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Tactoids

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One of the most commonly used organically layered silicates is
derived from montmorillonite (MMT)
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Nanoclays in their pristine form are hydrophilic, thus incompatible with most
polymers
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These factors make the intimate contact between the polymer matrix
and the nanoclay difficult
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”
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96 nm
and a lateral dimension of 100– 200 nm
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These stacks ofunit layers are known as
tactoids and occur in different shapes and sizes
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The dispersion of the tactoids into discrete monolayers is further
hindered by the intrinsic incompatibility of hydrophilic clay and hydrophobic
engineering polymers
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Moreover, high surface area and energy of the nanoclays may highly induce
formation of platelet stacking or tactoids, thus inhibit full function of the
nanoclay as reinforcing nanofiller
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Therefore, surface modification of the clay nanofiller using organic surfactants is
commonly performed to impart its hydrophobic characteristic and subsequently
improve compatibility between the nanoclay and the hydrophobic polymer
matrix
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This is because; the
agglomerated MMT has high tendency to form intracellular reactive oxygen
species (ROS) which can induce cell membrane damage through localized
oxidative stress
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Generally, the quality of organo-MMT dispersion and distribu- tion in the EVA
matrix was slightly reduced as the nanofiller loading increased from 1 to 5 wt %
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In contrast, the addition of the
pre- dispersed organo-MMT (MMT(W)2m_ut) into the EVA resulted in reduced
hydrolytic degradation effect
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poorly-dispersed organclays are more likely to leach out and pose safety risk as
compared to the well-dispersed organoclays, due to their high tendency of
forming large tactoids, which can easily phase separated from the host polymer
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Vigorous stirring and adequate shear energy might be needed in order to break
the tactoids and fully exfoliate this par- ticular nanofiller for better dispersing
ability inside the polymer matrix
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When using water medium, the surfactant’s hydrophobic tails would attempt to
“hide” from the hydrophilic environment, accumulate, and cause precipitation
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Conse- quently, this could hinder larger degree of
tactoid loosening dur- ing the pre-dispersing process
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With regards to this factor, it was postulated that upon the pre-dispersing
process, the organo-MMT powder was in the form of loosely packed tactoids
(destabilized condition) rather than swelling
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As a result, the tactoid size distribution measured
using this method can be directly related to the exfoliation state of clay mineral
tactoids without changing the experimental conditions
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Images were taken at different magnifications in order to include in the analysis
different types of clay platelets (individual sheets, thinner tactoids, thicker tactoids,
and agglomerates) to provide a good statistics of the distribution of the filler in the
matrix
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1 g of Na-Mt was dispersed in 100 ml of
this medium in a 500 ml beaker, then sonicated for 1 h at room temperature with the
aim of breaking clay tactoids and making the solvent molecules intercalate into the
interlayer space
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Afterwards, the pH of the suspension was reduced to 4 by means of a 1 M solution of
HCl
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Extruders and three roll
mill or ball mill are designed to achieve exfoliation of nanoclay through high shear
forces by controlling speed and temperature
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, 2008; Kk & Ko, 2014; Kotal &

Bhowmick, 2015; Osman, Kalo, Hassan, Hong, & Azmi, 2016; Sridhar, Narasimha
Murthy, Pattar, Vishnu Mahesh, & Krishna, 2012)
References
Ali, S
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(2015)
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Applied Clay Science, 114, 85–92
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org/10
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clay
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05
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, Abouelmagd, A
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(2017)
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Applied Clay Science, 146(June), 439–448
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org/10
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clay
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06
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, Garofalo, E
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, & Incarnato, L
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Effect of polymer/organoclay
composition on morphology and rheological properties of polylactide nanocomposites
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https://doi
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1002/pc
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, Stubbings, H
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, Duncan-Smith, J
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W
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F
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Regional clinical registry data show increased incidence of cutaneous melanoma
in Cape Town [7]
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https://doi
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1016/
Kk, G
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(2014)
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Journal of Material Science & Engineering, 04(01), 1–5
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org/10
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1000151
Kotal, M
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K
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Polymer nanocomposites from modified clays: Recent
advances and challenges
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https://doi
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1016/j
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2015
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001
Osman, A
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, Kalo, H
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S
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W
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(2016)
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Journal of Applied Polymer Science,
133(11), 43204–43220
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org/10
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43204
Sridhar, R
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N
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, Vishnu Mahesh, K
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, & Krishna, M
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Parametric study of twin screw extrusion for dispersing MMT in vinylester using
orthogonal array technique and grey relational analysis
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https://doi
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1016/j
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2011
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025

Note
This excerpts is taken from various journals for my research
You can read the full text from journals mention above

Yours sincerely

-MAIZI-



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