Mechanical Properties of CNFs

The main reason for the recent popularity of nanotechnology is that the reduction of the dimensions of a material to nanosize leads to new specific properties [82]. It is crucial to understand the intrinsic mechanical properties of CNFs in order to incorporate them into polymer resins to fabricate CNFs-reinforced nanocomposites. Because of the structural complexity of CNFs derived from variations in inner and outer wall thickness, cone angle, orientation of graphite plane, and C-C bonds, determination of their mechanical properties had posted considerable difficulties. To date, direct measurement of tensile properties of CNFs is accessible only with the aid 

Another mechanical properties measurement of CNFs was achieved by Joseph et al. [84] via three-point-bending method. In that work, CNFs were mounted on copper grid through the deposition of platinum pads 

---

The superb mechanical properties of CNFs make them a good reinforcement agent for different synthetic materials. In comparison with macroscopic fibers, a lower quantity of nanofibers is required to attain the same reinforcement result and reduce brittleness their large specific surface area promotes relaxation processes in the matrix as well, which improves the impact strength of the reinforced matrix. More than that, the small diameters of CNFs provide very limited refraction of fight, which makes them transparent in matrices [82]. 

Jonoobi et al. (2010) studied mechanical properties of CNF reinforced PLA composites. The tensile strength and modulus were improved with increased nanofiber contents. The modulus of the PLA was increased from 2.9 to 3.6 GPa with the addition of 5 wt% nanofibers, a 24 % increase. Similarly, a 21 % increase in tensile strength was observed for nanocomposites compared to neat PLA. On the other hand, strain to failure of nanocomposites was decreased with increase in nanofiber content. Classical models of Halpin-Tsai and Krenchel were used to compare the predicted theoretical data with the experimental data. It was found that experimental data were nearer the predicted value of Krenchel than Halpin-Tsai, which was a confirmation of the random distribution of nanofibers in the matrix, as hypothesized by Krenchel, rather than aligned in longitudinal direction, as hypothesized by Halpin-Tsai. 

George and Bhowmick [147] have also studied the influence of the polarity of EVA (40, 50, 60, and 70% vinyl acetate content) and the nature of the nanofiller [expanded graphite (EG), multiwall carbon nanotubes (MWCNTs), and CNFs] on the mechanical properties of EVA/carbon nanofiller nanocomposites. They pointed out that the enhancement in mechanical properties with the addition of various... 

Carbon-based nanocomposites refer to a class of composites modified or reinforced by carbon nanostructures such as carbon nanotube (CNT), carbon nanofiber (CNF), and particulate nanodimond (PND). Here, the strategy of utilizing carbon nanostructures, primarily CNT and CNF, to improve osteogenic property and bioactivity of the nanocomposites is primarily discussed. The strategy of promoting mechanical properties of orthopedic implants by creating carbon-based nanocomposites will be discussed in Chapter 5. 

Table 5.3 Applications of CNT and CNF in improving mechanical properties of orthopedic implants...

FIGURE 3 Influence of CNF on elastic mechanical properties of vulcanized EPDM. 

Jonoobi, M., Harun, J., Mathew, A. R, Oksman, K. (2010). Mechanical properties of cellulose nanofiber (CNF) reinforced polylactic aeid (PLA) prepared by twin screw extrusion. (12), 1742-1747. 

Previous studies on nanocomposites made with highly conductive nanoparticles and amorphous polymers have been reported (Jimenez and Jana, 2007 Mathur et al., 2008) such nanocomposites possessed a strain-to-failure of less than 5%. In a recent study (Vdlacorta et al., 2012), we have investigated the EM SE and electrical properties of heat-treated CNFs dispersed in a flexible linear low-density polyethylene (semiciystalhne) matrix. This chapter explores the effect of two other carbon-based modifiers on the EM SE of composites prepared by multiple melt-mixing routes with LLDPE for potential use in ductile/flexible EMC apphca-tions. Attention is also directed to the electrical and mechanical properties of such composites in relation with their electromagnetic shielding performance. 

Jain S, Thakare VS, Das M, Godugu C, Jain AK, Mathur R, Chuttani K, Mishra AK (2011) Toxicity of multiwalled carbon nanotubes with end defects critically depends on their functionalization density. Chem Res Toxicol 24(11) 2028-2039 Jeena JK, Narasimha Murthy HNM, Rai KS, Krishna M, Sreejith M (2010) Effect of amine functionalization of CNE on electrical, thermal, and mechanical properties of epoxy/CNF composites. Polym Bull 65(8) 849-861... 

Carbon nanotubes (CNTs) have incredible mechanical properties and high aspect ratio [1-3], and they seem to be superior reinforcement fibers to improve the mechanical properties of ceramic materials. We have combined carbon nanofibers (CNFs) with the average diameter of 104 nm which were a type of multi-walled CNT with alumina [4,5]. 

The mechanical properties of the chitin nanofiher, CNF- -PBLG, and CNF-fl -PLGA network films were evaluated by tensile testing. 

CNF reinforced UP and UP-GF composites have been prepared. The addition of CNFs can improve both thermd and mechanical properties of the UP resin. Compared with the pre-mixing approach, our new prebinding method can reduce the filter effect of long fibers on CNFs and prepare the composites with better distribution of nanoparticles, resulting in better mechanical properties. This study also proves that the incorporation of nanoparticles into the polymer matrix is a promising way to improve the properties of FRPs in the transverse and/or thickness direction. 

Recently, the remarkable properties of carbon nanotubes (CNTs) and related structures, such as carbon nanofibers (CNFs) and onionlike carbons, have attracted an increasing interest from the catalysis community [66], Although these materials are most often used as supports for active phases, some applications as catalysts have been reported, the oxidative dehydrogenation of ethylbenzene to styrene being the most frequently cited example [67-73], These reports basically confirm the mechanism proposed previously, based on a redox cycle involving the quinone surface groups. 

The analysis of adsorption, electronic, mechanical, and thermal properties of CNTs and CNFs, with respect to catalytic requirements, is needed to evaluate their stability and to predict how the metallic particles could anchor to the support and how the reagents could interact with these metal-supported catalysts, and to understand what such novel carbon forms could bring to catalysis. The possibility of nanofilamentous carbon shaping and sizing to prevent handling problems is also discussed. 

---