Simulation The Pre-oxidation And Carbonization Of Mesophase Pitch Fibers By Thermal Analysis

Mesophase pitch based carbon fibers, obtained from mesophase pitch through refining, spinning, oxidation, carbonization, owns so many excellent properties as high modulus, low thermal dilatability, thermal and electrical conductivity. Pre-oxidation and carbonization as key processes among the preparation of carbon fibers, both controlling the appropriate degree of oxidation and optimizing of oxidation process are crucial for the performance of carbon fiber and the production efficiency, especially for different raw mesophase pitch, choosing appropriate oxidation temperature in order to achieve optimal performance. In addition, carbonization as the next heat treatment, associated with the process of oxidation reaction. Studying the weight loss during the carbonization of mesophase pitch fibers with different oxidation degree by thermogravimetric analysis (TG), can be a reference for the future industrial production and laboratory Judgment the oxidation process. Research work of this thesis as follows:(1) Choosing naphalene-based pitch (M-A) and petroleum pitch was prepared by thermal polycondensation method (M-B), as raw materials. The stabilization processes of spun fibers were studied by Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TG). The structure and mechanical properties of carbon fibers was characterized by scanning electron microscopy (SEM) and single filament tensile test. The results showed that the oxidation stabilization was a dehydrogenative process, where the hydrogen removed was mainly aliphatic and oxygen uptake was mainly in the form of C-O-C and C=O groups. The more aliphatic chain of M-A accelerated the stabilization process with respect to M-B. M-A showed a higher oxidation activity but a section radiated structure, high temperature oxidation treatment would accelerate the formation of defects in fibers, which reduced the mechanical properties of carbon fibers. M-B showed less oxidation reactivity, and need a higher oxidation treatment temperature to stabilization.(2) The weight loss during the carbonization of mesophase pitch fibers with different oxidation conditions was monitored by TG. The chemical structure of the oxidized fibers in terms of functional groups, distribution of gas products, the microstructure and mechanical properties of carbonized fibers were characterized by FT-IR, thermogravimetric mass spectrometry (TG-MS), SEM and single filament tensile test, The results indicated that TG can be used to characterize the carbonization process to optimize the oxidation for pitch fibers and performance of carbon fibers.(3)The changes of chemical functional groups?microstructure and performance of mesophase pitch based fiber in the process of carbonization were characterized by FT-IR, XRD and monofilament tensile device, respectively. During the process of carbonization, the absorption peak of hydroxy and methyl weakened, the absorption peak of benzene ring and C-O disappeared after 600?, The absorption peak of C=C was enhanced, showed that there exited crosslinking, cyclizing condensation, polymerization and aromatization have been reacted. At the same time the degree of order of microcrystalline structure and mechanical properties improved continually.(4) Based on the carbonization reaction and characteristics of weight loss rate curve, three phase continuous reaction pseudo components model was established, through the comparative analysis of the simulated values and measured values to verify the effectiveness of the model.The results all above showed that it is necessary to choose suitable oxidation temperature for mesophase pitch fibers of different properties and structure characteristics, and using TG to study the carbonization prosses of mesophase pitch fibers, provided a good reference for the Judgment of the oxidation process and the weight loss analysis.