Research On Influence Of Pre-oxidized Structure On Carbonization Cracking Characteristice

During the preparation of PAN-based carbon fiber,complex structural changes have been happened within the molecule of oxidation and carbonization.These changes have influence on physical and chemical properties and processing performance of fiber.The difference in the structure of PAN-based pre-oxidized fiber leads to a large difference during pyrolysis and recombination.In this article,pre-oxidized fibers were prepared at different temperature range from 160? to 280?.And sample numbers corresponding to precursor and temperature classes(160?-280?)are from T1 to T14.The relationship between the structural transformation and pyrolysis has been studied by using FT-IR,DCS,Tg,SEM and NMR.Structural changes of oxidization are observed by making use of Tg to simulate pyrolysis and dissolved amount in different temperatureThrough making dissolution experiments,it can be learned that initial reaction temperature of PAN-based pre-oxidized fibers is 180?.When higher than 180?,the internal structure of the fiber will change dramatically,increasing insoluble system.And insoluble amount of fiber will also reach a maximum of about 97%at 240?.With temperature rising,insoluble amount of fiber no longer increases significantly.The sample shows characteristic absorption peak at 1580cm-1.This means that PAN-based pre-oxidized fiber begins to undergo an internal cyclization reaction.There is no change in the peak at 1360cm-1 and 1450cm-1.And it means that there is no dehydrogenation reaction at 170?.Through analyzing characteristic absorption peak,it can know that with temperature rising,-CH2 of fiber changes into-CH and-C=N changes into-C=O.And structure of-C=O and-CH becomes more and more.Internal structure becomes more stable and oxygenated structure of fibers increased significantly.According to the relationship of physical and chemical properties of PAN-based pre-oxidized fiber,we analyze the relationship between physical and chemical properties and temperature.If the degree of pre-oxidization is increased,it will make fiber accelerating pyrolysis,form larger defects and adversely affect the tensile properties and densification of the fiber.By adjusting temperature reasonable and regulating the skin-core structure of fibers,it can adjust oxygen content and pyrolysis of the fiber.And finally we get a product with better comprehensive performance.