By Sean Fenske, Editor-in-Chief
 
The EU has been looking at materials that could potentially be hazardous for some time and more recently, the U.S. EPA has been following suit. For many industries, this is an inconvenience as a new material needs to be identified and sourced. In the medical device manufacturing industry, however, this type of change can be incredibly disruptive and create significant costs.
 
Since the medical device industry is regulated, a change in material for a device that’s already gained the OK from a regulatory agency means the potential for a product shortage. For devices that have not yet been reviewed, it could lead to delays with getting to market or cost increases as a new material is identified. As such, it’s best to heed warnings when they are delivered and then plan the best course of action.
 
Since NMP is one such potentially problematic material, a pair of experts from Confluent Medical took time to address the questions arising around the use of this material and highlighted the most important factors designers and manufacturers should know. Shane Wood, director of technology—polymers, and Dean Burke, business development director, explained the possible problems with NMP and offered solutions in the following Q&A.
 
Sean Fenske: Can you please explain what NMP is and why it’s used in polyimides? What advantages does it offer?
 
Shane Wood: N-Methyl-2-pyrrolidone (NMP)—the molecular formula is C₅H₉NO—is an organic solvent consisting of a five-membered ring with an attached methyl group. Due to its unique properties, including high boiling point, low volatility, and high chemical solubility, it is an ideal solvent for a variety of compounds. Due to these properties, NMP is used in numerous industrial applications, including polymer processing.
 
Fenske: In what medical device applications is this material being used?
 
Dean Burke: Due to polyimide’s combination of high stiffness and column strength along with outstanding electrical insulator properties, it is used in a variety of catheter applications including electrophysiology, cardiovascular, and urological stone retrieval.
 
Fenske: Why is the EPA taking a closer look at polyimide materials that contain NMP?
 
Burke: In a recent finding that could have ramifications in the industry, the EPA has found that NMP, as a whole chemical substance, presents “an unreasonable risk of injury to human health when evaluated under its conditions of use.” It was found to pose risks from both acute and chronic exposures through inhalation and dermal contact, including developmental and reproductive toxicity. In addition to the reproductive hazards posed, additional risks included liver and kidney toxicity, immunotoxicity, and neurotoxicity.
 
Due to these findings, it was determined NMP posed an unreasonable risk to health in 29 of 37 use cases, which include domestic manufacturing, import, processing in plastics manufacturing, various other industrial uses, as well as disposal. The EPA is expected to propose a set of risk management actions, which will then be followed by a public comment period. There is still substantial uncertainty as to the final restrictions, which puts the established filmcast polyimide supply chain in question.
 
Fenske: Depending upon the agency’s decision, what might this mean for the supply chain for medical device manufacturers using this material?
 
Burke: The outcome could range from more stringent personal protective equipment (PPE) requirements to targeted restrictions in specific applications, up to a ban on manufacture, import, and use. The proposed regulations are anticipated to be released in 2024 followed by a public comment period.
 
Fenske: Are there alternative options that device manufacturers should be examining?
 
Wood: As your audience is likely aware, NMP is already subject to certain restrictions under the European Union’s REACH regulation (Registration, Evaluation, Authorization, and Restriction of Chemicals). REACH is a comprehensive regulation aimed at ensuring the safe use of chemicals within the EU to protect human health and the environment. Companies utilizing medical device components that contain NMP are responsible for ensuring compliance with REACH restrictions.
 
There are two possible pathways to achieve REACH compliance. One pathway is to ensure sufficient residual NMP is removed during processing. This pathway can be expensive, time-consuming, and somewhat unpredictable due to material and process variation. Another pathway, and the direction we have chosen at Confluent Medical, is to utilize raw materials with solvent systems that are not REACH-restricted. This minimizes the burden on the device manufacturer to ensure compliance.
 
If additional NMP supply chain restrictions are imposed by the EPA, this becomes an even more critical challenge for medical device manufacturers. While there is still substantial uncertainty as to the final restrictions, NMP is the primary solvent used in the vast majority of filmcast manufacturing today. Migrating to a filmcast polyimide solution that does not contain NMP will serve to mitigate any potential issues due to these restrictions.
 
Fenske: What’s your recommendation for medical device manufacturers to potentially get ahead of any negative decision by the EPA that could impact supply?
 
Burke: Requalifying alternate materials vendors is often no small feat. It is recommended to get ahead of the curve by requalifying an NMP-free supply chain to proactively mitigate the risk before potentially being forced into abrupt action.
 
Fenske: Do you have any additional comments you’d like to share based on any of the topics we discussed or something you’d like to tell medical device manufacturers?
 
Burke: We realize customers have a choice in choosing partners for their supply chain needs. Confluent’s REACH-compliant polyimide option takes the guesswork out of the equation since it does not involve NMP and is available in lead times of three to four weeks. Our comparative studies have shown equivalent performance to traditional polyimide. In addition, Confluent Medical will soon be offering REACH-Compliant TPU outerjackets.
 
Confluent Medical is here to answer any questions and we also offer the industry’s best lead times. If you would like to personally evaluate material, whether for an existing program or something in early-stage prototyping, please reach out to our experts.
 
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