“We are looking for a medical-grade adhesive for bonding PEBAX (72D MED) tubing to latex nature rubber. We need shore hardness of a UV adhesive below 50D after cured. What is the best adhesive for this application? Also, which pre-surface treatment is suitable for PEBAX?

We also need a medical-grade adhesive for bonding PEBAX (72D MED) tubing to a colored ABS hub. Which fast setting adhesive is suitable for this?”

Latex nature rubber can typically be bonded with cyanoacrylates, also referred to as Super Glue. The Dymax medical grade 222 series cyanoacrylates might be a good place to start.

For bonding PEBAX I would suggest looking at Dymax 208-CTH-F, which is a medical grade, light-curable adhesive with shore D55. To combine PEBAX with latex or colored ABS, light-curable adhesives might not be suitable due to low adhesion to latex and problems with light curing through the colored ABS hub. Therefore, a cyanoacrylate is most likely the adhesive of choice.

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“We currently employ a solvent process using Cyclohexanone to bond a PVC tubing with an ABS molded hub. We are going to be switching from ABS to a Pebax (thermoplastic elastomer). We believe there are issues with the Cyclohexanone creating the bond with the Pebax that we desire, and I’m looking for some info regarding our process - is it appropriate to continue to solvent bond (maybe with a different solvent) or to switch to a new process (UV adhesive for example)?”

Solvent bonding typically works with amorphous thermoplastics such as PVC, ABS, PC, PMMA, and PS. Pebax belongs to the family of thermoplastic elastomers and has a good resistance to solvents in general. Depending on the grade and softness, it may swell in certain solvents but will not behave like amorphous thermoplastics do. If you replace the ABS with Pebax, you need to switch to a new bonding process. UV light-curable adhesives are a good option. I would recommend trying Dymax medical grade adhesives 204-CTH-F and 209-CTH. They both adhere well to PVC and Pebax and several other commonly used plastics.

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“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.

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“I need to bond PE to both metal and Pebax^®. If possible, a light-cure product is preferable. Would the surface treatment be the same for PEBAX to PE? Do both materials need to be treated?”

There are a few light-curable adhesives that come to mind that will bond to both metals and plastics, and have good adhesion to both PEBA and PE. Treatment of the PE is a good idea, and methods include corona treatment of the PE, or plasma treatment with an oxygen-gas attachment. Regarding adhesion to PEBA, (as a block copolymer) this material can have different levels of a nylon characteristic. Usually, the higher the durometer, the more like nylon it will behave, which is a little more difficult to bond to. A lower durometer PEBA is typically easier to stick to. If you are bonding PEBA to PE, you would generally only need to treat the PE. If you are using a high durometer PEBA it would be a wise test to treat the PEBA and see if better bond results are found.

If you are looking for a recommendation from DYMAX, I suggest evaluating either 1161-M or 1168-M. Other competitive companies offer some very good adhesives for these substrates, and I am sure their technical support groups can help make a proper recommendation. There is a new technology available which can actually let you see the blue colored adhesive as it is dispensed, and upon cure will become clear. The See-Cure technology, as found in a product like 1202-M-SC, can bond to metal, PEBA, and PE (with treatment), as well as provide a safety feature by allowing the operator to see where the adhesive is dispensed, and when it has reached full cure.

Adhesives, Medical Pebax, See-Cure

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?”

Answer:

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. 

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