Abstract: Improved resin/filler compositions for use in forming coated abrasives having a substrate/bonding system/abrasive composite structure, are provided. Also, methods for making such improvements are described. In general, the improvements result from inclusion in the resin/filler composition, a coupling agent providing for bonding between the resin and the filler. Preferred classes of coupling agents comprise: silanes, titanates, and zircoaluminates. Improvements effected by methods according to the present invention concern: viscosity of resulting resin/filler mixtures, retention of filler in suspension with a resin, and improved performance characteristics of products made according to the method, in particular improved resistance to deterioration upon contact with water, or upon use and/or storage in humid environments.