An expandable medical balloon, the expandable medical balloon comprising a first balloon wall, the first balloon wall comprising a first balloon layer of polyethylene terephthalate having a first intrinsic viscosity, the first layer is outer to a second layer of polyethylene terephthalate, the second balloon layer of polyethylene terephthalate having a second intrinsic viscosity, the second layer is an inner layer, wherein the intrinsic viscosity of the first balloon layer is higher than the intrinsic viscosity of the second balloon layer by about 0.05 dl/g or more.