“I would like to attach 72D Pebax extruded tubing into the ID of a Polycarbonate tube. What is the appropriate gap-per-side if I want to use DYMAX 204-CTH UV- curable adhesive?”
The optimum gap size for UV bonding applications (in general) is 0.002-0.006 inches, or 0.05-0.15 mm. In catheter bonding applications, where a Pebax tube is being bonded into a Polycarbonate Y-connector, we often see bond gaps around 0.1 mm per side. The DYMAX 204-CTH-F family is a very good choice of products to use for this type of application and substrate combination. Another product to consider is 208-CTH-F.
Adhesives, Catheter Bonding, Medical
A question that came through:
“What is the best adhesive for bonding a polyethylene terephthalate (PET) balloon to a polyether block amide (Pebax) substrate? What is the recommended surface preparation? Are other catheter-shaft substrate materials more suitable than Pebax for bonding to a PET balloon?”
You should select a medium-flexibility light-curing adhesive with the viscosity to achieve the level of wetting and gap filling appropriate to your design. For example, DYMAX’s 204-CTH-F and 208-CTH adhesives have viscosities ranging from 155 to 500 cP. Such adhesives bond well to both PET and Pebax. In addition, it is important to choose an adhesive that fluoresces under a black light, enabling operators to detect and fix voids or air bubbles before the assembly is cured. This feature results in a better-quality bond and greater yields during production.
You can perform a surface treatment using plasma together with oxygen gas. While a plasma treatment with air gas—which has a lower O2 content than oxygen—is also effective, it is not as advantageous as using an oxygen plasma treatment. The oxygen deposits onto the surface of the material and increases the number of bond sites to which the adhesive can stick.
You ask whether other catheter-shaft substrate materials are more suitable than Pebax for bonding to a PET balloon. Pebax is commonly used for manufacturing catheter shafts because adhesives bond well to it. A polyether/nylon copolymer, the material can be mixed with higher proportions of nylon (polyamide) to create higher-durometer materials (72D), or it can be mixed with lower proportions of nylon to create lower-durometer materials (35D). The greater the amount of nylon in the Pebax, the farther apart are the bond sites and the more difficult it is to bond. For example, bonding PET to 35D Pebax is easier than bonding it to 72D Pebax. If you can incorporate a small layer of 35D Pebax at the bond location while retaining 72D Pebax underneath to achieve greater material stiffness, the bonding application will be improved.