disclosed is a method of bonding two layers of thermosetting plastic . a thin sheet of thermoplastic material is interpositioned between two layers of thermosetting plastic and the combination is subjected to temperatures sufficient to cause the thermosetting plastic layers to bond and cure . the thermosetting plastic contains mold release agents which are absorbable by the thermoplastic sheet , and crosslinking monomers in which the thermoplastic sheet is dissolvable at molding temperatures .