Presspan are employed in electrical machines for layer insulation, slot, insulation, slot closure and interphase insulation as a result of the general frenf fowards performance increase these materials are submitted to high electrical and thermal stresses. Good mechanical strength is the prerequisite for automatic processing by the customer. These demands are met in particular by combined flexible insulating material in multi-layer structures of pressboard, polyester and polymidde foils, of aramide paper and various non-woven fabrics.