材料專業(yè)文獻(xiàn)翻譯

材料專業(yè)文獻(xiàn)翻譯材料專業(yè)文獻(xiàn)翻譯 Interfacial Interactionsin PP MMT SEBS NanopositesABSTRACT The intercalation capability ofpoly styrene b ethylene butylene b styrene SEBS in nanopositesof isotacticpolypropylene PP with5wt of organicallymodified montmorillonite C20A prepared by melt blending has beeninvestigated X ray diffraction XRD and transmissionelectron microscopy TEM studies haveshown the presence ofintercalated structuresin the nanoposite In aprevious research we studied the intercalationcapability of a mercialpatibilizer Those results with thestudy wepresent in this work allow usa betterunderstanding of the mechanismof patibilization and adeeper characterizationof the structure and morphology of the nanoposite Scanning transmissionX ray microscopy STXM has been used Because of the excellentchemical sensitivityand thehigh spatialresolution 40nm of thistechnique we haveproved thatC20A is not indirect contact with the PP phasebecause the clay isalways locatedinside the elastomer domains The elastomer is surrounding the nanoclay hindering the clay exfoliationand preventingits dispersionin the PP matrix On theother hand we haveobserved that the presenceof theclay causedthe SEBSparticles to bee elongatedin shapeand retardedthe coalescence of theelastomer particles Introduction Phenomenaand processesatthenanometric scalehave openedrevolutionary possibilitiesin thedevelopment ofnew nanostructuredmaterials In polymersystems the additionof layered silicates leads to agreat improvementin theproperties of the matrixsuch asthermal stabilityand mechanical performance withvery lowfiller contents This isbecause thehigh surfacearea of these particleswith nanometricdimensions increasesthe interfacialinteractions betweenmatrix andclay Therefore the keyfactor for the enhancementin performanceof thepolymer clay nanopositesis thedispersion of the fillerin thematrix sincethe finalproperties dependon the structure andmorphology generatedduring theprocessing Consequently a significantresearch effortis dedicatedto characterizethe nanostructurein polymernanoposites In thisstudy we haveprepared isotacticpolypropylene montmorillonite poly styrene b ethylenebutylene b styrene elastomer positesfrom themelt consideringthat thisprocessing methodis the most attractivefor industrialapplication The additionof SEBSas athird ponentin theposite isintended to provide abetter dispersionand intercalationof thesilicate and also toprovide atoughness improvement Montmorillonite isthe mostmonly usedlayeredsilicatefor thepreparation ofnanoposites becauseof itshigh aspect ratio large surfacearea and surfacereactivity Its structureconsists onthe stackingof aluminosilicatelayers 1nmthick with aregular spacingbetween themof 1 5nm Its highcation exchangecapacity offersa wayof modifyingthe interlayerspacing tomake itlarger andmore patiblewith polymers However unlike polymerswith polargroups likepolyamides in nonpolarpolymers likepolypropylene PP the organicmodification of theclayisnotenough to achieve agood levelof dispersionand hardlyleadstomixed structures Therefore patibilizers likepolypropylene graft maleic anhydride PP g MA are monlyused toimprove interactionsbetween theorganic polymerand theinorganic filler In thiswork we havestudiedthe intercalationcapability ofastyrene ethylene butylene styrene triblockcopolymer SEBS as analternative tothe useof monpatibilizers such asthe PP g MA mentionedabove in PP montmorillonite nanoposites In PPnanoposites an elastomerphase isnormally used to pensateforthereduction oftoughness causedby addinginorganic fillers In principle SEBS canaid thepolypropylene chainsto getinto the nanoclay layers Therefore it can be expectedthat SEBSfavors theintercalation and or exfoliation On theother hand it has been reportedthat in these kindsof blendsof immisciblepolymers e g PS PP orPBT PE the nanoclayacts modifyingthe interphaseproperties andso improvingthe patibilitybetween the different polymeric phases SEBS presentsa phase separated morphology and consequently its interactionswith themontmorillonite and its intercalationcapability willbe verydifferent fromthe onesof monpatibilizers The aimof thiswork isto investigatethe structure morphology and interfacesof isotacticpolypropylene clay elastomer nanopositesprepared bymelt mixing X ray diffraction XRD and transmissionelectron microscopy TEM are usedto characterizetheintercalationcapabilityof the polymers TEM microscopyalone cannotprovide conclusiveinformation aboutthe patibilizationrole ofSEBS in thePP clay system since althoughthe lackof chemicalcontrast between the SEBSand PPpolymericphasescould beovere byOsO4staining thedifferentTEM magnificationsneeded toobserve therubber phase in therange ofmicrometers and theclays in therange ofnanometers would makedifficult toobserve the three ponentssimultaneously Besides no positionalchemical informationis provided by thistechnique Experimental SectionMaterials Experimental SectionMaterials The polypropylene PP used asmatrix was an isotactichomopolymer with apolydispersity of4 77 provided byREPSOL It ischaracterized byan isotacticityof95 determined bysolution NMR and aviscosity averagemolecular weightof179000g mol obtained byintrinsic viscositymeasurements The organicallymodified montmorillonite MMT clay usedinthisstudy wasCloisite20A C20A obtained fromSouthern ClayProducts The individualplatelets aretypically1nm inthickness with anaspectratiolarger than50 The interlayerspacing determined byXRD is d001 2 52nm The elastomerused wasa triblockcopolymer SEBS Calprene H 6110 providedbyDYNASOL with30wt of styrenecontent a molecularweight valueof Mw 85000g mol and Mw Mn 1 45 as determinedby gelpermeation chromatography GPC Preparation of PP MMT Composites Polymer blendsand positeswere prepared bymeltblending ina HaakeRheomix600internal mixerattached toa Haake Rheocord90corotating twin screw mixingchamber A temperatureof190 C mixing timeof5min and arotor speedof100rpm weredetermined tobe the optimum processingconditions In theposite PP C20A SEBS 80 5 15 clay loadingwas5wt as itis demonstratedtobetheoptimumcontent formechanicalperformance In orderto parethe patibilizeractivity ofSEBS withmercial patibilizers theelastomer content was15wt because asseen in the literatureweight ratiosof clay mercial patibilizersof1 3give betterresults ofclay dispersion Binary positesPP C20A 95 5 and binaryPP SEBS blends 90 10 and 80 20 with10and20wt elastomercontent resp ectively were usedfor parison Films of the nanopositematerial werepression molded at100Mbar byheating thepellets at190 C for5min withsubsequent quenchingoftheformed filmbetween water cooled metalplates Characterization XRD X ray diffraction XRD was usedto measurethe interlayerspacing oftheclay XRD patternswere obtainedat roomtemperature usinga PhilipsPW1050 70diffractometer at1 min ina2 range between2 and35 using Ni filtered CuKR radiation TEM The dispersionofthenanoclays andposite morphologyonamicroscopic scalewere examinedby transmissionelectron microscopy TEM Images wereobtained witha PhilipsTeai20microscope Ultrathin sections 50 100nm inthickness were cryogenicallymicrotomed witha diamondknife at 60 C Sections werecollected oncopper TEMgrids STXM To identifythe chemicalposition ofthe positesand toobserve simultaneouslyall theponents inthe nanostructure scanning transmissionX ray microscopy STXM measurements wereconducted usingthe STXMat BL5 3 2oftheAdvanced LightSource atLawrence BerkeleyNational Laboratory STXM allowsa detailedchemical andpositional analysiswith excellentchemical sensitivityandahigh spatialresolution The BL5 3 2STXM canprovide imageswith 30nm spatialresolution forX ray photonsof250 600eV with anenergy resolutionof about0 1eV The energyrange includesthemostimportant absorptionedges inpolymer chemistry C 1s at280eV N 1s at400eV and O 1s at520eV We haveused NEXAFSmicroscopy toobtain imageswith nanometricresolution andabsorption contrastbetween thetwo polymerponents making useofthedifferent X ray absorptionofthedifferent ponents The spectrashown arenormalized tothe maximumheight forparison purposes Image sequences usedtoprovide detailedchemical mapping were convertedto chemicalponent mapsusing pixel by pixel curvefitting withsuitable XANESspectra fromreference ponents Details aboutthis instrumentand experimentcanbefound elsewhere To obtainthe mapshown below a pletesequence ofimages atphoton energiesenpassing theC 1s region wasrecorded correspondingtoatypical XANESenergy scan In thisway each pixel representing amorphological andspatial dimension contains afull XANESspectrum Conclusions Aninvestigation ofthestructureandmorphologyofPP C20A SEBS nanopositepreparedbymelt processinghasbeencarried outwith specialemphasis onthestructureoftheinterface STXM hasbeenusedtoprovideimages andspatially resolvedpositional informationsimultaneously ofthethreeponents andhas alloweddetermining therole ofSEBS inthe nanopositestructure From theXRD experiments an intercalatedstructure wasdetermined forthenanoposite TEM observationsshowed amixed morphologyin whichstacks coexistedwith intercalatedregions andsome individualexfoliated layers However thenanoclaywas notwell dispersedinthematrix anditwas notpossible todistinguish whichpolymer wasinteracting withit The stacksdid notappear linedup butbent andtwisted and theclay exfoliationseemed tobe hindered The NEXAFSmicroscopy experimentsclearly showedthat theelastomerissurroundingthenanoclay and althoughinside the rubbery phasethere isintercalation SEBS doesnot actasapatibilizer agentsince C20A isnot incontactwithPP The dispersionofthemontmorillonite inthePP matrix isdominated bythe patibilitybetweenthepolymeric ponentsand thenanoclay On theother hand thepresenceofthenanoclay causesa decreaseinthecoalescenceoftherubberyphase There isa reductionofthesize ofSEBS domainsin parisonwith binaryPP SEBS systems and thesedomains arebetter distributedinthePPmatrix PP MMT SEBS納米復(fù)合材料的界面相互 作用摘要插層能力的聚 苯乙烯 嵌段 乙烯 丁烯 嵌段 苯乙烯 SEBS 的納米復(fù)合材料由等規(guī)聚丙烯 PP 與5 重量 的有機(jī)改性的蒙脫土 C20A 通過熔融共混制備 已經(jīng)被研究 X 射線衍射 XRD 和透射電子顯微鏡 TEM 研究顯示了納米復(fù)合材 料夾層結(jié)構(gòu)的存在 在以前的研究中 我們研究了其在商業(yè)下的插層能力 在這項(xiàng)研究中我們得到的結(jié)果 讓我們更好地理解了增容機(jī)制和更 深的納米復(fù)合材料結(jié)構(gòu)和形態(tài)的表征 掃描透射X射線的顯微鏡 STXM 已被使用 由于這種技術(shù)具有出色的化學(xué)敏感性和高空間分辨率 40nm 我 們已經(jīng)證明C20A不是與PP相直接接觸 因?yàn)檎惩量偸俏挥趦?nèi)部的彈 性體域 彈性體圍繞著納米粘土 阻礙粘土去角質(zhì)化 并防止其在PP基體中 的分散 另一方面 我們已經(jīng)觀察到的粘土的存在引起的SEBS顆粒成為細(xì)長(zhǎng) 的形狀和滯后的彈性體顆粒的聚結(jié) 介紹納米尺度現(xiàn)象和進(jìn)程為新納米結(jié)構(gòu)材料的發(fā)展打開了革命的可 能性 在聚合物體系中 非常低的層狀硅酸鹽填料含量的加入導(dǎo)致界面的 性質(zhì) 如熱穩(wěn)定性和機(jī)械性能有很大的改善 這是因?yàn)檫@些納米尺寸顆粒的高表面積增加了基體和粘土的界面之 間的相互作用 因此 聚合物 粘土納米復(fù)合材料增強(qiáng)性能的關(guān)鍵因素是基體中的填 料分散液 因?yàn)樽罱K性能取決于處理過程中所生成的結(jié)構(gòu)和形態(tài) 因此 一個(gè)重要的研究工作是專門表征聚合物納米復(fù)合材料納米結(jié) 構(gòu)特點(diǎn) 在這項(xiàng)研究中 我們已經(jīng)考慮到在工業(yè)應(yīng)用中利用熔融法制備全同 立構(gòu)聚丙烯 蒙脫土 聚 苯乙烯 乙烯 丁烯 苯乙烯 彈性體復(fù)合材料這種方法是最有吸引力的 在復(fù)合材料中作為第三組分添加的SEBS目的是提供一種更好的分散 性 并且嵌入的硅酸鹽還提供一種韌性的改善 蒙脫土被最常用來制備納米復(fù)合材料 因?yàn)樗哂懈叩目v橫比 比 表面積大和表面反應(yīng)性 它的結(jié)構(gòu)是上層約1納米厚的硅鋁酸鹽層 它們之間具有規(guī)則的間距 約為1 5nm 它的高陽(yáng)離子交換容量提供了一種方法可以修改層間距 使其更大 更能與聚合物相容 然而 不像等極性基團(tuán)的聚酰胺 在非極性聚合物中如聚丙烯 PP 粘土的的有機(jī)改性不足以實(shí)現(xiàn)良好的分散水平 并且?guī)缀醪粫?huì)形 成混合結(jié)構(gòu) 因此 像聚丙烯接枝馬來酸酐 PP 克 MA 這樣的增容劑被常用來改善有機(jī)聚合物和無機(jī)填料之間的相互 作用 在這項(xiàng)工作中 我們研究了苯乙烯 乙烯丁烯 苯乙烯三嵌段共聚物 SEBS的插層能力 作為一種替代的共同使用 的相容劑 如上述的在聚丙烯 蒙脫土納米復(fù)合材料中的pp g MA 在理論上 SEBS可以有助于聚丙烯鏈進(jìn)入納米粘土層 在聚丙烯納米復(fù)合材料中 彈性體相通常被使用來補(bǔ)償通過添加無 機(jī)填料引起的韌性降低 因此 可以想象SEBS有利于插層和剝離 另一方面 已經(jīng)報(bào)道 在這些不混溶的聚合物中 例如 PS PP或PB T PE共混物 納米粘土行為修改了界面特性 從而改進(jìn)了不同聚合 物相之間的相容性 SEBS提出了相分離的形態(tài) 因此 蒙脫石的相互作用和插層能力和 共同的相容劑有很大不同 通過熔體混合 這項(xiàng)工作的目的是研究等規(guī)聚丙烯粘土橡膠納米復(fù) 合材料的結(jié)構(gòu) 形態(tài)和接口 X 射線衍射 XRD 和透射電子顯微鏡 TEM 用于表征聚合物的嵌入 能力 雖然可以克服鋨染色下的SEBS和PP聚合物相的化學(xué)對(duì)比缺乏 但是T EM顯微鏡還不能提供SEBS在PP 粘土系統(tǒng)作用下增容作用的確鑿信息 需要不同的透射電子顯微鏡去觀察橡膠相 在微米的范圍內(nèi) 和粘 土 在納米級(jí)范圍內(nèi) 這些難以同時(shí)觀察 此外 這種技術(shù)不提供組分的任何化學(xué)信息 實(shí)驗(yàn)部分材料用作基質(zhì)的聚丙烯 聚丙烯 是全同立構(gòu)均聚物 多 分散性為4 77 由REPSOL提供 它的特點(diǎn)是全同立構(gòu)規(guī)整度為95 通過溶液的NMR測(cè)得 粘均分子 量為179000g mol 由特性粘度測(cè)量確定 在這項(xiàng)研究中所用的有機(jī)改性的蒙脫土 MMT 是有機(jī)黏土Cloisite 20A C20A 是南方粘土產(chǎn)品 個(gè)別厚度通常為1nm 在縱橫比大于50 通過XRD確定了層間間距 d為2 52納米 所使用的彈性體是由DYNASOL提供的三嵌段共聚物SEBS Calprene H 6110 其中苯乙烯含量為30 重量 分子量為Mw 85000克 摩 爾 Mw Mn 1 45 這些數(shù)據(jù)通過凝膠滲透色譜 GPC 確定 PP MMT復(fù)合材料的制備聚合物共混物及復(fù)合材料的制備是在連接著Haak eRheocord90同向旋轉(zhuǎn)雙螺桿混合室的Haake RHEOMIX600內(nèi)部混合器內(nèi)熔融共混而成的 190攝氏度 5分鐘的混合時(shí)間 和100rpm的轉(zhuǎn)速被確定為最佳的加 工條件 在復(fù)合材料中 PP C20A SEBS 80 5 15 和粘土負(fù)載為5 重量 因?yàn)樗蛔C明是機(jī)械性能的最佳含量 為了與商