Kaolin properties

Properties Kaolin-base dRCF High purity RCF RCF with 2irconia RCF with chromia Poly-crystalline alumina... 

Following wet processing, fine particle size kaolins may be calcined, ie, heat treated at about 1000°C. This treatment converts the kaolin to an amorphous pigment of significantly higher brightness and opacity (8). Properties of the various types of kaolins used in paper are shown in Table 2. 

Properties. The properties of kaolin that make it useful in the paper industry are brightness, viscosity, and particle si2e and shape. 

Other tests on kaolins that relate to use properties are carried out by kaolin suppHers. 

Although kaolins are easily wetted by both oil and water, surface treatment may sometimes be used to enhance the oleophilic properties. The kaolin in paint may represent 20—30% of the pigment. 

In the pulp and paper industry, anionic and cationic acrylamide polymers are used as chemical additives or processing aids. The positive effect is achieved due to a fuller retention of the filler (basically kaoline) in the paper pulp, so that the structure of the paper sheet surface layer improves. Copolymers of acrylamide with vi-nylamine not only attach better qualities to the surface layer of.paper, they also add to the tensile properties of paper in the wet state. Paper reinforcement with anionic polymers is due to the formation of complexes between the polymer additive and ions of Cr and Cu incorporated in the paper pulp. The direct effect of acrylamide polymers on strength increases and improved surface properties of paper sheets is accompanied by a fuller extraction of metallic ions (iron and cobalt, in addition to those mentioned above), which improves effluent water quality. 

The table data show that the stress/strain properties of compositions are improved by additional dispersion (mixing). Ultrasonic analysis is sufficiently reliable and informative as a means of mixing quality assessment. The very small change of the characteristics for filled compositions (chalk + kaolin) can be due to the fact that these fillers are readily distributed in the matrix as they are. 

Table 9. Effect of silane treatment on the mechanical properties of kaolin-filled polyethylene compositions [276]...

In [276] the properties of kaolin-filled polyethylenes were investigated. The filler was pre-treated with silanes of two kinds, vinyl triethoxysilane (VTES) (I) and gamma-methacryloxypropyl trimethoxysilane (II). The results are presented in Table. 9. 

Tari, G., Bobos, I., Gomes, C. and Ferreira, J. (1999) Modification of surface charge properties during kaolinate to halloysite-7A transformation. Journal of Colloid and Interface Science, 210, 360. 

Kaolinite, 2 345t 6 659-664, 686-687, 718 composition in bauxite used for alumina production, 2 346t structure and composition, 6 668 in unit layer mixtures, 6 671 Kaolins, 6 686. See also Kaolin dry process, 6 673-675 estimated total production, 6 683 grades for polymer applications, 6 694t properties relating to applictions, 6 686t uses, 6 686-696 wet process, 6 675-679 Kapok, 11 297... 

Many inert pigments (often known as fillers) are incorporated into paper in addition to the cellulosic fibres. They may be added to improve certain optical properties—in particular opacity and brightness—or simply as a cheap replacement for costly fibre. The two most common pigments are kaolin (china clay) and chalk (limestone), but talc and speciality pigments such as titanium dioxide are also used. The particle size for general purpose fillers is normally expressed as an equivalent spherical diameter (esd) and this is determined from sedimentation data. Values for the common paper-... 

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