Fillers dispersion chain mobility

Oils of the three types are offered in a range of viscosities and this will influence their processing character to some extent, although there is little evidence that it will have much influence on the ultimate compound physical properties, at least in natural rubber compounds. The small additions of oil to a compound help with filler dispersion by lubricating the polymer molecular chains and thus increasing their mobility. There will also be some wetting out of the filler particles which enables them to achieve earlier compatibility with the rubber and improve their distribution and dispersion speed. 

In addition to particle breakup, the coalescence process may be affected as well. It has been speculated that exfoliated clay platelets or well-dispersed nanoparticles may hinder particle coalescence by acting as physical barriers [19,22]. Furthermore, it has been suggested that an immobilized layer, consisting of the inorganic nanoparticles and bound polymer, forms around the droplets of the dispersed phase [50]. The reduced mobility of the confined polymer chains that are bound to the fillers likely causes a decrease in the drainage rate of the thin film separating two droplets [44]. If this is the case, this phenomenon should be dependent on filler concentration this is shown in Figure 2.8, which shows the effect of nanoclay fillers on the dispersed particle size of a 70/30 maleated EPR/PP blend [19]. 

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. 

Based on both these morphological and thermal evaluations, it was possible to get a better representation of the overall structure of the nanocomposite. The latter is a multiphase system in which filler particles are covered by a trans-crystalline interphase in which polymer chains display a reduced segmental mobility [confinement]. These coated filler fibers proved to be dispersed in an "unaffected bulk-like continuous iPP phase in which the polymer crystal perfection is lower than the one of the lamellae grown perpendicularly to the filler surface. 

In his model Nielsen assumed that the filler particles are impermeable to the permeant molecules, and are uniformly and completely dispersed in the polymer. Moreover the plates are oriented parallel to the polymer film siuface and the filler has no effect on the mobility of the polymer chains. Figure 11.3 illustrates the general type of pafii that molecules must take to get through the polymer. Based on simple geometrical considerations the following Equation (11.3) can be derived ... 

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