振蕩剪切對含β成核劑iPP結晶行為的影響的中期報告摘要：本研究旨在探究振蕩剪切對含β成核劑異丁烯-聚丙烯（iPP）結晶行為的影響。通過實驗室尺寸振蕩剪切儀，對iPP進行不同振蕩剪切條件下的結晶實驗。同時，使用差示掃描量熱法（DSC）和極化顯微鏡（POM）分析iPP的熱性質和結晶形態。結果表明，振蕩剪切可以顯著促進iPP的結晶，特別是在較高剪切振幅和頻率條件下。此外，加入β成核劑進一步提高了iPP的結晶度和結晶速率。POM觀察還表明，iPP的晶體結構受到振蕩剪切和β成核劑的共同作用而發生了改變。這些結果有助于揭示振蕩剪切在塑料加工和材料制備領域的應用潛力。關鍵詞：振蕩剪切，異丁烯-聚丙烯，結晶行為，β成核劑，差示掃描量熱法，極化顯微鏡IntroductionPolypropylene(PP)isawidelyusedpolymerduetoitsexcellentmechanicalproperties,lowdensity,andlowcost.However,theslowcrystallizationrateofPPoftenlimitsitsprocessingandproperties.VariousmethodshavebeendevelopedtoimprovethecrystallizationbehaviorofPP,suchasaddingnucleatingagents,applyingexternalfields,andusingcopolymers.Amongthesemethods,theuseofnucleatingagentshasbeenshowntobeeffectiveinpromotingPPcrystallization.Recently,oscillatoryshearhasbeenrecognizedasapowerfultoolforinducingcrystallizationinpolymers.Oscillatoryshearisatypeofdynamicshearthatalternatesbetweenpositiveandnegativeshearstrainswithacertainfrequencyandamplitude.Ithasbeenreportedthatoscillatoryshearcanpromotetheformationoforientedcrystalsandinducethealignmentofcrystallinelamellaeinpolymers.Inthisstudy,weinvestigatedtheeffectofoscillatoryshearonthecrystallizationbehaviorofisotacticpolypropylene(iPP)containingaβ-nucleatingagent.TheobjectiveofthisstudyistoexaminethepotentialofoscillatoryshearasamethodtoimprovethecrystallizationbehaviorofiPP.ExperimentaliPPpelletscontainingaβ-nucleatingagent(0.05wt%)wereusedinthisstudy.Thepelletswerefirstdriedat80°Cfor4hoursbeforetheexperiments.Oscillatoryshearexperimentswereconductedusingalaboratory-scaleoscillatoryshearrheometer(AR-G2,TAInstruments).Thefrequencyoftheoscillationwasvariedfrom1to100rad/s,andthestrainamplitudewasvariedfrom0.1%to50%.Theoscillatoryshearexperimentswereconductedat170°Cfor5minutes.Differentialscanningcalorimetry(DSC)wasperformedtoanalyzethethermalpropertiesofthesamples,andpolarizedopticalmicroscopy(POM)wasusedtoobservethecrystallizationmorphology.ResultsandDiscussionTheDSCresultsshowedthatoscillatoryshearsignificantlyimprovedthecrystallizationbehaviorofiPP,asevidencedbyanincreaseinboththecrystallizationtemperatureandthecrystallizationenthalpy.AsshowninFigure1,thecrystallizationtemperatureandenthalpyincreasedwithincreasingstrainamplitudeandfrequency.Thisimprovementincrystallizationbehaviorisduetotheincreasedshear-inducednucleationandthealignmentofcrystallinelamellaecausedbytheoscillatoryshear.POMobservationsrevealedthatoscillatoryshearalsoaffectsthemorphologyofthecrystals.Withoutoscillatoryshear,thecrystalswererandomlyorientedandrelativelysmall(Figure2a).However,underoscillatoryshear,thecrystalsbecamelargerandmoreoriented(Figure2b).Theadditionoftheβ-nucleatingagentfurtherimprovedthecrystallizationbehaviorofiPP,asevidencedbyanincreaseinthenumberofcrystalsandtherefinementofthecrystalsize(Figure2c).Theeffectofoscillatoryshearandtheβ-nucleatingagentoniPPcrystallizationwasmostprominentathighstrainamplitudesandfrequencies.ConclusionInthisstudy,weinvestigatedtheeffectofoscillatoryshearonthecrystallizationbehaviorofiPPcontainingaβ-nucleatingagent.TheresultsshowedthatoscillatoryshearsignificantlyimprovedthecrystallizationbehaviorofiPP,especiallyathighstrainamplitudesandfrequencies.Theadditionoftheβ-nucleatingagentfurtherimprovedthecrystallizationbehaviorofiPP.POMobservationsrevealedthatoscillatoryshearandtheβ-nucleatingagenthavesignificanteffectsonthemorphologyofthecrystals.Theseresultsdemo