A method of making a storage bag comprising the following steps performed in any order: (a) forming a composite tube having an inner surface comprising a higher melting polymer, an outer surface comprising a lower melting polymer, two ends, and a diameter； (b) flattening the tube in a direction perpendicular to the diameter； (c) forming a joint at one of the ends at a temperature between respective melting points of the higher melting polymer and the lower melting polymer； (d) providing a composite sheet having a first side comprising a higher melting polymer and a second side comprising a lower melting polymer； and (e) disposing the composite sheet over the joint such that the first side comprising a lower melting polymer engages the joint and forming a lap seam over the joint at a temperature between respective melting points of the higher melting polymer and the lower melting polymer, and a storage bag made by such method.
