Mechanical reinforcement, nanocomposite

By analogy with the works which dealt with cellulose micro crystal-reinforced nanocomposite materials, microcrystals of starch [95] or chitin [96, 97] were used as a reinforcing phase in a polymer matrix. Poly(styrene-co-butyl acrylate) [95,96], poly(e-caprolactone) [96], and natural rubber [97] were reinforced, and again the formation of aggregates or clustering of the fillers within the matrices was considered to account for the improvement in the mechanical properties and thermal stability of the respective composites processed from suspensions in water or suitable organic solvents. 

Due to unprecedented mechanical, electrical and chemical properties, CNTs have been considered as an ideal material for various applications as well as for new fundamental investigations (1,2). In this review chapter, we will only discuss mechanical and electrical properties. In most composite structures, nanotubes are used as mechanical reinforcing agents or conductive fillers. This is also the case of PVA/nanotubes nanocomposites. 

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. 

Carbon nanotubes (CNTs) and carbon nanofibers (CNFs), due to their unique structure and properties, appear to offer quite promising potential for industrial application [236]. As prices decrease, they become increasingly affordable for use in polymer nanocomposites as structural materials in many large scale applications. In fact, three applications of multiwall CNT have been discussed recently first, antistatic or conductive materials [237] second, mechanically reinforced materials [238,239] and third, flame retarded materials [240,241]. The success of CNTs in the field of antistatic or conductive materials is based on the extraordinary electrical properties of CNTs and their special geometry, which enables percolation at very low concentrations of nanotubes in the polymer matrix [242]. 

Cellulose is one of the most attractive bio-resources for energy and chemicals [6-9]. Most cellulose is utilized as raw material in the paper industry for the production of paper and cardboard products. Cellulose based nanocomposites have emerged as a new type of advanced materials, attracting great interest in their research and development. Cellulosic nanocomposites are formed by adding cellulose nanoscale fillers in various polymer matrices resulting in mechanical reinforcement and alteration of other properties. 

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

AyatoUahi, M. R., Shadlou, S., and Shokrieh, M. M., Multiscale modeling for mechanical properties of carbon nanotube reinforced nanocomposites subjected to different types of loading. Composite Structures, 93, 2250-2259 (2011). 

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... 

Masenelli-Varlot, K., Vigier, G., and Vermogen, A. 2007. Quantitative structural characterization of polymer-clay-nanocomposites and discussion of an "ideal" microstructure, leading to the highest mechanical reinforcement. 

This chapter reviews the use of the sepiolite/palygorskite group of clays as a nanofiller for polymer nanocomposites. Sepiolite and palygorskite are characterized by a needle-like or fiber-like shape. This peculiar shape offers unique advantages in terms of mechanical reinforcement while, at the same time, it allows to study the effect of the nanofiller s shape on the final composite properties. The importance of the nanofiller shape for the composite properties is analyzed in Section 12.2, introducing the rationale of the whole chapter. After a general description of needle-like nanoclays in Section 12.3, the chapter develops into a main part (Section 12.4), reviewing the preparation methods and physical properties of polyolefin/needle-like clay nanocomposites. 

Key words ballistic fibers, micro-Raman spectroscopy, nanotechnology, reinforcement mechanisms, reinforcing polymer nanocomposite fibers. 

Nanocomposites with silica nanoparticles have been prepared in poly-dimethylsiloxanes, butadiene, styrene-butadiene, acrylonitrile-butadiene, acrylic and ethylene-propylene diene rubber. Nanocomposites in isoprene rubbers are here examined. In a nutshell, these nanocomposites were prepared adopting the three methods summarized above and nano-silica was reported to promote the mechanical reinforcement of poly (isoprene) matrices, less that CB but more than conventional silica, with lower viscosity. 

Dufresne AJ (2006) Comparing the mechanical properties of high performance polymer nanocomposites from biological sources. J Nanosci Nanotechnol 6 322-330 Dufresne A (2008) Polysaccharide nano crystal reinforced nanocomposites. Can J Chem 86 484—494 Dufresne A, Vignon M (1998) Improvement of starch film performances using cellulose microfibrils. Macromolecules 31 2693-2696... 

In recent years, lamellar nanofiUers have been established as the most important filler type for barrier and mechanical reinforcement. Dal Point et al. reported a novel nanocomposite series based on styrene-butadiene rubber (SBR latex) and alpha-zirconium phosphate (a-ZrP) lamellar nanofiUers. The use of surface modified nanofiUers improvement the mechanical properties. However, no modification of the gas barrier properties is observed. The addition of bis(triethoxysilylpropyl) tetrasulfide (TESPT) as coupUng agent in the system is discussed on the nanofiUer dispersion state and on the fiUer-matrix inteifacial bonding. Simultaneous use of modified nanofillers and TESPT coupling agent is found out with extraordinary reinforcing effects on both mechanical and gas barrier properties [123]. 

Schmidt, D. F. Giannelis, E. P., Silicate Dispersion and Mechanical Reinforcement in Polysiloxane/Layered Silicate Nanocomposites. Chem. Mater. 2010,... 

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