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The Faster, Cleaner Method of Securing Medical Tubing - Coventry Swelling Agents

Coventry is known globally for solving the most critical application challenges. Our high purity swelling solvents offer medical equipment manufacturers an innovative way to efficiently secure tubing onto connectors.

Coventry swelling agents provide a cleaner, faster and easier bonding method than other common alternatives like thermal bonding, solvent bonding, and bonding with medical grade adhesive. Swelling agents expand silicone elastomers and tubing for fitment onto components, and then evaporate allowing the tubing to shrink back to its original dimensions.

To use Coventry swelling agents with silicone tubing:

Tub in liquid

  1.        Dip about 1” of the end of the tubing into the swelling agent.
  2.        Hold it in the solvent from 5 to 10 seconds, depending on the type and thickness of the silicone.
  3.        Withdraw the tube from the solvent.
  4.        The solvent causes the elastomer of the tubing to swell, increasing the size of the opening.
  5.        Slide tube over barb on the connector.   
  6.        The solvent will flash off, causing the tube opening to shrink over the connector, forming a secure, permanent bond. This can take from five to 15 minutes depending on the size of the tubing. Bonded parts can be handled within minutes.


The traditional methods of securing medical tubing have their own advantages and disadvantages:

  • Hot welding, hot bonding, thermal welding, thermal bonding - One method of attaching tubing to a connector is to apply heat, melting together the tube and connector material. The disadvantage of this method is it stresses and potentially weakens the connector, increasing the risk of breakage. In addition, plasticizers and other materials within the polymers could leach out.
  • Solvent welding, solvent bonding - The solvent bonding method of attaching silicone tubing to a barbed connector involves using an aggressive solvent to partially break down or dissolve the materials. Once they harden, the tube and connector mechanically bond together. Similar to hot welding (above), the aggressive solvents can stress the parts. Rigid plastics can actually craze or crack as the solvents attack the material. In addition, most solvents used in this process are toxic to serious health concerns. Thorough ventilation is required to keep everyone safe. Entrapped solvent within the barbed areas of the connector after the bonding process is also a concern because it is a potential source of contamination.
  • Medical grade adhesive bonding - Adhesives are available to bond connectors to tubing. This method can be very effective, but costly. The curing process can also add complexity and potential contamination. UV curable adhesive only cures line-of-site, so cloudy or opaque tubing or connectors can block light and cause contamination from the partially cured adhesive.

In contrast to solvent welding, thermal bonding, and medical grade adhesive bonding, Coventry Swelling Solvents have low toxicity, do not stress the assemblies, do not risk contamination from extractables, and utilize a fast, efficient bonding process.


Coventry 12803 Heptane Precision Swelling and Cleaning Solvent


Coventry Heptane Solvent is a highly purified grade of n-heptane, providing the cleanest chemical grade available. It is an ideal bonding agent for silicone and urethane elastomers and tubing.  Heptane can also be used as a silicone lubricant carrier fluid for devices, or to remove oils, greases and particulates. Heptane is a fast drying solvent that has very low surface tension, so it is able to reach into tight crevices. It evaporates quickly and cleanly, leaving behind no residue.


Coventry 12857 Nonflammable Swelling Solvent and Cleaner


Coventry Nonflammable Swelling Solvent and Cleaner is a low-VOC, nonflammable solution developed for safely swelling silicone near sensitive plastics. It is ideal for swelling silicone elastomers and tubing for fitment onto components while in proximity to titanium, PEEK and stainless materials without harming any of the materials. It is also effective at quickly removing oils, dirt, dust, and other contaminants from surfaces and assemblies.  It has a very low surface tension, so it is able to reach into tight crevices. It evaporates quickly and cleanly, leaving behind no residue, and is safe on sensitive metals.


Coventry 12855 Zero-VOC Swelling Solvent


Coventry Zero-VOC Swelling Solvent provides outstanding swell characteristics for silicone tubing and components, and has zero volatile organic compounds (VOCs). VOCs are closely regulated in many areas because they contribute to smog. It also can be used to clean and removes mold release compounds. It has a very low surface tension, so it is able to reach into tight crevices. It evaporates quickly and cleanly, leaving behind no residue, and is safe on sensitive metals.


So if you are looking for a fast, efficient, easy and residue-free method of attaching medical-grade tubing to connectors, evaluate the great options from Coventry. Contact a technical specialist at 770-424-4888 or to find the right solution for your requirements.

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