Mechanical, atomic force microscopy and focussed ion beam studies
of isotactic polystyrene/titanium dioxide composites
Selvin P. Thomas
a,1
, Sabu Thomas
a,
*
, Sri Bandyopadhyay
b
a
School of Chemical Sciences, Mahatma Gandhi University, P.D. Hills PO, Kottayam, Kerala 686 560, India
b
School of Materials Science and Engineering, University of New South Wales, Sydney 2052, NSW, Australia
article info
Article history:
Received 13 November 2006
Received in revised form 17 September
2008
Accepted 5 October 2008
Keywords:
A. Polymer-matrix composites (PMCs)
A. Particle-reinforcement
B. Mechanical properties
D. Electron microscopy
abstract
Composites of isotactic polystyrene with different loading of titanium dioxide were prepared by melt
mixing in a Brabender Plasticorder at a rotor speed of 60 rpm at 180 °C. Mechanical properties of the
composites were measured by various techniques and most of the properties were found to be increasing
with filler loading. Tapping mode atomic force microscopy was used to study the surface characteristics
of the composites. Various AFM analytical parameters like power spectral density, roughness analysis and
section analysis were measured. The mechanical properties of the composites were correlated with ana-
lytical data obtained from the AFM studies. The focused ion beam technique was also used to characterize
the dispersion of the filler in the polymer matrix.
Ó 2008 Elsevier Ltd. All rights reserved.
1. Introduction
Polymer composite is a combined material created by the
assembly of two or more components such as filler or reinforcing
agent and a compatible matrix in order to obtain specific charac-
teristics and properties. The composites often offer the properties
that neither constituent has. The components of a composite do
not merge completely into each other but nevertheless they do
act in concert and are divided generally by direct boundaries. These
components as well as the interface between them can usually be
physically identified and it is this behaviour, and properties of the
interface that generally control properties of the composite. The
properties of a composite cannot be achieved by any of the compo-
nents acting alone. For obtaining the optimal properties in com-
posites their components have to be chosen so as to have sharply
different but complimentary properties [1–8]. There are several
examples of polymer composites such as fibre-reinforced ones,
mineral filler added ones and recently nanocomposites.
A large number of literatures are available about the properties
related to these polymer composites. Among these the mechanical
behaviour of the filled polymer systems has been studied exten-
sively [9–14]. In these reports various mechanical properties such
as modulus, tensile strength, strain at break, flexural behaviour,
etc., were studied. We can see that the easiest mechanical property
to be estimated is the modulus of the system. This is because it is a
bulk property that depends primarily on the geometry, particle size
distribution and concentration of the filler. The tensile strength of a
filled polymer is more difficult to predict because it depends
strongly on local polymer–filler interactions as well as the above
factors [15–18]. The filler/matrix interaction and dispersion of fill-
ers into the matrix can be estimated by various techniques such as
DSC, SEM, AFM, etc.
Atomic Force Microscopy is a versatile technique, which can be,
used for the characterization of the polymer films, polymer–filler
interactions, etc. AFM is one of the most important microscopic
techniques used for the surface analysis of polymers on a nanome-
ter scale. The added advantage of using AFM is that it can give dis-
tinguished surface topography and surface heterogeneity. In AFM,
a probe consisting of a sharp tip (nominal tip radius of the order
of 10 nm) located near the end of a cantilever beam is scanned
across the sample surface using piezoelectric scanners. During
scanning, a particular operating parameter is maintained at a con-
stant level and images are generated through a feedback loop be-
tween the optical detection system and the piezoelectric
scanners. Three imaging modes can be used to produce topo-
graphic images of sample surfaces, namely contact mode, non-con-
tact mode and tapping mode, which is more applicable on soft
samples. Tapping mode AFM is exclusively used in this work. Sev-
eral studies related to the multiphase polymeric systems using
AFM were reported in the literature. Raghavan et al. have elabo-
rated a procedure for mapping polymer heterogeneity using AFM
focussing mainly on the tapping force employed to obtain the
phase images of varying contrast levels [19]. Skolnik et al. have
1359-835X/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.compositesa.2008.10.005
* Corresponding author. Tel.: +91 481 2730003; fax: +91 481 2731002.
E-mail address: sabut552001@yahoo.com (S. Thomas).
1
Visiting Research Associate, School of Materials Science and Engineering,
University of New South Wales, Sydney 2052, NSW, Australia.
Composites: Part A 40 (2009) 36–44
Contents lists available at ScienceDirect
Composites: Part A
journal homepage: www.elsevier.com/locate/compositesa