A vascular graft, such as an AAA stent graft, includes a core zone of PET fabric with a non-porous coating comprising a polyurethane, such as Thoralon, disposed on at least one surface. The coating provides a barrier to prevent short and long term leakage of fluids through the pores of the PET fabric core zone. A method for sealing the pores of a porous PET graft includes the step of coating at least one surface of said graft with at least one polyurethane, or mixtures and combinations thereof. Preferably, the coating is Thoralon. A method for making a vascular prosthesis includes the steps of providing a core zone of PET fabric, and coating at least one surface of the core zone with at least one polyurethane, or mixtures and combinations thereof, such as Thoralon. Finally, a method of repairing or treating a defective vessel includes the step of reinforcing or replacing the defective vessel with a graft according to the invention.