Coated abrasive

Useful thermosetting resins are obtained by interaction of furfural with phenol. The reaction occurs under both acidic and basic catalysis. Other large uses of furfural together with phenol are in the manufacture of resin-bonded grinding wheels and coated abrasives (5). 

Abrasive appHcations for industrial diamonds include thek use in rock drilling, as tools for dressing and tmeing abrasive wheels, in polishing and cutting operations (as a loose powder), and as abrasive grits in bonded wheels and coated abrasive products. 

Silica. SiHca (qv) comes in various forms including quartz [14808-60-7]. It has found wide use as an abrasive in the past, particularly as an inexpensive coated abrasive for woodworking. The term sandpaper is stiU used as a generic term for coated abrasives in many quarters although the use of sand in coated abrasives has been almost entirely elkninated because of the hazard of siHcosis to the user and its inferior grinding properties (especially for metals). 

Another sol—gel abrasive, produced by seeding with a-ferric oxide or its precursors, has been patented (30). A magnesium-modified version of this abrasive, also called Cubitron, is being produced as a replacement for the earlier type. Yttria [1314-36-91-vnc>A V eA sol—gel abrasives have also been patented (31), as well as rare earth oxide modified materials (32). These abrasives are all produced by 3M Corporation they have performed very well ia various applications such as ia coated abrasives for grinding stainless steel and exotic alloys. 

Coated abrasive products, once limited to sandpaper in woodworking shops, are versatile and efficient industrial tools. Machines ranging from portable Sanders to giant slab conditioners and roU grinders utili2e coated abrasives. Abrasive belt machines now perform many of the operations that were once the exclusive province of grinding wheels. 

Wearable coated abrasive wheels of the radial-fiap type can grind and polish contours that are almost impossible for bonded abrasive wheels. 

A new form of coated abrasive has been developed that consists of tiny aggregates of abrasive material in the form of hoUow spheres. As these spheres break down in use, fresh cutting grains are exposed this maintains cut-rate and keeps power low (44). 

Coated abrasives are suppHed in widths ranging from 3.175 mm to 2.2 m in standard 45.7-m roUs. They are also formed into sheets, disks, and molded cods or rods. Belts, regularly suppHed in the widths mentioned, have been made up to 3 m wide. 

Coated Abrasive Sales. There has been a steady rise in the sale of coated abrasives in the United States in 1938 sales were about 12 million in 1988 sales exceeded 700 million. World sales of coated abrasives for 1988 were estimated at over 2 bdHon. 

The abrasive industry is highly competitive and many small companies worldwide successfully compete by specializing in a particular segment of the business, eg, disk wheels, mounted points, and mbber wheels. Costs in the fused abrasive industry are primarily in materials and electric power. Thus manufacturers seek out plant sites having the lowest power costs. Costs for coated abrasive manufacturers are capital and labor intensive and they seek out sources of low cost labor. 

Coated abrasives, such as sheets, disks, and dmms, are used for polishing and finishing. Here, too, the abrasives, such as aluminum oxide and siHcon carbide, have replaced the flint and garnet of common sandpaper. These industrial coated abrasives are manufactured from cloth or tough paper base. 

New opportunities are arising for coated abrasive belts in high pressure grinding. High strength backing has been developed and zirconia media are available for grinding. 

Zirconium oxide is fused with alurnina in electric-arc furnaces to make alumina—zirconia abrasive grains for use in grinding wheels, coated-abrasive disks, and belts (104) (see Abrasives). The addition of zirconia improves the shock resistance of brittle alurnina and toughens the abrasive. Most of the baddeleyite imported is used for this appHcation, as is zirconia produced by burning zirconium carbide nitride. 

In the United States, a number of physical tests are performed on siUcon carbide using standard AGA-approved methods, including particle size (sieve) analysis, bulk density, capillarity (wettabiUty), friabiUty, and sedimentation. Specifications for particle size depend on the use for example, coated abrasive requirements (134) are different from the requirements for general industrial abrasives. In Europe and Japan, requirements are again set by ISO and JSA, respectively. Standards for industrial grain are approximately the same as in the United States, but sizing standards are different for both coated abrasives and powders. 

Coated Abrasives Manufacturers Institute (CAM ) data sheets, Cleveland, Ohio, 1990. 

Web-coating polymerizations (e.g., as used for photographic film and coated abrasives) literally achieve a piston flow reaction environment. Mechanically driven screw devices used as finishing reactors for PET closely approximate piston flow. Motionless mixers can do this as well. However, polymer reactors that closely approximate piston flow are the exception. 

Coated Abrasive Manufacturing Institute (CAMI), silicon carbide standards by, 22 537... 

Coated abrasives -phenolic resins [PHENOLIC RESINS] (Vol 18)... 

Coated abrasives consist of a flexible backing on which films of adhesive hold a coating of abrasive grains. The backing may be paper, cloth, open-mesh cloth, vulcanized fiber (a specially treated cotton rag base paper), or any combination of these materials. The abrasives most generally used are fused aluminum oxide, sol-gel alumina, alnmina-zirconia. silicon carbide, garnet, emeiy, and flint. 

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