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The Effects of Pore Structure on the Oxidative Stabilization of Polyacrylonitrile Fiber

Author: YueQiWei
Tutor: LvYongGen
School: Donghua University
Course: Materials Science and Engineering
Keywords: Polyacrylonitrile fiber Pre-oxidation Pore ??structure Oxygen diffusion model
CLC: TQ342.31
Type: Master's thesis
Year: 2010
Downloads: 81
Quote: 0
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Abstract

After the advent of the carbon fiber (CF) since the 1950s, with its unique excellent performance caused widespread concern and increasing dosage. If we say that the quality of PAN precursor is the premise of the preparation of high-performance carbon fiber, pre-oxidation process is a bridge between the past and the original wire and carbon fiber, has an important impact on the structure and mechanical properties of the final carbon fiber. First, based on synchrotron radiation small-angle X-ray scattering techniques, PAN-based carbon fiber quantitative characterization of pore structure (average pore size, porosity) of used of Precursors and pre oxygen wire. Compared with other testing methods of the pore structure, the accuracy of the method of testing, outside influence, making simple sample. Accurate characterization of the pore structure of polyacrylonitrile fiber for the study of pre-oxidation process oxygen diffusion process and ultimately affect the mechanical properties of carbon fiber is important. In addition, the work by TG DMA test results found that the thermal performance of the polyacrylonitrile fiber in different atmosphere there is a larger difference. The raw silk only occurs through the nitrogen thermal molecular cyclization, and no occurrence of intermolecular crosslinking occur simultaneously, while through the air treatment, the fiber molecule of intramolecular and intermolecular crosslinking. This work was introduced in the original model based on the porosity parameters, to establish a quantitative relationship polyacrylonitrile raw silk pore structure and oxygen self diffusion coefficient, and figure out the oxidation kinetics. On this basis, the fiber sample in a different atmosphere DSC test to obtain oxidative crosslinking heat release. Combined with the pore structure of the fiber, the establishment of a theoretical model of the diffusion coefficient of oxygen system to study the fibers in the pre-oxidation process oxygen diffusion coefficient and the porosity and the average pore size of the original wire, oxygen diffusion and the fibers were The oxygen content of pre-oxidation. The PAN precursor very significant chemical and physical changes occur in the thermal reaction process, the original linear molecular structure is transformed to planar heat trapezoidal stable structure. The need to apply a certain draft in order to suppress the shrinkage, increase the degree of orientation of the fibers and the final mechanical properties. The present work has found that in the pre-oxidation process, as the temperature increases, pore structure trends are not very obvious. When applying a certain drawing, the degree of orientation of the fiber and the crystal size were increased, while the pore structure of the fibers are also affected, and the porosity and average pore size were decreased to some extent, thus affecting the diffusion of oxygen. This leads to the drawing exceeds a certain level, not fully pre-oxidized and is not to improve the oxidative crosslinking structure is formed in the carbonization process, severe destruction of the fibrous structure, resulting in the decline of mechanical properties of fiber final. When the polyacrylonitrile fiber porosity of ≥ 5%, the average pore size ≥ 1.25nm for the diffusion of oxygen, the oxygen content of the oxide filaments, degree of orientation, and the final strength can better meet the requirements. Process conditions and should therefore be strictly controlled during the spinning process, the porosity and average pore size are more appropriate the polyacrylonitrile carbon fibers with the raw silk.

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CLC: > Industrial Technology > Chemical Industry > The chemical fiber industry > Synthetic fiber > Polyacrylonitrile Department of fibers > Polyacrylonitrile fibers ( acrylic )
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