Mechanical reinforcement, nanocomposite morphology

Nanocomposites encompass a large variety of systems composed of dissimilar components that are mixed at the nanometer scale. These systems can be one-, two-, or three-dimensional organic or inorganic crystalline or amorphous. A critical issue in nanocomposite research centers on the ability to control their nanoscale stmcture via their synthesis. The behavior of nanocomposites is dependent on not only the properties of the components, but also morphology and interactions between the individual components, which can give rise to novel properties not exhibited by the parent materials. Most important, the size rednction from microcomposites to nanocomposites yields an increase in snrface area that is important in applications such as mechanically reinforced components, nonlinear optics, batteries, sensors, and catalysts. 

S-H. Wu, F-Y. Wang, C-C.M. Ma, W-C. Chang, C-T. Kuo, H-C. Kuan, and W-J. Chen, Mechanical, thermal and morphological properties of glass fiber and carbon fiber reinforced polyamide-6 and polyamide-6/clay nanocomposites, Mater. Lett., 49, 327-333 (2001). 

Zimmermann, T., Pohler, E., Schwaller, P. Mechanical and morphological properties of cellulose fibril reinforced nanocomposites. Adv. Eng. Mater. 7, 1156-1161 (2005)... 

W. S. Chow and S. S. Neoh, Dynamic mechanical, thermal, and morphological properties of silane-treated montmorillonite reinforced polycarbonate nanocomposites. Journal of Applied Polymer Science, 114 (2009), 3967-75. 

Ganter, M., Gronski, W., Reichert, P and Muhlhaupt, R. (2001). Rubber Nanocomposites Morphology and Mechanical Properties of BR and SBR Vulcanizates Reinforced by Organophilic Layered Silicate. Rubber Chemistry and Technology, 74, 221. 

M. Ganter, W. Gronski, P. Reichert, R. MUlhaupt (2001) Rubber nanocomposites morphology and mechanical properties of BR and SBR vulcanizates reinforced by organophilic layered silicates, Rubber Chem. Technol. 7, 221. 

Chow WS, Abu Bakar A, Mohd Ishak ZA, Karger-Kocsis J, Ishiaku US. Effect of maleic anhydride-grafted ethylene-propylene rubber on the mechanical, rheological and morphological properties of organoclay reinforced polyamide 6/polypropylene nanocomposites. Eur Polym J 2005 41 687-96. 

Recent demands for polymeric materials request them to be multifunctional and high performance. Therefore, the research and development of composite materials have become more important because single-polymeric materials can never satisfy such requests. Especially, nanocomposite materials where nanoscale fillers are incorporated with polymeric materials draw much more attention, which accelerates the development of evaluation techniques that have nanometer-scale resolution." To date, transmission electron microscopy (TEM) has been widely used for this purpose, while the technique never catches mechanical information of such materials in general. The realization of much-higher-performance materials requires the evaluation technique that enables us to investigate morphological and mechanical properties at the same time. AFM must be an appropriate candidate because it has almost comparable resolution with TEM. Furthermore, mechanical properties can be readily obtained by AFM due to the fact that the sharp probe tip attached to soft cantilever directly touches the surface of materials in question. Therefore, many of polymer researchers have started to use this novel technique." In this section, we introduce the results using the method described in Section 21.3.3 on CB-reinforced NR. 

Crucially, structure of CNTs and polymers plays a key role on mechanical properties and load-transfer of nanocomposites. Efficient load-transfer is only possible when adequate interfacial bonding strength is available. Interfacial failure may compromise the reinforcement effect and then the full potential of CNTs may not be realized (11). Therefore, it is of great importance to understand the effect of molecular structure, interfacial structure and morphology characteristics on the tensile properties of nanocomposite materials. 

TPV nanocomposites of LLDPE/reclaimed rubber with nanoclay and 1 wt.% MA-grafted PE and curative were prepared using a Brabender internal mixer at 170°C (Razmjooei et al., 2012). Contents of the reclaimed rubber, nanoclay, and compatibilizer were varied up to 30, 7, and 21 wt.%, respectively. The blends without the compatibilizer were also prepared. Morphological, thermal, and mechanical properties of the nanoclay-reinforced TPV nanocomposites indicated intercalation and partial exfoliation by the high-shear stress during mixing with the reclaimed rubber. Vulcanization of rubber phase led to an increase of viscosity. The size of rubber particles in TPV was reduced with the addition of nanoclay and compatibilizer. 

The reinforcement of polypropylene and other thermoplastics with inorganic particles such as talc and glass is a common method of material property enhancement. Polymer clay nanocomposites extend this strategy to the nanoscale. The anisometric shape and approximately 1 nm width of the clay platelets dramatically increase the amount of interfacial contact between the clay and the polymer matrix. Thus the clay surface can mediate changes in matrix polymer conformation, crystal structure, and crystal morphology through interfacial mechanisms that are absent in classical polymer composite materials. For these reasons, it is believed that nanocomposite materials with the clay platelets dispersed as isolated, exfoliated platelets are optimal for end-use properties. 

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