高岭土在pvc线缆应用

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1、MetakaolinsinPVCinsulationsDavidSkelhornImerysPigments&AdditivesGroup100MansellCourtEast,Suite300Roswell,GA30076IntroductionMetakaolinisaspecialtycalcinedclayproductthatisusedextensivelyinPVCwireandcableinsulationtoenhancetheelectricalinsulationpropertiesoftheformulation.Thisreportreviewsthemanufac

2、turingprocessesusedandcomparesanumberofcommerciallyavailablemetakaolinproductsini)aconventionalPVCinsulationformulationand,ii)thesameformulationwithreducedstabilizercontentinordertodetermineheatstabilityoftheinsulations.CalciningDifferentialThermalAnalysisPlotforKaoliniteDehydroxylationLossofresidu

3、alcrystallinityEndothermExotherm(Heattabsored)(Heatreleased)MetakaolinDefectSpinel(Amorphousform)HeatFlow1001100300500700900TemperaturedegreesCelsiusMass100%80%90%13.5%massreductionassteamisevolvedNomasschangeKaolinregion8m2/gSurfaceArea7m2/gSurfaceArea13m2/gSurfaceArea(duetoporosity)Metakaoliniscr

4、eatedwhenkaolinisheatedtoaspecifictemperatureinthe750-950oCregion.Kaolin,alayeredmineralwithalternatingSiliconOxideandAluminumHydroxidelayers,undergoesseveralchangesincharacteristicswhenheated.ThesechangesarebestillustratedbylookingattheDifferentialThermalAnalysis(DTA)plotforkaolinasitisprogressive

5、lyheatedfromroomtemperaturetoover1100degreesCelsius.DTAisananalyticaltechnique,whichshowsheatflowintooroutofamaterialduringheating.Whentemperaturereachesapproximately450oC,HydroxylgroupsfromtheAluminumHydroxidelayerbreakdowntorelease13.5%ofitsmassaswater,leavingamodifiedcrystallinestructure,metakao

6、lin,whichismicro-porousasaresultofwaterwhichevolvedassteam.Thisreactionisendothermic,asevidencedbyTGAandissubstantiallycompletebyapproximately750oC.Metakaolinhasanincreasedsurfaceandismoderatelyreactive.ItiscapableofscavengingionicmaterialssuchasCl-,whichdegradedielectricbehavior.Brightnessisalsoin

7、fluenced,beinglowerintheMetakaolinstatethaneitheritsprecursororitshigher-temperatureanalogue.Astemperatureisraisedfurtherthemetakaolinundergoesinternalre-structuring,losingitscrystallinityaltogether.Thistra