Thermally resistant magnetic tape

A magnetic recording member comprised of

• a polyimide film supporting member
• a magnetic recording surface on one surface of the support film, this layer being made up of 65-80 weight percent synthetic gamma-Fe.sub.2 O.sub.3 dispersed in a polyester-urethane binder which is crosslinked with a triisocyanate, said binder and crosslinking agent comprising 20-30 weight percent of the layer and the remainder of the layer made up of 3.7% of a conductive oilfurnace black and 2% to 4% dispersing aids and lubricants and
• A second layer on the other surface of the support film, this layer being made up of 40-50 weight percent of a conductive oil-furnace black dispersed in a polyether-urethane binder which is crosslinked with a triisocyanate, said binder and crosslinking agent comprising 50-60 weight percent of the layer and the remainder of the layer made of 1% to 5% dispersing aids and lubricants
• Said first and second layers being chemically inert with one another as evidenced by failure to stick to one another when in spooled backing-to-facing contact at 400.degree.F.

A process for making a reeled magnetic tape which is magnetically stable in an environment of temperatures to at least 700.degree.F comprising the steps of

• a. coating one side of a substrate with a polyester polyurethane-based resin matrix containing a member selected from the group consisting of a conductive carbon black and iron oxide and,
• b. coating the other side of said substrate with a resin-based matrix which is chemically incompatible with said polyurethane resin containing the other of said group consisting of conductive carbon black and iron oxide,
• c. curing said matrices until they are chemically incompatible with one another as evidenced by failure to stick to one another when in spooled backing-to-facing contact at 400.degree.F, and
• d. winding said coated substrate on a reel with said matrices in backing-to-face contact.

A process for improving the resistance to delamination of a magnetic tape formed of a polyimide substrate and a polyurethane facing thereover, comprising the steps of

• 1. applying a polyester polyurethane coating on one side of the tape and applying a polyether polyurethane coating on the other side of the tape,
• 2. filling one of the aforesaid coatings with a conductive carbon black,
• 3. the other said coating comprising a magnetic pigment readable after exposure to temperatures all or above 400.degree.F., and
• 4. curing said coatings until they are chemically incompatible with one another as evidenced by failure to stick to one another when in spooled backing-to-facing contact at 400.degree.F.