Fillers absorption coefficient

The effect of the modification of the fibre surface consists in the shift of the sound absorption maximum towards higher frequency range and is accompanied by the decrease of the sound absorption coefficient a. The reduction of the coefficient a is not large. It amounts 2.5 % in the case of composites with pine wood and rapeseed straw Californium. For the samples with beech wood filler the coefficient a remains unaffected after modification. The exception is the composite containing the rapeseed straw Kaszub as a filler that shows the decreasing in the sound absorption of 7%. The reduction of the a coefficient value at the frequency related to the maximum of the sound absorption can be associated with the increase in the density of the composite after modification (Table 1) due to better adhesion between filler particles and polypropylene matrix. The fact implies that the specific acoustic impedance of... 

A filler such as titanium dioxide, having a refractive index much higher than that of the polymer, will therefore exhibit considerable scattering and will give white products, unless its absorption coefficient is high in which case dark, opaque composites will be produced (carbon black or black iron oxide are the ultimate in this instance). 

Fig. 4. Dependence on filler concentration (

As the filler concentration increases so does the initial slope of Wt = f(j/x), see Fig. 12. According to Eq. (5) this may be due either to an increase of the diffusion coefficient or to the increased effective thickness of the specimen due to the addition of the filler that does not absorb water. Initially, there are small increments of the relative content of absorbed water, but the absolute quantity (referred to the binder) is almost independent of the filler concentration however in the next stages the absolute quantity of absorbed water becomes proportional to the microsphere concentration. Thus there are different absorption mechanisms effective in the course of time. 

Perfectly transparent, light-fast color filters and UV absorbers can be obtained by combining metal clusters of coin metals (silver, gold, etc.) with optical polymers [i.e., amorphous polymers with a visible refractive index close to 1.5, such as polystyrene, poly(methyl methacrylate), or polycarbonate]. The high extinction coefficients that characterize the surface plasmon absorption of these metals allows intensive coloration at very low filling factors, and the nanoscopic filler size makes possible the realization of ultrathin color filters [Carotenuto, 2001 Zheng et al., 2001]. 

Molecular H absorption onto graphite was studied in order to obtain information on the true H diffusion coefficient in graphite, on the O effect and on the mechanism of H trapping. The H could permeate into a filler grain in the form of H molecules, diffuse through crystallite boundaries, and finally be trapped as H atoms at the edge surface of a crystallite. The diffusion coefficient could be described by ... 

Effect of fillers addition on the thermo-optical parameters of prepared composites was detailed in fig 3 and fig 4. Those two figures show the reflection coefficient for different wavelength ranges. They were used to calculate the solar absorption and the total emissivity of composites. 

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