Medical device balloons with improved strength properties and processes for producing same
A tubular parison for forming a medical device balloon. The parison is formed of a polymeric material, for instance a thermoplastic elastomer. The parison has an elongation at break which is not more than 80% of the elongation of the bulk polymeric material. The elongation of the parison is controlled by altering extrusion conditions. Balloons prepared from the parisons provide higher wall strength and/or higher inflation durability than balloons prepared from conventional parisons of the same material.
1. An expandable medical balloon, the expandable medical balloon comprising:
a balloon wall comprising a thermoplastic elastomer, the balloon having a calculated burst strength of 32,000 psi or greater in a pre-sterilized condition as defined by the following equation:
Strength =( P×D/ 2 t )
where P = internal pressure when the balloon bursts (kg/cm 2 )(1 kg/cm 2 =14.2 psi); D is the exterior diameter (mm) of the balloon when a pressure of 6 kg/cm 2 (85.2 psi) is applied; and t is the wall thickness (mm) of the portion of the balloon with the larger exterior diameter.
2. The expandable medical balloon of claim 1 wherein the expandable medical balloon has a calculated burst strength of about 34,000 or greater in a pre-sterilized condition.
3. The expandable medical balloon of claim 1 wherein the expandable medical balloon has a calculated burst strength of about 37,000 or greater in a pre-sterilized condition.
4. The expandable medical balloon of claim 1 wherein the expandable medical balloon has a calculated burst strength of about 32,000 or greater in a post-sterilized condition.
5. The expandable medical balloon of claim 1 , the expandable medical balloon comprising poly (ether-block-amide) block copolymer.
6. The expandable medical balloon of claim 1 , the expandable medical balloon comprising alternating layers of poly(ether-block-amide) block copolymer.
7. The expandable medical balloon of claim 6 wherein the alternating layers comprise a layer of poly(ether-block-amide) comprising a Shore D hardness of about 70 and a layer of poly(ether-block-amide) comprising a Shore D hardness of about 72.
8. The expandable medical balloon of claim 1 , the expandable medical balloon comprising a nominal diameter of about 3 mm at 6 atm.
9. The expandable medical balloon of claim 1 comprising a poly(ether-block-amide) comprising a bulk elongation per ASTM D-638 of about 400%.
10. The expandable medical balloon of claim 1 wherein the thermoplastic elastomer is a poly(ether-block-amide) comprising a Shore D hardness of about 70.
11. The expandable medical balloon of claim 1 wherein the thermoplastic elastomer is a poly (ether-block-amide) comprising a Shore D hardness of about 72.
12. The expandable medical balloon of claim 1 wherein the thermoplastic elastomer is polyester/polyether block copolymer.
13. The expandable medical balloon of claim 1 wherein the thermoplastic elastomer is polyurethane.
14. The expandable medical balloon of claim 1 wherein the thermoplastic elastomer comprises a blend of thermoplastic elastomers.
15. The expandable medical balloon of claim 1 comprising improved resistance to repeat inflation bursts versus a control utilizing the same thermoplastic elastomer extruded to keep a parison elongation at break above 80% of the published elongation of the polymer.