28/07/2014 Novels - Magazines
In such a composition, the co-abrasive or secondary filler particles 18 are of a much smaller size than the primary abrasive resistant particles 16 and these smaller particles fill the voids or interstices between the large abrasive particles. The co-abrasive filler 18 protects the polymer matrix 14 from being worn away from the abrasive resistant particles. As a result,zenith mining machines the abrasive resistant particles remain in place in the matrix longer providing a longer wearing surface. The abrasive resistant particles and co-abrasive filler are maintained in suspension in the polymer matrix during mixing and curing operations by means of a thixotropic agent.
While many polymers, abrasive resistant particles, co-abrasive fillers and thixotropic agents may be found suitable for a composition to be used in this invention, a more specific and particularly desirable composition is obtained by the use of high alumina ceramic beads as the abrasive resistant particles. More specifically, the use of metal coated alumina ceramic particles of the type sold by Coors Porcelain Company of Golden,iron ore mining machinery Colorado under the trademark "METLX" has been found to produce an outstanding abrasive resistant coating. This ceramic is a high alumina (90% type) which has very fine grain (crystal) boundaries to give good abrasive resistance. A coating of metal is placed on the surfaces of ceramic particles. It has been found that polymers and other matrices bond better to the metal coating than they do directly to ceramic. The particles used may be on the order of a fraction of an inch, for example approximately one-sixteenth of an inch, in their largest dimension.
A co-abrasive filler found to function particularly well in a wearing composition in accordance with this invention may be silicon carbide, 180 mesh size. However, other fillers may be used as long as they are about as hard as the material being handled, in other words, the material causing the wear on the surface being protected. By way of example, but not of limitation, the following substances may be used as fillers: Diamond dust, boron carbide, boron nitride, tungsten carbide, alumina ceramic, silica sand, taconite, etc. The cost of the wearing composition used in connection with the method of this invention may be reduced by matching the co-abrasive filler to the material causing wear. For example, where sand is the abrasive material causing the wear, silica sand or silica flour may be used as the co-abrasive filler.