ENGINEERING INSIGHT
 |
Cyrolite G-20 Hiflo multipolymer compound is used to make chemically resistant, biocompatible check valves for use in IV drug-delivery systems.
|
When sourcing a material for its check valves, a manufacturer of device components identified processability, sterilizability, and strength as key properties. An acrylic-based multipolymer compound from Cyro Industries (Rockaway, NJ, USA) met all these demands—and then some.
ITW Filtration Products (Elk Grove Village, IL, USA) specializes in producing components with a complex shape. For its check valves, the company required a tough yet easy-to-process material that would lend itself to mass manufacturing practices. The firm chose the Cyrolite G-20 Hiflo compound.
“Our check valves must be durable,” says Christine Fredricks, business coordinator at ITW Filtration Products. “Impact-modified Cyrolite G-20 Hiflo compound results in a tough component that will function properly in the field over time.”
Preventing Backflow
Check valves are a common component of IV 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 would impede treatment effectiveness.
ITW’s check valve is normally closed in the static state. Other check valves close only when backward fluid pressure is present; this can cause a problem when small amounts of liquid flow back, as the check valve may not close effectively.
Check valves must withstand exposure to many solutions, including harsh chemotherapy agents, antibiotics, and saline. Due to its chemical and lipid resistance, Cyrolite G-20 Hiflo does not craze or leach out after repeated contact with fatty, oily, or chemical solutions. The compound also withstands 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 coloured as well as transparent in order to facilitate the assembly process.
The ITW check valve, moulded and assembled in a Class 100,000 cleanroom, consists of a clear cover and a white housing. A silicone disc is assembled between the two parts. The low-priming check valve opens easily without intense fluid pressure to allow effective drug delivery to the patient.
Melt Flow and Consistency
For the check valve to function properly, its housing and cover must be moulded to specification. The material’s melt flow and consistency facilitate accurate moulding and ease of fabrication. “The compound flows consistently into the mould and ensures that the cavity is properly packed out,” says Fredricks. This eliminates the production of so-called short shots (incompletely formed devices caused by improperly packed-out moulds). Also working well with hot-runner systems, the material reduces the risk of uneven moulding, 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. Because of its rigidity, 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 energy is dissipated 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 is a result of the precision moulding and ultrasonic welding capabilities, and overall expertise, that ITW brings to the production process.
To learn more about these companies, select #7 for Cyro Industries and #8 for ITW Filtration Products on the reader service card, or go to RequestLink at www.devicelink.com/emdm.
