New ecologicalfire proof foam materials

"SiFOAM"

What are they?Porous, fully inorganic materialspossesing properties offire resistant building materialsbut prepared at much lowertemperatures (below 350 oC).

Sol­gel foamsilicates

How are they obtained?They are prepared bythe sol­gel processand thermal induced foaming using:

Conventional heatinglow cost method (common lowtemperature furnaces),large forms,different shapes,boards (sandwich panels).

Microwavesfoaming in situ at a building site,forming or molding (e.g. pipes),with some exceptions like metalsubstrates.

Electrofoamingfoaming in situ at a building site,all types of substrates.

Sol­gel foammaterials

Form

Technology and materials allow toreceive different forms, directlyshaped into:­ large forms,­ different shapes,­ boards (panels),­ foaming in situ at a building site,­ forming or molding (e.g. pipes).

Material can alsobe cut with standard toolsof construction.

Sol­gel foamsilicates

CompositionMaterial possesses verygood adhesiveproperties what providespossibility of receivingsandwitch type panelsafter direct:application to:

­ sheet metal,­ ceramics,­ aluminum foil,­ glassMaterials can also beapplied and sticked usingsol gel.

Sol­gel foamsilicates

CompositionThe insulating material can befilled by:­ Phosphogypsum­ Industrial dust­ Glass wool­ Mineral­ Substances which cause vitrificationsurface structureThe resulting material has a differentcolor and physicochemical properties.

Sol­gel foamsilicates

The major properties of the proposedmaterial­ Non­flammable­ Insulating­ construction

Materials suitable for application in:­ Low­energy building­ Ecological building­ Fire Protection Systems­ Anti­terrorism systems­ Systems for military applications

Potential applications of thetechnology:­ Thermoinsulating Materials­ EMC materials­ Block of radiation

Brussels Innova 2011

Sol­gel foamsilicates

Thermoinsulating silica based refractory materialsobtained by the sol­gel methodM. Pietrzak, D. Hreniak, P. Psuja, W. Stręk

Institute of Low Temperature and Structure ResearchPolish Academy of Sciences, Wroclaw, Poland

AbstractProperties of new porous, non­flammable, thermal insulators are studiedand analyzed. Materials were fabricated by the sol–gel method mainlyfrom silicon oxide, sodium water glass and waste powders (slimic,diatomite). As a result of sintering at temperature below 650oC, blocks ofso­called foam glass were obtained. Basic properties such as a thermalconductivity, real and apparent densities and porosity were determined.Mechanical testing, chemical analysis, effects of heat and thermalresistance of obtained samples were studied. It is proofed, that presentedtechnology is safe for the natural environment and obtained materials aremechanically stable up to temperature 650oC and fireproof and intoxic upto 1300oC.

1. Introduction

At present, the market of thermal insulatingmaterials is dominated by polymericmaterials such as foamed polyurethane orpolystyrene. Unfortunately, in addition tomany benefits they have one very seriousdisadvantage: as all organic materials theyare flammable or unstable at hightemperatures. Moreover, during burningprocesses organic insulators emit gaseswhich may include, but not limited to, carbonmonoxide, carbon dioxide and oxides ofnitrogen, which may also present a risk torespiratory tract and eyes [1]. The materialsthat does not demonstrate the disadvantagesdescribed above and presenting comparablethermo insulating properties are so­called

foam glasses, viz. lightweight and opaqueinorganic amorphous materials having aclosed­cell structure. History of the foamedglass began in the ‘40s of the XXth century.At the beginning they were used for boatbuilding, replacing the cork. Industrialproduction of foam glass started after 1945 inthe United States. The foam glasses areproduced in result of by mixing granulatedglass material, water glass and foamingagents [2] by different methods [3­7]. Heatingof such slurry at higher temperature (usuallymax. 600oC) leads to formation of gases, andin the result of rapid foaming processporosity of material increases. After cooling,the obtained material is characterized by alarge number of pores filled with air or aspecific gas. The smaller volume the pores

causes that the heat transfer by convection isvery limited. Therefore, the best thermalinsulating properties should be expected forthe nanoporous material composed of veryresistant solid network and empty pores.Other important parameters that describe thefoam glass are: apparent density, thermalconductivity, absorption, heat resistance andcompressive strength. Investigation of theseparameters is required and essential todecide if the material could be used asinsulating constructive material.In this work, we report thermal and somemechanical properties of new thermalinsulating refractory (TIRS) foam glassesbased on sol – gel method.

2. Experimental

Different foam glass materials characterizedby different chemical composition andporosity by using sol – gel method wereprepared. Detailed procedure was describedelsewhere [8]. Briefly, the sodium water glassas a main precursor was used. Othercomponents were: silicon oxide, and wastepowders (slimic, diatomite). After mixing ofsubstrates, the samples were heated in steelforms in electrical oven for 2 hours at 600oC.As a result, blocks of foam glass wereobtained. Sizes and shapes of materialswere determined by the used forms. Someexamples of obtained samples are shown inFigure 1. All measurements were carried outaccording to standard requirements inLaboratory of Refractory Materials­Testing,Refractory Materials's Branch, Gliwice,Poland.

3. Results and discussion

The results of measurements of density andporosity of fabricated samples depending onaddition of admixtures carried out usingmercury porosimeter obtained are shown inTable 1. As it can be seen, typically for highporous materials, the apparent and realdensities differ by one order of magnitude.Total porosity of materials is directlyconnected with real and apparent densities

and can be calculated according to followingequation [9]:

One can note, that obtained values of totalporosity are typical for foam glass materials(usually 80­95%), however fabricated atmuch lower temperature (usually around1000oC) [4­7]

A key feature of any thermal insulatingmaterials is a thermal conductivity. Todetermine the thermal stability of thefabricated samples thermogravimetricanalysis (Thermal Gravimetrical Analysis(TGA) and Differential Thermal Analysis(DTA) were carried out. It was found, that formaterial containing of diatomite themaximum temperature cannot exceed 600oC,with slimic 700oC and without addition ofadmixtures 800oC. Above thesetemperatures the respective samplesundergo some phase transitions andadditionally weight loss making themeasurement unreliable. The value of thethermal conductivity coefficient (k)determined using hot­wire method for allstudied samples are presented in Figure 2.As it can be seen, the values of k parameterincreases with the temperature for allsamples by about factor of 2 in the rangefrom the room temperature to 600oC (from~0.14 W/mK to ~0.35 W/mK). Two the mostthermal resistant samples (the samplewithout any admixtures and the samplecontaining slimic) were found to have arelatively low thermal conductivity (~0.5W/mK) even up to 800oC. For comparison,at the room temperature, the expandedpolystyrene foam (EPS) is characterized byvalue of k parameter ~0.035­0.04W/mK, the

commercial foamed glass ~0.07­0.093W/mKand the extruded polystyrene foam (XPS)~0.03­0.04W/mK. However, because ofsoftening and thermal decomposition, theusual working temperature for polystyrenefoams is below 85oC and for referenced foamglass based on quartz sand, dolomite andsodium carbonate below 430oC [2].

In the next step, the materials were studiedalso at high temperatures. The sample offoam glass without addition ischaracterized by loss of weight 11.39%(833˚C) and 11.52% (1009˚C), the samplecontaining slimic – 7.01%(833˚C) and7.37%(1009˚C) and finally sample withdiatomite addition 5.52% (833˚C).

Basing on the obtained results,refractoriness of the materials wasdetermined according to standardsrequirements. The best refractoriness wasfound for the sample of a foam glasswithout any admixtures and reached1340˚C. For material with slimic resistancewas only slightly worse (1310˚C) and it wasfound to be the lowest for the samplecontainingdiatomite (950˚C).Additionally,refractorinessunder load wasalso measured andit was found to beagain the highest(540˚C) for thefoam glass samplewithout anyadmixtures. The

remaining samples fell down attemperatures 50˚C (diatomite) and 390˚C(slimic).Compressive strength was measured atroom temperature. Both samples, with slimicand diatomite are characterized by 100kPacompressive strength. Material with noadmixture has not mechanical resistance.For instance, typical thermal insulatingmaterials are characterized by such values ofcompressive strength: 120­140kPa (foamedglass), 60­200kPa (EPS), 150­700kPa (XPS)or 500­1700kPa (cellular glass) [2].

The chemical analysis of obtained foamedsilica materials was performed. The chemicalcomposition of all samples is presented inTable 3. As it can be seen all samplescontain more than 75% of silica.

The X­Ray Powder Diffraction patterns(XRD) collected for all as­prepared sampleshave mainly amorphous phase. After heatingat high temperatures (800 and 1000˚C) thepartially crystallization of the samplesoccurred. The quantitative and quantitativeanalysis of the obtained results are shown inTable 4.

Figure. 2. Thermal conductivity coefficient depending ontemperature and admixtures.

4. Conclusions

The new thermal insulating refractory silica(TIRS) foam glasses were fabricated by sol­gel technology. We have demonstrated thathigh quality thermal insulating silica basedmaterial may be obtained even with largeadmixture of waste powders (slimic anddiatomite) what is very attractive forrecycling technogies. Their morphologycharacteristics such as apparent and realdensities, and porosity were determined.Also the principal thermal characteristicswere measured. It was observed that theTIRS foam glasses were characterized bylow thermal conductivity and high thermalresistivity. One can suppose that thepresented TIRS foam glasses may findbroad applications as a thermal­insulatorsin high temperature technologies as well asin building constructions.

AcknowledgmentsAuthors thank to MSc.Eng. Halina Wałęga­Chwastek and Dr. Renata Suwak fromLaboratory of Refractory Materials Testing,Refractory Materials's Branch for a helpfuldiscussion.

References

[1] Modern Plastics, April 1978[2] M. Pfundstein, R. Gelert, M.H. Spitzner, A.Rudolphi, Insulating Materials, Regensburg 2008[3] United States Patent Application Publication,W. Gene Ramsey, “Foamed glass ceramiccomposite materials and a method for producingthe same”, US 2007/0194476 A1[4] United States Patent, K. Fukumoto, K.Kawanishi, R. Nakada, J. Yamano, “Skin­surfaced foam glass title” , 5069960[5] United States Patent, D. Solomon, M.Rossetti, “Foam glass manufacture”, 5516351[6] United States Patent, B. Wang, “Foam glassproduct”, 7459208 B2[7] United States Patent, Y. Seki, M. Nakamura,“Method for manufacture of foam glass”, 3951632[8] Patent pending No. P388764 (submitted10.08.2009)[9] F. Mear, P. Yot, R. Viennois, M. Ribes,Ceram. Int. 33 (2007) 543­550

Wrocław Research Centre EIT+ Ltd.ul. Stabłowicka 147

54­066 Wrocław, POLANDjaroslaw.majka@eitplus.plpatrycja.radek@eitplus.pl

Institute of Low Temperature and Structure ResearchPolish Academy of Sciences

ul. Okólna 2, 50­422 Wrocław, POLANDw.strek@int.pan.wroc.pld.hreniak@int.pan.wroc.plj.doskocz@int.pan.wroc.pl