Simple four-step test evaluates long-term resistance of plastics to hospital disinfectants

A funny thing happened to the folks from Eastman Chemical (Kingsport, TN) on the way to MD&M West in Anaheim, CA, last week. They were bringing some samples to the show as visual aids for conversations they wanted to have around the effect of hospital disinfectants on various materials. Three molded parts made of Tritan copolyester MXF121, PC/ABS and PC/PBT had been soaked in Virex TB for 12 hours prior to being packed. When they were unpacked, the Tritan MXF121 was in pristine condition, while the screw bosses in the PC/ABS had disintegrated and the PC/PBT part had yellowed and the screw bosses were cracked. They expected the Tritan-based part to weather the flight without incident, but they were surprised at how fast and how severely the other parts showed degradation. That made for a serendipitous introduction to Eastman’s new four-step testing protocol to help medical device OEMs determine the long-term impact of hospital disinfectants on a variety of materials, which it presented at MD&M West.

Medical device manufacturers are avidly seeking information about the impact of disinfectants on materials simply because hospitals are asking for it, said Ellen Turner, Global Market Development Manager, Specialty Plastics, Medical, from the Eastman booth. To prevent hospital-acquired infections, healthcare establishments are using more-powerful disinfectants to clean housings and medical equipment. Hence, there is intense interest in the capabilities of plastics to withstand these chemicals over long periods of time. This test provides one means to determine that. 

The next rendezvous for the medical device supply chain happens in Cleveland, OH, on March 29 and 30, 2017. UBM America’s newest design and manufacturing trade show and conference, Advanced Design & Manufacturing (ADM) Cleveland showcases five zones—medical manufacturing, plastics, packaging, automation and robotics, and design and manufacturing. Numerous conference sessions are targeted to the medical manufacturing, automotive and other key industry sectors. Go to the PLASTEC Cleveland website to learn more and to register to attend.

In a video (embedded below) demonstrating the test, Medical Application Development Scientist Yubiao Liu, PhD, who developed the protocol, subjects a number of materials, including Eastman’s own Tritan MXF121, PC/PBT, PC/polyester, PC/ABS 1, PC/ABS 2 and PVC to several commonly used disinfectants. The steps are as follows:

  1. Select a jig with the appropriate strain level.
  2. Load plastic flex bars onto the jig.
  3. Apply commonly used chemicals in hospitals such as disinfectants, lipids and drugs to the flex bars and enclose the jig and samples in a plastic bag to prevent evaporation.
  4. After 24 hours, remove the jig from the bag and unload the samples.

“You may already see changes in some of the plastics,” says Liu, “but don’t stop there. There might be crazing and cracking that is not visible to the naked eye.” He recommends running an impact test and recording the impact strength of the exposed and control samples.

“This test will help you to determine which plastics will craze, discolor, get sticky or otherwise fail in your application,” explained Turner. While other materials performed well only under a narrow set of parameters, Tritan MXF121 achieved stellar results across the board, as you can see in the table below.

Eastman Chemical

Housings and hardware will be the initial target applications of the material, said Turner, but “Eastman Chemical continues to innovate based on customer feedback.” Further applications will include fluid management components, notably enteral feeding connectors that are compliant with ISO 80369 to prevent misconnections, and parts that are resistant to oncology drugs. In the latter application, there is a market shift to Tritan, said Turner, since PC and ABS can’t be used.

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