Nanometer dimension fillers

The unique properties of elastomers particularly their durabiUty and reversible high deformation are of enormous industrial importance [ 1,2]. To improve the resilience and strength of rubber material further, extensive use of different types of filler materials have been considered for last few decades. Nanometer dimension fillers having large surface areas have added advantages with greater interactions at the... 

In recent years the incorporation of low concentrations of nanometer-sized fillers has become an important strategy to improve and diversify polymeric materials. A polymer nanocomposite can be defined as a two-phase system, where at least one dimension of the reinforcing filler is on the nanometer scale. Nanocomposites can vary from the inclusion of isodimensional... 

D nanomaterial composites - Two dimensions of the nanomaterials are oti the nanometer scale. Fillers include materials such as carbon nanotubes, cellulose whiskers, metal whiskers, and rod-like clay fillers. 

Nanoclays. Nanocomposites are materials that contain nanofillers, or fillers of nanometer dimensions. The successful synthesis of nylon-clay nanocomposites (57-59) ushered in nylon nanocomposites that could attain high modulus, heat distortion temperature, dimensional stabiUty, impermeabiUty, and strength with only a few percent modified clay nanofillers. Although it has been long known that poljuners could be mixed with appropriately modified clay minerals and synthetic clays, the field of polymer-layered silicate nanocomposites has gained... 

Filler, in general, can be defined as finely divided particles that are often used to enhance the performance and various desirable properties of the host matrix, depending on a typical application. A great deal of research endeavors have been dedicated to the development and the use of different fillers with a dimension at the nanometer level. In rubber technology the term nano is not unfamiliar to a rubber specialist. Since the start of the twentieth century, carbon black and silica have been utilized as effective reinforcing agents in various rubber formulations for a variety of applications. The primary particle sizes of these fillers remain in the nanometer range. However, with these conventional fillers the dispersion toward individual... 

The already mentioned limited lateral dimensions of packing models of just several nm makes it impossible to simulate complete membranes or other polymer-based samples. Therefore, on the one hand, bulk models are considered that are typically cubic volume elements of a few nanometers side length that represent a part cut out of the interior of a polymer membrane (cf. Figure 1.1). On the other hand interface models are utilized, for example, for the interface between a liquid feed mixture and a membrane surface or between a membrane surface and an inorganic filler (cf. Figure 1.2). 

The nanoscopic fillers, as mentioned above, have at least one characteristic length that is of the order of nanometers. Uniform dispersion of these nanoscopically sized particles or nanoelements can lead to ultra-large interfacial area between the constituents (approaching 700 m /cm in dispersions of layered silicates in polymers) and also to ultrasmall distance between the nanoelements (approaching molecular dimensions at extremely low loadings of the nanoparticles). 

In addition, by scaling the filler size to the nanometer scale, it has been shown that novel material properties can be obtained. Nanoscaled fillers are those having at least one dimension in the range of nanometers (< 100 nm) [3]. When the dimensions of the reinforcement approach the nanometer scale, a number of effects make the properties of the corresponding composites different from those of composites reinforced with micro-scaled fillers. The major influencing factors of the properties of nanocomposites are nanofiller dispersion, dimensions, volume fractions, nature of the matrix material, interfacial properties between filler and matrix, and manufacturing process [4]. 

Furthermore, it is expected that the dispersion of fillers with dimensions in the nanometer level having very large aspect ratio and stiffness in a polymer matrix could lead to even higher mechanical performances. These fillers include layer silicates and carbon nanotubes. Carbon nanotubes have a substantially higher aspect ratio (-1000) in comparison with layered silicates (-200) and they also have very high strain to failure. 

If all the dimensions of the filler are in nanometer scale, then the fillers have the form of spherical nanoparticles. If two dimensions of the filler are in nanoscale, whereas... 

The third type of nanocomposite is characterized by only one dimension in the nanometer range. Here the fillers is in the form of sheets of one to a few nanometer thick to hundreds to thousands nanometers long. Clays and layered silicates belong to this family and the composites are known as polymer layered silicates nanocomposites (PLSNs). 

Spherical Particles Nanofiller with three dimensions in the nanometer regime are the spherical nanofillers obtained by sol-gel process [9, 10]. In sol-gel process the organic/inorganic hybrid material can be formed by the condensation reaction between the functionalized prepolymer and the metal alkoxides, leading to the formation of a chemical bond between the polymer and the inorganic filler. Therefore, the incorporation of filler particles in polymer through the sol-gel process avoids the aggregation of filler. 

D nanomaterial composites — Three dimensions of the nanoparticle fillers are on the nanometer scale. These fillers are also called isodimensional nanoparticle composites. Examples include silica obtained by in-situ sol-gel methods, semiconductor nanoclusters that are dispersed in polymers, and systems in which polymers are subsequently polymerized around nanostractures. 

The demand for material properties to meet superior and more severe specifications has motivated vigorous research on polymer nanocomposites, that is, polymer matrices incorporated with fillers with at least one dimension in the nanometer range. In a nutshell, these advanced materials exhibit enhanced thermal, mechanical, barrier, and fire retardant properties over virgin polymers [32-37], while their performance depends on the level and the homogeneity of nanofillers dispersion, as well as on the potential for interfacial bonding between the filler and the matrix. 

While there is no precise definition, nano-fillers can be considered as particles which, when dispersed in polymers, are very small in at least one dimension. This concept is pushed quite far in some of the literature, with particles of up to at least a hundred nanometers being described as nano-particles. A reasonable working definition would seem to be that at least one dimension of the effective particle, when dispersed in a polymer matrix, should be no more than 20 nm, or 200 A. As a result, the specific surface area, which plays a significant role in the effects observed, will be at least 150 m /g. The term effective particle is used to eliminate fillers, such as carbon blacks, where the primary particle could be in the specified range, but are strongly aggregated into larger structures, that become the effective particles. 

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