Abstract: Methods of forming a stent-graft prosthesis including two layers of ePTFE with at least one stent positioned between or encapsulated within the ePTFE layers include utilizing one or more direct heating elements that are positioned within or in close proximity to a mandrel upon which the stent-graft prosthesis is placed in order to reduce the temperature and/or time required to couple the two ePTFE layers together. An internal heating element may be positioned within a lumen of the mandrel and/or an external heating element may circumferentially surround the mandrel in close proximity thereto. The direct heating elements may be utilized to couple the two layers of ePTFE together without an adhesive or melt layer therebetween.