Heat shrink tubing comes in a range of materials for many medical applications. Custom materials are also available.
Justin Fry, TE Connectivity Medical
There is a lot more to medical tubing than extruded polymers. Heat shrink tubing, for instance, provides a range of materials intended to improve designs and solve engineering and manufacturing problems.
For instance, the variety of medical grade heat shrink tubing provides a versatile set of products useful as process aids, in joint bonding, for chemical resistance, and electro-mechanical protection for critical medical components. Each area deserves more discussion:
- Medical shaft lamination/reflow and bonding: As a process aid, heat shrink tubing facilitates the reflow and bonding of medical shaft materials. The heat shrink tubing ensures a uniform compression during this process and is removed once the bond and reflow process is complete. The primary material used for this application is FEP (Fluorinated Ethylene Propylene) due to its temperature and compression profile.
- Welding applications: Many medical device manufacturing processes require bonding dissimilar materials, such as medical balloons to shaft substrates. Heat shrink tubing can be used to temporarily secure a balloon to a substrate during laser welding. The exceptional clarity of the tube lets a laser pass through and complete the weld, while the dimensional consistency is compatible with high-speed automated manufacturing. Once the weld is complete the heat shrink is removed and discarded.
- Joints and strain relief: Heat shrink tubing can permanently bond, secure or encapsulate joints between dissimilar materials and irregular shapes. With shrink ratios as high as 4:1, heat shrink tubing can be used in a wide range of joining applications where geometry is otherwise difficult to manage. Strain reliefs near wire terminations and product transitions are common applications. Heat shrink can also be lined with adhesives to ensure a more robust bonding of materials.
- Chemical resistance: Many heat-shrink materials are resistant to the chemicals common to hospital environments such as cleaning and sterilizing solutions.
- Electro-mechanical protection: When a device or component needs protection from abrasion, dielectric insulation, or encapsulation of critical elements, heat shrink tubing often delivers a cost effective solution.
As with much of the medical device industry, heat shrink tubing is trending toward smaller diameters and thinner wall sections. For example, with PEBA (polyether block amide), TE can manufacture heat shrink tubing with wall thicknesses down to 0.001 in., and recovered diameters as low as 0.006 in., small enough to insulate guidewires and other small instruments within the interventional market space. An advantage of the material is that it is durable, chemically resistant and can be made in both rigid and flexible durometers, making it a versatile thin wall.
The TE application experience lies in material formulation, extrusion, irradiation and expansion of high-performance heat shrink tubing. Several formulations are available for broad range of medical applications.
The accompanying table, A few general properties, lists the several product families, each of which works best in a particular area. The tubing is shipped, of course, in expanded sizes. The recovery temperature refers to the temperature which results in full reduction in diameter. The materials are durable, chemically resistant and stable so they maintain integrity at high temperatures, some up to 200°C.
Furthermore, the materials are compliant to RoHS and most are compliant to USP class VI biocompatibility. Select products are registered with FDA through the master file system and the tubing is manufactured to ISO 10993 standards accompanied by an ISO 13485 registered quality system. The company’s proprietary technology is an element in the design and manufacture of ISO 10993 and USP Class VI certified, medical-grade heat shrink tubing.
Justin Fry is the global product manager for medical tubing at TE Connectivity Medical in Wilsonville, Ore.