thermiculite® 866

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Tel. +44 (0)1274 851273 Fax. +44 (0)1274 300303 www.flexitallic.eu Email. [email protected]

Thermiculite 866® is ahigh temperature sealingmaterial designed forsolid oxide fuel cellapplications. It is basedupon the mineralvermiculite and containsno organic binder or anyother organic component.

THERMICULITE®866

Thermiculite® 866 is giving excellent sealingservice in SOFC applications and is beingused by many SOFC development groupsaround the world.

Vermiculite is a natural sheet silicate mineralformed by hydro-thermal modification ofbiotite and phlogopite mica, it retains all thethermal and chemical durability of mica andremains electrically insulating. Like mica,vermiculite occurs as plate morphologyparticles, “books”, consisting of thousands of individual platelets, each nanometresthick, positioned one on top of the next.These particles can be opened up,“exfoliated”, like the pages of a book toreveal the individual platelets.

The traditional method of exfoliation isthermal and in this thermally exfoliated form vermiculite is well known as a thermalinsulation, a packaging material and in many other applications. Another method of exfoliation is chemical exfoliation. This produces a dispersion of individualplatelets which are separated from eachother. These platelets are highly flexible andconform to the surfaces of other particles tobind them together.

This binding action allows a sheet materialto be manufactured without any organicbinding agents being present, thusThermiculite® 866 consists just of thechemically exfoliated vermiculite and asecond filler material. The second fillermaterial is a very familiar mineral, talc, alsoknown as steatite or soapstone. Like micaand vermiculite, steatite is also a naturallyoccurring, high temperature stable, sheetsilicate mineral but it is characterized in thatit is very soft.

The combination of the chemically exfoliatedvermiculite with steatite results in a materialthat retains all the chemical and thermaldurability usually associated with mica but whichis very soft and conformable. The manufacturingmethod used to produce the Thermiculite® 866results in the vermiculite and steatite plateletsbeing aligned parallel to each other and parallelto the plane of the foil.

The softness of the material and the plateletalignment result in a material which compressesunder very low load to produce a compactedmaterial that offers a very tortuous, passage-stopping, path to any gas trying to permeatethrough it in the plane of the sheet orperpendicular to that plane. This means that the material has superb sealing characteristicscombined with peerless thermal stability. This makes it admirable for SOFC sealingapplications.

A gasket must first create a seal and must then maintain that seal for the required lifetime.Thermiculite® 866 is excellent in both of theserespects.

It is soft and highly conformable and thereforecreation of both macro and micro sealing isreadily achieved. Also, maintaining the seal is not a problem as it contains no organiccomponents that would result in relaxation orcreep and, in a connection stressed by bolts, lead to loss of surface load on the gasket.

Until Thermiculite® 866 has been raised to 570oCor more for the first time it has poor waterresistance so care should be taken to ensure thatin areas where condensed water is likely to bepresent that no part of the gasket that is notcompressed protrudes into the area where thatwater is likely to be present.

This Data Sheet refers to the material assupplied. The information contained hereinis given in good faith, but no liability will beaccepted by the Company in relation to same.

We reserve the right to change the detailsgiven on this Data Sheet as additionalinformation is acquired. Customers requiringthe latest version of this Data Sheet shouldcontact our Applications EngineeringDepartment.

The information given and, in particular, any parameters, should be used for guidancepurposes only. The Company does not giveany warranty that the product will be suitablefor the use intended by the customer.

CODE. PDS 436. 06/14

PRODUCT DATASHEET

Thermiculite® 866 cut gasket samples

Gasket Stress (MPa)

x



CODE. PDS 356. 06/14

PRODUCT DATASHEET

Availability:Thermiculite® 866 is available as either cutgaskets or in sheet form. Thermiculite® 866is made at a width of 450mm and can besupplied in lengths of up to 1000mm. A popular sheet size is 450mm x 350mm.

Thermiculite® 866 is supplied at a density of 1.9gm / cm3 and thicknesses on 0.3, 0.5,0.7 and 1.0mm are routinely stocked withintermediate thicknesses being available on special request.

Thermiculite® 866 can be easily cut intocomplex shape gaskets by the traditionalgasket cutting techniques but laser andwater jet cutting methods should not beused. As a service to customers a gasketcutting service at no extra charge isavailable. For confidential gasket shapes a non-disclosure agreement will be signed to ensure the confidentiality of the shapeinformation supplied.

Typical Physical Properties:Figure 1 shows the compressioncharacteristics of Thermiculite® 866 of the standard thicknesses.

Figure 2 demonstrates the creep resistanceof Thermiculite® 866 at ambient andelevated temperature. The temperature of 450oC being a test equipment limitation,not a material limitation.

Figure 3 compares the sealing performanceof Thermiculite® 866 and mica and clearlydemonstrates, even at ambient temperature,the superiority of Thermiculite® 866. At anelevated temperature the difference wouldbe greater.

Continued

COMPRESSION & RECOVERY OF TH866 VS STRESS1

CREEP CHARACTERISTICS OF THERMICULITE® 866, 0.47mm2

COMPARISON OF SEALING OF THERMICULITE® 866 & MICA3

Thickness (mm)

0.25

0.2

0.15

0.1

0.05

00 5 10 15 20 25

0.3mm0.5mm0.7mm1.0mm

xx x x x x

x

x

x

Time Elapsed (Hours)

Gasket Thickness (m

m)

0.46

0.44

0.42

0.4

0.380 2 4 6 8 10 12 14 16 18

Stress constant at 20MPa throughout test period

Ambient

450oC0.4279mm 0.4289mm

0.3963mm 0.3951mm

Gasket Stress (MPa)

Leak Rate (mg/m/s)

1.00E+00

1.00E001

1.00E-02

1.00E-03

1.00E-04

1.00E-05

1.00E-060 5 10 15 20 25

Mica 0.83mm

Thermiculite® 866 0.685mm

p = 1 barT = 20oCHe

Gasket Stress (MPa)

Leakage Rate (m

g/m/s x 10.4)

250

200

150

100

150

0

0 2 4 6 8 10 12 14 16 18

3mm

4, 6, 8, 10, 12 & 15mm

Gasket Stress (MPa)

Leakage Rate (m

g/m/s x 10.4)

1400

1200

1000

800

600

400

200

00 2 4 6 8 10 12 14 16 18

Helium Pressure (bar)

Leakage Rate (m

g/m/s x 10.4)

45

40

35

30

25

20

15

10

5

00 0.1 0.2 0.3 0.4 0.5 0.6 0.7

Gasket Stress - 15MPa



PRODUCT DATASHEET

Typical Physical Properties:Figure 4 shows how the sealing ofThermiculite® 866 improves as thepressure to be sealed reduces.

Figures 5 and 6 show further how thesealing of Thermiculite® 866 is influenced by the gas pressure to be sealed and on thelandwidth of the gasket, the land width ishalf the difference between the compressedexternal and internal dimensions of thegasket.

Figure 7 shows the robustness of thesealing of Thermiculite® 866 againstthermal cycling. In this figure the sealingafter the five thermal cycles, shown asdashed lines, remains as expected from thedata obtained before the thermal cycles.

THE INFLUENCE OF THE INTERNAL PRESSUREON THE LEAKAGE RATE OF THERMICULITE® 866

4

THE EFFECT OF LAND-WIDTH ON THE LEAKAGE RATEHELIUM PRESSURE = 1 BAR

5

THE EFFECT OF LAND-WIDTH ON THE LEAKAGE RATEHELIUM PRESSURE = 0.3 BAR

6

7

4.0

3.0

2.0

1.0

00 100 200 300 400 500 600 700

Leak rate (m

l/min/m)

Time / h

3mm

4mm

6mm8mm

12 &15mm

THE ROBUSTNESS AGAINST THERMAL CYCLINGAND SEALING PERFORMANCE OF THERMICULITE® 866

7

25 mbar700oC0.1 MPa



CODE. PDS 356. 06/14

PRODUCT DATASHEET

Health & SafetyThis product is believed to present no healthand safety hazard during gasket cutting, inuse or on removal after service. In normaluse it is unlikely that the product will giverise to significant levels of exposure to theconstituent materials.

Flexitallic Thermiculite® 866 comprises onlychemically exfoliated vermiculite andsteatite.

Under harsh mechanical treatment (e.g. highspeed stamping operations or abrasion) theconstituents may give rise to irritant dustwhich, in extreme cases of exposure, couldlead to more serious respiratory problems.Occupational exposure to such dusts shouldtherefore be minimised and kept belowrelevant national exposure limits. Goodstandards of hygiene should be appliedduring gasket cutting operations and off-cutsshould be disposed of by transfer to a siteappropriately licensed to accept industrialmaterials of this nature.

Sample material for evaluationSample material or sample cut gaskets for evaluation can be obtained without charge from:

For Europe and AsiaJohn Hoyes www.flexitallicsofc.comEmail: [email protected]: + 44 7767 341985

For the Americas and ChinaStephen Bondwww.flexitallic.comEmai: [email protected]: +1 281 604 2477

Best Sealing Practice:To obtain the best performance from a sealingmaterial the following considerations apply justas much to an SOFC as to an industrial pipelinegasket:

• Minimize the gasket area as far as possibletaking into consideration the minimumlandwidth requirement for gasket handlingand sealing

• Maximize the compressive load available

• Use studs of the appropriate metal andstress to a high percentage of yield

• Minimize load loss by making the studs as compliant as possible by using theminimum stud diameter suitable and byusing extension collars or constant loadwashers such as Belville washers

• Tighten the studs in a cross pattern manner

• Tighten the studs using either controlled torque or hydraulic tensioners

• With torque tensioning use a reliable lubricanthaving a known friction factor

• Unless the gasket is compensating for connectiondefects, always use the minimum practicalthickness

• The surfaces to be sealed should preferably haveground rather than a turned finish but they shouldcertainly be free from transverse machining marksor scratches. An appropriate surface finish is N6,Ra 0.8µm, CLA 32µ” / Rz 3.20µm, 126µ” or better.

When correctly selected and used an appropriategasket is able to provide a seal, whilst allowing thecost of the SOFC stack to be reduced via the use ofless bolt load, less rigid stack components andreduced tolerances for the components to be sealed.

Electrical insulating resistance of Thermiculite® 866 determined by IE 167 (BS 2782: Part 2: 1992):Megohms

As Received After 50oC for 24 hours

0.5mm 0.33 7.5

0.7mm 0.50 7.5

The specific heat capacity of Thermiculite® 866:J / g / K

0.5mm 0.949

0.7mm 0.950

The thermal conductivity of Thermiculite® 866 determined by ISO 8301 (DIN 52612 & ASTM C518):W / m / K

0.7mm 0.19

thermiculite® 866

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