free of added crosslinking agents application_number US 83782377 A description the fabric used in the form of a disc or any other convenient shape may be any of those used in the prior art however cloth of a high strength material is preferred typical cloths comprise cotton dacron rayon nylon kelvar and glass glass being most preferred especially open mesh glass fabric in accordance with the invention the cloth is coated with a novolak phenolic resin the term novolak phenolic resin is defined for purposes herein as a novolak type phenolic resin with little or no added crosslinking agent thus the term excludes the resole resins and the two stage novolak resins where the crosslinking agent is added in anything other than a minor amount in accordance with this definition in the most preferred embodiment of the invention a novolak resin is used completely free of added crosslinking agent though amounts of crosslinking agent up to a maximum of 3 by weight can be tolerated with the understanding that the results obtained with this quantity of added crosslinking agent are less desirable than when the novolak is free of added crosslinking agent the resin is coated onto the fabric in conventional manner such as by immersing the cloth in a varnish.