Characterization of Fillers

Chemical composition, particle morphology, particle size and particle size distribution, brightness, refractive index, specific surface, particle charge and abrasiveness are commonly used to characterize papermaking fillers. Table 2.5 summarizes some chemical and physical data of fillers and fibers. More detailed information is given in the following paragraphs. 

Newsprint/Directory Recycled pigment, GCC, PCC, amorphous silicate, calcined clay, (Ti02) 

Europe N. America World Europe Europe World 

Filler Chemical Crystal Morphology ISO Refractive Density Specific 

In the papermaking process, most of the original filler particles form agglomerates or flocculates, by addition of different flocculating wet end additives. The degree of flocculation can be optimized by careful handling of the wet end chemistry. To obtain a highly uniform sheet, any excessive flocculation, of course, needs to be avoided. 

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Some small-angle X-ray scattering (SAXS) techniques have also been applied to elastomers. Examples are the characterization of fillers precipitated into elastomers, and the corresponding incorporation of elastomers into ceramic matrices, in both cases to improve mechanical properties [4,85,213]. 

Spectroscopic techniques are extremely useful for the characterization of filler surfaces treated with surfactants or coupling agents in order to modify interactions in composites. Such an analysis makes possible the study of the chemical composition of the interlayer, the determination of surface coverage and possible coupling of the filler and the polymer. This is especially important in the case of reactive coupling, since, for example, the application of organofunctional silanes may lead to a complicated polysiloxane interlayer of chemically and physically bonded molecules [65]. The description of the principles of the techniques can be found elsewhere [15,66-68], only their application possibilities are discussed here. 

Even if the relationship between filler dispersion and abrasion resistance is well established, relatively few studies have been done on the characterization of filler dispersibility. This is mainly due to the fact that carbon black dispersibility was commonly judged satisfactory, partly because it is indeed high, but more probably because all mixing apparatuses were designed for dispersing carbon blacks. 

Small-angle scattering techniques have been applied to polysiloxane materials. One important example is the characterization of fillers introduced into polysiloxane elastomers, or the reverse, the incorporation of such elastomers into ceramic matrices (in both cases to improve mechanical properties). - Another example is characterization of the anisotropy induced by strain in silica-PDMS composites. Chapter 9 describes some of this work. Elastic neutron scattering can be illustrated by the characterization of polysiloxane blends, and quasielastic neutron scattering by studies of the dynamics of PDMS. There have also been Monte Carlo calculations of PDMS particle scattering functions, including how they varied with chain length, chain structure, and temperature. ... 

Pan, G. Mark, J. E. Schaefer, D. W., Synthesis and Characterization of Fillers of Controlled Structure Based on Polyhedral Oligomeric Silsesquioxane Cages, and Their Use in Reinforcing Siloxane Elastomers. J. Polym. Sei., Polym. Phys. Ed. 2003,41,3314-3323. 

IGC is a well-established method for the surface characterization of fillers and fibers. Earlier experiments... 

Pan G, Mark JE, Schaefer DW (2003) Synthesis and characterization of fillers of controlled structure based on polyhedral oligomeric silsesquioxane cages and their use in reinforcing siloxane elastomers. J Polym Sci B Polym Phys 41(24) 3314—3323... 

A. Voelkel and B. Strzemiecka, Characterization of fillers used in abrasive articles by means of inverse gas chromatography and principal components analysis Int. J. Adhesion and Adhesives, 27(3), 188 (2007). 

E. Papirer, H. Balard, A. Vidal. Inverse gas chromatography a valuable method for the surface characterization of fillers for p>olymeis (glass fibres and silicas). Eur. Polym.., 24 (8), 783-790,1988. 

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