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Effect of carbon nanofibers on micro...

Lee, Sungho.

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Effect of carbon nanofibers on microstructure and properties of polymer nanocomposites.

Record Type:	Language materials, printed : Monograph/item
Title/Author:	Effect of carbon nanofibers on microstructure and properties of polymer nanocomposites./
Author:	Lee, Sungho.
Description:	187 p.
Notes:	Adviser: Amod A. Ogale.
Contained By:	Dissertation Abstracts International68-11B.
Subject:	Chemistry, Polymer. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3290717
ISBN:	9780549344315

Effect of carbon nanofibers on microstructure and properties of polymer nanocomposites.
Lee, Sungho.

Effect of carbon nanofibers on microstructure and properties of polymer nanocomposites. - 187 p.

Adviser: Amod A. Ogale.

Thesis (Ph.D.)--Clemson University, 2007.

Nano-modifiers are typically three orders of magnitude smaller in size than their micro-counterparts. Crystalline and orientational structure of CNF/polymer composites was investigated in this study.

ISBN: 9780549344315Subjects--Topical Terms:

1018428
Chemistry, Polymer.

Effect of carbon nanofibers on microstructure and properties of polymer nanocomposites.
LDR:05569nam 2200373 a 45 001 957409
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020 $a 9780549344315
035 $a (UMI)AAI3290717
035 $a AAI3290717
040 $a UMI $c UMI
100 1 $a Lee, Sungho. $3 1280761
245 1 0 $a Effect of carbon nanofibers on microstructure and properties of polymer nanocomposites.
300 $a 187 p.
500 $a Adviser: Amod A. Ogale.
500 $a Source: Dissertation Abstracts International, Volume: 68-11, Section: B, page: 7495.
502 $a Thesis (Ph.D.)--Clemson University, 2007.
520 $a Nano-modifiers are typically three orders of magnitude smaller in size than their micro-counterparts. Crystalline and orientational structure of CNF/polymer composites was investigated in this study.
520 $a First, the microstructure of two different grades of CNFs, MJ (experimental) and PR (commercial), was investigated as a function of different thermal treatments. Using Raman spectroscopy and XRD analysis, an enhancement of crystallite size was observed after heat treatment at 2200°C. The crystallite thickness increased from 1.6+/-0.1 nm to 10.9+/-0.5 nm for MJ fibers and from 3.1+/-0.3 nm to 11.7+/-0.4 nm for PR fibers. Also, an increase in thermal oxidation stability for heat-treated CNFs was observed. BET adsorption isotherms showed a significant reduction of specific surface area of MJ fibers after the heat treatment, resulting from a decrease of pore volume. However, even after heat treatment, MJ fibers possessed a rougher surface than did PR fibers. The role of such nano-texture was studied on two distinct types of polymeric matrices: flexible-chain and semi rigid-rod polymers.
520 $a Linear low density polyethylene (LLDPE), a flexible-chain polymer, is widely used for packaging applications because of its film-forming properties and good barrier characteristics. However, LLDPE has a poor electrical conductivity, which results in poor EMI/ESD shielding. Therefore, CNFs were incorporated into LLDPE to improve electrical conductivity. The Electrical percolation threshold was observed at approximately 15 wt% MJ (MJ15) and 30 wt% PR (PR30). Tensile modulus increased from 110 MPa for pure LLDPE to 200 MPa and 300 MPa for MJ15 and PR15, respectively. However, the tensile strength remained fairly unchanged at about 20 MPa. Strain-to-failure decreased from 690% for pure LLDPE to 460% and 120% for MJ15 and PR15, respectively. This indicates that the interfacial bonding of LLDPE matrix with MJ fibers is better than that with PR fibers, possibly due to rougher surface of the MJ fibers.
520 $a Crystallization behavior of LLDPE nanocomposites was investigated in the presence of three types of CNFs (MJ, PR, and PRCVD). During non-isothermal crystallization studies, all three crystalline melting peaks for LLDPE matrix were observed in the presence of PRCVD fibers up to 15 wt% content. However, at only 1 wt% MJ fibers, the disappearance of the intermediate melting peak was observed. The broad melting peak at the lower temperature became larger, suggesting an increase in the relative content of thinner lamellae in the presence of MJ fibers. The larger and the rougher surface of MJ fibers observed from the nano-textural study contributes toward the different crystallization behavior of MJ/LLDPE composites. TEM micrographs of nanocomposites revealed transcrystallinity of LLDPE on the surface of CNFs. Further, a broader distribution of LLDPE lamellar thickness was observed in TEM images of MJ composites.
520 $a The third major component of this research project was a study on the role of CNFs on a thermotropic liquid crystalline polymer (TLCP) matrix possessing a semi rigid-rod molecular structure. A variation of anisotropy of the TLCP was investigated in the presence of CNFs. Electrical percolation threshold was observed at approximately 5 wt% MJ fibers. Decrease of tensile modulus and strength was observed for composites. For a given type of flow, wide angle X-ray diffraction studies showed a decrease in Herman's orientation parameter from 0.85 for pure V400P to 0.71 for 5 wt% MJ composites. Thus, the presence of CNFs led to a reduction of the overall anisotropy of the nematic phase in the nanocomposite.
520 $a The disruption of molecular orientation of TLCPs was inferred by SEM and TEM analysis. SEM micrographs revealed a fibrillar structure for pure TLCPs at a macro-scale. However, this structure was not observed in composites at the same scale although micro-size fibrils were found with the addition of PR fibers. TEM micrographs displayed banded structures of pure TLCPs, but these structures were not significant in the vicinity of PR fibers. These results indicate that CNFs can help to reduce the severe anisotropy that is otherwise observed for TLCPs. In summary, this study establishes the significant role of CNFs as nano-modifiers that help modify the texture of the matrix while serving to enhance specific properties, such as electrical conductivity, for the nanocomposites. (Abstract shortened by UMI.)
590 $a School code: 0050.
650 4 $a Chemistry, Polymer. $3 1018428
650 4 $a Engineering, Chemical. $3 1018531
690 $a 0495
690 $a 0542
710 2 $a Clemson University. $b Chemical and Biomolecular Engineering. $3 1263063
773 0 $t Dissertation Abstracts International $g 68-11B.
790 $a 0050
790 1 0 $a Harrison, Graham M. $e committee member
790 1 0 $a Hirt, Douglas E. $e committee member
790 1 0 $a Lickfield, Gary C. $e committee member
790 1 0 $a Ogale, Amod A., $e advisor
791 $a Ph.D.
792 $a 2007
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3290717