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    About the deceleration principle of double screw extruder

    About the deceleration principle of double screw extruder

    • Categories:Industry News
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    • Time of issue:2020-07-17 16:40
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    (Summary description)Inmostextruders,thescrewspeedischangedbyadjustingthemotorspeed.Thedrivemotorusuallyrotatesatafullspeedofabout1750rpm,whichistoofastforanextruderscrew.Ifitisrotatedatsuchafastspeed,toomuchfrictionalheatwillbegenerated,andtheresidencetimeoftheplasticwillbetooshorttoprepareauniformandwell-stirredmelt.Thetypicalreductionratioshouldbebetween10:1and20:1.Bothgearsandpulleyblockscanbeusedinthefirststage,butgearsarebestusedinthesecondstageandthescrewispositionedatthecenterofthelastbiggear.Forsomeslow-runningmachines(suchasthetwin-screwusedforUPVC),theremaybethreedecelerationstages,andthemaximumspeedmaybeaslowas30rpmorless(aratioof60:1).Ontheotherhand,someverylongtwinscrewsusedformixingcanrunat600rpmorfaster,soaverylowdecelerationrateandmoredeepcoolingarerequired.

    About the deceleration principle of double screw extruder

    (Summary description)Inmostextruders,thescrewspeedischangedbyadjustingthemotorspeed.Thedrivemotorusuallyrotatesatafullspeedofabout1750rpm,whichistoofastforanextruderscrew.Ifitisrotatedatsuchafastspeed,toomuchfrictionalheatwillbegenerated,andtheresidencetimeoftheplasticwillbetooshorttoprepareauniformandwell-stirredmelt.Thetypicalreductionratioshouldbebetween10:1and20:1.Bothgearsandpulleyblockscanbeusedinthefirststage,butgearsarebestusedinthesecondstageandthescrewispositionedatthecenterofthelastbiggear.Forsomeslow-runningmachines(suchasthetwin-screwusedforUPVC),theremaybethreedecelerationstages,andthemaximumspeedmaybeaslowas30rpmorless(aratioof60:1).Ontheotherhand,someverylongtwinscrewsusedformixingcanrunat600rpmorfaster,soaverylowdecelerationrateandmoredeepcoolingarerequired.

    • Categories:Industry News
    • Author:
    • Origin:
    • Time of issue:2020-07-17 16:40
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    Information

    In most extruders, the screw speed is changed by adjusting the motor speed. The drive motor usually rotates at a full speed of about 1750rpm, which is too fast for an extruder screw. If it is rotated at such a fast speed, too much frictional heat will be generated, and the residence time of the plastic will be too short to prepare a uniform and well-stirred melt. The typical reduction ratio should be between 10:1 and 20:1. Both gears and pulley blocks can be used in the first stage, but gears are best used in the second stage and the screw is positioned at the center of the last big gear. For some slow-running machines (such as the twin-screw used for UPVC), there may be three deceleration stages, and the maximum speed may be as low as 30rpm or less (a ratio of 60:1). On the other hand, some very long twin screws used for mixing can run at 600 rpm or faster, so a very low deceleration rate and more deep cooling are required.

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    About the structure process analysis of twin screw extruder

    About the structure process analysis of twin screw extruder

    Next,theeditorofJuliwillgiveyouabriefintroductionaboutthestructureandprocessanalysisofthetwin-screwextruder:??1.Plasticizingarea??Theplasticizingzoneistoheattheinjectedresintoformamoltenstate.Theconditionssuchastheheatingtemperatureandtimeinthisregionarenotparticularlylimitedaslongasthefluoropolymerhavingaspecificunstableterminalgroupisinamoltenstate.Inthelatterhalfoftheplasticizationzone,itispreferabletoprovidedevolatilizationholestoremoveatleastapartofvolatilecomponentsundernormalpressureorreducedpressure.Then,thepartialpressureofvolatilecomponentsinthestabilizationregiondescribedlatercanbereduced,andthestabilizationtreatmentcanbeeffectivelypromoted.??2.Stabilizationtreatmentarea??ThestabilizationzoneistomeltandkneadandconvertspecificunstableendgroupsintoaCF2H.Thestabilizationtreatmentareaispreferablyformedbyusingakneadingdiscwithoutpropulsion.Here,melt-kneadingiscarriedoutinthepresenceofwaterandoxygen.Itcandirectlyintroducepurewater,ionexchangewater,etc.orwatervapor;itcanalsobeaccompaniedbythefluoropolymertobetreated.Theamountofwateraddedisthesameasthenumberofunstableterminalgroups,butitisactuallypreferabletosupplyanexcessamount,forexample,atleast10timestheamount.Thepressureinthestabilizationzoneisgenerallycontrolledat0.2~10MPa,andthesettemperatureiscontrolledat280~430℃.Thetimetomaintainpressurizationisusuallylessthan10minutes.??Accordingtotheprincipleoftheextrudertoremoveunstableendgroups,themelt-kneadinginthestabilizationzoneispreferablycarriedoutinthepresenceofoxygeninadditiontothepresenceofwater.Airisusuallyusedintermsofeconomy.Inthepresenceofoxygen,thecarbongeneratedbythemoltenkneadedproductisalsoburned,whichcaninhibitthecoloringofthefluoropolymer.Oxygenisaninertgastotheunstableterminalgroupscarboxylandfluorinatedacylgroups.Duringtheprocessofmeltingandkneading,itcanimprovethedevolatilizationefficiencyofvolatilecomponents.??Three,devolatilizationarea??Thedevolatilizationzoneremoveshigh-temperaturevolatilecomponentsgeneratedbythedecompositionofspecificunstableterminalgroups.Theabsolutepressurevariesaccordingtothemoltenstateofthemoltenkneadedproductandtheoperatingconditionsofthescrewofthekneader.Generally,thepressureisreducedtothepointwherethemoltenkneadedproductdoesnotintrudeintotheexhaustnozzle.Itcanbe0.01to0.1MPa,andthetemperatureiscontrolledat25O~Claughataround.??Inthepresenceofacertainamountofwaterandoxygen,FEPextrudingthroughatwin-screwextrudercaneffectivelyremovetheunstableterminalgroupsofFEP.SimplifiestheprocessingprocessofFEPunstableendgroupsandsavesproductioncosts.Whentheobtainedstabilizedpolymerismelt-formed,nobubblesorvoidsaregeneratedinthefinishedproduct,anditisnotcolored.?Formoreinformationabouttwinscrewextruders,pleasevisithttp://www.njjl.com/
    發布時間 : 2020-07-30 點擊 : 0

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