The Effect Of Oxidation Treatment Of MWCNT On The Properties Of PDMS Nanocomposite
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Date
2012-05
Authors
Mazlan, Norkhairunnisa
Journal Title
Journal ISSN
Volume Title
Publisher
Universiti Sains Malaysia
Abstract
MWCNT have a unique electrical properties, thermal conductivity which is
higher than diamond and a good mechanical properties where strength and stiffness
exceed any other current materials However, poor dispersibility and interfacial
adhesion of MWCNT in polymer matrix presents a considerable challenge in
developing nanocomposite with good properties. Oxidation treatment was done on
MWCNT as to improve the dispersion and interfacial adhesion between the
nanotubes and PDMS. The oxidation treatments of MWCNT were carried out by
oxidizing using either single acid (HNO3) or mixture of acids (HNO3/H2SO4) at 3:1
ratio. The treatments were done for different period of time (3 and 6 hours) and
temperature (80°C and 140°C). FTIR and XPS analysis showed the presence of
various functional groups such as C-O, C=O and COOH. The O/C ratio increased
from 0.17 for untreated MWCNT to 0.56 for oxidized MWCNT. Acid bes titration
showed increase in concentration of acid groups about 159%. The oxidation affects
the tubes more significantly when the temperature and time increased to 140°C and 6
hours respectively as the ID/IG ratio increased from 0.19 to 0.83 and reduction in
thermal stability. The presence of functional groups formed electrical double layer on
the MWCNT surface and thus, gave good dispersibility in water. This layer also
overcome the strong van der Waals force within the nanotubes and reduced
agglomeration. The presence of defects and catalysts were also observed by TEM.
For PDMS filled with MWCNT oxidized in HNO3 at 80°C for 3 and 6 hours, the
tensile strength increased to 5.06 MPa, while thermal and electrical conductivity
slightly increased for approximately to 24% and 42%, respectively over the untreated
MWCNT/PDMS nanocomposites. However, for PDMS filled with MWCNT
oxidized at 80°C for 6 hours in acid mixture, the thermal and electrical conductivities
were slightly decreased to 0.19 W/mK and -4.62 Log/Scm-1. Decrease in properties
was more significant for PDMS filled with MWCNT oxidized at 140°C for 6 hours
as the Tg value decreased for 9°C compared PDMS reinforced with MWCNT
oxidized at 80°C for 6 hours, in which its Tg was approximately -35°C. Aggressive
oxidation treatment reduces the capability of MWCNT to form good interfacial
interaction with the PDMS matrix. However, this type of MCWNT was suitable to be
used to increase the plasticity of the polymer matrix.
Description
Keywords
The effect of oxidation treatment of MWCNT , on the properties of PDMS nanocomposite