Medical Conveyor Polymer Materials

In minimally invasive interventional medical devices, stents and covered stents are commonly used. These devices and conveyors constitute a complete interventional medical device. After the transporter is transported, it has to complete the disposal process of withdrawing from the body after placement, so it is usually a disposable appliance. Even so, the performance of the conveyor will directly affect the smoothness of the operation process and postoperative recovery process, and more importantly, it will affect whether the treatment device can be stably and accurately placed at the designated site.

During the treatment process, it is necessary to choose an easy-to-puncture venous or superficial arterial approach, and it is necessary to transport the treatment device to the lesion through tortuous blood vessels, which requires the delivery device to have good tracking performance, smoothness and twist control sex etc. Various polymer materials with different properties provide various directions for conveyor materials, such as polyether block amide copolymers, fluorine-based polymer materials, etc.

1. Polyetheramide block copolymer (Pebax)

Pebax obtains products with different hardness by combining different types and ratios of hard linear polyamide segments and soft segment polyether segments. Among them, the polyether soft segment provides ductility and flexibility, while the polyamide hard segment provides physical crosslinking. Not only a wide range of hardness, Pebax material also has good mechanical properties, biocompatibility and easy processing, so it has attracted extensive attention.

Due to the good compatibility and thermal welding strength between different types of Pebax, when used as a catheter for minimally invasive interventional therapy equipment, different Pebax materials are used as different parts according to requirements to obtain a gradient in hardness and a better fit. catheter. For example, the part of the blood vessel that bends in the human body at the front end needs to be softer to reach the lesion; while the back end needs a certain degree of hardness to maintain sufficient support; in the transition, it needs to be smooth and have good connection strength to ensure that it can be relieved during use. Minimal puncture to blood vessels and resistance during advancement while remaining intact during treatment. It can be seen that Pebax materials are very important in minimally invasive interventional therapy devices.

2. Fluorine polymer materials

In minimally invasive interventional medical device materials, fluorine-based polymers have attracted widespread attention due to their low friction coefficient and excellent biocompatibility. Among them, polytetrafluoroethylene (PTFE) has the smallest friction coefficient, so that it can be directly used as a delivery tube, and is one of the most commonly used materials in minimally invasive interventional therapy devices.

However, PTFE is a non-polar polymer material and cannot be directly glued or thermally welded. Therefore, it can only be connected by mechanical methods; in addition, the modulus of PTFE is low, and it will be easily elongated and deformed when subjected to frictional resistance and stretching during use, thus limiting the application of pure PTFE directly as various catheters . Usually when used it needs to be made into composite materials.
Polyvinylidene fluoride (PVDF) and perfluoroethylene propylene copolymer (FEP) have the lowest melting point, making them easier to heat weld or glue, so they have a higher friction coefficient and processing in minimally invasive interventional medical device materials. Used when requested.

When the fluoropolymer is used as a catheter or a delivery device, it can reduce the resistance of the treatment device and improve the controllability and accuracy of the release of the treatment device. In addition, the fluorine-based polymer material can also be used as the material used for the outer surface coating of the metal catheter to reduce the resistance in the human body.

3. Polyamide material (PA)

Compared with the previous types of materials, polyamide polymer material (PA) has the characteristics of moderate friction coefficient, easy processing, high strength, etc., and can also be used as a catheter for minimally invasive interventional therapy. In addition, PA and its copolymer polymer materials are wear-resistant and have high modulus, so they can also be used as the primary material for preparing balloons.

For example, the FXminiRAIL double guide wire balloon dilatation catheter contains PA in the balloon part and the outer layer of the catheter trunk, and a water-based coating composed of polyvinylpyrrolidone and polyacrylonitrile is coated on the outer surface of the catheter. layer, so it is widely used in improving coronary arteries. The balloon of another type of MissouriPTCA balloon dilation catheter is also made of PI, and its proximal tube is supported by stainless steel coated with PFTE.

4. Polyimide material (PI)

Polyimide (PI) has stable chemical properties, the best overall performance, high temperature resistance can even reach above 400 °C, and has corrosion resistance, no obvious melting point, poor water absorption, mechanical strength (1×106Psi) and modulus ( 42×105 Psi) and other advantages. Its high strength and low elongation. It can be made into the material of the conveyor used in minimally invasive interventional therapy devices with thin tube walls (0.03-0.05 mm), which minimizes the cross-sectional area of the conveyor and reduces the risk of surgery. Materials made of PI are also suitable for various other medical devices, such as vascular structures, delivery sheaths and other materials.

5. Composite polymer materials

Although the above-mentioned various materials have their own excellent characteristics, if they are used alone as a conveyor material, they usually have many disadvantages. For example, the conveyor made of polyether block amide copolymer is easy to break and has a small modulus. And the resistance encountered when releasing the medical device will increase, and in some cases, the sheath tube will be stretched and deformed, which will increase the risk of minimally invasive interventional surgery. Therefore, it is necessary to combine their advantages to prepare composite materials to meet the needs of minimally invasive interventional therapy devices.

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