Thesis-2007-Leesirisan.pdf (5.59 MB)
Polyethersulphone/graphite conductive composites for coatings
thesis
posted on 2013-11-19, 15:16 authored by Siriwan LeesirisanIn this research, the electrical conductivity and thermal properties of
polyethersulphone (PES) insulating polymer were improved, at its optimum
micromechanical properties, by filling with electrically and thermally conductive
graphite, for use in coatings for electrostatic dissipation applications. The graphite
employed was a micro-/nano-graphite with aspect ratios in the range 100-600.
Two types of the graphite, untreated and treated, were used for PES composites
and LiCI-doped PES composite fabrication via a solution method. The treated
graphite was surface functionalised by concentrated nitric acid treatment. FT-IR
indicated the effectiveness of concentrated nitric acid treatment in introducing
additional -COOH groups on the surfaces of the graphite. XRD, SEM and TEM
revealed the dispersion of the graphite throughout the PES matrix in both an
immiscIble and disordered manner, and the existence of aggregates of graphite.
Nanoindentation testing showed insignificant decreases in the nanohardness and
elastic modulus of the PES/treated graphite composites when the treated graphite
content was not more than 5 wt%; whereas, increasing the content of the treated
graphite increased the nanoscratch resistance of the composites. Due to the high
aspect ratio of the graphite, the electrical conductivities of the PES/untreated and
PES/treated graphite composites were enhanced at low loadings. An initial
conducting pathway was formed at lower than 3 wt% of the filler. The
enhancement by 2 orders of magnitude of the electrical conductivity of a
PES/treated graphite composite could be accomplished by doping with 0.06 wt%
of LiC!. MDSC showed improvements in the thermal conductivity of the PES
matrix by 165 and 91% with the addition of 5 wt% of the untreated and treated
graphite, respectively. DSC curves illustrated higher glass transition temperatures
of the PES/graphite composites and doped PES/graphite composites, compared to
the pure PES. Decreases in relaxation enthalpy WIth time, due to physical ageing
of PES, were smaller when the PES was filled with the graphite or LiCI-doped
graphite. The decrease in relaxation enthalpy of the materials was accompanied by
increases in glass transition temperature and characteristIc length. Physical ageing
also led to a decrease in the electrical conductivities of the PES/graphite
composites and doped PES/graphite composites.
History
School
- Aeronautical, Automotive, Chemical and Materials Engineering
Department
- Materials
Publisher
© Siriwan LeesirisanPublication date
2007Notes
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.EThOS Persistent ID
uk.bl.ethos.479457Language
- en