Kong, Kenneth Thean Soon
(2012)
Studies On The Processing And Properties Of Conductive Single Fillers And Hybrid Fillers Filled Silicone Elastomer Composites.
Masters thesis, Universiti Sains Malaysia.
Abstract
Multi-walled carbon nanotubes (MWCNTs) filled poly(dimethyl siloxane)
(PDMS) composites were produced via two different processing methods. The first
method is the solution mixing method where MWCNT were dispersed in a solvent
using an ultrasonicator before mechanically mixed with PDMS. The second method
entails the use of a mini-extruder to disperse and mix the MWCNTs and PDMS.
Scanning Electron Microscopy (SEM) micrographs revealed that samples produced
by mini-extruder exhibited shorter nanotubes, but better nanotubes dispersion
compared with solution mixing. The composites prepared using the mini-extruder
was found to have higher tensile strength and thermal conductivity. On the other
hand, the composites prepared via solution mixing show higher electrical
conductivity and better thermal stability. Functionalization of nanotubes with –OH
and –COOH improves the tensile strength, thermal conductivity and thermal stability
but does not contribute to the electrical conductivity enhancement. The properties of
PDMS/exfoliated graphite nanoplatelet (xGnP) are comparable to that of
PDMS/MWCNT. Composites filled with 4 wt% hybrid fillers with an
xGnP/MWCNT-OH ratio of 3/1 show the highest thermal conductivity, electrical
conductivity, and the lowest coefficient of thermal expansion. In general, the hybrid
fillers can be used to produce composites with improved properties at lower cost due
to the cheaper cost of xGnP.
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