The appropriate selection of component materials is often very important in the development and sustainability of a medical device. For many devices, that selection often begins with a designer’s consideration of a range of known medical polymers.
So, What is a Medical Grade Polymer?
While the question seems simple enough, it may surprise you that a globally accepted, agreed-upon definition and standard does not exist.
Globally, the vast majority of polymers produced are used in industrial and consumer segments, with only a small percentage the polymer volume being used in medical devices. In order to differentiate grades supplied into the medical device market, raw material suppliers distinguish these material as “medical grade.” Currently there is no regulatory definition of a medical grade polymer and no prescriptive regulatory requirements for raw materials used in medical devices, so material suppliers and others in the medical device industry have assigned their own meaning to “medical grade polymer.” Consequently, polymers designated as medical grade from different suppliers are not necessarily equivalent in performance, quality and associated support. This situation can create confusion and uncertainty for the device designer when selecting materials.
When it comes to specifying medical device materials, considerations need to be given not just to product specification and required performance attributes but the robustness of quality systems, manufacturing consistency, management of changes and understanding the possible implications on a finished device so the process is well managed by the supplier and effective communication systems are in place.
In this post, the Lubrizol Life Science Health (LLS Health) team examines the complexities surrounding medical grade polymers and what you should know when selecting your medical device materials.
Considerations When Selecting Medical Polymers
Medical device development is often a long-term endeavor, requiring rigorous testing, quality control systems, and compliance to an ever-evolving set of regional and global regulatory requirements. As the need for new and innovative medical devices grows, the need for materials (especially polymers) to support device development becomes stronger.
The choice of polymer for a specific device application is often based on many considerations. For example, an interventional guidewire may need a polymer coating to provide a cushioning tip, biocompatible hydrophilic surface, radiopaque character and abrasion resistance while maintaining manufacturing efficiencies in the guidewire production process. Selection of a material for a pacing or neuromodulation lead may hinge more on a material’s blood/tissue biocompatibility and resistance to degradation in-body (oxidative and hydrolytic resistance) over many years, its dielectric properties, its physical strength and flexibility and the ability to produce the material in thin-walled constructions and assemble over electrical wires and other components.
A list of common considerations in polymer selection are shown below:
- Biological Performance
- Biocompatibility
- Biostability
- Hemocompatibility
- Infection risk
- Application Performance
- Strength
- Flexibility
- Fatigue resistance
- Heat and/or electrical resistance
- Chemical Resistance
- Cleaning product resistance
- Drug resistance
- Sterilization stability
- Processability
- Thermal methods (extrusion, molding, forming)
- Solvent (casting, dipping, spinning)
- Secondary assembly (reflow, bonding)
- Compatibility with other materials within the device
- Regulatory and Compliance Requirements
- Does the material contain REACH, RoHS or other substances of concern?
- Has the material been used in devices cleared by regulatory agencies?
- Cost:
- Volume specific pricing
- Annual access, licensing and/or royalty fees
In addition to balancing the complex set of material related requirements above, a device designer may also consider whether to evaluate only materials designated by a supplier as “medical grade.” This consideration can quickly become challenging, as although regulatory scrutiny of devices and demands for polymer performance has increased, there is no universally accepted or regulated definition of a “medical polymer.”
Beyond Biocompatibility: Why A Robust Medical Polymer Goes Further
While formulation, manufacturing and testing of materials for biocompatibility is a distinct and important characteristic of a medical grade polymer, other services such as regulatory support, change management and security of supply are of utmost importance, and may sometimes be overlooked during initial material selection activities.
The Association of German Engineers, VDI, recently published a voluntary guidance document for defining “Medical Grade Plastics.” The document attempts to provide both polymer suppliers and medical device manufacturers and designers clarity on best practices relating to polymer use.
Within the document, the following are described as essential for a medical grade plastic:
- Intended to be used in a medical device, in-vitro diagnostic or pharmaceutical packaging application
- Maintained under a change management system for the polymer’s specification, composition, regulatory status and manufacturing technology and site
- Quality management system for a polymer’s development, production and handling
- Provided by the supplier with support to the end device owner to fulfill required regulatory requirements
- Security of supply, availability and logistics considerations
While a globally accepted definition for a medical grade polymer is not yet established, the above attributes speak to LLS Health’s core definition of a medical grade thermoplastic polyurethane (TPU). As a leader in TPU materials for medical devices, we are encouraged and supportive of efforts to clarify and explain essential requirements for medical grade polymers. 
Is a Non-Medical Grade Polymer “Good Enough”?
In some cases, a non-medical grade polymer may seem attractive from a perceived efficiency perspective, especially when OEMs plan to conduct their own biocompatibility evaluation(s). In such cases, it can be easy to overlook the value of change control and notification for materials specifically designed for medical applications.
In other cases, a non-medical grade polymer may have been used in a device for decades, as it was evaluated prior to the availability of medical grade materials and the validation cost to the OEM to change materials is significant. Often, however, any efficiencies accrued by selecting a non-medical grade polymer are more than negated when changes or discontinuations are made to non-medical grade polymers. Non-medical grade polymers are designed for applications that do not require evaluation of impact on biocompatibility and medical device regulatory and compliance status. These situations can leave OEMs in danger of getting stuck in a constant and costly re-validation loop for their important product lines without the benefit of supporting material biological and medical regulatory information.
In rare cases, a medical grade polymer that meets all the device’s performance needs may not be available as a standard “off-the-shelf” grade. As non-medical grade polymers are designed to address a very wide variety of applications, they can sometimes offer unique chemistries, functional additives and performance options not available as standard in medical grade polymers. In these instances, direct discussion with the material supplier to discuss options for medical grade customizations may be warranted.
While non-medical grade polymers are of high quality and performance, in most cases, medical grade polymers are best positioned to address both the immediate and long-term requirements for high performing sustainable medical devices.
What Does “Medical Grade Polymer” Mean to Lubrizol?
LLS Health provides a full range of TPU material solutions and specializes in polymer customization to help achieve optimal clinical outcomes for medical device manufacturers. We work in collaboration with our customers to create polymer solutions for use in medical devices.
Lubrizol’s medical grade TPUs offer the following support:
- Assistance with regulatory and product compliance requirements such as providing information necessary to support device filings with the US FDA and other national/regulatory bodies
- Biocompatibility testing performed and results summaries available
- Comprehensive quality systems with manufacturing and quality record retention
- ISO 9001 certified manufacturing facilities with plant audits or audit packets available upon approval
- Extensive commercial product change management and change notification process:
- Ensures changes are not made to process, procedures or composition without review and approval by all key LLS Health product design groups
- If a change to commercial product manufacturing location, composition, specification or other significant properties is necessary, notification will be provided prior to implementing the change in commercial products.
- Documentation of the change will be provided, including reason and timing of the change.
- Documentation will be provided as far in advance as possible ahead of the change.
- Every effort will be made to ensure minimal impact to the material end user or processor, including (where possible), options for last-time-buy of products prior to change implementation to allow for technical and regulatory evaluation of any required material changes.
When it comes to selecting materials for development of a medical device, it is clear OEMs have many options and factors to consider. It is not only important to work with a partner that has the expertise to help sift through those complexities, but also work with a polymer supplier that has a robust portfolio of materials, capabilities and quality and regulatory support systems in place to ensure optimal performance of your medical device throughout its lifecycle. Our team understands polymer selection, can answer your questions, and help you identify the right materials for your medical device.
Disclaimer:
Lubrizol Advanced Materials, Inc makes no warranties, express or implied, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose. No warranties or guarantees are made as to the suitability of the products for the applications disclosed. Full-scale testing and end product performance are the responsibility of the user. Lubrizol Advanced Materials, Inc. shall not be liable for and the customer assumes all risk and liability of any use or handling of any material beyond Lubrizol Advanced Materials, Inc.'s direct control. The SELLER MAKES NO WARRANTIES, EXPRESS OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. Nothing contained herein is to be considered as permission, recommendation, nor as an inducement to practice any patented invention without permission of the patent owner.
