简介:TheencapsulationofstearicacidcoatednanometerCaCO3byapolystyrene(PS)networkviaemulsionpolymerizationisdescribed,whereγ-methacryloxypropyltrimethoxysilane(MPS)wasusedasanefficientcrosslinker.TheimportantfactorssuchasthetypeandamountofsurfactantandinitiatorandthecontentofCaCO3areinvestigatedaswellastheroleofMPS.IthasbeenshownthatlittlePSwasextractablewithonly0.6wt%ofMPS(relativetostyrene).Thecationicsurfactantcetyltrimethylammoniumbromide(CTAB)provedmoreeffectivethantheanionicsurfactantsodiumdodecylsulfonate(SDS).Theyieldrises,particlesbecomesmallerandsizedistributionbroadenswithincreasedamountofCTAB.Itisalsofoundthateither2,2′-azobis(isobutyronitrile)(AIBN)orammoniumpersulfate(APS)issuitableforattaininghighmonomerconversion.WithincreasedamountofCaCO3,theencapsulationratiocanbevariedfrom17.9to3.6,whilemonomerconversionandyielddecreaseslightly.FT-IRspectraoftheproductsafterextractionindicatetightencapsulationbetweenPSandCaCO3,andTEMphotographsofcompositeparticleswithwell-definedcore-shellstructuregivedirectevidenceofencapsulation.
简介:Lens-likevateriteCaCO3microringscomposedofCaCO3nanoparticlesweresynthesizedviaamicro-emulsion-mediatedrouteatroomtemperaturewithethanolandn-hexanolasco-surfactant.Thisprocessdidnotde-mandanyadditionalenergysuchasheatingorcontinuousagitation.Itwasthefirsttimetouseethanolasco-surfactantinthesynthesisofmicroornanomaterials.AndtheethanolwasbelievedtoplayanimportantroleintheaggregationfashionofCaCO3nanoparticles.Moreover,shuttle-shapednanorods,hexagonalnanoplates,andrice-likenanoparticleswerealsofabricatedbymodulatingthegrowthparameters.Additionally,theintroduceofethanolintomicroemulsionsasco-surfactantmaybegeneralizedasanovelgreenroutetocontrolthestructureofotherfunctionalmaterials.
简介:TheeffectsofHDPEmatrixtoughnessonthebrittle-ductiletransitionofHDPE/CaCO3blendsareinvestigated.NotallHDPEcanbetoughenedbyCaCO3particles.TheabilityofthematrixtoyieldplaysafundamentalroleindetermingwhetherHDPEcanbetoughenedornot.Thereexistsacriticalmatrixtoughness(Isc≈45J/m)belowwhichHDPEcannotbetoughenedobservablybyCaCO3particleatgivenaveragesize,andabovewhichthecriticalmatrixligamentthickness(τ?)isproportionaltomatriximpactstrength.
简介:ThisstudypresentsanovelprocessofinsitusurfacemodificationofCaCChnanoparticlesusingamultipleorificedispersionmicroreactor.CO2/Ca(OH)2precipitationreactionwasemployedtoprepareCaCO3nanoparticleswithsodiumstearatesurfactant.SynthesizedCaCChproductswerecharacterizedbythermogravimetricanalysis(TGA),infra-red(IR),X-raydiffraction(XRD),transmissionelectronmicroscopy(TEM)andBrunauer-Emmet-Telleranalysis(BET).Theeffectofvariousoperationparametersonnanoparticlesandthedosageofsodiumstearateweredetermined.Theresultsshowedthatthepreparationprocesscouldbepreciselycontrolledwithefficientmasstransferprocess.Theparticleswerehighlyhydrophobicwithacontactangleof117andmonodispersewithanaveragesizeof30nm.Theadsorptionsofsodiumstearateandcalciumiononsolidparticlesduringtheinsitusurfacemodificationprocesswereinvestigated.
简介:TheeffectofyttriaonthesolidreactionmechanismofaCaHPO4·2H2O+CaCO3systematdifferenttemperatureswasexperimentallystud-ied.Thesampleswithandwithoutyttriaweresubjectedtothermogravimetric/differentialscanningcalorimetrymeasurement.ThesampleswereheattreatedatthetemperaturescorrespondingtothepeaksontheDSCspectra,andtheresultedphasecompositionswereidentifiedbyX-raydiffraction.Thetransformationmechanismwasdeducedbycomparingthephasesobtainedatdifferenttemperatures.Theresultsshowthatthetransformationsatbelow1073Karenotaffectedbyyttria,butallthoseatabove1073Karecompletelyaltered.Theformationtem-peratureofhydroxyapatitedecreasesby134K,andthedecompositiontemperatureincreasesby38K.ThepolymorphoustransformationofCa3(PO4)2fromβphasetoαphaseincreasesby47K.Thethermodynamicpropertiesofthetransformationsatabove1073Karealsomodi-fiedbytheadditionofyttria;thatis,theendothermalpeaksaresubstitutedbyexothermalpeaks.
简介:hard-core/soft-shell钙碳酸盐(CaCO3)的合成/poly(甲基methacrylate)(PMMA)混合结构化的nanoparticles(<100nm)由把分裂成原子的微乳液聚合,过程被报导。聚合物链通过acoupling代理人的使用被抛锚到nano-CaCO3的表面上,triethoxyvinylsilane(TEVS)。铵persulfate(APS),钠dodecyl硫酸盐(SDS)和n-pentanol分别地被用作开始者,表面活化剂和cosurfactant。coreshell乳胶粒子的聚合机制被讨论。由PMMA的nano-CaCO3的封装用一台传播电子显微镜(TEM)被证实。coreshell粒子的grafting百分比被thermogravimetric分析(TGA)调查。nano-CaCO3/PMMAcoreshell粒子被Fourier变换描绘红外线(FTIR)光谱学和微分扫描热量测定(DSC)。FTIR结果在nano-CaCO3粒子和PMMA的接口揭示了一个强壮的相互作用的存在,它成功地暗示聚合物链是grafted到通过联合代理人的连接的nano-CaCO3粒子的表面上。另外,TGA和DSC结果与纯nano-PMMA的相比显示了coreshell材料的热稳定性的改进。nano-CaCO3/PMMA粒子被混合进聚丙烯(PP)矩阵由融化处理。它能也用扫描PMMA锁住的电子显微镜学(SEM)被观察grafted在聚合物矩阵(PP矩阵)防碍到CaCO3nanoparticles上CaCO3的聚集并且因此与PP矩阵改进CaCO3nanoparticles的相容性。
简介:通过界面改性,制备了以CaCO3为核,马来酸酐接枝(乙烯/辛烯)共聚物(POE-g-MAH)弹性体为壳的高密度聚乙烯(HDPE)/PoE-g-MAH/CaCO3三元复合材料。由于“核-壳”结构的形成,弹性体和CaCO3表现出协同的增韧作用。在相同的POE-g-MAH含量时,与未经表面处理的CaCO3相比,表面处理的CaCO3由于与弹性体形成粘结更强的界面,使得三元复合材料的“脆-韧”转变提前。
简介:采用铝锆偶联剂对纳米CaCO3进行表面改性,对改性纳米CaCO3水相分散体系的流变数据进行测定,并借助非牛顿流体模型实现流变参数的拟合。结果表明,在低剪切速率下,改性纳米CaCO3水相分散体系的表观黏度随着剪切速率的增大而下降,即剪切变稀,呈现假塑性流体特性;在高剪切速率下,随着剪切速率的增大,分散体系的表观黏度变化很小,呈现近牛顿型流体特性。采用铝锆偶联剂对纳米CaCO3进行表面改性,可明显改善纳米CaCO3在水相体系中的流动性,使屈服应力、零剪切黏度及极限黏度都明显减小。根据Herschel-Bulkley模型拟合结果,未经表面改性的纳米CaCO3水相分散体系的流动特性指数和屈服应力分别为1.489和2.767Pa,呈现剪切变稠流动趋势,表明分散体系的不稳定性,部分粒子发生团聚;而经2.0%铝锆偶联剂改性的纳米CaCO3水相分散体系的流动特性指数和屈服应力分别为0.880和1.250Pa,呈现明显的假塑性流体特性,分散体系流动性较好。