PEBAX is a low-density, lightweight thermoplastic plastic. It features greater customizability compared with other thermoplastic elastomers, enabling fine-tuning of properties including hardness, chemical resistance and processability. As a block copolymer composed of polyether and polyamide, its structural formula is shown in Figure 1. The outstanding performance of PEBAX stems from its unique two-phase crystalline and amorphous structure, which delivers a balanced combination of merits typical of thermoplastic elastomers:

① Light weight; ② Low-temperature stability; ③ Oxidation and corrosion resistance; ④ Fatigue resistance and antistatic property; ⑤ Excellent elasticity; ⑥ Precise dimensional stability; ⑦ Low friction coefficient; ⑧ Favourable processability.

For these reasons, PEBAX has seen growing adoption in the medical industry, especially in the field of medical catheters.

Nevertheless, PEBAX is a low-surface-energy polymer with intrinsically hydrophobic surfaces and strong chemical inertness. Problems such as insufficient bonding strength and coating delamination frequently occur during adhesive bonding and coating processes.

At present, an increasing number of medical device manufacturers adopt plasma surface treatment technology. This technology drastically improves the wettability and adhesion performance of PEBAX catheter surfaces without altering the bulk properties of materials, and has become a key manufacturing process for medical catheters.

Plasma Treatment Technology

Plasma treatment is a physicochemical surface modification technology relying on bombardment of material surfaces by high-energy particles. It improves surface properties by introducing active functional groups or modifying surface topography. High-energy electrons, ions and free radicals within plasma interact with the material surface to regulate surface hydrophilicity, wettability, adhesion and biocompatibility, while preserving the intrinsic bulk performance of substrates. Boasting advantages such as high efficiency, environmental friendliness and broad applicability, this technology has been widely deployed in medical catheters, thin-film materials, biosensors and other areas. Compared with alternative surface modification methods, plasma surface modification achieves treatment within shorter cycle times.

How Does Plasma Enhance Hydrophilic Adhesion of PEBAX Catheters?

1. Removal of Organic Contaminants

During extrusion, cutting and transportation, medical catheter surfaces tend to accumulate contaminants including oil residues, release agents and migrated additives. These contaminants form a weakly adherent interlayer on the surface. Adhesives merely rest on top of the contaminants, resulting in poor wetting and extremely low bonding strength. Oxygen plasma features strong oxidizing capacity. It triggers oxidative decomposition reactions with organic contaminants, breaking them down into CO₂ and H₂O.

2. Introduction of Polar Functional Groups

This serves as the core mechanism for adhesion improvement. Oxygen plasma generates polar groups on the PEBAX surface, including hydroxyl groups (–OH), carbonyl groups (C=O) and carboxyl groups (–COOH). These functional groups greatly increase surface polarity and boost the hydrophilic wetting capacity of adhesives.

3. Micro-roughening Effect

Ion bombardment from plasma gently etches the PEBAX surface and creates nano-scale rough textures. This enlarges the actual contact area, strengthens mechanical interlocking and elevates adhesive bonding force. In contrast to mechanical sanding, this process produces no particulate contamination and causes no dimensional damage to catheters, making it highly suitable for micro-catheters.

Thanks to comprehensive superior properties, PEBAX medical catheters have become a vital material for high-end interventional medical devices. However, its low-surface-energy characteristic creates challenges for bonding processes. Low-pressure plasma treatment significantly improves the hydrophilicity and adhesion performance of PEBAX catheters by removing surface contaminants, introducing polar functional groups and performing micro-etching, while keeping the bulk properties of the material intact.