Originally Published MPMN July 2006

PROFILE

Acrylic Multipolymer Adds Durability to Check Valve Design

A chemically resistant material improves a key component in drug-delivery systems

To provide patients with high-quality treatment and care, doctors rely on the integrity of each and every drug-delivery device and component. Because of the role check valves play in intravenous (IV) drug delivery, ITW Filtration Products (Elk Grove Village, IL; www.itw filtration.com) takes special care when making these devices.

ITW specializes in producing components with a complex shape. One example is check valves, which are included in many IV delivery sets. By inserting a check valve into an IV line, fluid backflow is prevented. This becomes especially important when patients receive multiple fluids. To maximize patient comfort, multiple solutions from different bags converge into one IV line at a y-site, allowing the use of just one entry site for drug administration. By eliminating backflow, check valves prevent dilution of one solution into the other solution, which could impede treatment effectiveness. Check valves must withstand exposure to many solutions, including harsh chemotherapy agents, antibiotics, and saline.

ITW required a tough, yet easy-to-process material to mass manufacture effective, durable check valves. With this in mind, the firm chose Cyrolite G-20 Hiflo acrylic-based multipolymer compound, a product of acrylics manufacturer Cyro Industries (Rockaway, NJ; www.cyro.com). The material's transparency and chemical and lipid resistance made it suitable for use in check valves.

"Our check valves must be durable. The impact-modified Cyrolite G-20 Hiflo compound results in a tough part that will function properly in the field over time," Christine Fredricks, ITW's business coordinator, explains.

Due to its chemical and lipid resistance, Cyrolite G-20 Hiflo compound does not craze or leach out after repeated contact with fatty, oily, or chemical solutions. The compound also offers resistance to gamma, E-beam, and EtO irradiation, which has proven to be a benefit for ITW. "Our customers can sterilize our check valves by the method they prefer without being limited by the properties of the check valve material," says Fredricks. The material can be transparent as well as colored in order to facilitate the assembly process.

ITW check valves, molded and assembled in a Class 100,000 cleanroom, consist of a clear cover and a white housing. A silicone disk is assembled between the two parts. With a low priming volume, the check valves open easily without intense fluid pressure to allow effective drug delivery to the patient.

For proper function, it is extremely important that both parts of the check valves, the housing and the cover, be molded to specifications. The melt flow and consistency of Cyrolite G-20 Hiflo compound facilitate accurate molding and ease of fabrication. "The compound flows evenly into the mold and ensures that the cavity is properly packed out," says Fredricks. This eliminates the production of short shots, the term for devices not fully formed due to improperly packed-out molds. Because it works well with hot runner systems, the material reduces the risk of uneven molding and minimizes resin waste and product rejects.

To create a leak-free seal in the check valves, the housing and cover are ultrasonically welded in an automatic assembly process. Due to its hardness, the compound performs well with this process. Ultrasonic welding is not as effective with parts made from softer materials, such as PVC and most urethanes and olefins, because the ultrasonic energy is scattered rapidly in these compounds.

All ITW check valves are 100% in-line tested for backflow failure on automated assembly machines. The extremely low reject level of the check valves comes as a result of the polymer's precise molding and ultrasonic welding capabilities, combined with ITW's extensive experience. Backflow protection is enhanced because the check valves are designed to be closed in the static state. Other check valves close only when backward fluid pressure is present. This can cause a problem when liquid backflow amounts are small, as the check valve may not effectively close. Because the ITW check valves are normally closed, backflow prevention is maximized.

The check valves also pass the USP Class VI tests for biocompatibility. Meeting these criteria shows that the Cyrolite G-20 Hiflo compound is acceptable for use in healthcare applications. Fredricks says, "The chemical resistance and durability of the Cyrolite G-20 Hiflo facilitates the strong performance of our check valves in the field, helping them to effectively impede backflow and meet all relevant industry standards."

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