Ti-News n. 14 // July 2015 - page 3

Ti news
Nanocomposites consisting of polymers and layered silicate belong to an emerging class of organic-inorganic
hybrid materials promise great potential for tailoring the property profile of polymers in a multitude of
applications. In many polymer matrices, clay minerals have been used to improve mechanical, barrier,
thermal, degradation, flame resistance and rheological properties. Due to their large specific surface area
(SSA), organoclays act as highly effective functional fillers for polymers provided that the particles are evenly
dispersed in thematrix. To achieve good dispersion in a hydrocarbon polymermatrix, the inorganic claymineral
is compatibilized with coupling agents such as silanes or by substituting the exchanging inorganic cations like
sodium ions with organo-cations, thus forming what is called an organoclay (OC).
Clay minerals consist of nano-sized thin platelets of high “aspect ratio”, which means the edge length of the
platelets is much larger than their thickness. Clay fillers have been used to improve the barrier properties
of polypropylene. Among other parameters like solubility and mobility, the concentration gradient Δc / Δs
across the walls of a polymer container defines the diffusion rates of penetrating molecules.
Since the concentration of such penetrants inside and outside such a container is fixed, the only way to
reduce the concentration gradient is to increase the diffusion path length. Various continuum models
have been proposed to predict the permeability of clay-polymer composites. These models are generally
based on clay platelets aligned at random parallel and perpendicular to the permeation direction
(randomly in only two directions).
Schematic representation of the different types of composites produced from the interaction between layered compounds and polymers: (a)
Intercalated Nanocomposite; (b) Exfoliated Nanocomposite.
Scientific Corner
Barrier properties of
Clay-Polymer Nanocomposite
1,2 4,5,6,7,8,9,10,11,12,13,...20
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