Four adhesive chemistries can all technically bond a connector to a length of tubing — the one that actually holds up in service depends on flex requirements, cure speed, and how the finished component will be sterilized.
Scope of This Guide
This guide covers adhesive chemistry selection and process control for external and disposable fluid-path components — connector, hub, and tubing-set assembly. It excludes implantable or permanently indwelling devices, which require a separate and more extensive validation pathway.
Why Adhesive Bonding Replaced Mechanical and Thermal Methods
Mechanical fasteners add bulk and create stress concentrations exactly where a fluid-path assembly can least afford them. Thermal welding can alter the physical properties of sensitive polymers like PEBAX or polyurethane at the weld zone. Adhesive bonding distributes stress evenly across the joint, preserves the flexibility of the surrounding material, and — critically for multi-material assemblies — joins dissimilar substrates that welding simply can’t touch.
The Four Chemistry Families
Cyro-Weld™ 5000-series light-curable adhesives are the industry standard for high-volume assembly, curing in seconds under UV or visible light with on-demand alignment and immediate quality verification once triggered. Many formulations include fluorescing agents for automated optical inspection. Best suited to balloon-to-shaft, hub-to-shaft, and tip-attachment bonding where speed and inspectability both matter.
Cyro-Weld™ CM-series cyanoacrylates cure almost instantly on contact with ambient moisture, delivering high shear strength on difficult-to-join plastics and elastomers with no cure equipment required. The tradeoff is some brittleness and the risk of a white “blooming” residue if handling isn’t tightly controlled — manageable with correct dispensing practice but worth planning for in process design.
Epoxy adhesives, available as one-part heat-cured or two-part room-temperature systems, deliver superior chemical resistance and heat resistance along with strong gap-filling — appropriate where maximum structural integrity outweighs the need for a fast cycle time.
Polyurethane adhesives balance strength with genuine flexibility, a good fit where the bond line itself needs to move with the assembly rather than resist all motion, and they generally bond well to the same medical-grade plastics used elsewhere in the assembly.
Compliance Baseline
Any adhesive in this category should be formulated to meet ISO 10993-5 for in vitro cytotoxicity — the relevant standard for external and short-term-contact applications. Select grades are separately validated for EtO or Gamma radiation sterilization compatibility where the finished component requires it; that validation doesn’t transfer automatically between sterilization methods, so confirming per grade against your actual process matters more than assuming compatibility from the chemistry family alone.
Substrate Notes
PEBAX shafts bond well with most UV-curable adhesives. TPU takes well to biocompatible adhesive formulations and generally bonds easily with acrylics and urethanes. Nylon sections used for pressurized segments need adhesive formulations specifically suited to sustained pressure loading. Low-surface-energy plastics like PTFE and certain polyolefins need plasma treatment, corona treatment, or a chemical primer before any adhesive chemistry will hold reliably.
Process Control: Dispensing and Curing
Fluid-path components are typically bonded with microliter-precise adhesive volumes — excess creates flash that can obstruct flow or create a snag point, while too little leaves a weak joint. Automated needle dispensing or jetting valves maintain the tight tolerances this requires. For light-curable grades, LED curing systems have become the standard for their consistent output, long service life, and cool operation that avoids heat damage to thin-walled tubing; depth-of-cure validation confirms the adhesive is fully polymerized through the entire joint, not just at the surface. Email Us if you’re setting up a new dispensing and curing process for fluid-path assembly.
Joint Design Considerations
Joint geometry should maximize bonded surface area while minimizing stress concentration at the edges — lap joints and sleeve joints are standard in this category for exactly that reason. Fit and clearance between mating parts need to be tuned to the viscosity of the adhesive chosen, since a joint designed around a thick, gap-filling epoxy won’t perform the same way with a thin, capillary-flow light-curable formulation.
Quality Assurance
Pull (tensile) testing verifies bond strength exceeds a defined threshold under simulated handling and use forces. Leak testing under pressurized air or water confirms hermetic sealing. Fluorescing formulations allow non-destructive visual verification under blacklight, letting inspectors or automated cameras confirm correct adhesive placement without disassembling the part.
Selecting between these four chemistry families comes down to matching cure speed, flexibility, and sterilization compatibility to your specific joint — not defaulting to whichever adhesive is already on the shelf. Incure formulates both the Cyro-Weld™ CM-series and 5000-series specifically for this kind of external fluid-path assembly work. Contact Our Team to discuss which chemistry and grade fits your process.
Related reading: our comparison of UV glue versus epoxy for quick repairs and how CTE mismatch causes adhesive bond failure.
Visit www.incurelab.com for more information.