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Afterscrutinizingin-situcomposites,polymerblendsofthermoplasticsandthermotropicliquidcrystallinepolymers(TLCPs),aconceptofin-situhybridcompositeshasbeenputforward.Consistingofmatrixpolymer,reinforcingfiberorfiller,andin-situformedTLCPfibril,thisgroupofcompositeshasdecreasedmeltviscosityandfiberbreakage,favoredfiberorientation,andimprovedperformanceswithreinforcingoffibersandmicro-crackblockingofTLCPfibrils.Areinforcedstructurebothatmicrometerandsubmicrometer,andbalancedflowpropertyandmechanicalperformancesarereachedexperimentally.Duetotherigidityofmolecularchains,TLCPsexhibitshear-thinningbehaviorinthenematicphasesothatin-situhybridcompositeshaveexcellentprocessingpropertyovercommonpolymercomposites.Underproperconditions,TLCPmeltdropletsaredeformedintofibrilsofsub-micrometerdiameters.ThesefibrilswithlargeL/Dratios,keptbythelongrelaxationtimeofrigidchains,notonlyblockthepropagationofmicrocracksinthecomposite,butalsoenhancethereinforcingeffectofthemainloadbearerssuchasfibers,andendowpolymercompositeswithexcellentmechanicalperformances.Theseresultshavebeenreachedincompositessuchascarbonfiber(CF)/polyethersulfone(PES),CF/polyetheretherketone(PEEK),glassfiber(GF)/polycarbonate(PC)andGF/polyamide6(PA6).Furthermoreinterestingly,theaforementionedmeltviscosityofthesecompositesisevenlowerthanthematrixpolymeranditblendswithTLCP.Thisextensivelyexistingphenomenonhasbeentermedastheologicalhybrideffectwithitsdefinitionof"aphenomenoninwhichthemeltviscosityofaternarypolymerblenddecreaseswithincreasingoffillerloading,influencedbytheminorpolymerphaseintheblend".ThelubricanteffectofTLCPismagnifiedbytheadditionoffibersorfillers,i.e.,themorefilleradded,themoresignificanttheviscosityreductionis.ThiseffecthasbeenobservedmoreorlessinTLCP/polymersystemscontainingfillerswiththeirsizeatmicro-meterandnanometerscale,andtheshapeofcylinder(GF),flake(clay),needle(whisker)andsphere(glassbeadandnano-silica).TheviscosityreductioncorrelateswellwiththeTLCPfibrillation.ThebetterfibrillationofTLCPphase,themoresignificanttheviscosityreductionis.Thethermodynamic,theologicalandtopologicalparametersinfluencingtheTLCPfibrillationhavebeeninvestigated.A11thedetailsfromthemicrostructuredesigntoprocessingtheologyhavebeensummarizedcl],andwillbediscussedinthistalk. |
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