the invention provides a low energy loss , multi - layered polypropylene / metal foil product useful for further processing into printed circuit boards and antenna boards for microwave circuitry . a continuous process for manufacture of the product is described . the process comprises the steps of : providing metal foil ; optionally , extrusion coating molten polypropylene upon said metal foil , to obtain a foil coated with a polypropylene foundation layer ; casting a molten polypropylene tie - layer upon said metal foil or upon said coated metal foil ; and laminating a polypropylene sheet on said tie layer . in the process , heat is applied to induce fusing of the layers of the multi - layered product .