Abstract: A metallic laminate of the type comprising sheet metal, such as galvanized sheet steel, and aluminium foil, with an interposed thermoplastic, such as polyethylene, which, under heat and pressure, adheres to the foil and sheet metal, has its bond strength substantially increased winding it as a coil under tension, the laminate being heated, before and/or after coiling. Subsequently the coil, while clamped radially to prevent relative movement of the coil convolutions, is cooled from the outside, the coiling under tension, the heating and the cooling all causing inter-layer pressures in the coil which, with the heat, bring about a useful increase in the bond strength.

Abstract: Metal foil is applied to sheet metal by a film of polythene adhering to both and separating the two from direct contact, for improving the heat-insulating qualities of the sheet metal, by superimposing the film on the sheet metal, superimposing the foil on said film, and drawing the laminated assembly under tension along a convex curved surface, said foil next to said surface, and simultaneously heating said sheet metal to heat, by conduction, said film, heat and pressure on said foil causing it to bond to said foil and said film.