pan纤维低温碳化过程结构演变规律研究

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1、3．在纤维后续的热裂解和结构重组阶段，二次环化效果具有继承性，经较佳的二次环化温度处理后的纤维，其碳纤维的石墨结构更加规整，纤维的碳收率提高，体现出良好的综合效能。4．PAN预氧纤维环化程度的升高对二次环化后的纤维的热稳定性影响不大，氧含量的升高对二次环化后的纤维的热稳定性影响较大。本论文的研究明确了PAN预氧纤维在低温碳化过程的结构演变规律，并探讨了二次环化阶段处理温度的不同对纤维热稳定性的影响，对碳纤维制备过程中工艺的选取具有指导意义。关键词：聚丙烯腈纤维，环化结构，含氧结构，石墨结构，热稳定性Abstr

2、actSTUDYOFSTRUCTUREEVoLUTIONOFPoLYACRYLONITRILEFIBERSDURINGLOWTEMPERATURCARBoNIZATIoNABSTRCATAfterthestabilizationprocessinthepreparationofpolyacrylonitrilefiber,thestructureinprecursorhastransformedintoladderstructurewhichiscausedbycyclization，dehydrogenat

3、ionandoxidationreaction．DSCcurvedisplaysthatafterthestageofstabilization，therearestillalargenumberofexothermicreactionsinfiber．TherearemanyfunctionalgroupsofC----Nwhohavenotcyclized．Throughfurtherheat-treatmentininertatmosphere，thecompositionandstructureofp

4、olyacrylonitrilepreoxidedfiberwillcontinuetoevolve．Comparetostabilizationprocess，fewpeoplehasresearchedtheevolutionofpolyacrylonitrilepreoxidedstructureandtheevolutionofthestructureinthewholestageoflowtemperaturecarbonization．Usingtestsof13Csolidnuclearmagn

5、eticresonance，X-rayphotoelectronspectroscopy,thermo-gravimetricanalysis，differentialscanningcalorimetry,ElementalanalysisandRamanspectralanalysis，thestructuraltransformationofpolyacrylonitrilefiberanditseffectonthermalstabilitywereinvestigated．Theresultsind

6、icatedthat：北京化工大学硕士学位论文1．Therearetwocharacteristicstructuresinpolyacrylonitrilepreoxidedfiber．OneiscyclicstructurecharacterizedbyC=CandC=N，theotherisoxygen—containingstructurecharacterizedbyC=OandC—OH．Thestageoflowtemperaturecarbonizationcanbedividedintothr

7、eestagesthroughthermalbehavioranalysis．Thefirststageistwicecyclization，thesecondstageispyrolysis，andthethirdstageisstructuralrearrangement．2．Inthestageoftwicecyclization，intramolecularcyclizationreaction，intermolecularcyclizationreaction，therearrangementofc

8、yclicstructureandoxygen-containingstructuretakesplace．Alongwiththeincreasingofprocessingtemperature，thecontentofquaternaryaromaticcarbonatomsincreaseandtheoxygen-containingstructuresreduce．Theeffectofc