原位气泡拉伸法制备聚合物基纳米复合材料的研究

原位气泡拉伸法制备聚合物基纳米复合材料的研究Aninvestigationonthedispersioncapabilityoftheinsitububbledispersionmethodinpreparationofnano-polymercomposites北京化工大学吴大鸣1.常用分散方法及其局限性Shearingrate:103-104s-1Veryhighshearingratewillleadtodegradationofthepolymera.螺杆分散b.超声波分散Ultrasonicwaveisstrongenoughtodispersetheaggregatednano-granules,butitisusedonlytopre-treatthenano-granulesinthesolution.Theattempttoadopttheultrasonicwavetothepolymermeltinextrudersisupagainstverylowefficiencyofenergytransmission.c.DispersionbyIntercalationpolymerizationNylon6/clay(1987OkadaA,KawasumiMetal.)Thismethodisonlyusedfordispersingnanogranuleswithlayeredstructure,asmontmorillonite,hydrotalcites,etc.2.原位气泡拉伸分散法a.SplittingInflationofthebubbleinpolymerfoamingHan,C.D.RheologyinPolymerProcessing;NewYork,1976.Thesameresultaboutveryquiklystretchrateupto106s－1wasalsomadeIndoctoraldissertationofprof.MengQ.Y.(BUCT,2003).原位气泡拉伸法分散模型InSituBubbleStretchModel(ISBS)团聚粉体初始气泡气泡膨胀膨胀气泡分散的粉体b.原位气泡拉伸法（ISBSmodel）ISBS的理论基础：•发泡过程气泡膨胀倾向于围绕无机分散相进行；•适当控制发泡条件，气泡周围聚合物熔体的拉伸速率可以达到105-107s-1,高于螺杆的分散能力；•气泡膨胀产生对周围熔体进行双向拉伸，使得分散相分散的自由度；•在一定条件下，气泡可以产生超声频率的气泡振荡，对分散十分有利。Shearingdispersion567.4s-1ISBSdispersionFE-SEMimagesofHDPE/CaCO3compositeShearingdispersion2047.6s-1FE-SEMimagesofHDPE/LDHscompositeISBSdispersionFE-SEMimagesofISBSdispersioneffectviaspacefromthebubblesurfacec.EvaluationofthedispersioncapabilityofISBSThesphericalcoordinateswereusedfordescribetheCellmodelforbubbleinflation•Forsphericalcoordinates:0),,(VVtVVrr•Bymomentumequationandcontinuityequation:0)(122rVrrr(1)(2)•Consideringboundaryconditions)(tRdtdRVrRr(3)Theradialspeedofthebubblewallis:22)(rtRRVr(4)•Therelationbetweenthestretchingrateofpolymermeltandtheinflationspeedofthebubblemaybewrittenas:rVr1(5)•From(4)and(5)thedistributionofstretchingrateofthepolymermeltcanbeeducedas:)(32tRrR(6)•Asaresult,thedistributionofthestretchingrateofthepolymermeltwithadistanceofLfromthebubblesurfaceisobtainedas:32)(LRRR(7)050100150200-1x10401x1042x1043x1044x1045x1046x1047x1048x1049x1041x1051R=5m/s2R=10m/s3R=30m/sdistancetobubblesurfaceL(m)stretchingrate(s-1)123Fig.1Distributionofthestretchingrateofthepolymermeltwithdifferentinitialinflatingspeedofbubblesurface:initialstretchingrate105S1-2502550751001251501752001021031041051061R=5m/s2R=10m/s3R=30m/sdistancetobubblesurfaceL(m)stretchingrate(s-1)123Fig.2Distributionofthestretchingrateofthepolymermeltwithdifferentinitialinflatingspeedofbubblesurface:initialstretchingrate106S1Fig.3Distributionofthestretchingrateofthepolymermeltwithdifferentinitialinflatingspeedofbubblesurface:initialstretchingrate107S-1-2502550751001251501752001031041051061071R=1m2R=5m3R=10mstretchingrate(s-1)distancetobubblesurfaceL(m)12305101520256080100120140160averageparticlesizer(nm)distancetobubblesurfaceL(m)Fig.4Thedistributionoftheaveragegranulesizeinpolymermelt3.复合材料的消泡采用高速气流粉碎机粉碎并经排气挤出机造粒可以消除气泡。由于被分散的粒子包覆着聚合物，使得其空间位阻明显高于原生粒子。当两个纳米颗粒逐渐接近时，聚合物包覆层可能存在的总构像数下降，这种熵的减少使得大分子自由能增加，彼此之间产生排斥效应，阻止已分散粉体的团聚。Fig.5TEMimagesofgrindedISBSsample4.ISBS方法的应用(1)聚合物的阻燃•Effectivelyenhancetheoxygenindex•AcarbonlayeriscoveredontheflamingsurfaceofthecompositeofLDPE/nm-Mg(OH)2•NodrippageLDPE/nm-Mg(OH)2(2)ISBS方法制备纳米增强复合材料Asreportedintheliterature,theincreaseoftensilestrengthofthepolymerbyaddinginorganicadditivesislimitedtoabout10%,moreover,theelongationatbreakofthecompositedecreasesveryquicklywiththecontentofadditives.EventheincreasesoftensilestrengthofPolyamide/CarbonNano-tubescompositealsodid’texceed10%.ReinforcementofLDPEbyISBStechnologyMechanicalTestingDataandComparisonwithPureLDPEContentofMg(OH)2phrTensileStrengthMPaElongationatBreak%ExtensionmodulusMPaComparisonwithPureLDPE*TensileStrengthElongationatBreakExtensionmodulus014.420058.41019.411459.3+34.7%－43%+1.5%1221.414051.7+48.6%－30%－11.5%1523.813366.9+65.3%－33.5%+14.6%2021.712767.1+50.7%－36.5%+14.9%2521.110869.7+46.5%－46％+19.3%3019.310968.2+34.0％－45.5％+16.8%结论ISBS可有效地用于分散各种纳米粉体；消泡过程已分散的粉体重新团聚的概率很低；用ISBS方法制备的nanoMg(OH)2/LDPE复合材料，性能明显优于常规制备方法；用ISBS方法制备的nanoMg(OH)2/LDPE，燃烧时表面形成炭层，且无滴落。ContactProf.WuDamingBeijingUniversityofChemicalTechnologyE-mail:[e-mail]敬请指导！