4-step plastic testing regimen

Medical devices across the United States are under a sustained and coordinated attack from harsh solvents and disinfectants. The nearly decade-long effort to combat healthcare-associated infections (HAIs) through more stringent cleaning protocols has degraded protective housings, forcing manufacturers to re-evaluate their material choice decisions in light of cracking, crazing, discoloration, and premature device failure.

Fortunately, a newly-developed testing protocol is available that helps medical device manufacturers combat the consequences as they look to develop the next generation of devices or retrofit current lines.

A look back

In 2008, the U.S. Department of Health and Human Services (HHS) established the prevention and reduction of HAIs as a top priority. An HHS steering committee, along with scientists and program officials, developed a roadmap for HAI prevention in acute care hospitals, including action steps such as reporting infection rates of specific HAIs and, starting in 2015, reducing Medicare/Medicaid reimbursements to hospitals with the highest infection rates. New cleaning protocols were introduced, including the repeated application of isopropyl alcohol (IPA), IPA plus chlorhexidine, bleach, and other harsh chemical disinfectants.

Fortunately, HAI rates have tumbled and patient well-being has dramatically improved. The downside: problems with medical device housings have skyrocketed because many of the plastics materials specified for these device housings begin to degrade after repeated exposure to harsh disinfectants. In many instances this has led to equipment failures and reduced service life.

The medical device design industry has been unaware of the need to specify materials that can withstand aggressive disinfectants. Furthermore, testing protocols that can help guide decision-making have been lacking. Medical device manufacturers now have an ally in their quest to design and develop more rigorous housings: a 4-step testing protocol.

This 4-step testing process, developed by material scientists at Eastman Chemical Co., allows device manufacturers to evaluate the heavy toll harsh disinfectants take on different plastics. The test enables designers to make more- informed, better decisions regarding material choice.

The fourth step of the process – the reverse side impact test – determines a material’s required robustness. It offers a more accurate assessment of how a given material will hold up in a hospital environment in light of today’s HAI cleaning protocols.

Comparing materials

Certain plastic housings perform better than others due to a variety of factors, including the material and how it is molded and assembled. With the number of legacy plastics on the market, medical device designers have skillfully managed to design out some of the stress in particular device components.

Because designers have become familiar with common plastics, such as polycarbonate, polycarbonate/PBT, polycarbonate/ABS, and PVC, they have grown accustomed to the relative strengths and weaknesses of each material. In this new era of stringent cleaning demands, designers need more accurate and advanced testing to evaluate standards and new materials.

Materials meet HAI challenge

Standard plastics lack the strength to withstand HAI challenges, but a new generation of advanced plastics can address this. New plastics can lead to more-durable medical device equipment, with a cost difference that frequently pales in comparison to the repair and service costs of a failed device. 

Specialty copolyester Eastman MXF221 displays greater impact resistance and durability than a host of legacy plastics before and after disinfection. The halogen-free polymer is currently being deployed or considered for use in a variety of applications that include magnetic resonance imaging (MRI) coils, ultrasound probes, buttons, handles, and portable patient monitor units.

Equipment originally designed to last 8-to-10 years is encountering early lifecycle failures. From a patient’s perspective, devices that appear to be old and discolored can be quite unsettling. They are less likely to fault the manufacturer than to question whether the hospital is using the best and most up-to-date technology.

While successfully combating HAIs has greatly improved patient well-being and generated desirable bottom-line results for hospitals, it has disrupted how medical devices need to be designed and manufactured. New testing protocols, and new materials, will drive the next wave of improved performance and durability.

Eastman Chemical Co.
www.eastman.com

About the author: Yubiao Liu, Ph.D., medical application development scientist at Eastman Chemical Co., has more than 12 years of experience in the medical industry specializing in polymer synthesis and material evaluation. For more information, contact plasticsmedicalteam@eastman.com.