Low-bloom cyanoacrylate for catheter assembly
Low-blooming cyanoacrylate adhesives are designed for catheter and tubing assembly, where joints must be completely sealed while maintaining a clear appearance. The adhesive cures in seconds without leaving white residue around the bond, helping products meet cosmetic and visual inspection requirements.
Catheters are high-value products subject to strict cosmetic inspection. White residue around a bond, even if it does not affect function, can still cause a product to be rejected.
What is blooming
Cyanoacrylate cures by reacting with moisture on the surface. Some of the monomer evaporates, reacts with moisture in the air and then settles around the bond as a fine white powder, known as blooming or frosting. This effect is more pronounced when too much adhesive is used, when humidity is low or when the bond is in an enclosed space.
How low-blooming adhesives differ from standard ones
Low-blooming grades typically use alkoxy-ethyl monomers, which have lower vapor pressure than ethyl cyanoacrylate, so they evaporate less and have less odor. The adhesive is also more flexible, making it suitable for PVC, PU or PEBAX tubing, which are highly elastic. Medical grades are certified to ISO 10993 and can be sterilized by ethylene oxide or gamma radiation.
In many cases, blooming comes not from the adhesive but from excess adhesive. When we reduced the drop size with a smaller dispensing needle and added an accelerator, the bonds came out clean while bond strength still met requirements.
Application Engineer, AMS Vietnam
Catheter assembly techniques with cyanoacrylate
- Clean the surfaces with isopropyl alcohol and allow them to dry completely.
- Use a polyolefin primer if either part is PE or PP.
- Dispense the minimum amount of adhesive with a metering system, avoiding overflow outside the joint.
- Assemble quickly within the open time and hold in place for a few seconds.
- An accelerator, or UV exposure with light-curing hybrid cyanoacrylate grades, can be used to instantly cure any squeeze-out.
Production environment
- Maintain room humidity at about 40–60% for consistent curing.
- Provide local exhaust ventilation at the bonding station.
- Store unopened adhesive in a refrigerator and let it reach room temperature before opening the cap.
When evaluating a new adhesive, test joint pull strength after immersion in saline at 37°C for several days to simulate actual use conditions, as some plastic and adhesive combinations lose significant bond strength in warm, humid environments.
AMS distributes medical cyanoacrylate adhesives from Henkel Loctite and Dymax and supports bonding trials on actual tubing materials. Contact AMS Vietnam for advice on catheter assembly processes.
