Elastomeric nanocomposites

Wu et al. [32] introduced the MRF of 0.66 for the platelet-like fillers into established composite models to account for the lower contribution of the plateletlike filler to the Young s modulus than the contribution of the fiber-like filler. This apparently improved the predicting ability of the models in the case of elastomeric nanocomposites. 

Furthermore, another advantage of nanofillers is not only to reinforce the rubber matrix but also to impart a number of other properties such as barrier properties, flammability resistance, electrical/electronic and membrane properties, and polymer blend compatibility. In spite of tremendous research activities in the field of polymer nanocomposites during the last two decades, elastomeric nanocomposites... 

Polymer nanocomposites multicomponentness (multiphaseness) requires their stmctural components to be quantitative characteristics determination. In this aspect, interfacial regions play a particular role, as it has been shown earlier, that they are the same reinforcing element in elastomeric nanocomposites as nanofiller actually [ 1 ]. Therefore, the knowledge of interfacial layer dimensional characteristics is necessary for quantitative determination of one of the most important parameters of polymer composites, in general,— their reinforcement degree [2, 3]. 

As it is known [13, 14], the scale effects are often found at the study of different materials mechanical properties. The dependence of failure stress on grain size for metals (Holl-Petsch formula) [15] or of effective filling degree on filler particles size in case of polymer composites [16] are examples of such effect. The strong dependence of elasticity modulus on nanofiller particles diameter is observed for particulate-filled elastomeric nanocomposites [5], Therefore, it is necessary to elucidate the physical grounds of nano- and micromechanical behavior scale effect for polymer nanocomposites. 

The calculated dimensions D, based on the aforementioned method, are adduced in Table 6.2. The values for the studied nanocomposites are varied within the range of 1.10-1.36, i.e., they characterize more or less branched linear formations ( chains ) of nanofiller particles (aggregates of particles) in elastomeric nanocomposite structure. Let us remind that for particulate-filled composites polyhydroxyether/graphite, the value changes within the range of 2.30-2.80 [4, 10], i.e., for these materials filler particles network is a bulk object, but not a linear one [36]. 

TABLE 6.2 The dimensions of nanofiller particles (aggregates of particles) structure in elastomeric nanocomposites... 

In addition, let us consider the physical grounds of smaller values for elastomeric nanocomposites in comparison with pol5mier microcomposites, i.e., the causes of nanofiller particle (aggregates of particles) chains formation in the first ones. The value D can be determined theo-... 

Hence, the aforementioned results have shown that nanofiller particle (aggregates of particles) chains in elastomeric nanocomposites are physical fractal within self-similarity (and, hence, fractality [41]) range of -500-1,450 nm. In this range, their dimension can be estimated accord-... 

Hence, the aforementioned results have shown that elasticity modulus change at nanoindentation for particulate-filled elastomeric nanocomposites is due to a number of causes, which can be elucidated within the frameworks of anharmonicity conception and density fluctuation theory. Application of the first from the indicated eoneeptions assumes that in nanocomposites during nanoindentation proeess loeal strain is realized, affecting pol5mier matrix only, and the transition to macrosystems means nanocomposite deformation as homogeneous system. 

The elastomeric nanocomposites reinforcement degree EJE description was derived as in what follows [3] ... 

Meanwhile the following formula can be used for determining the degree of elastomeric nanocomposite reinforcement (EJEJ ... 

From Eq. (1.37) it follows, that the nanofiller particles (aggregates of particles) surface dimension d is the parameter, controlling the degree of reinforcement of the nanocomposites. From Eqs. (1.4)-(1.6) it follows unequivocally, that the value of ri is defined only by the size of the nanofiller particles (aggregates of particles) R. In turn, it follows from Eq. (1.37), that the degree of reinforcement of the elastomeric nanocomposites EJEJ is defined by the dimension <7 only, or by the size only. This means, that the reinforcement effect is controlled by the nanofiller particle (aggregates of particles) size only and this is the true nano-effect. 

Kozlov, G. V. Yanovskii Yu.G. Kubica, S. Zaikov, G. E. A nanofiller particles aggregation in elastomeric nanocomposites the irreversible aggregation model. Przetworstwo Tworzyw, 2011, 5,413-416. 

TABLE 6.2 The Dimensions of Nanofiller Particles (Aggregates of Particles) Structure in Elastomeric Nanocomposites... 

Hence, the stated above results have shown, that elasticity modulus change at nanoindentation for particulate-filled elastomeric nanocomposites is due to a number of causes, which can be elucidated within the frameworks of an harmonicity conception and density fluctuation theory. Application of the first from the indicated conceptions assumes, that in nanocomposites during nano indentation process local strain is realized, affecting polymer matrix only, and the transition to macrosystems means nanocomposite deformation as homogeneous system. The second from the mentioned conceptions has shown, that nano- and micro systems differ by density fluctuation absence in the first and availability of ones in the second. The last circumstance assumes that for the considered nanocomposites density fluctuations take into account nanofiller and polymer matrix density difference. The transition from nano to Microsystems is realized in the case, when the deformed material volume exceeds nanofiller particles aggregate and surrounding it layers of polymer matrix combined volume [49]. 

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