Filler loading effects

Mechanical Properties. In addition to the hydrodynamic effects of particulate fillers on polymer flow behavior, an enhanced stiffening effect is observed in filled poljmiers. For soft polymers, such as elastomers, with diluted filler loading, effects of filler on modulus are proportional to that on viscosity and can be represented by the Einstein equation, equation 1, with viscosity terms replaced by modulus terms. However, this viscosity to modulus relationship only holds when the poljmier is incompressible, such as elastomers with Poisson s ratio of 0.5, and when the rigidity of the filler is very much greater than that of the poljmier. 

The primary failure modality identified clinically for restorations in posterior teeth is loss of material through abrasion. The complex nature of this failure mode in composite materials makes it difficult to correlate this phenomenon with any one mechanical property. A number of studies have suggested improvements in the system by using various mechanical properties as evidence. These studies have identified major factors such as ceramic filler loading and type of filler [186-191]. Some effects have been identified related to the... 

It has been suggested that the three-dimensional network structures discussed above, which are believed to occur from particle interactions at high filler loadings, may, in the case of plate-like particles, lead to anisotropic shear yield values [35]. Although this effect has not been substantiated experimentally, further theoretical interpretation of shear yield phenomena in talc- and mica-filled thermoplastics has been attempted [31,35]. 

Interfacial structure is known to be different from bulk structure, and in polymers filled with nanofillers possessing extremely high specific surface areas, most of the polymers is present near the interface, in spite of the small weight fraction of filler. This is one of the reasons why the nature of the reinforcement is different in nanocomposites and is manifested even at very low filler loadings (<10 wt%). Crucial parameters in determining the effect of fillers on the properties of composites are filler size, shape, aspect ratio, and filler-matrix interactions [2-5]. In the case of nanocomposites, the properties of the material are more tied to the interface. Thus, the control and manipulation of microstructural evolution is essential for the growth of a strong polymer-filler interface in such nanocomposites. 

In order to understand the effects of filler loading and filler-filler interaction strength on the viscoelastic behavior, Chabert et al. [25] proposed two micromechanical models (a self-consistent scheme and a discrete model) to account for the short-range interactions between fillers, which led to a good agreement with the experimental results. The effect of the filler-filler interactions on the viscoelasticity... 

Fig. 29 Effect of filler loading on a AC conductivity and b dielectric constant. EVA-EG, EVA-T, and EVA-F represent EVA-based nanocomposites reinforced with EG, MWCNTs, and CNFs, respectively...

Fig. 30 a Shielding effectiveness of various composite systems (at 12 GHz), b EMI shielding effectiveness as a function of conductivity at 16 wt% filler loading... 

The Payne effect values of the plasma-coated carbon black at various filler loadings in SBR are shown in Fig. 27. The plasma-coated carbon black shows a lower Payne... 

Because the conductive filler is located into a single component of the blend, these materials show an onset in the electrical conductivity at very low filler loadings of 2-3%. These findings have been explained by a double percolation effect. The CNT filled blends show superior mechanical properties in the tensile tests and in impact tests (25). 

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