Comparative study on the structural change of homopolymerized and copolymerized polyacrylonitrile-based precursor fibers during pre-oxidation
The gradient pre-oxidation treatment of homopolymerized and copolymerized polyacrylonitrile-based precursor fibers were carried out under the same process conditions,and the variation rules of the microstructures of the two types of precursor fibers in pre-oxidation process were analyzed by organic elemental analysis,X-ray diffraction,Fourier transform infrared spectroscopy,and optical microscope.The effects of the introduction of copolymer monomers on the structures of precursor fibers and pre-oxidized fibers were thoroughly explored with the aim of providing certain theoretical basis for the actual production of carbon fibers.The results showed that the introduction of copolymer monomers affected the regularity of PAN molecular chains,reduced the crystallinity of the precursor fibers,increased the intergranular spacing and grain size,so that the crystal structure of the precursor fibers was more likely to be destroyed during pre-oxidation process.It could make the pre-oxidation reaction of the precursor fibers become gentle,and more PAN molecular chains form a stable cross-linking structure,and at the same time,it could attenuate the skin-core structure and improve the homogeneous properties of the fibers.
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