Elastomeric epoxy nanocomposites: Nanostructure and properties
, J.M. Hutchinson
Institute of Polymer and Dye Technology, Technical University of Lodz, Stefanowskiego 12/16, 90-924 Lodz, Poland
Centre for Research in NanoEngineering (CRNE) and Departament de Màquines i Motors Tèrmics, ETSEIAT, Universitat Politècnica de Catalunya, Colom 11, 08222 Terrassa, Spain
Received 6 October 2011
Received in revised form 12 January 2012
Accepted 15 January 2012
Available online 24 January 2012
B. Mechanical properties
D. Transmission electron microscopy (TEM)
In polymer layered silicate nanocomposites, signiﬁcant differences have been reported between the
effects of the nano-reinforcement on rigid and elastomeric nanocomposites. In this paper, we have stud-
ied elastomeric nanocomposites based upon DGEBA epoxy resin ﬁlled with montmorillonite (MMT) and
cured with a long-chain polyoxypropylene diamine, for comparison with analogous rigid nanocompos-
ites. Ultrasonic mixing was used to disperse the MMT in the matrix to improve homogeneity and
decrease the agglomerate size. Two different methods of nanocomposite preparation were used in which
the MMT was ﬁrst swollen with either the curing agent or the epoxy before the addition of, respectively,
DGEBA or diamine. A better dispersion of the nanoclay in the matrix and a greater amount of intercalation
occurred when the MMT was ﬁrst swollen with the diamine. The effect of MMT concentrations up to
8 wt.% on the mechanical behaviour of the epoxy/MMT nanocomposites was investigated. It was found
that the addition of MMT increased the tensile strength and modulus, although SAXS and TEM indicated
that a signiﬁcant fraction of the clay layers were not exfoliated. Nevertheless, the addition of the clay
resulted in changes in the fracture surfaces, as indicated by SEM, consistent with the tensile results
and indicative of toughening.
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Polymer layered silicate (PLS) nanocomposites based on ther-
mosetting polymers are of interest as a new class of materials char-
acterised by improved mechanical, thermal and physico-chemical
properties. Such nanocomposites are generally obtained by ﬁrst
mixing the resin monomer with the organically modiﬁed clay, in
the form of stacks of lamellae of thickness about 1 nm and several
hundred nanometres long and wide [1,2]. After curing, the ﬁnal
properties of the nanocomposite are signiﬁcantly inﬂuenced by
the dispersion of the clay particles in the polymer matrix and by
the degree of exfoliation of the clay layers. In fully exfoliated PLS
nanocomposites, an ideal nanostructure that is in general difﬁcult
to achieve, the clay lamellae would be completely separated and
uniformly distributed throughout the polymer matrix, and the
property enhancement would be optimised.
For epoxy-based PLS nanocomposites, the structure of the
three-dimensional network formed can be signiﬁcantly different,
depending on the type of resin, curing agent and curing conditions
used, which has an inﬂuence on the properties and performance of
the cured materials . Furthermore, by curing the epoxy with
cross-linking agents of increased chain length, it is possible to
obtain nanocomposites with rubber-like rather than rigid proper-
It has become clear that, in the case of rigid epoxy PLS nanocom-
posites, the procedure involved in the nanocomposite preparation
and the curing conditions strongly inﬂuence the exfoliation of the
clay layers [9–12]. For signiﬁcant property enhancement in the
nanocomposite materials, it is essential to disperse the clay
homogeneously and then exfoliate the individual clay platelets.
Unfortunately, in general it still remains a problem to achieve
well-dispersed MMT particles in the epoxy matrix. Numerous
methods, such as mechanical, ultrasonic and solvent mixing have
been applied by many authors in an attempt to obtain a homoge-
neous dispersion of MMT in the nanocomposite [13–15].
Besides the effect of these different mixing methods, the proce-
dure used for the preparation of elastomeric epoxy/organoclay
nanocomposites in particular also plays an important role. One
procedure is to swell the clay in the epoxy resin before adding
the cross-linking agent and curing the system, while another is
to add the clay directly to the mixture of epoxy and cross-linking
agent [4,5]. As a further alternative, Boukerrou et al.  proposed
the swelling of the MMT in the curing agent before the addition
of the desired amount of the epoxy resin. This method of prepara-
tion resulted in a better dispersion of the clay and a greater extent
of intercalation (larger d-spacing) of the curing agent in the MMT
compared with that obtained by swelling the clay in the resin.
The montmorillonite concentration is another important
parameter to consider. In the case of elastomeric epoxy/clay
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Corresponding author. Tel.: +34 93 739 8123; fax: +34 93 739 8101.
E-mail addresses: email@example.com (M. Lipinska), firstname.lastname@example.org.
edu (J.M. Hutchinson).
Composites Science and Technology 72 (2012) 640–646
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