Balloon angioplasty is a widely used procedure for expanding constricted body passageways, such as arteries and other blood vessels, or various ducts (e.g., of the biliary system). In an angioplasty procedure, an uninflated angioplasty balloon attached to a catheter is delivered to a constricted region of a body passageway. Once the balloon is in position at the constricted region, fluid is injected through a lumen of the catheter and into the balloon. The balloon consequently inflates and exerts pressure against the constricted region to expand the passageway. After use, the balloon is collapsed, and the catheter is withdrawn. Although treatment of constricted arteries in the vasculature is one common example where balloon catheters are used, this is only one example of how balloon catheters may be used and many other uses are possible. For example, balloon catheters may also be used to temporarily occlude vessels during medical procedures to prevent blood or other fluids from flowing through a vessel. Balloon catheters may also be used to expand other intraluminal devices without dilating the surrounding vessel wall, such as stent-grafts that may be used to treat aneurysms. The above-described examples are only some of the applications in which balloon catheters are used by physicians. Many other applications for balloon catheters are known and/or may be developed in the future.
Balloons have a number of important design parameters. One is rated burst pressure, which is the statistically-determined maximum pressure to which a balloon may be inflated without rupturing. In order to expand hard, calcified lesions, it is desirable that the balloon have a rated burst pressure of at least 15 atm. It is also desirable that the balloon have a low wall thickness to minimize the profile of the delivery system. A wall thickness of about 0.03 millimeters or lower is generally preferred. For a given balloon material, however, there is a trade-off between burst pressure and wall thickness, in that the burst pressure generally decreases when the wall thickness is reduced. Accordingly, there is a need for a means of increasing the strength of balloon materials to attain higher rated burst pressures at lower wall thicknesses.