Filler volume contents

Table 1. The values of the characteristic parameters of a series of iron-epoxy particulates for various filler volume contents of... 

Fig. 10. The variation of the mesophase moduli Ej(r) for the various filler volume contents of iron-epoxy particulates, versus the polar distance from the filler-matrix boundary...

Figure 21. Comparative log-log plot of the conductivity of nanocomposites containing cata-lytically grown carbon nanotubes and carbon black as a function of the filler volume content. ...

Alumina particles are one of the commonly used fillers for improving the thermal conductivity of adhesives in particular insulation adhesives. Aluminum and silver powders or flakes are used to improve the thermal and electrical conductivities for adhesives intended to be an electrical or thermal path. The filler volume content level is very important to get sufficient conductivity. However, excessive filler content might cause degradation in mechanical properties of the adhesives (Kahraman and Al-Harthi 2005 Kahraman et al. 2008). 

Fillers represent the largest part in terms of weight for many sealants. Calcium carbonate is the most widely used filler for sealant formulations. As a filler for sealants, calcium carbonate acts as an inert extender to reduce formulation cost, modifier for mechanical properties, and a rheological modifier. Normally, properties of fillers such as particle size, shape, and surface properties are very important factors for sealant properties. O Figure 13.4 shows the typical effect of particle size on the viscosity in common adhesives (Chew 2003). Filler volume contents can vary significantly with being dependent on the primary resin and the formulation. 

As soon as the Ar s were determined and the values of r s are found, the values of the adhesion coefficient A may be readily defined by using relation (27). The values of A s for the different inclusion-volume contents studied are given in Table I for iron-epoxy particulate composites with different amounts of fillers, up to 25 percent l4>. 

CNM obtained by pyrolysis with diameter 40-80 nm and length to 1 micrometer have elasticity module greater in more than 3 times, than that applied in UPA. Considering CNF nanosize, their capability for uniform distribution in polymer matrix we should achieve higher physical and mechanical features of the composite at lower volume content of the carbon filler. 

The other reason for variable density is traced to air voids in the material, related to the method of filler incorporation. Figure 5.4 shows the relationship of recorded densities for copper particles of different sizes in polyamide. The particle size did not have an influence. The variations were related to incorporation methods and filler content. The lines show calculated densities at different void volume contents. The void volume content varied between 10 and 20%. ... 

Heat conductivity of composite materials are severely and adversely affected by structural defects in the material. These defects are due to voids, uneven distribution of filler, agglomerates of some materials, unwetted particles, etc. Figure 15.18 shows the effect of filler concentration on thermal conductivity of polyethylene. Graphite, which is a heat conductive material, increases conductivity at a substantially lower concentration than does quartz. These data agree with the theoretical predictions of model. Figure 15.19 shows the effect of volume content and aspect ratio of carbon fiber on thermal conductivity. This figure should be compared with Figure 15.17 to see that, unlike electric conductivity which does depend on the aspect ratio of the carbon fiber, the thermal conductivity is only dependent on fiber concentration and increases as it increases. 

The effect of technological additives on permeability of pol3Tuers is connected with variations in their sorption capacity, formation of defects and interactions of the electrolyte and additives. Impregnation of fillers improves, as a rule, permeability of polymers and intensifies clusterization of water and the penetrant. When polyethylene is filled by talc, HCl and H2O clusters formed in the polymer can be observed in microscope. Water and HCl sorption increases proportionally to the volume content of talc up to 17% concentration. Further increase in talc concentration does not result in sorption growth because of filler particle aggregation in the polymer binder. 

For lower filler volume fractions the first effect is stronger raising the sample modulus, while with the increase of filler content the second one becomes dominating and the modulus drops. Let us notice that the alternate explanation of the modulus increase for lower - and its decrease for higher filler concentrations seems to be invalid as it would require strong polymer filler adhesion in the initial stages of deformation decreasing with the increase of filler content. The shape of ef/ EP YF EP curves can be explained... 

It was found experimentally that system 1 complies with the Einstein model up to volume content of solid phase particles not exceeding 0.07 system 2 does so up to experimental results and representing the tangent of the slope of the dependence of relative viscosity 77/770 on volume content of the filler particles, does not vary with temperature in the interval examined, but it is different for each of the three dispersions studied and takes values of 19.5, 29.6, and 78.8 for systems 1, 2, and 3, respectively. 

In Section 23.2 was discussed the theory of reinforcement of polymer and elastomers which refers to the Guth-Gold-Smallwood equation (Equation (23.1)) to correlate the compound initial modulus (E ) with the filler volume fraction ( ). Moreover, it was already commented on the key roles played by the surface area and by the aspect ratio (/). Basic feature of nanofillers, such as clays, CNTs and nanographites, is the nano-dimension of primary particles and thus their high surface area. This allows creating filler networks at low concentrations, much lower than those typical of nanostructured fillers, such as CB and silica, provided that they are evenly distributed and dispersed in the rubber matrix. In this case, low contents of nanofiller particles are required to mutually disturb each other and to get to percolation. Moreover, said nanofillers are characterized by an aspect ratio /that can be remarkably higher than 1. Barrier properties are improved when fillers (such as clays and nanographites) made by... 

Concerning the modulus evaluatirai of the fillers is always problematic. The modulus has been evaluated. Different composites had been processed with increasing LCFo i content. The fillers modulus has been estimated by fitting a semiempiri-cal Halpin-Tsai model on the evolution of the composites Young s modulus as a function of fillers volume fraction. By extrapolation at 100% of fillers, we obtain the filler modulus which is estimated at 6.7 GPa. This value is coherent with wheat straw data given in the literature (Hornsby et al. 1997 KrtMibergs 2000). 

Fig. 17.7 Fittings on the evolution of the modulus of LCFo i-based biocomposites versus filler volume fraction content (Takayanagi, Voigt and Reuss models). Reproduced with permission (Averous and Le Digabel 2006). Copyright of Elsevier...

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