ORGANICALLY MODIFIED LAYERED CLAYS

1. ORGANICALLY MODIFIED LAYERED CLAYS
SOLUTION MIXING
RIYA THANKACHAN
2ND M.Sc BPS
CBPST, KOCHI

2. LAYERED SILICATE-EPOXY
NANOCOMPOSITES
 The inorganic particle layered silicate commonly known as nanoclay or
organoclay has a lamellar structure consisting of hydrous magnesium or
aluminum silicates.
 Having high aspect ratio, large surface area, and good interfacial
properties, layered silicate clay added to a polymer matrix can contribute
to significant cost savings as a property enhancer. Clay-containing polymer
nanocomposites may offer beneficial properties
• such as good mechanical properties, dimensional stability, barrier
properties, flame retardancy, optical properties,and thermal stability.
 Polymer clay composites exhibit three distinct morphologies, that is
• conventional segregated clay phase and intercalated and exfoliated
structures.

3.  Improved mechanical, thermal, and barrier properties are
usually obtained for an exfoliated architecture; that is,
individual silicate lamellae are homogenously distributed in
the polymer matrix.
 The degree of clay exfoliation and intercalation depends on
• The type of clay , cation exchange capacity , chemical
nature of the interlayer cations , curing agent, curing
temperature and time, resin type, and dispersion method.
 There are several processing routes that can lead to well-
dispersed layered silicate nanocomposite;
• These are in situ intercalative polymerization, exfoliation-
adsorption, and melt processing

4. The unique intercalation/exfoliation behavior of smectite clay minerals
which is responsible to the high aspect ratio of this clay type makes them very
important and powerful as reinforcing filler for polymers.

5. • Individual silicate layers provide excellent
stiffness and strength in two dimensions due to
their high aspect ratio, stiffness, and interaction
at the molecular level.
• nanoclay has the ability to simultaneously
increase toughness and stiffness of a polymer.
• In a study, Zilg et al. observed that the extent of
layered silicate exfoliation is directly related to
nanocomposite stiffness, while fracture
toughness is inversely affected by the exfoliation
state.

7. • The fracture and deformation mechanisms of nanoclay-
filled epoxy have qualitatively shown evidence of crack
deflection, crack pinning, cavitation, and matrix
deformation phenomena that improved crack propagation
resistance in nanocomposites.
• Zerda and Lesser. documented crack deflection and
branching by intercalated nanoclay diverting cracks in a
tortuous path while creating additional fracture surface
area.
• In epoxy-clay nanocomposites, formation of microcracks
within the clay interlayers and subsequent propagation
associated with the creation of new surface area due to
crack deflection were considered to be the primary energy
dissipation mechanisms.

9. MECHANICAL DISPERSION
• At first, the nanoclay was dried in an oven at 120°C for 24 hours and
subsequently allowed to cool down to room temperature.
• Then, a measured amount of nanoclay was added to preheated EPON 826
resin at 60°C and mechanically mixed for 30 minutes with an impeller-type
mechanical mixer running at 900 revolutions per minute.
• Then, a stoichiometric amount of the curing agent (i.e., 36 g of EPIKURE
9551 was used per 100 g of EPON 826) was added to the epoxy-clay
solution, followed by mechanical mixing at 60°C for five minutes.
• Any entrapped air and volatiles formed during mixing with the curing
agent were evacuated by a vacuum pump operated at 80 kPa for 20
minutes.
• The final mixture was cured in an open mold made with mild steel having
interior dimensions of 21 cm by 11.5 cm by 2.5 cm. Curing of the epoxy
and nanoclay blend occurred in an oven at 120°C for two hours.
Composite samples having 1 wt%, 2 wt%, and 3 wt% of clay were
produced using this method.

10. Material
• For this study a bisphenol-A epoxy resin (EPON
826, epoxide equivalent weight 178–186 g/eq)
and non-MDA polyamine curing agent (EPIKURE
9551) were obtained from Momentive
(Columbus, OH, USA).
• Commercially available organoclays
Nanomer (CH3(CH2)17NH3-MMT) and
Nanomer (CH3(CH2)17N(CH3)3-MMT) and PGW—
an unmodified sodium montmorillonite clay (Na-
MMT).

11. Preparation of the Epoxy-Clay
Nanocomposites
.• Nanocomposites were synthesized by two
separate nanoclay dispersion schemes. In situ
intercalative polymerization was performed
using a mechanical agitator; this is hereafter
termed as mechanical dispersion.
• An exfoliation-adsorption process was carried
out using an ultrasonic probe with the aid of
the solvent acetone, which is hereafter
designated as ultrasonic dispersion

12. The surface modification of clay layers can be achieved through a cation
exchange process by the replacement of sodium and calcium cations present in
the inter layer space or claygalleries by alkylammonium or alkylphosphonium
(onium) cations .
 In addition to the surface modification and increasing the
hydrophobisity of clay layers, the insertion of alkylammonium or
alkylphosphonium cations into the galleries causes to somedegree of
increasing in the inter layer spacing which promotes the following
intercalation of polymer chains into the galleries during nanocomposite
preparation.
Also the alkylammonium or alkylphosphonium cations can provide
functional groups which interact with polymer chains or initiate the
polymerization and therefore increase the interfacial interactions.
 Figure shows the organically modification of clay layers using
alkylammonium cations via the ion exchange process.

14. PARTICLE DISTRIBUTION
• Transmission Electron Micrographs of the representative samples were
taken to study the distribution of the nanosilica particles in the composite
prepared.
• A fine agglomerate –free and uniform dispersion of the nano particle.
• The particle size was found to be in narrow distribution range of 6 to 20
nm.
• In addition,the transparency of the resin was retanied upon
reniforcement.this is due to fact that light scattering is minimized owing to
the good dispersion of the very small particles within the matrix .
• Atomic force micrographs ,taken from the fractured surface of the nano
composites, also revealed the distribution of the nano particles. In
addition, a good coupling of the particles with the matrix is seen.

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18. FRACTURE TOUGHNESS
• Upon nanosilica reinforcement, the fracture toughness of the amine catalysed epoxy
matrix system was found to increase by 73%.
• Apart from some scatter in the lower volume fraction range,the value increased
almost linearly with the nanosilica content.
• Fracture toughness is a measure for the ability of a material to resist the growth of
pre-existing crack or flaw.

19. Thank you….