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Expert insights on choosing the right plastics for medical applications

Plastic resins
As with any product, the material’s physical properties, the environment(s) in which it will be used, its cost and the manufacturing process must be taken into consideration during the material selection process. Depending on the medical device, however, there may be added layers of complexity.

The material selection process for a medical application must consider many of the same issues as for any other product—the material’s physical properties, the environment(s) in which the product will be used, the cost of the material, the manufacturing process, and so forth. Depending on the medical device, however, there may be added layers of complexity, such as the material’s biocompatibility, sterilizability, lubricity and resistance to harsh disinfectants typically used in hospitals. A panel of experts at the co-located PLASTEC East and Medical Design & Manufacturing (MD&M) East in New York next month will offer their insights during a session—Choosing the Right Plastic for Your Medical Device—at the Medtech Hub (booth 1669). In advance of the event, some of the panelists shared with PlasticsToday what they consider to be key elements of the material selection process.

At a high level, it’s critical to consider the full use cycle of the device, said Lauren Bobrek, Business Development Leader at materials supplier Sabic. “The use cycle encompasses application requirements (including functionality, performance and regulatory), the manufacturing process (including secondary operations) and the environment in which the device will be used,” explained Bobrek.

The application requirements typically will dictate the properties of a thermoplastic, such as creep resistance, wear resistance and impact strength, and most medical devices will require the use of biocompatible materials, advised Bobrek.

“I start with the physical mechanical strength properties, as well as biocompatiblility requirements in material selection,” added Ken Breeding, New Business Development Associate, Eastman Chemical Co. He concurs with Bobrek that “a good understanding of product life” is essential to effective material selection.

The manufacturing process under consideration will limit the materials that can be used “because most thermoplastic grades are formulated for specific processing methods,” said Bobrek. Similarly, secondary operations such as assembly and labeling will steer the selection process. “Knowing what downstream assembly requirements are in play . . . is critical,” added Breeding. As an example, Bobrek cites pad printing, “which requires a material compatible with the ink.” Also, part design, such as thin walls and complex geometries, may require a material with a higher melt flow, she adds. 

The use environment has taken on significant importance with the expansion of the home-care market. If the device is going to be used by the patient, aesthetics and ergonomic features may be prioritized. A nonclinical appearance can be a big plus in medical devices used in the home, and informed material selection can be one element in achieving that outcome.  On the other hand, “if the device will be exposed to sterilization cycles or harsh disinfectants [in a hospital setting], chemically resistant and/or thermally resistant thermoplastics with hydrolytic stability may be needed,” said Bobrek.

Not considering the complete use cycle of a device during the material selection process can lead to “material problems and even failures,” stressed Bobrek.

In addition to a full understanding of the technical requirements of the final product, it’s essential to have a grasp of the regulatory requirements and attributes that each material has to offer, said Ed Flaherty, Application Development Engineer at Nexeo Plastics. Medical-grade materials differ from commercial grades in many aspects, explained Flaherty. While they may have the same chemical composition, “control and monitoring of healthcare-grade materials, both during and after the material is produced, is the difference,” said Flaherty. These materials typically include “formulation lock, change notification from the supplier that can span 18 to 36 months, dedicated and cleaner logistics, test reports to support regulatory compliance and manufacturing controls.”

Because of the intricacies of the material selection process, Bobrek recommends that medical device OEMs take advantage of their suppliers’ in-depth knowledge. “Major suppliers may have expertise in the medical device sector and translatable experience from other industries. They undoubtedly possess a deep knowledge of their candidate thermoplastics, as well as part design and processing, that can complement and extend the resources of device OEMs,” said Bobrek. Moreover, they may be able to suggest materials that are still in the development pipeline or recommend customization of existing resins. “Perhaps most important, suppliers bring a fresh perspective and proven practices that can help prevent costly mistakes or rework and accelerate time to market,” added Bobrek.

The panel discussion, which also includes the participation of Foster Corp. CEO Larry Acquarulo, at PLASTEC East won’t solve every material selection dilemma you may face, but it can help you to start asking the right questions. At least, that’s the objective of Michael Paloian, President of Integrated Design Systems Inc., who will be moderating the conversation. “People tend to use resins they are familiar with and don’t always do the research on alternatives. My goal is to have attendees come away from the panel discussion with an understanding of the right questions to ask regarding materials for specific applications. The questions you don’t ask will go unanswered—you need to know what to look for and ask the right questions.”

The Choosing the Right Plastic for Your Medical Device session is scheduled for June 11 at noon at the Medtech Hub, booth 1669, at MD&M East and PLASTEC East, part of the largest annual advanced design and manufacturing event on the east coast. Four other shows—Automation Technology Expo (ATX) East, EastPack, Atlantic Design & Manufacturing and Quality Expo—are co-located at the event, which runs from June 11 to 13 at the Jacob K. Javits Convention Center in New York. Visit the event website for more information and to register to attend.

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