Clay-Filled Nanocomposites

Fig. 25 WAXD analysis of clay-filled nanocomposites MMT and OMMT in CR matrix (a), LDH and OLDH in CR matrix (b)...

Maiti and Bhowmick reported exciting results that a polar matrix like fluoroelastomer (Viton B-50) was able to exfoliate unmodified clay (Cloisite NA ) as well as the modified one (Cloisite 20A) [93]. They studied morphology, mechanical, dynamic mechanical and swelling properties of fluoroelastomer nanocomposites. The unmodified-clay-filled systems showed better properties than the modified ones (Table 2.3). 

Maji et al. [136] have examined the effect of 30B loading on the mechanical properties of hyperbranched polyurethane (PU) nanocomposites. The extent of clay loading was varied from 2 to 16 phr. The nanocomposite containing 8 wt% 30B clay shows a 100% increase in the tensile strength as compared to unmodi-fied-clay-filled samples. Above 8 wt% clay loading, the mechanical properties decrease. The efficiency and good dispersion of 30B in the hyperbranched PU40... 

PAN 05] Pandey J.K., Singh R.P., Green nanocomposites fiom renewable resources effect of plasticizer on the structure and material properties of clay-filled starch , Starch-Starke, vol. 57, no. 1, pp. 8-15,2005. 

In the past decade, clay-based polymer nanocomposites have attracted considerable attention from the research field and in various applications. This is due to the capacity of clay to improve nanocomposite properties and the strong synergistic effects between the polymer and the silicate platelets on both a molecular and nanometric scale [2,3], Polymer-clay nanocomposites have several advantages (a) they are lighter in weight than the same polymers filled with other types of fillers (b) they have enhanced flame retardance and thermal stability and (c) they exhibit enhanced barrier properties. This chapter focuses on the polymer clay-based nanocomposites, their background, specific characteristics, synthesis, applications and advantages over the other composites. 

In recent years, a new and emerging class of clay-filled polymers called Polymer-Clay Nanocomposites (PCN) was developed. Properties such as superior mechanical strength, reduction in weight, increased heat-resistance and flame retardancy, improved barrier properties against oxygen, carbon dioxide, ultraviolet light, moisture and volatiles, as well as conservation of flavor in drinks and beverages are achievable with these novel composites [17-21]. 

TEM analysis demonstrated the achievement of highly filled nanocomposites with a quite homogeneous distribution of the clay and a satisfactory dispersion. By varying MAO contact time in the pretreatment and experimental polymerization conditions, it was possible to tune the final morphology of the composites (Figure 6.10). 

There are several challenges in the area of rubber nanocomposites. Complete exfoliation and uniform dispersion of nanofillers in rubber matrix still remains to be a challenge. Efficient surfactants have to be designed for the excellent dispersion. In the case of clay filled rubber nanocomposites, the extent of exfoliation-intercalation has not been quantified yet. The orientation of nanoplatelets in rubber matrix by special extrusion is also a major challenge. 

Nagendiran, S. Premkumar, S. Alagar, M., Mechanical and Morphological Properties of Organic-Inorganic, Hybrid, Clay-Filled, and Cyanate Ester/SUox-ane Toughened Epoxy Nanocomposites. J.Appl. Polym. Sci. 2007,106, 1263-1273. 

The weight of polymer clay nanocomposites is also lower than conventionally filled nanocomposites, due to the relatively low levels of clay addition needed to realize property improvements. 

In the past two decades, many academic or industrial researchers have paid attention to polymer/layered-silicate nanocomposites (PLSs), especially to poly-mer/organically modified clay (organoclay) nanocomposites. These PLS materials often exhibit remarkable improvement in properties over those of both virgin polymer and conventional filled systems, and many represent a better choice... 

Although the incorporation of microscale particles as fillers into polymers has been well explored scientifically, the decrease in size of particles to nanometers, and the simultaneous increase in interface area, results in extraordinary new material properties.In one such application, the flammability properties of polymers have been improved with the addition of nanoscale particles. These filled nanocomposites provide an attractive alternative to conventional flame retardants. At present, the most common approach to improving flammability is the use of layered silicates such as clays, as described in Chapter 3. However, there are many different shapes and types of nanoparticles. (Here, a nano scale particle is defined as having at least one dimension on the nanometer scale.) When all three dimensions are on the order of nanometers, we are dealing with true nanoparticles, such as spherical silica particles, having an aspect ratio of 1. Another type of nanoparticle has only one dimension on the nanometer scale. Such nanoscale... 

In modem era, consumers expect safer food of good quality, high sensory attributes, and inexpensive with increased shelf life. Nowadays, clay filled polymers termed as polymer clay nanocomposites (PCN) has been developed. The PCN exhibit more mechanical strength, increase heat resistaiKe, improved barrier properties against moisture and volatiles as well as conserves the flavor, and taste of varions drinks and beverages. 

Accordingly, a two-step method, named masterbatch process, has been approached for the preparation of PCL layered silicate nanocomposites by combining the in-situ intercalative polymerization and the melt blend intercalation process d. In such a process, a highly clay-filled (organo-modified) PCL is first prepared by in-situ intercalation pol)mierization of e-CL, followed by its addition as masterbatch, that is blended with the molten polyester matrix (commercial PCL CAPA 650). As it will be shown, this method permits to prepare PCL-based nanocomposites with a high degree of exfoliation, which cannot be achieved by directly mixing PCL and clay. 

Figure 5.3 Schematic of the microstructures that can be developed in clay-filled polymer nanocomposites.

Sengwa, R.J., Choudhary S., and Sankhla, S. (2010) Dielectric properties of montmorillonite clay filled poly(vinyl alcohol)/poly(ethylene oxide) blend nanocomposites. Composites Science and Technology, 70,1621-1627. 

S. Balakrishnan, P. R. Start, D. Raghavan, and S. D. Hudson. The influence of clay and elastomer concentration on the morphology and fracture energy of preformed acrylic rubber dispersed clay filled epoxy nanocomposites. Polymer, 46 (2005), 11255-11262. 

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