Physical properties of polymer nanocomposites

Rheological properties Rheology is the study of the deformation and flow of matter under the influence of an applied stress. The measurement of rheological properties is helpful to predict the physical properties of polymer nanocomposites during and after processing. Oberdisse [44] studied the rheological properties of a special nanocomposite material obtained by film formation of mixtures of colloidal silica and nanolatex solutions by means of uniaxial strain experiments. 

The physical properties of polymer nanocomposites are greatly dependent upon their microstructure, that is, an intercalated or exfoliated structure. XRD at a small angle is an efficient way to measure the hnear dimension of the regular structure in a solid sample so that with XRD, it is easy to decide whether the nanocomposite is intercalated or exfoliated. Rgure 20.2 is a sche-... 

In an effort to understand how geometric factors, such as aspect ratio and dispersion of nanoplatelets, influence the mechanical and physical properties of polymer nanocomposites, significant research efforts have been carried out in recent years [6-9], However, fundamental knowledge is still largely lacking. 

It has been found that the HNBR/SP nanocomposite provides the best thermal and mechanical properties when HNBR is dissolved in Ch and SP is dispersed in MEK. XRD, AFM,TEM, and optical transmittance studies show that the dispersion of clay is best in the Ch/MEK solvent combination and, hence, polymer-filler interaction is also highest in this system. Thus, rather than implying that the solvent selection directly affects the physical properties of the nanocomposite, solvent acts on the properties through its influence on the developed morphology. 

The effect of high shear mechanical mixing and soni-cation methods on the physical properties of the nanocomposites has been analyzed [84] using modified clays with a quaternary ammonium salt and calcium carbonate [85] and silane-treated clays [31]. Although the nanoclay is usually chemically modified to make it organophilic and compatible with the polymer matrix, untreated MMT was... 

According to some reports on studies conducted to improve the physical properties of polymer-clay nanocomposites, a small amount of clay was added to a nylon 6-clay nanocomposite and various improvements were achieved higher polymer strength, higher heat resistance, low linear expansion, low gas permeability, and so on. 

The relationship between microstructure and physical properties of ternary nanocomposites has been the subject of intense investigation due to their very complex nature. In this section, the mechanical properties of polymer blend nanocomposites are reviewed in the context of their microstructure. Following this, the various strategies that have been employed to obtain improved filler dispersion and interfacial interactions are mentioned. 

The characterization methods used in the analysis of the chemical structure, microstructure, and morphology as well as the physical properties of the nanocomposites are varied. Many of these techniques are specific for characterization of particular properties of nanocomposites, and the properties of nanocomposites are also correspondingly discussed. To fully understand the structure-property relationships, several characterization techniques are often used. The properties of the polymer blend nanocomposites strongly depend on their composition, size of the particles, interfacial interaction, etc [35],... 

This chapter describes recent progress in studies aimed at understanding effects of various chemical modification methods on the state of dispersion of clay particles in a high-temperature PI matrix and on the physical properties of polymer/clay nanocomposite films. Three different modification methods and their effects on the Pl/clay nanocomposite... 

Yu Z-Z, Dasari A and Mai Y-W (2006) Polymer-clay nanocomposites - a review of their mechanical and physical properties, in Processing and Properties of Polymer Nanocomposites (Ed. Advaiii S G) World Scientific Publishers, Singapore, pp. 307-358. 

Powell, C.E., Beall, G.W., 2006. Physical properties of polymer/clay nanocomposites. Current Opinion in Solid State and Materials Science 10, 73—80. 

When a thermoplastic polymer is mixed with layered silicate particles, it either intercalates or exfoliates the layered silicates, as schematically shown in Fig. 1. The state of dispersion (intercalation vs exfoliation) of the aggregates of layered silicate in nanocomposites is commonly assessed by X-ray diffraction (XRD) or transmission electron microscopy (TEM). Generally exfoliation is preferred to intercalation, although exfoliation may not necessarily be required for certain industrial applications (e.g., for an enhancement of flame retardant characteristics). It should be mentioned that the greater the extent of exfoliation of layered silicates, the larger will be the total surface areas of the dispersed layered silicates, giving rise to enhanced mechanical/physical properties of the nanocomposites prepared. 

---