Coextruded

Principle

This process consists of extruding several materials together in the same tooling so that each of the materials can be separately confined in a specific zone of the section.

Why use coextrusion ?

To include X-ray opaque lines in the wall of a transparent tube.
To have an internal layer which is compatible with the conveyed liquid, and an external layer which determines the mechanical aspects of the tube.
To allow a coloured marker line.
To combine the mechanical properties of two materials.

Process limitations

Limitations are associated with the compatibility of the materials: in most cases, the different materials must adhere together.
When the tube is manufactured, the temperatures must be compatible as well as the rheological behaviours of the materials.

Examples

Tubing for epidural catheters (x-ray opaque lines)
Extension tubing for sensitive medicine (coextruded PE/adhesive/PVC )
High-pressure extension line

Reinforcement

Description

This technique consists of including one or several metallic or organic threads in the wall of the tube in order to improve the mechanical performance.

Why use reinforced tubing ?

To improve crush resistance: one or more metallic threads with either a circular or rectangular section are included as a coil. A better effect is gained if the threads are made of cold-drawn steel.
To improve the transmission of the torque: several metallic threads are included as a braid. Flexibility and torque transmission depend on the angle of the braiding. A flat thread section strand allows a reduction of the tube wall thickness.
To improve the performance under pressure resistance: several synthetic fibres are included as a braid. The number of threads and their diameter determine the performance under pressure of the final product.

Process limitations

In the case where a spring wire is used, the manufacturing technique requires that the ratio of coil diameter to wire diameter remains over a minimal value.
Reinforcing a tube is a continuous process, we cannot therefore break the reinforcement wires thoughout the length of the tube.
In most cases, the tubing must be delivered in pre-determined cut lengths.

Examples

Crush resistant tubing
Catheters
High-pressure extension lines

Multilumen

Description

This extrusion technique allows us to obtain any kind of profiled tubing and in particular allows several independant channels inside the same tube. The specific profile is developped with customised tooling.

Why use multilumen tubing ?

To inflate a balloon
To allow heat-transfer fluid circulation
To measure distal pressure
To insulate electrical conductors
To allow introduction of a guide wire

Process Limitations

The specific shape of the desired profile can have an impact on the material flow in the tooling. For this reason it is sometimes difficult to obtain preciseness for some shapes. The result also depends on the material which is transformed. Whenever possible, it is preferable to maintain a consistent wall thickness throughout the profile of the tube.

Examples

Venous catheter
Balloon catheter
Cannula