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Study on the Preparation of Carbon Nanofibers by Polymer Blend Technique

Author: LingFen
Tutor: LiGuang
School: Donghua University
Course: Materials Science
Keywords: carbon nanofibers polymer blend carbonization PF PAN
CLC: TQ342.742
Type: Master's thesis
Year: 2007
Downloads: 70
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Abstract


Carbon nanofibers (CNFs) have been the focal point of numerousresearch programs in the past ten years because of their unique physicaland chemical properties. Recently polymer blend technique has beendeveloped as a novel method to prepare carbon nano materials, includingcarbon nanotubes and carbon nanofibers. In this paper, CNFs with thediameter less than 200nm were prepared by blend spinning process. Theinfluence of the compatibility, spinning condition, carbonizationtemperature on the morphology and structure of the CNFs was discussed.The CNFs were dispersed throughout epoxy resin matrices by sonicationto fabricate the composites. The effects of loading and dispersion ofcarbon nanofibers on the structures and properties of composites wereinvestigated. The whole research work contains three parts.Firstly, the phenol-formaldehyde (PF) and polypropylene (PP) blendfibers were prepared by melt-spinning technique and carbonized at high temperature under a nitrogen atmosphere. After carbonization of theblend fibers, the PP component was removed and the PF component leftin the form of thin carbon fibers. The compatibility of PP/PF blend andthe effects of experimental parameters, such as the content of chemicaldegradation agent and the draw ratio, on the morphology of the thincarbon fibers were investigated via FTIR and SEM. Craphite structures ofthe thin fibers under different carbonization conditions were investigatedvia XRD and Raman spectra. Results showed that the diameter of theproduced carbon fiber was decreased with the increasing of draw-ratioand increased with the increasing of chemical degradation agent content.PP/PF/chemical degradation agent =60/20/20 was selected as the optimalblend ratio and CNFs prepared at optimal condition were smaller thantwo hundred nanometers. XRD and Raman spectra showed that the PP/PFblend treated at 600℃produced some graphite crystallite. But thegraphitization degree of CNFs treated at 900℃was still lower, and itbelonged to the range of amorphous carbon.Secondly, polymethyl methacrylate (PMMA) was used as thermallydecomposable polymer(TDP); and Polyacrylonitrile (PAN) as carbonprecursor polymer (CPP). CPP and TDP polymer blends were preparedthrough solution mixing. The blend fibers were obtained afterwet-spinning. Oxidization and carbonization were made to remove TDP.Effectes of spinning condition, draw ratio and carbonization condition on properties and structure of the resulted carbon nanofibers were discussedby means of SEM, TGA, FTIR, electrical conductivity test, Ramanspectra, etc. The results showed that porous carbon fibers obtained whenthe blending ratio of PAN/PMMA was 7/3 and superfine carbon fibersobtained when the blending ratio of PAN/PMMA was 3/7. The carbonnanofibers obtained in this work had good conductivity and it alsobelonged to the range of amorphous carbon.Finally, CNFs /epoxy resin composites were fabricated by usingultra-sonication method. Electrical conductivity, tensile strength, andthermal stability of the composites were studyed. The electrical resistivitywas decreased as the increase of carbon content. The composite showedan electrical resistivity of 10~4Ω·cm when the CNFs loading was 5 wt%.The tensile strength of them first increased and then decreased with theincreasing of CNFs content, and the composite with 2 wt% CNFs contentshowed higher tensile strength than others.

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CLC: > Industrial Technology > Chemical Industry > The chemical fiber industry > Synthetic fiber > Special fiber > Carbon fiber to maintain the fiber > Carbon fiber
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