TIMREX® Graphites and Cokes for Friction Materials - Timcal

Graphites and Cokesfor friction materials

www.timcal.comWho are we?About frictionmaterialsTIMCAL Group has a strong traditionand history in graphite manufacturing. Itsfirst manufacturing operation was foundedin 1908. Today, TIMCAL Group facilitiesproduce and market a large variety of syntheticand natural graphite powders anddispersions of consistent high quality.Adhering to a philosophy of Total QualityManagement and continuous processimprovement, all TIMCAL manufacturingplants comply with ISO 9001-2000.TIMCAL is committed to produce highlyspecialized graphite and carbon materialsfor today’s and tomorrow’s friction materialsindustries.TIMCAL has an international presencewith facilities and commercial officeslocated in the key markets around theGlobe. The Group’s industrial and commercialactivities are implemented by an experiencedmulti-national team of nearly 300employees from seven countries on threecontinents.TIMCAL Group is a member ofIMERYS, a world leader in adding value tominerals.TIMREX ® Graphites combine technicaland economic advantages: their optimalprice/performance ratio helps maintaing ahigh quality level in the finished part while, atthe same time, reducing manufacturing costs.Bodio, SwitzerlandWillebroek, BelgiumLac des Îles, CanadaRapid developments over the past fewyears within the automotive industry haveresulted in a growing demand for high-qualityfriction materials.The main requirement to be met by abrake lining is, besides a high level of energyabsorption, a high brake efficiency within awide temperature range. Comfort aspects,life-time, and absence of noise are factorswhich also demand important consideration.These requirements are fulfilled by meansof high performace brake pads in which carbonpowders such as graphite and coke playa key role.The extreme consistency of TIMREX ®Carbons provides the predictable propertiesthat makes development and productionvery efficient.This documentation is intended to helpour customers make the best possible selectionfrom the wide range of TIMREX ®Graphite and Coke materials available foruse in their high performance friction applications.Terrebonne, CanadaChangzhou, ChinaFuji, Japan

Graphite andCoke Powdersfor Brake Liningsand ClutchFacingsThe MarketBrake Linings and Brake PadsNon- metallic organic brake pads (NAO)Resin-bonded metallic pads (semimetallic)Low-metallic organic brake padsSintermetallic materials for aircrafts,high speed trains, heavy duty machinesCFC- and C/C-materials as well as brake padsfor C/C-brake discs(CFC: Carbon fiber composites; C/C: Carbon composites)Linings for drum brakesOrganic brake pads for trainsClutch Facingsfor Dry and Wet ApplicationsSintered metallic clutch facingsOrganic-bonded paper- and fiberclutch facingsTIMREX ® Graphitesand Cokes witha common keyword:consistencyTIMREX ®Primary Synthetic GraphiteTIMREX ® Primary Synthetic Graphitesare produced in a unique highly controlledgraphitization process wichassures narrow specifications andunequalled consistent quality due to:monitoring of all production and processingstages, strict final inspection, andclearly defined development processes.TIMREX ® Primary Synthetic Graphitesshow unique properties thanks to thecombination of a consistent purity, perfectcrystalline structure and well definedtexture.TIMREX ®Natural Flake GraphiteTIMREX ® Natural Flake Graphite is producedin a wide range of products distinguishedby particle size distribution, chemistryand carbon content. Timcal mines thegraphite from its own source in Lac-des-Îles,Quebec, Canada. This unique “close-to-customer”location guarantees very fast andreliable deliveries.All TIMREX ® “Naturals” are thoroughlycontrolled in our laboratories to ensure quality,consistency and above all, total customersatisfaction.TIMREX ® CokeTIMREX ® Petroleum Coke is calcined atappropriate temperature with low ash andsulfur content, well defined texture and consistentparticle size distribution.

www.timcal.comTIMREX ®Carbons forFriction MaterialsTypical valuesAsh(%)Moisture(%)CrystalliteheightLc (nm)Tapdensity(g/cm 3 )DBP absorbtion(Dibutylphthalate)(g/100g)T GraphiteT 750.070.1> 1000.21*103T 15-750.030.02> 1000.33*70T 1500.090.05> 1000.5159T150-6000.090.05> 1000.5923T 8000.080.05> 1000.6433T 200-20000.080.03> 1000.73210 500 1000 15002000Particle size range d (µm)* Scott densityKS GraphiteKS 750.070.1> 1000.24*98KS 5-75TT0.040.02> 1000.41*45KS 1500.060.05> 1000.6052KS 5000.060.04> 1000.8025KS 150-600SP0.060.04> 1000.7717KS 300-12500.060.04> 1000.72140 500 1000 1500Particle size range d (µm)* Scott density

Particle shapeAdvantages and applicationsangular flakes, microporousSuitable especially for organicbonded clutch facings (paper, fiber)and organic brake linings(semimetallic, non-metallic,low-metallic).Good lubrication propertiesReduction of the friction level and smoothingof the friction coefficientGood thermal conductivityReduction of hot spots and difference thickness vibration(DTV) by spring back and good thermal conductivityHigh effectivness of wear-reduction at relatively lowgraphite concentrationsGood damping behaviour due to internal lubricityand micropores - noise reductionGood wettability with organic binders and high adhesionstrength between binder and graphite particleirregular spheroidsSuitable especially for sinteredmetallic clutch facings andbrake pads.Good lubrication propertiesGood transfer film formationSmoothing of the friction coefficient at the required levelGood thermal conductivityReduction of hot spots and DTVGood mixability with metal powdersSufficient mechanical strength of sintered parts even atmedium density - no lamination

www.timcal.comTIMREX ®Carbons forFriction MaterialsTypical valuesAsh(%)Moisture(%)CrystalliteheightLc (nm)Tapdensity(g/cm 3 )DBP absorbtion(Dibutylphthalate)(g/100g)Natural FlakeGraphiteGA 95/75-150 mesh FR< 5< 7< 0.5< 0.5> 350> 3500.520.659141-100 mesh FR< 7< 0.5> 3500.7542- 80 mesh FR< 7< 0.5> 3500.693780 x 150 mesh FR< 7< 0.5> 3500.741650 x 100 mesh FR< 7< 0.5> 3500.781150 x 80 mesh FR< 7< 0.5> 3500.82100 250 500 750 1000Particle size range d (µm)20 x 50 mesh FR< 7< 0.5> 3500.7710CokeFC 250FC 800FC 250-15000.070.070.070.020.020.02~2.5~2.5~2.50.911.000.906.06.05.60 500 1000 1500Particle size range d (µm)

Particle shapeAdvantages and applicationsflakesSuitable for all organic bondedfriction materials, especially forlinings in drum brakes as well as inbrake pads for trains.Good transfer film formationGood thermal conductivityExcellent lubricating propertiesirregularSuitable for all kind ofsintered and organic bondedfriction materials.Low wear of counterpart due to low ash contentStable friction coefficient, non-fadingHigh thermal stabilityReduction of noise, especially medium and highfrequency sounds

www.timcal.comPowderPropertiesGraphite and cokeand their role in frictionmaterialsTIMCAL Group is in the position to provideanalytical and test results for graphiteand coke powders and the correspondinggraphite compacts. Based on this information,conclusions can be drawn from theproperties of the final products and viceversa.CokeGraphitePowder propertiesPurityAsh contentMoistureTrace elementsCrystalline structureCrystallinityTextureBET surface areaXylene densityScott densityOil absorptionParticle sizeParticle size distributionLaser diffraction, sieving methodsOther propertiesThermal conductivityMechanical propertiesDamping behaviourProduction of ourmodel brake liningsMixingCompactingSintering, CuringApplication propertiesof model brake liningsWear of discWear of liningsDisc temperatureLining temperatureCoefficient of frictionFading behaviourNoiseCompressibilityCoefficient of friction µ0.50.40.30.20.100 50 100 150 200Crystallite size (nm) - (Inspired by S.A. Griffith and S. Marsch)In the following pages there are some ofthe results of experimental work carried outon TIMREX ® Graphite and Coke at ourTechnical Centre.

GraphiteProperties:Density and internalporosityGraphiteProperties:Damping behaviourMeasuring methodThe density of carbon particles is usuallymeasured pycnometrically by the xylenemethod.ConclusionGraphite has a theoretical density of 2.26g/cm 3 , and calcined petroleum coke about2.05 g/cm 3 whereas tap densities are relativelylow therefore high volume concentrationscan be achieved using graphite andcoke even in relatively low quantities.With TIMREX ® Graphite powders, theoreticaldensity - excluding internal closedpores - is achieved in the fine powders.As particle size increases, particle densitydrops - an effect of internal closed porosity.Micro- and mesopores in the range of

www.timcal.comGraphiteProperties:Oil absorption (DBP)Measuring oil absorption to define thecharacteristic features of carbon blacks is anormal standard procedure. Use of thismethod on other powders and fillers hasshown that oil or dibutylphthalate (DBP)absorption values are helpful to determinebinder consumption in filled materials(filled plastics, resin-bonded carbon brushesand organically-bonded friction modifiers).Measuring methodThe oil absorption test is a special centrifugationmethod showing high reproducibility,developed by TIMCAL.A special centrifuge tube is filled with0.5 g of TIMREX ® graphite powder andthen covered with dibuthylphthalate(DBP). After centrifuging for 90 minutesat a relative acceleration of 453 g, the tubeis weighed and the oil absorption of 100 gof powder is calculated (based upon theweight increase of the 0.5 g sample).ConclusionAbsorption depends on particle size, bulkdensity, specific surface area, crystallinityand the wettability of the surface. The proportionof fines in the graphite powders hasa particularly marked effect on absorption.By reducing the amount of fines, DBPabsorption, and hence binding agent consumption,drops substantially(KS 5-75TT, KS 150-600SP, T 150-600and 50x100 mesh FR).GraphiteKS 5-75TTKS 150-600SPT 150-60050x100 mesh FRFC 250-1500DBP-Absorption(g/100g)451723116The use of these graphite powders in liningcompounds, gives the user greater freedomwhen formulating the mixture, andfrequently permits an increase in the concentrationof fine-grained additives (e.g.oxides, sulfides). Alternatively, the proportionof binding agent can be reduced whichgenerally leads to a lower tendency towardsfading.AccelerationDBP-Absorption of graphite powders -especially powders with reduced finesTubeCentrifugationDBPSampleFilterSieve

GraphiteProperties:Thermal conductivityMeasuring methodThe thermal conductivity is measured ona cylindrical hipped sample of TIMREX ®Graphite.The powders are compacted withoutbinder, machined and equipped with thermocouples.The samples have a diameter of6 to 8 mm and a length of 20 mm.The graphite samples are pressed to consistentdensity to reduce the influence of thedensity over the thermal conductivity.The measurement is carried out by usingstationary Kohlrausch method as shownbelow.Cork PlateElectric HeaterDC-Power sourceAmmeterSampleMicrovoltmeterDiff. Cu-ConstantanThermocoupleThermostaticCu-PlateConclusionThe thermal conductivity of graphitesdepends upon their crystallinity (crystallitesize, c/2) and particle size.The thermal conductivity of the coarsegraphites used mainly in friction linings isvirtually independent of grain size. The primarysynthetic TIMREX ® KS and TGraphites, show a 20-30 % higher thermalconductivity than secondary syntheticgraphites.Good thermal conductivity coupled witha high specific thermal capacity of approx.0.5 J/(g.K) in the range of 20°C to 100°C,and rising thermal capacities in higher temperatureranges (0.99 J/(g.K) at 200°C)produces a series of interesting advantagesto the user:• a more homogenous temperaturedistribution in the brake lining, therebyminimizing tension cracks.• the reduction of hot spots and hotbands in discs and linings, whichis coupled with reduced thermo-elasticinstability (TEI).• the friction coefficient is lessdependent upon temperature, thusreducing juddering, and in turn noiseand shearing stress in the lining.• the materials are subject to lowerlocal temperatures, leading to areduction in wear caused by burn-offor welding.The thermal conductivity of KS and Tgraphites represents a good compromisebetween contradictory requirements such as:• high thermal conductivity to compensatefor temperature differences in thefriction zone.• low thermal conductivity to protectthe braking fluid from thermal overload.GraphiteNaturalKSTScrapCokeThermalconductivity λW/(m.K)19014013011012Typical data of thermal conductivity of graphite powderspressed to density ≈2.2 g/cm 3 , 25°CHipped sample of TIMREX® Graphite(HIP, 350 Mpa, 1900°C) with thermocouples

www.timcal.comGraphiteProperties:Spring back andelasticity of singleparticlesThe force-displacement behaviour of singlecarbon particles describes qualitativelythe mechanical properties of the particles asparticle strength, brittleness and elasticityand gives an idea about deformation mechanism,wear and wear mechanism in thefriction process.displacementMeasuring methodTesting of single carbon particles is carriedout in compression mode by axial loadingof particles between parallel plates inthe range of 0-100 mN, 0-1000 mN respectively.Spring back measurements of compactedpowders give also an idea about the elasticproperties of the graphite (see also ourbrochure TIMREX ® Graphites for CarbonBrushes and Carbon Parts).ResultsLoadparticle diameterCarbon particleThe graph shows typical load-displacement-curvesof TIMREX ® T, KS andNatural Graphite up to higher loads. Theresults correlate with the results at low loadpresented in the table.TIMREX ® Graphites show high plasticand elastic deformation properties. The highplastic particle deformation causes smoothfriction surfaces to form on the brake liningand disc. At the same time the formation of astable, dense and smooth transfer film is alsopromoted.The relatively high elasticity reduces the riskof fatigue failure at the edges of the particles;it also reduces dust formation and wear in thelining.Moreover, the elasticity of the graphite particlescontributes towards the elasticity of theentire lining. It helps to smooth out roughspots on the surfaces, and increases the effectivecontact surface between friction partners.Wear caused by surface rough spots and noisecaused by difference thickness vibration(DTV) are reduced.T Graphites are particularly suitable fororganically-bonded brake linings (NAO) andKS Graphites for sintermetallic linings.In their mechanical properties, secondarysynthetic graphites more closely resemblecokes than graphites. Because of their lowplastic deformation, they have a lower tendencyto the transfer film formation. Lowerelasticity could cause particle failure andhigher wear.CarbonT graphiteKS graphiteScrapTIMREX® CokeNatural Graphite FRplasticdeformation (%)2.61.40.470.215.2TIMREX ® Cokes are characterized by ahigh level of grain stability. Their elasticity,which is relatively high for cokes, reducesdust and hence wear and noise. By contrast,gas and metallurgical coal cokes, which arevery brittle, tend to produce dust in the frictionprocess which leads to increased wearand is linked to noise in the quiet zone.Displacement (% of particle height)10080604020Natural00 2.00E4.00E 6.00-01 -01 -01Load (N)Load - displacement - response (hysteresis) forTIMREX® Graphite particles (typical curves) reported up tohigh loads.elasticdeformation (%)1.11.40.220.11.2plastic+elasticdeformation (%)3.72.80.690.316.4Deformation of single carbon particles at low pressures(15 N/cm 2 ) and low displacements from load displacementhysteretic measurements (in % of the particle height).TKS

Coke Properties:Coke structureThe structure of coke is determined by oilquality, the coking technology used and theduration and temperature of the calcinationphase. TIMREX ® Cokes have excellent textureswith anisotropic flow and mosaicstructures to ensure a high level of grain stabilityand a relatively high elasticity.The figure shows a polished section inpolarized light in which these structures areclearly visible.The visible, slit pores are usually openpores and ensure that the grain is firmlyanchored in the binding matrix.Structure of TIMREX® CokeCoke propertiesTIMREX ® Cokes are characterised bylow and constant ash content (approx.0,07%), low sulfur content (approx. 1%)and the absence of volatile substances.• The low ash content accounts for the lowrate of wear of brake linings with TIMREX ®Cokes; no scoring can occur on the brakedisc.• TIMREX ® Cokes are low in dust, owingto their grain fractions and the milling/screening processes used. They are thereforeeasy and clean to process.• To guarantee good wetting properties andadhesion to the binding resin, no dustbindingagents are used during production.• Because of the high calcination temperature,these cokes do not contain any volatilehydrocarbons. The presence of volatile substancesfrequently leads to the formation ofcracks in brake linings at high temperatures.

www.timcal.comApplicationproperties ofmodel brakeliningsGraphite and cokein sintermetallicfriction materialsSintermetallic friction materials areused predominantly in braking systemsfor heavy construction machines, inclutch linings, and in some high-speedapplications; high-speed trains and aseries of motorcycles with higher performancesare also fitted with sintermetallicbrake linings.TIMREX® Cokes, and especiallyTIMREX® Graphites play a particularlyimportant role as friction modifiers inFe and Cu alloy materials.MethodThe following results were obtained withsintered cylindrical model linings(d=37mm, h=18mm) on a friction testpiece and a gyrating mass dynamometer.Technical data of the friction test piece:Speed:Contact pressure:Technical data of the dynamometer:Simulated moment of inertia range:Initial speed:Contact pressures:constant = 42 km/h67 N/cm 24 - 80 kg/m 233 - 111 km/h30, 60, 82 N/cm 2GraphiteGraphite is the main additive in many Cufriction materials - the proportions by volumeused are frequently up to 30%. Otheradditives are oxides such as Al2O3, SiO2,carbides such as SiC or chromium carbidesand cokes. The friction behaviour of thelining is essentially dependent upon thetype of graphite used, the grain size and theconcentration.

Applicationproperties ofmodel brakeliningsGraphite and cokein sintermetallicfriction materialsResults and ConclusionsBoth for KS and T graphites, a rise in thefriction coefficient commensurate with thegraphite grain size was ascertained. In particular,a reduced proportion of fine grains inthe graphite grain band (KS 5-75TT,KS 150-600SP) led to an increase in the frictioncoefficient with simultaneous reductionof abrasion of the lining. A frequent, undesirableside-effect, however, is an expansion ofthe friction coefficient range (minimum µ -maximum µ). By adding a tiny quantity offine graphite powder the properties of thefriction lining can be optimised.Friction coefficient µFriction coefficient µ0.70.60.50.40.30.20.10KS 6 KS 15 KS 44 KS 75 KS 5-75TTGraphite type0.70.60.50.40.30.20.10T 44Graphite typeKS 150-600SPT 75 T 800 T 150-600Friction coefficient of sinteredCu-C -brake pads with 10%TIMREX® KS Graphite as afunction of the particle sizeSinterconditions: 850°C, 3 hSinterdensity: 55% of the theoret. densityFriction coefficient of sinteredCu-C -brake pads with 10%TIMREX® T Graphite as afunction of the particle sizeSinterconditions: 850°C, 3 hSinterdensity: 55% of the theoret. densityWhere grain sizes were identical, the Tgraphites were generally observed to havehigher friction coefficients than model liningswith KS graphites. The higher friction coefficientsof T graphite linings cause greater wearof the linings, however.Friction coefficient µ0.70.60.50.40.30.20.10 0T 150-600KS 150-600SPGraphite type0.70.60.50.40.30.20.1Wear (mm)Friction coefficient and wear of sinteredCu-C -brake pads with 10%TIMREX® KS 150-600SPand T 150-600 GraphiteSinterconditions: 850°C, 3 hSinterdensity: 55% of the theoret. densitywear

www.timcal.comApplicationproperties ofmodel brakeliningsGraphite and cokein sintermetallicfriction materialsOne reason for the different levels of wearand tear of sinter linings with T and KSgraphites lies in the varying shapes of thegraphite particles. The more flaky T graphiteparticles tend to align vertically to the directionof pressure during the compressionprocess. This leads to lamination of the grainand anisotropic mechanical stability after sintering.Under heavy stress in the frictionprocess, shearing forces can lead to greaterwear and tear of the lining.Coke resultsCokes may be added in a concentrationrange of 5-10% of the powder mixture toregulate the friction coefficient. As the grainsize and concentration of the coke increase,so the friction coefficient is reduced.Abrasion of the lining is reduced whenused in combination with graphite powders.KS graphites do not tend to align themselvesin any particular direction duringthe compression process because their particlesare irregularly shaped, and their texturesare more homogenous after sintering.0,60,50,4Use of less fine-grained graphites alsohelps to reduce wear and tear: Cu particlesare usually enveloped by any fine graphiteparticles present in the mixing process.The graphite-coated Cu surfaces are thenno longer available in the sinter process forthe formation of sinter contacts, leading toa reduction in grain stability and toincreased wear and tear in the frictionprocess.Friction coefficient µ0,30,20,10FC 250 FC 850 FC 250-1500Coke typeFriction coefficientof sintered Cu-C -brakepads with 10% TIMREX® CokeSinterconditions: 850°C, 3 hSinterdensity: 53% of thetheoret. densityLargely isotropic and undisturbed Cu sintertextures are obtained by using KSgraphites with a reduced proportion of finegrains.KS 150-600SP and KS 5-75TT graphitepowders are predestinated for sintered brakelinings based on Cu. KS 75 is particularlysuitable for large surface clutch linings withlow surface compression.

Applicationproperties ofmodel brakeliningsGraphite and cokein organic bondedfriction materialsGraphiteMethodGraphite powders are used as solidlubricants, and should fulfill the followingprinciple functions:Test samplesConcentration (mass%)Formulationof test samplesSet the required friction coefficientin a range from 0.38 to 0.45.Level off the friction curve.Reduce wear and tear on discand lining.AdditiveGraphiteBaryteformul. 1800formul. 24040formul. 32060formul. 41070The suitability of a raw material for aspecific brake lining can only be clearlyestablished in a dynamometer test and byvehicle road tests. However, tests usingmodel linings on friction testbeds canfrequently give an indication of the tribologicalbehaviour of graphites, and canbe an aid to formulation.AluminaPhenolic resinParameter164diameter:height:Naturalgraphite 116414.3 mm4 mmT 800164Naturalgraphite 2164T 200-2000Investigated graphitepowdersAsh (%)5.2 0.11.80.05Particle size (µm)0-300fine flakes0-700500-2000grains200-2000Test equipment:Standard F.A.S.T. MachineSliding speed: 7 m/sSliding time: 90 minProcedure: Heavy duty brake

www.timcal.comApplicationproperties ofmodel brakeliningsGraphite and cokein organic bondedfriction materialsResult and conclusionAs graphite concentration decreases, thefriction coefficient rises and finally reaches aconstant value at 20% graphite. Fine-grained,flaky, nat. graphite 1, is an exception with afurther increase at 10% of graphite. Frictioncoefficient fluctuations are largely constantfor all graphite concentrations, and increasemarginally at 10%. The start-up period tosteady conditions decreases with reducinggraphite concentration.The test material with 10% T 200-2000does not appear to have an instable start-upperiod, and reaches the required frictionlevel immediately with the least frictioncoefficient fluctuations.Wear characteristics vary considerably fornatural graphites and TIMREX ® T 800 andT 200-2000 graphites. With TIMREX ®Graphite friction materials, wear reduces atlower graphite concentrations, but tends toincrease with natural graphites. In the concentrationrange of around 10%, which isof interest to the user, TIMREX ® Graphitefriction materials demonstrate less wear.We therefore recommend the T 800 andT 200-2000 coarse graphites for use inorganically bonded brake linings.T 150-600 is particularly suited toachieving specific grain densities. By reducingthe proportion of fine grain in thegraphite powder, extra space is availablebetween the coarse graphite particles so thatother fine fillers such as oxides, sulfides,baryte or cokes can be added.Friction coefficientµ-level0,50,40,30,20,1WearSpec. wear rate s.w.r.0,0250,0150,010,005nat. graphite 1 T 800 nat. graphite 2 T 200 - 2000080 40 20 10 80 40 20 10 80 40 20 10 80 40 20 10Graphite type / graphite content (%)0,020nat. graphite 1 T 800 nat. graphite 2 T 200 - 200080 40 20 10 80 40 20 10 80 40 20 10 80 40 20 10Graphite type / graphite content (%)Friction level of test samples as afunction of graphite type and graphiteconcentration after the periodof bedding, friction load: 15 lbsCourtesy: ITT AutomotiveS.W.R. of test samples as a functionof graphite type and graphiteconcentration.Courtesy: ITT Automotive

Applicationproperties ofmodel brakeliningsGraphite and cokein organic bondedfriction materialsTIMREX ®Graphite has found its placein the field of friction materials as areliable, high quality product. Manyproblems can be solved thanks to thebroad range of TIMREX ®Graphites.Our specialists will be glad to help youin the selection of the most suitableproduct for your application.CokeCoke powders are used as frictionmodifiers, and should fulfill the followingprinciple functions:Reduce weight by using a filler withlow specific weight.Set the required total concentrationof carbon by volume (graphite and coke).Reduce fading.Reduce wear and tear of the lining.Friction coefficient µ / aver. val.FC250 FC400 FC800 FC250-1500Coke typeAverage friction coefficient of TIMREX®Cokes in model brake pads(90% coke, 10% phenolic resin,compacting pressure: 200 bar,curing temperature: 160°C)MethodTest samplesModel brake padsFormulation 90% coke, 10% Phenolic resinThickness 12 mmTemperature (°C); hydr. pressure (bar)500 0.64000.50.43000.32000.210000.100 0.1 0.2 0.3 0.4 0.5 0.6 0.7Time / stopsFriction coefficient µT-discfrictioncoefficientT-brakehydr. pressureSurface areaTest equipment:35 cm 2DynamometerSpecial TIMCAL procedure(modified VW-Audi test)TIMREX ® Cokes are characterised by ahigh friction coefficient and low wear - especiallyby contrast with other petroleum andmetallurgical coal cokes. The friction coefficientof the brake lining can be influenced bythe grain size of the TIMREX ® Coke. A constantfriction coefficient throughout a widetemperature range, and excellent fadingbehaviour during successive stop brake applicationsis of importance to the user.Fading behaviour of FC 250-1500 inmodel brake pads (90% coke, 10%phenolic resin,compacting pressure: 200 barcuring temperature: 160 °C)

Leading the way.Commercial OfficesManufacturing PlantsDistributors / Agents(full list available on request)TIMCAL Ltd.Head Office of the GroupCH-6743 Bodio, SwitzerlandPhone: +41 91 873 20 10Fax: +41 91 873 20 19info@ch.timcal.comTIMCAL America Ltd.Representative Office29299 Clemens Road 1-LWestlake, Ohio 44145, USAPhone: +1 440 871 7504Fax: +1 440 871 6026info@us.timcal.comTIMCAL Deutschland GmbHRepresentative OfficeD-56564 Neuwied, GermanyPhone: +49 2631 890 737Fax: +49 2631 890 752info@de.timcal.comChangzhou TIMCAL Graphite Corp. Ltd.188# Taishan Road,Hi-Tech Zone, Changzhou213022 P.R. ChinaPhone: +86 519 5100801Fax: +86 519 5101322info@cn.timcal.comOffered by your local Distributor/Agent:© 2003 TIMCAL Ltd., CH-BodioNo part of this publication may be reproduced inany form without the prior written authorisationof TIMCAL Ltd.Printed in Switzerland.TIMCAL Japan K.K.Representative Office7F Sagamiya Bldg.6 Ichibancho Chiyoda-kuTokyo 102-0082 JapanPhone: +81 3 3511 2078Fax: +81 3 3511 2077info@jp.timcal.comTIMCAL in FranceRepresentative OfficeTour Maine Montparnasse33, avenue du MaineF-75755 Paris Cedex 15, FrancePhone: +33 1 4538 3850Fax: +33 1 4538 3851info@fr.timcal.comTIMCAL Canada Inc.990 rue Fernand-PoitrasTerrebonne (Québec)Canada J6Y 1V1Phone: +1 450 622 9191Fax: +1 450 622 8692info@ca.timcal.comTIMCAL Belgium SAAv. Louise 534B-1050 Bruxelles, BelgiumPhone: +32 2 626 01 43Fax:+32 2 647 38 50info@be.timcal.comFRICT. 09.2003