXPERIMENTAL PROCEDURESMaterialsKaolin (HR1-F grade) with a particle size distributionof 38.20 m was procured from Commercial Minerals,Sydney, Australia. The potassium silicate solution wasobtained from PQ Australia Pty. Ltd. Potassium sili-cate composition was SiO2/K2O 2.00, SiO2 29.3(wt %), and K2O 14.5 (wt %), with density 1.42gcm3. Table I shows the chemical composition andphysical properties of kaolin. 5M KOH solution wasprepared in the laboratory from KOH pellets fromBdh, Merck Pty. Ltd. The epoxy resin used in thestudy was diglycidyl ether of bisphenol-A (DGEBA),commercially known as DER-331, from Dow ChemicalCompany, Australia. The curing agent used in thisexperiment was a mixture of 3,5-diethyltoluene-2,4-diamine and 3,5-diethyltoluene-2,6-diamine (Etha-cure-100) obtained from Albemarle Corp., USA.INORGANICORGANIC HYBRID GEOPOLYMER COMPOSITES 113SynthesisInorganic geopolymers were synthesized by the reac-tion of kaolin, potassium silicate, and potassium hy-droxide solution at room temperature. Initially, thedesired amount of potassium silicate was mixed witha 5M potassium hydroxide solution and then 20 gkaolin was added and mixed at different periods oftime. The viscous mix was then added to a mixture ofDGEBA epoxy resin and curing agent with constantstirring for 15 min. The mixture was then placed intothe PTFE-coated molds and was cured at 60C for 6 h,followed by post curing at 180C for 2 h.To fabricate clay-dispersed composites for compar-ison, 20 g of pure kaolin was mixed with the mixtureof DGEBA epoxy resin and curing agent for 1 h. Themix was then placed in a PTFE-coated mold, cured at80C for 6 h, followed by post curing at 180C for 2 h.The sample was then cut, ground, and polished forthermal analysis, cone calorimetry, and microstruc-ture analysis.CharacterizationA range of techniques were used to monitor cure, andcharacterize the nal products. The formation ofgeopolymers within the epoxy matrix was character-ized by X-ray diffraction analysis by Rigaku wide-angle goniometer. An acceleration voltage of 40 kVand current of 22.5 mA were applied using Ni lteredCu K radiation. Fourier transform infrared (FT-IR)was recorded on a PerkinElmer FT-IR spectrometer.The mechanical loss tangent (tan ), in particular thedetermination of the glass transition temperature (Tg),of the epoxy phase of the cured samples was deter-mined on a Rheometric scientic dynamic mechanicalthermal analyzer, DMTA IV. The cured samples wereclamped in a medium frame using a small centerclamp in the dual cantilever mode. Frequency sweepscans were performed from 80 to 260C at 2C/minusing frequency 1Hz and having a strain of 1%.Thermo gravimetric analysis (TGA) was performedon the cured samples using a TG-92 Setaram thermalanalyzer. The thermographs were obtained at a heat-ing rate of 10C/min using 1015 g of the powderedsample. The experiments were made in a static airatmosphere.Fire performance tests, including time to ignition(TTI), rate of heat release (RHR), time to reachmaximumRHR, smoke density, carbon monoxide and carbon di-oxide evolution, and sample mass loss, were determinedby cone calorimeter in accordance with the proceduredescribed in an ASTM standard method.14 The heat uxproduced was 50kW/m2 on the specimen, which had anexposed surface of 100 100 mm. The testing equip-ment consisted of a radiant electric heater in trunk-conicshape, an exhaust gas system with oxygen monitoringand instrumentation to measure the gas ux, an electricspark for ignition, and a load cell to measure the weightloss. The test was terminated after 500 s of exposure. TTImeasures the time to achieve sustained aming combus-tion at a particular cone irradiance. Smoke density ismeasured by the decrease in transmitted light intensityof a helium-neon laser beam photometer, and expressedin terms of specic extinction area (SEA), with units ofm2/kg. For RHR, themaximumvalue and the average to180 s after ignition and the overall average values aredetermined. The total mass after the desired test timewas calculated as a percentage of the initial samplemass.RESULTS AND DISCUSSIONXRD analysisFigure 1 shows the X-ray diffraction patterns of kaolinas received and the geopolymer-epoxy composites de-pending on the geopolymer synthesis (mixing withkaolin, potassium silicate, and potassium hydroxide)time (5, 15, and 30 min) followed by 15 min mixingwith the epoxy matrix. From Figure 1, it is clear thatthe distinct peaks A, B, C, D, and E of kaolin can beobserved at 12.0, 19.221.2, 24.0, 26.5, and 35.040.02-theta angle. However, no peak was observed at 12.0degrees for kaolin (001) in geopolymer-epoxy compos-ite mixes at different times between 5 min30 min. Thekaolin peak at position B is signicantly lower inintensity in the 5 min mix synthesized geopolymer-epoxy composites, and gradually disappears when thegeopolymer is synthesized for 1530 min. Similarly,kaolin peaks at positions C, D, and E signi-cantly decrease, nally disappearing with longergeopolymerization times. No crystalline peak was ob-served in geopolymer-epoxy composites after reactionfor 30 min. This XRD pattern suggests that during thegeopolymerization of kaolin, the kaolin crystallinestructure converts to an amorphous inorganic poly-mer due to the formation of an Si-O-Al network. TheTABLE ITypical Chemical and Physical Properties of KaolinComposition/PropertyChemicalComposition/units Wt %/valueSilica SiO2 53.3%Magnesia MgO 0.2%Alumina Al2O3 30.3%Ferric Oxide Fe2O3 1.2%Lime CaO 0.2%Potash K2O 0.5%Soda Na2O 0.2%Titania TiO2 2.6%Loss on ignition (1000C) 11.4%pH (20% slurry) 8.4Specic gravity - 2.71Surface area (cm2/g) 25,300Oil absorption (mls/100g) 50Bulk density g/cm3 0.6114 HUSSAIN ET AL.disappearance of kaolin characteristic peaks at AEconrms a complete dissolution of crystalline kaolinparticles during the geopolymerization. It is also con-rmed from the XRD pattern that complete geopoly-merization of kaolin required 1530 min.FT-IR analysisThe formation of geopolymers was further conrmedby FT-IR analysis. Figure 2 shows the FT-IR spectrumof DGEBA epoxy, kaolin, 20% geopolymer (5 minFigure 1 X-ray diffraction of kaolin and geopolymer-epoxy composites at various mixing times.Figure 2 FT-IR spectra of kaolin-epoxy and geopolymer-epoxy composites.INORGANICORGANIC HYBRID GEOPOLYMER COMPOSITES 115mixing), and 20% geopolymer (30 min) mixing. Char-acteristic kaolin stretching vibration OH peaks wereobserved at 3600 and 3610 cm1. However, thesepeaks gradually decreased with mixing time and -nally disappear when mixed for 30 min due to geopo-lymerization. The broad peak assigned at 3428 cm1 isdue to the presence of an OH group in epoxy mole-cules. The phase transformation into geopolymers isFigure 3 DMTA spectra of kaolin-epoxy and geopolymer-epoxy composites.Figure 4 TGA spectra of kaolin-epoxy and geopolymer-epoxy composites.116 HUSSAIN ET AL.thus shown by the decrease and disappearance ofvarious kaolin bands, namely the Si-O-Si symmetricstretching band at 710 cm1.15 Al-OH stretching inkaolin also decreased gradually with mixing time, andnally disappeared due to the formation of Al-O-Sibonds at 910 cm1. The band at 540 cm1 is charac-teristic of the octahedral co-ordinate Al shifting tohigher wavelength. The band at 465 cm1 in kaolin-DGEBA composites was found for kaolin bendingSi-O-Si and O-Si-O. However, this gradually disap-peared due to formation of the geopolymer zeolitephase.16Thermal properties of compositesDynamic mechanical thermal analysis (DMTA)The glass transition temperature and dynamic-me-chanical properties of DGEBA, 20% kaolin-DGEBA,and 20% geopolymer-DGEBA were determined. Fig-ure 3 shows the tan spectra from dynamic mechan-ical analyses of the cured DGEBA and its composites,respectively. Cured DGEBA showed a Tg around201.0C; addition of kaolin reduces this value to 195C.The effect on the Tg of clay addition has been widelystudied by many researchers, some reporting an in-crease in Tg,17,18 others nding a slight decrease or nochange.19,20 Becker et al.21 reported that a decrease inTg of clay-modied composites is due to interferenceof the clay with crosslink density, epoxy homopoly-merization, and plasticization. The incorporation ofgeopolymers into the DGEBA epoxy showed an evenlower Tg of around 170C. The geopolymer-DGEBAcomposites prepared by mixing for 5 min showed aneven lower Tg than those of composites prepared bymixing for 30 min. This conrms that complete geopo-lymerization is not able to occur when mixed for 5 minalthough it is complete after mixture for 30 min. Thelower crosslink density of kaolin-modied DGEBAcaused by the introduction of the ller is conrmed bythe greater height of the tan peak, shown in Figure 3,which is indicative of greater relaxation strength. Thelower relaxation strength and Tg of geopolymer-mod-Figure 5 RHR spectra of kaolin-epoxy and geopolymer-epoxy composites.TABLE IIThermal Properties of DGEBA Epoxy and Modied DGEBA-Epoxy CompositesTemperature (C)at 10% wt lossChar yield400CChar yield450CChar yield600CPure DGEBA epoxy 463 100.0% 90.0% 16.0%20% kaolin modied-DGEBA 384 90.0% 82.0% 46.5%20% geo-poly modied-DGEBA (5 min mix) 382 89.0% 82.0% 42.0%20% geo-poly modied-DGEBA (30 min mix) 380 88.0% 82.0% 39.0%INORGANICORGANIC HYBRID GEOPOLYMER COMPOSITES 117ied composites are believed to be due to structuralinhomogeneity, later explained by SEM images.Thermogravimetric analysis (TGA)Thermogravimetric analysis was performed to ex-amine the effect of geopolymer and kaolin additionon the thermal stability of cured DGEBA. Figure 4shows the weight loss for the unmodied DGEBAepoxy, kaolin modied DGEBA, and differentgeopolymer-DGEBA composites. Pure DGEBA ep-oxy resin shows a one-step degradation mechanism.However, kaolin or geopolymer modied DGEBAshowed a three-step degradation mechanism. TableII reects the thermal properties of pure DGEBAepoxy resin and modied-DEGBA epoxy resin. Inthe unmodied, cured DGEBA system, initial deg-radation commences at around 430C; however, therate of degradation signicantly increases above450C and results in a char yield of 16% remainingat 600C. The degradation temperature at 10%weight loss was 463C for DGEBA and around 380384C for modied DGEBA composites. These re-sults indicate that the thermal stability of the mod-ied epoxy resin at lower temperature (400C) isfound not superior to that of the pure DGEBA epoxyresin. However, the char yield of the modied ep-oxy resin at 600C is much higher than that of theunmodied DGEBA epoxy resin. High char yieldformation prevents the production of combustiblegases material and thus decreases the thermal con-ductivity of the surface of the burning materials.22Figure 6 SEA spectra of kaolin-epoxy and geopolymer-epoxy composites.TABLE IIICone Calorimetric Data Measured With an Irradiance of 50kWm2Fire properties DGEBA20% kaolin-DGEBA20% geo-poly-DGEBATime to ignition(s) 65 69 60Peak RHR (kW/m2) 1396 1100 735Av. HRR(kW/m2) 399.8 426 364.1Av. HRR at 180s 501 562.5 471Time to max HRR(s) 155 170 185Av. effective heat of combustion (MJ/kg) 21.2 25.3 24.7Av. CO yield (Kg/Kg) 0.0454 0.06 0.059Av. CO2 yield (Kg/Kg) 1.48 1.99 1.955Total heat evolved (MJ/kg) 89.65 115.24 95.68Mass loss % 82.8 73.9 74.7118 HUSSAIN ET AL.Flammability testing by cone calorimetryThe cone calorimeter provides important informationon the combustion behavior of a material under ven-tilated conditions. The peak rate of heat release of amaterial is one of the important factors to determinethe potential behavior during re. Figure 5 shows therate of heat release (RHR) of unmodied DGEBA andmodied DGEBA variation with time at a heat ux of50 kWm2. The peak rate of heat release for DGEBA ishigh at around 1400 kWm2 after 150 s. However, 20%kaolin modied DGEBA has a lower peak rate ofrelease at 1100 kWm2, signicantly reduced by 21.5%compared to unmodied DGEBA. In contrast, DGEBAmodied with 20% geopolymer showed a peak releaseFigure 7 CO2 emission of spectra of kaolin-epoxy and geopolymer-epoxy composites.Figure 8 CO emission spectra of kaolin-epoxy and geopolymer-epoxy composites.INORGANICORGANIC HYBRID GEOPOLYMER COMPOSITES 119rate at 702 kWm2, which is 47% lower than that ofunmodied DGEBA. An increase in ame retardancyin modied DGEBA can be attributed to the residualmasses or char obtained during ring. A higher per-centage of mass residue or char indicates a condensed-phase ame retardance mechanism.23 Other importantparameters obtained from the epoxy and modiedepoxies by cone calorimetry are given in Table III.Evaluation of the re performance of epoxy resinsinvolves quantifying smoke generation at specic ex-tinction areas (SEA) and quanties production of COand CO2. SEA, which measures the total obscurationarea of smoke produced, divided by the total massloss during burn. Figure 6 shows the SEA of DGEBAand kaolin/geopolymer modied DGEBA as a func-tion of time. The SEA value of DGEBA was found tobe maximum around 200s and decreased rapidly.However, modied DGEBA showed a relatively lowervalue at 200s and maximum value observed at 250 sand 325 s for kaolin and geopolymer modiedDGEBA, respectively. This can be explained by thefact that unmodied DGEBA readily converts intosmoke more easily when it burns and does so over alonger period of time. CO2 emission during burningshows in Figure 7 that the CO2 emission rate is alwayshigher for the unmodied DGEBA system comparedto the modied epoxy resin system. The maximumCO2 emission was observed after 200s of ignition. Thelower production level of CO at 200s of modied andunmodied DGEBA is shown in Figure 8. However,CO level drastically increases for unmodied DGEBAresins after 200s and reaches maximum CO produc-tion of 0.45 kg/kg with respect to time. CO emissionfor the modied DGEBA system remained constantfor a longer period of time. The higher CO productionof unmodied DGEBA indicates incomplete combus-tion, and possible for the gas phase activity. Thus, theaddition of kaolin or geopolymer showed the reduc-tion of RHR.Fire performance of a material can also be calculatedfrom the re performance index (FPI), which is theratio between the time of ignition (time) and the peakrate of heat release (RHR). Table IV shows the reperformance index of the unmodied-DGEBA and themodied DGEBA system. DGEBA, without any mod-ication, shows the lowest re performance at 0.046sm2/kW. However, when DGEBA is modied withFigure 9 SEM images of spectra of kaolin-epoxy andgeopolymer-epoxy composites.TABLE IVFire Performance Index of Unmodied DGEBA andModied DGEBA SystemDGEBA systemPeak RHR(kW/m2)Time toignition(s)FPI(sm2/kW)DGEBA only 1396 65 0.04620% kaolin-DGEBA 1100 69 0.06220% geopolymer-DGEBA 735 60 0.081120 HUSSAIN ET AL.kaolin, the FPI increased to 0.062, an increase of 35%.In comparison, the geopolymer modied DGEBA FPIincreased to 0.081 sm2/kW and improved 76%.Microscopic morphologyFigure 9 shows the SEM micrographs of 20% kaolinmodied-DGEBA and 20% geopolymer-DGEBAmixed for 5 min and 30 min, respectively. It is clearfrom Figure 9(a) that kaolin particles were homoge-neously dispersed into the DGEBA matrix. No ag-glomeration was observed. However, in the geopoly-mer-DGEBA system, a different microstructure wasobserved. When the geopolymer was prepared by 5min mixing, a discontinuous island like structure wasobserved, as shown in Figure 9(b). This discontinuousisland like structure gradually increased to a cocon-tinuous structure when the geopolymer was preparedby 30 min mixing, as observed in Figure 9(c). It isevident from the micrographs that incorporation ofthe geopolymer into the organic polymeric system ispossible with good microstructure. This type of micro-structure, however, showed a lower relaxation behav-ior and Tg but exhibited higher thermal stability andhigher re performance capability. Other properties ofmaterials, mainly the mechanical properties, beforeand after ring tests of the composites should be in-vestigated further.CONCLUSIONSIn this experiment, inorganic polymers (geopolymers)were incorporated into an epoxy resin system to in-vestigate the re performance capability. The additionof only 20% kaolin into the DGEBA epoxy matrixshows the thermal stability was improved. This im-provement was further increased when 20% geopoly-mer was added into the epoxy system. The probabilityof chemical bonding between the inorganic polymerand the organic polymer is also under investigation.References1. Demarco, R. A. Composites Applications at Sea, Fire RelatedIssues. Proc. 36th Int. SAMPE Symposium, 1518 April 1991, pp.19281938.2. Hathaway, W. T. Fire Safety in Mass Transit Vehicle Materials.Proc. 36th Int. SAMPE Symposium, 1518 April 1991, pp. 19001915.3. Hill, R. G.; Eklund, T. I.; Sarkos, C. P. Aircraft Interior Panel TestCriteria Derived from Full-Scale Fire Tests. DOT/FAA/CT 85/23, 1985.4. Engineering Materials Handbook, Vol. 1, Composites; ASM In-ternational: Metals Park, OH, 1987.5. Kashiwagi, T.; Gilman, J.; Butler, K.; Harris, R.; Shields, J.;Asano, A.; Lewin, M., Eds. 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