简介:Thephotopolymerizationoftwokindsofprepolyesterscontainingconjugateddiacetylene(PDA-6andPDA-12)wasinvestigatedusingDSC.BymeasuringtheendothermicenthalpyoftheprepolymersafterdifferentUV-irradiationtimes,thepolymerizationswerefoundtofollowthefirst-orderratelawwhichagreedwiththeresultsofotherinvestigatorsusingadifferentmethod.TheendothermicenthalpymeasurementsofPDA-6andPDA-12beforeUV-irradiationprecludedthepossibilitythatthedecreaseofendothermicenthalpywascausedbythermalpolymerization.
简介:Themolecularstructureofpolyethylene(PE)sampleswithvariouscomonomersincludingpropylene,1-buteneand1-hexenewasinvestigatedbyDSCand13C-NMRtechniques.Thedensityofthesamplesvariesfrom0.948g/cm3to0.917g/cm3,andthemolecularweightdeterminedbytheGPCmethodisintherangeof1~2×105.Thebranchpointcontentofthesampleswasdeterminedby13C-NMRmeasurementsandwasfoundtobelessthan20per1000Catomsalongthemainchain.CrystallizationsegregationDSCtechnique(CSDSC)wasusedtocharacterizethebranchpointdistributionorthesegmentlengthdistributionofPEs.Thecrystallizationsegregationwasperformedinasuccessiveannealingprocessatdecreasingtemperatures.Theintervaloftwosuccessiveannealingtemperatureswas6K,andthetimelengthofeachannealingstepwas2.5h.TheCSDSCresultsclearlyindicatethatallthePEsamplesused,includingsomemetallocenePEs,moreorlessexhibittheirnon-uniformityinsegmentlengthdistribution,andbimodalormultimodalCSDSCcurveswereusuallyobserved.ForquantitativecharacterizationoftheCSDSCcurvesandthesegmentlengthdistributiontwoparameters,theaveragemeltingpoint,TmAV,andtheroot-mean-squaredeviationofmeltingtemperature,(ΔTmAV2)1/2,wereproposed.TmAViscorrespondingtotheaveragesegmentlengthduetobranchingand(ΔTmAV2)1/2givesinformationaboutthewidthofthesegmentlengthdistribution.Experimentalresultsshowthatboththedegreeofaveragemeltingtemperaturedepressionandthewidthofthedistributionseemtoincreasewithincreasingthebranchingcontentandaredependentonthetypeofcomonomers.VerygoodreproducibilityandadditivityoftheCSDSCmethodwereevidencedexperimentally.ItwasconcludedthattheCSDSCtechniqueisasensitiveandconvenientmethodforcharacterizingthesegmentlengthdistributionofbr
简介:摘要以混合硝酸酯和混合硝酸酯的高能粘合剂作为原料,通过添加不同的杂质,研究了杂质及其含量对硝酸酯安定性的影响。结果表明,随着Fe3+、Cl-、NO3-杂质离子浓度的增加,混合硝酸酯的安定性均降低,NO3-离子对混合硝酸酯安定性的影响最大;Fe2(SO4)3、FeCl3、Fe(NO3)3对混合硝酸酯高能粘合剂安定性的影响依次减弱,且浓度越大,对安定性影响越大。在三种贮存温度下,随着pH值增大,高能粘合剂的安全贮存时间呈现先增大后减小的趋势,混合硝酸酯高能粘合剂pH=7.08时,安定性最好,安全贮存时间最长;随着高能粘合剂中含水量的增加,高能粘合剂的安全贮存时间也相应降低。
简介:13kindsofironores(6fromAustraliaand7fromBrazil)werestudiedontheirpropertiesconcerningCW(CombinedWater)decomposition,Fe2O3decompositionandsoftening-meltinginairatmospherethroughthecharacterizationmethodofTG-DSC(Thermogravimetry-DifferentialScanningCaloremetry).TheexperimentalresultsoftheAustralianoresandBrazilianoresdifferintermsoftheinitialtemperature,temperaturerangeandendothermicamountofCWdecomposition,andbesides,thecontentofCW.ItisestimatedthatforeverypercentincreaseofCWcontentinsinteringrawmaterial,theextrathermalamountabsorbedintheprocessisabout1.83×104kJ,whichequalstothethermalcapacityof0.625kgofstandardcoalburningupcompletely.AstothedecompositionofFe2O3,theinitialtemperatures,terminaltemperaturesandtemperaturerangesoftheAustralianandBrazilianoresarequiteclose.However,theendothermicamountofFe2O3decompositionofthetwoturnsoutratherdifferent:theendothermiccapacityofFe2O3decompositionoftheAustralianoresisgreaterthanthatoftheBrazilianores.Furthermore,theliquidamountgeneratedinthesoftening-meltingprocessiscloselyrelatedtotheSiO2contentinironore.ThehigherSiO2contenttheorecontains,themoreliquidvolumeitwillgenerateinthesoftening-meltingprocessofironore.