Polymer composites filler-rubber interactions

In the case of rubber blend clay composites good state of exfoliation of the clay, sufficiendy strong filler-rubber interactions as well as the compatibility between different rubber phases are playing major role. The presence of intercalated organoclays restricts the mobility of the rubber chains due to their confinement between the layers. As the concentration of nano filler increases the loss modulus increased. This can be explained in terms of the friction between the filler particles and the rubber matrix when the filler particles are uniformly dispersed in the mbber matrix. The damping values are found to decrease with the amount of filler due to the restricted mobility of the polymer chains owing to the intercalation of polymer chains into the layers of silicates. 

The glass-rubber transition temperature, Tg, of cellulose whisker filled polymer composites is an important parameter, which controls different properties of the resulting composite such as its mechanical behavior, matrix chain dynamics, and swelling behavior. Its value depends on the interactions between the polymeric matrix and cellulosic nanoparticles. These interactions are expected to play an important role because of the huge specific area inherent to nanosize particles. For semicrystalline polymers, possible alteration of the crystaUine domains by the cellulosic filler may indirectly affect the value of Tg. 

Micron-sized fillers, such as glass fibers, carbonfibers, carbon black, talc, and micronsized silica particles have been considered as conventional fillers. Polymer composites filled with conventional fillers have been widely investigated by both academic and industrial researchers. A wide spectrum of archival reports is available on how these fillers impact the properties. As expected, various fundamental issues of interest to nanocomposites research, such as the state of filler dispersion, filler-matrix interactions, and processing methods, have already been widely analyzed and documented in the context of conventional composites, especially those of carbon black and silica-filled rubber compounds [16], It is worth mentioning that carbon black (CB) could not be considered as a nanofiller. There appears to be a general tendency in contemporary literature to designate CB as a nanofiller - apparently derived from... 

Polymer composites contain several matrices such as elastomers, thermosets, thermoplastics, which contains several materials like aliphatic and aromatic polyamides, PTFE, polyolefins, polyester, aminoplast, phenoplast, rubber materials including butyl rubber, and other mbbers. Mostly, these bio-composite polymeric materials were used in industries like constraction materials, fibrous fillers, dental filling, car tires, and various coaling industries. These properties of polymer can able to change by intramolecular interaction of polymer (Mikitaev et al. 2009). 

Abstract This chapter describes the influence of three-dimensional nanofillers used in elastomers on the nonlinear viscoelastic properties. In particular, this part focuses and investigates the most important three-dimensional nanoparticles, which are used to produce rubber nanocomposites. The rheological and the dynamic mechanical properties of elastomeric polymers, reinforced with spherical nanoparticles, like POSS, titanium dioxide and nanosdica, were described. These (3D) nanofillers in are used polymeric matrices, to create new, improved rubber nanocomposites, and these affect many of the system s parameters (mechanical, chemical, physical) in comparison with conventional composites. The distribution of the nanosized fillers and interaction between nanofUler-nanofiUer and nanofiller-matrix, in nanocomposite systems, is crucial for understanding their behavior under dynamic-mechanical conditions. 

In the rubber industry the distribution of particle size is considered to be important as it affects the mechanical properties and performance. Aggregate size also varies with particle size. Aggregates can have any shape or morphology. The fundamental property of the filler used in a filled elastomer is the particle size. This affects the reinforcement of elastomer most strongly. One of the sources of reinforcement between the carbon black surface and the rubber matrix is the van der Waals force attraction. Also, rubber chains are grafted onto the carbon black surface by covalent bonds. The interaction is caused by a reaction between the functional group at the carbon black particle surface and free radicals on polymer chains. Hence, filler-rubber interface is made up of complex physical-chemical interaction. The adhesion at the rubber-filler interface also affects the reinforcement of rubber. When the polymer composites are filled with spherical filler (aspect ratio of the particle is equal to unity), the modulus of the composite depends on the modulus, density, size, shape, volume ratio, and number of the incorporated particles. 

The properties of rubber-rubber blend composites depend on the size and shape and concentration of nano particles and their interactions with the individual mbber matrix. The interaction between the filler and the matrix are improved by surface modification. In the mbber industry the uniform distribution of nano particles is considered to be important as it affects the mechanical properties and performance of the composite. For mbber-mbber blend composites fillers like carbon black prefer to migrate to less polar, less viscous mbber phase whereas silica and clay particles migrate to more polar mbber phase. CNTs mainly reside in the highly polar and non-polar mbbers but not in weakly polar ones. The Tg remain unaltered for a completely incompatible blend. In the case of partially compatible blends, the Tgs of the blend components are expected to shift towards each other as compared with the pure components. Shifting of Tg of polymers to lower or higher values in a blend depends on the polarity difference and the difference in the thermal expansion coefficient of the respective polymers in the blend. 

Polymer composites have attracted a great deal of interest in recent years. In most cases, fillers are used as additives for improAdng the mechanical behavior of the host polymeric matrix. The reinforcement of elastomers by mineral fillers is essential to the rubber industry, because it yields an improvement in the service life of rubber compounds. The state of filler dispersion and orientation in the matrix, the size and aspect ratio of the particles as well as the interfacial interactions between the organic and inorganic phases haw been shown to be crucial parameters in the extent of property improvement [1,2]. 

The effect of polymer-filler interaction on solvent swelling and dynamic mechanical properties of the sol-gel-derived acrylic rubber (ACM)/silica, epoxi-dized natural rubber (ENR)/silica, and polyvinyl alcohol (PVA)/silica hybrid nanocomposites was described by Bandyopadhyay et al. [27]. Theoretical delineation of the reinforcing mechanism of polymer-layered silicate nanocomposites has been attempted by some authors while studying the micromechanics of the intercalated or exfoliated PNCs [28-31]. Wu et al. [32] verified the modulus reinforcement of rubber/clay nanocomposites using composite theories based on Guth, Halpin-Tsai, and the modified Halpin-Tsai equations. On introduction of a modulus reduction factor (MRF) for the platelet-like fillers, the predicted moduli were found to be closer to the experimental measurements. 

Next 129Xe experiments on an EPDM terpolymer, which is present as the elastomer component in a composite material with carbon black will be discussed. The question investigated for these materials is whether the existence of any polymer-filler interaction can be detected by 129Xe NMR. This interaction influences the mobility of the elastomer chains in a relatively large shell around the filler particles. This fraction is called the bound rubber fraction. It is generally believed that the bound rubber fraction influences the mechanical and frictional properties of the filled elastomer [17, 18]. 

Flocculation studies, considering the small strain mechanical response of the uncross-linked composites during heat treatment (annealing), demonstrate that a relative movement of the particles takes place that depends on particle size, molar mass of the polymer as well as polymer-fiUer and filler-filler interaction (Fig. 36.4). This provides strong experimental evidence for a kinetic cluster-cluster aggregation (CCA) mechanism of filler particles in the rubber matrix to form a filler network. 

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