Polymer/clay nanocomposites nanocomposite properties

The addition of small amormts of high aspect ratio (of the order of -200) nanoclay platelets to a polymer matrix, through melt mixing, leads to significant improvements in the polymer/clay nanocomposite properties such as stiffness, tensile strength, barrier properties as well as melt... 

Meneghetti, P. and Qutubuddin, S. 2006. Synthesis, thermal properties and applications of polymer-clay nanocomposites. Thermochimica Acta 442 74-77. 

Usuki, A., Hasegawa, N. and Kato, M. Polymer-Clay Nanocomposites. Vol. 179, pp. 135-195. Uyama, H. and Kobayashi, S. Enzymatic Synthesis and Properties of Polymers from Polyphenols. Vol. 194, pp. 51-67. 

Polymer-clay nanocomposites (PCN) are a class of hybrid materials composed of organic polymer matrices and organophilic clay fillers, introduced in late 1980s by the researchers of Toyota (Kawasumi, 2004). They observed an increase in mechanical and thermal properties of nylons with the addition of a small amount of nano-sized clays. This new and emerging class of pol miers has found several applications in the food and non-food sectors, such as in constmction, automobiles, aerospace, military, electronics, food packaging and coatings, because of its superior mechanical strength, heat and flame resistance and improved barrier properties (Ray et al., 2006). 

The term polymer clay nanocomposite (PCN) refers to a material composed of two-phase materials, where one phase (clay) is dispersed in the second phase (polymer matrix) at a nanometer level. Composites exhibiting structural and compositional changes at the molecular scale have demonstrated several physical property enhancements that are otherwise unavailable in conventional composites. Of these, layered silicates have proven themselves vital as a reinforcing agent when dispersed into engineering plastics. Nanolayers, however, are extremely difficult to disperse in polymer matrices because of their tendency for face-to-face... 

Polymer clay nanocomposites exhibit very low flammability. For instance, the heat release rate during the combustion of polyamide 6-clay nanocomposite is reduced by 63% with a clay content of 5wt%. The nanocomposite structure also enhances the property of the char through reinforcement of the... 

Polymer clay nanocomposites have, for some time now, been the subject of extensive research into improving the properties of various matrices and clay types. It has been shown repeatedly that with the addition of organically modified clay to a polymer matrix, either in-situ (1) or by melt compounding (2), exfoliation of the clay platelets leads to vast improvements in fire retardation (2), gas barrier (4) and mechanical properties (5, 6) of nanocomposite materials, without significant increases in density or brittleness (7). There have been some studies on the effect of clay modification and melt processing conditions on the exfoliation in these nanocomposites as well as various studies focusing on their crystallisation behaviour (7-10). Polyamide-6 (PA-6)/montmorillonite (MMT) nanocomposites are the most widely studied polymer/clay system, however a systematic study relating the structure of the clay modification cation to the properties of the composite has yet to be reported. 

As pointed out before, the polymer may be functionalized with polar groups to enhance compatibility with the modified clay. Bellucci et al. [92] have reported that the formation of polymer-clay nanocomposites depends mostly on the polymer properties, clay characteristics, and type of organic modifier. 

Since Nylon-6/clay nanocomposites with excellent thermal and mechanical properties were reported by many scientists and polymer/clay nanocomposites have attracted much attention. The improvements in thermal. 

Polymer clay nanocomposites are already used in many applications to enhance existing properties of a particular material, and development should be focused on the true multifunctional materials. Certainly, clay nanocomposites will continue to be used for enhanced mechanical, flammability, and gas barrier properties, but fundamental limits in clay chemistry prevent them from being used easily in applications requiring electrical/ thermal conductivity or optical properties. Similarly, combinations of... 

Investigating the use of functional surfactants for the modification of clay and the properties of the resultant polymer/clay nanocomposite, Hartmann s team [69, 70] used surface-active RAFT agents. The appropriate functionalization of these RAFT agents made their attachment to clay platelets possible. As a result, a controlled growth of polymer chains from the surface of the clay platelets was achievable. They extrapolated to miniemulsion for the first time [71] their studies on styrene polymerization performed in bulk [72] in the presence of Montmorilloniteclay modified with PCDBAB and DCTBAB (Fig. 6). 

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