TAILIEUCHUNG - Materials Handbook 15th 2010 Part 13

Tham khảo tài liệu 'materials handbook 15th 2010 part 13', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 840 SILICA Silica flour made by grinding sand is used in paints as a facing for sand molds and for making flooring blocks. Silver bond silica is water-floated silica flour of SiO2 ground to 325 mesh. In zinc and lead paints it gives a hard surface. Pulverized silica made from crushed quartz is used to replace tripoli as an abrasive. Ultrafine silica a white powder having spherical particles of 157 to 984 in 4 to 25 m is made by burning silicon tetrachloride. It is used in rubber compounding as a grease thickener and as a flatting agent in paints. Aerosil of Cabot Corp. is this material. Silica powder of Praxair Inc. is a white amorphous powder with maximum particle size of 1 969 nin 50 nm . Other natural amorphous silicas come in an average particle size of 59 in m with no particles larger than 394 in 10 m . Quso of Philadelphia Quartz Co. is a soft white powder with small particles 394 to 787 nin 10 to 20 nm . It is used in cosmetics and paper coatings and as an anticaking agent in pharmaceuticals. As a filler in plastics it gives a plasticizing action that aids extrusion. These fine silicas are also marketed as dust-free agglomerate particles which disperse easily in solution to the discrete hydrophyllic particle. Arc silica of PPG Industries used as a flatting agent in clear lacquers is produced directly from silica sand in an arc furnace at 5432 F 3000 C . It has crystals of in m agglomerated into translucent grains 79 to 118 in 2 to 3 m . Valron of Du Pont originally called Estersil is ester-coated silica powder of to 8- to 10-mm particle size for use as a filler in silicone rubbers printing inks and plastics. Ludex of the same company is another colloidal silica with the fine particles negatively charged by the incorporation of a small amount of alkali. It forms a sol or high-concentration solution without gelling. Min-U-Sil of Pennsylvania Glass Sand Corp. for making molded ceramics has tiny crystalline particles. Syton of .

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