Medical device including improved expandable balloon

This invention relates generally to medical devices and, more particularly, to devices for deploying another medical device such as a stent into a patient or for expanding a narrowed or obstructed passage or lumen in a patient. A medical device () includes a catheter shaft () including inner and outer catheter shafts (and ), and an expandable balloon () carried by the catheter shaft (). The balloon () is made from an irradiation cross-linked mixture of a polyamide elastomer and at least one additional cross-linking reactant. The polyamide elastomer can be a polyester amide, a polyether ester amide or a polyether amide, and is preferably a nylon block copolymer. The cross-linking reactant can be: (a) a difunctional material, (b) a trifunctional material, (c) a tetrafunctional material, or (d) an aromatic molecule containing at least two ring substituents, each of the ring substituents having labile hydrogens at a benzylic site therein. The cross-linking reactant can also be diallyl phthalate or meta-phenylene dimaleimide. Irradiation is carried out by exposure to an electron beam or to ultraviolet, X- or gamma radiation, preferably at a total fluence of about 0.5 to about 20 megarads. The amount of the cross-linking reactant is selected to avoid the formation of gelling during the process by which the balloon () is made, and the amount of the cross-linking agent and the irradiation fluence are selected to give the balloon a strength generally about equal to that which would be obtained by mere irradiation.