Mechanical properties of nanocomposites

Haraguchi K, Farnworth R, Ohbayashi A, Takehisa T (2003) Compositional effects on mechanical properties of nanocomposite hydrogels composed of poly(N,N -dimethylacrylamide) and clay. Macromolecules 36 5732-5741... 

MAT 08] Mathew A.P., Thielemans W., Dufresne A., Mechanical properties of nanocomposites from sorbitol plasticized starch and tunicin whiskers . Journal of Applied Polymer Science, vol. 109, no. 6, pp. 4065 074,2008. 

Zhang, C., Luo, J., Li, W., Chen, D. 2003. Mechanical properties of nanocomposite TiN/Si3N4 films synthesized by ion-beam assisted deposition. J. Tribal. 125 445 48. 

Siqueira, G., Bras, J., Dufresne, A. Cellulose whiskers versus microfibrils influence of the nature of the nanoparticle and its surface functionalization on the thermal and mechanical properties of nanocomposites. Biomacromolecules 10, 425 32 (2009)... 

Dufresne, A. Cellulose Whiskers versus Microfibrils Influence of the Nature of the Nanoparticle and its Surface Functionalization on the Thermal and Mechanical Properties of Nanocomposites. Can. J. Chem. 86, 484—494 (2008)... 

Unfortunately, both these modifications are complicated processes to carry out. There is also a negative side effect of using modified cellulose whiskers. It has been shown that modified whisker have less reinforcing effect than unmodified whiskers. Grunert and Winter [74] prepared nanocomposites with a hydrophobic thermoplastic matrix using trimethylsilylated cellulose whiskers. They found that unmodified whiskers showed a better reinforcing performance than the trimethylsilylated whiskers. Similarly, the mechanical properties of nanocomposites containing chemically modified chitin whiskers from crab shell were found to be inferior to the unmodified nanocomposites [75]. 

The uniformity and stability of nanotube dispersion in polymer matrices are most important parameters for the performance of composites. A good dispersion leads to efficient load transfer concentration centres in composites and to uniform stress distribution. Many scientists have reviewed the dispersion and functionalisation techniques of CNT for polymer-based nanocomposites, as well as their effects on the properties of CNT/polymer nanocomposites. They demonstrated that the control of these two factors led to uniform dispersion. Overall, the results showed that a proper dispersion enhanced a variety of mechanical properties of nanocomposites. 

From the above, it is clear that the specific surface area of the filler, which is closely related to filler shape, is of fundamental importance in the xmderstanding of the structtue-property relationship of nanocomposites. The change in particle diameter, layer thickness, or fibrous material diameter from micrometer to nanometer, changes the ratio by three orders in magnitude. At this scale, there is often distinct size dependence of the material properties. Furthermore, with the drastic increase in interfadal area, the properties of the composite are dominated more by the properties of the interface or interphase [2] and they play a much more important role in enhancing the mechanical properties of nanocomposites than in conventional composites or bulk materials [ 1 ]. 

The mechanical properties of nanocomposites based upon a thermoplastic polyurethane filled with BN, M0S2, and WS2 have been investigated by Coleman et al. as shown in Fig. 13. They showed that there were substantial levels of reinforcement upon the addition of these 2D nanocrystals that were comparable to the best results achieved using graphene or nanoclays as fillers. 

Hossain, K.Z., Ahmed, I., Parsons, A., Scotchford, C., Walker, G., Thielemans, W., et al. Physico-chemical and mechanical properties of nanocomposites prepared using cellulose nanowhiskers and poly(lactic acid). J. Mater. Sci. 47, 2675-2686 (2012)... 

It is well known that one of the major requirements of polymer nanocomposites is to optimize the balance between the strength/stifihess and the toughness as much as possible. Therefore it is usually necessary to characterize the mechanical properties of nanocomposites from different viewpoints. Several criteria, including tensile strength, impact strength, flexural strength, hardness, fracture toughness, and so forth, have been used to evaluate the nanocomposites. 

Bragaiifa et al. [97] showed the importance of the clay lamellar intercalation and exfoliation to define the material mechanical properties of nanocomposites. In this study, montmorillonite clay with different interlamellar cations (NaL Li+, K+, and Ca +) was mixed with styrene-acrylic latex and dried to produce nanocomposites. An ultra-thin cut of the sample was analyzed by ESI-TEM. The elemental maps of carbon, silicon, and calcium were used to identify the polymer, clay, and cation domains, as presented in Fig. 8.13. 

Skakalova V, Dettlaff-Weglikoska U and Roth S (2005) Electrical and mechanical properties of nanocomposites of single wall carbon nanotubes with PMMA, Synth Met 152 349-352. 

Most of the research has been on the mechanical properties of nanocomposites at room temperature, and only a few researchers have studied the cryogenic properties of epoxy and its composite [68-70]. 

EFFECTS OF SURFACE-MODIFIED CELLULOSE NANOCRYSTALS ON STRUCTURE AND MECHANICAL PROPERTIES OF NANOCOMPOSITES... 

---