Clay properties aspect ratio

The Halpin-Tsai and Mori-Tanaka theories based on first-principle arguments adequately model the mechanical properties provided by the reinforcement of montmorillonite as a dispersed phase in all polymers [5,20]. The significant independent variables that correlate to reinforcement are aspect ratio, modulus, and the alignment of the montmorillonite in the direction of the applied stress. It is enlightening to examine some of the general predictions of these theories as they relate to the effect of clay loading, aspect ratio, and the modulus of the pristine... 

Maiti and Bhowmick [205] have established a good correlation between the aspect ratio of clay in fluoroelastomer/clay nanocomposites and the transport properties of solvent. For fluoroelastomer/clay nanocomposites, permeability decreases significantly with the addition of only 4 phr of the unmodified mont-morillonite clay (0.14 x 10 s cm2 s ) compared with that of neat polymer (2.29 x 10 8 cm2 s-1)-... 

In order to obtain good interfacial adhesion and mechanical properties, the hydrophilie elay needs to be modified prior to its introduction in most polymer matriees, which are organophilie. When nanometric dispersion of primary clay platelets is obtained, the aspect ratio of the filler particle is increased and the reinforcement effect is improved [75-25],... 

Hollow tubes extracted from the silica/alumina clay halloysite exist naturally as particles roughly 500 nm long, and they do not have the exfoliation issues of platy nanoclays. Thus, these nanofillers do not require the same specialized equipment and processing that nanoclays require for proper dispersal. As fillers, nanotubes provide high properties because of their very high aspect ratios. 

However, the tensile strength of in-situ polymerized nanocomposites is higher than other systems. The improvement in tensile property of nanocomposites occurs at the expense of strain to failure. The clay platelets dispersion and interaction with polyamide matrix are important factors that influence the mechanical properties. The high aspect ratio of the clay platelets and exfoliated clay platelets in nanocomposites are responsible for the improvement in mechanical properties. 

Durmus, A., Woo, M., Kasgoz, A., and Macosko, C. W. 2008. Mechanical properties of linear low density polyethylene (LLDPE)/clay nanocomposites Estimation of aspect ratio and interfacial strength by composite models. Journal of Macromolecular Science, Part B Physics 47 608-619. 

Lu, C. and Mai, Y. W. 2005. Influence of aspect ratio on barrier properties of polymer-clay nanocomposites. Physical Review Letters 95 088303 1-4. 

---