An endotracheal tube connector separating during use is one of the more serious device failures an airway product can have, which is why the bond between tube shaft and connector hub gets more scrutiny than almost any other joint in respiratory device manufacturing.
Why This Joint Carries Outsized Risk
Endotracheal tubes combine a flexible PVC or silicone shaft with a rigid connector hub at the proximal end, a joint that has to withstand axial pull force, torsional stress from handling, and repeated positioning adjustments during use, all while maintaining an airtight seal. Unlike many other tubing joints on less critical devices, a partial separation here doesn’t just cause a leak — it can compromise the entire airway pathway, which is why manufacturers typically specify pull-force requirements well beyond what a standard tubing connection would need.
That risk profile is exactly why adhesive selection at this joint deserves more rigor than treating it as a generic tube-to-connector bond.
Selecting the Right Incure Grade for Endotracheal Connector Bonds
The Incure Cyro-Weld™ 5013 is a capillary-action wicking adhesive (750–1,500 cP) designed to draw fully into the annular gap between the tube shaft and connector hub, forming a complete 360° fillet rather than a partial bond — critical given the axial pull-force requirements this joint typically has to meet, with a working range of -55°C to 80°C.
For programs that need inline inspection confirmation of full fillet coverage rather than relying on pull testing alone, the Cyro-Weld™ 5002F (300–600 cP urethane acrylate) is formulated for hermetic hub bonding and cures within seconds under 365–405 nm exposure, with a service range of -55°C to 80°C, giving a second validated option for this joint depending on your specific gap tolerance.
Rigid connector hubs bonded to flexible PVC or silicone shafts are a common example of CTE mismatch causes adhesive bond failure, which is worth accounting for given the temperature range these tubes see between manufacturing, sterilization, and use.
Sterilization and Biocompatibility Validation
Both grades are formulated to meet ISO 10993-5 cytotoxicity standards and are validated for Ethylene Oxide (ISO 11135) and Gamma (ISO 11137) sterilization pathways, the two most common routes for airway device manufacturing. As with all Incure materials, this reflects formulation-level validated data, not a finished-device clearance — confirming pull-force performance after your specific sterilization cycle, at the actual force levels your device specification requires, remains part of your own device qualification.
Given the criticality of this joint, Email Us with your specific pull-force requirement and tube material so our applications team can help confirm the right grade before you finalize a bonding process.
Common Failure Modes at the Hub-to-Shaft Joint
Partial fillet coverage is the most consequential failure mode at this joint, since a connector can appear fully bonded on visual inspection while a section of the annular gap remains unfilled — this typically traces back to inconsistent dispensing pressure or an oversized gap in a specific region of the joint rather than the adhesive chemistry itself. Annular gaps exceeding roughly 0.15 mm reduce wicking reliability regardless of viscosity, so dimensional control on both the tube OD and hub ID matters as much as adhesive selection.
Torsional failure under handling stress is a second pattern, generally linked to a bond that met axial pull-force requirements but wasn’t separately verified against torque, since clinicians routinely rotate and reposition a connector during use. Testing both axial pull and torque on a representative sample, rather than pull force alone, gives a more complete picture of real-world joint performance.
FAQ
Q: Is 100% fillet coverage verification necessary on every unit, or is sampling sufficient?
A: Given the criticality of this specific joint, many manufacturers move beyond standard statistical sampling toward inline inspection methods — such as automated vision systems or fluorescing-grade adhesives — precisely because a partial bond at this joint carries more consequence than at a less critical connection point elsewhere on the device.
Q: Should torque testing be part of routine lot release for endotracheal connectors?
A: It’s worth considering in addition to axial pull testing, since torsional stress from clinical handling is a realistic use condition that a pull test alone doesn’t fully capture.
Q: Does tube material affect which adhesive grade performs best?
A: Yes — PVC and silicone shafts have different surface energies and different flexibility profiles, so a grade validated on one material shouldn’t be assumed to perform identically on the other without its own adhesion verification.
Endotracheal tube connector bonding deserves a higher standard of verification than most tubing joints, given what’s at stake if the bond underperforms. Our technical team can review your specific pull-force spec and tube material — Contact Our Team for grade recommendations and sample material.
Visit www.incurelab.com for more information.