Custom Extrusion of Medical Plastics

Medical thermoplastics like PEEK are compatible with several conversion processes, including custom extrusion. During extrusion, the plastic is melted and converted into a continuous, uniform segment that is suitable for several medical applications. Extruding PEEK, however, is a challenge that few polymer converters are capable of handling. It takes perfectly calibrated extrusion equipment, PEEK conversion experience and a commitment to quality.

Drake Medical Plastics can provide all three, with a 12,000 square foot facility dedicated to high-performance polymer conversion.

Why should medical facilities consider medical plastic extrusion?

Extrusion is the ideal conversion process when long, uniform polymer segments are required. Extruded PEEK segments are a viable alternative to glass, aluminum or steel, as they possess excellent column strength and tensile strength. PEEK also has an impressive flexural modulus, so it’s flexible enough to allow for precise navigation, but stiff enough to resist deformation. PEEK is also a proven biomaterial, with long-term biocompatibility that means it can be safely implanted.

With these combined properties, PEEK tubing is a frontline choice for catheter tubing and cardiovascular delivery devices. Extremely thin PEEK tethers are also found in some advanced surgical procedures, including the Less Invasive Ventricular Enhancement (LIVE) procedure.

Why Medical Facilities Need An Experienced Converter For Custom PEEK Extrusion

High performance polymers like PEEK require specialized experience during the conversion process. Though PEEK is converted using some of the same methods other polymers are subjected to, additional considerations must be made when handling the polymer.

PEEK readily reacts to heat, so thermal control is a major part of the PEEK extrusion process. Though it has one of the highest melting points of any polymer (300 degrees Centigrade, or 572 degrees Fahrenheit), PEEK component quality is heavily dependent on keeping the extrusion temperature range steady.

There isn’t an ideal temperature for PEEK extrusion because it depends on the extruder’s design and size. One extruder may optimally convert PEEK at 675 degrees Fahrenheit, while another may perform optimally at 750 degrees Fahrenheit. There isn’t a formula to follow, so it can take a while before an inexperienced converter has an extruder that can properly handle PEEK.

Once PEEK reaches its melting point, its molecular weight starts dropping. If it drops too much, this may compromise the polymer’s properties, so experienced converters prioritize minimal dwell time (how much time the polymer spends in the extruder). Minimal dwell time, though, is only possible if the extruder’s heat profile is precisely controlled. That, again, takes an experienced PEEK converter.

Further, PEEK converters must keep their extrusion equipment as clean and polished as possible, or abnormalities (termed gels) may appear. Gels emerge when molecular weight is uneven across the extruded product, and this can lead to cosmetic or functional issues. For example, if gels form on the outside of the tube, it may result in dimensional changes that could cause discomfort or tissue damage. An experienced PEEK converter has methods in place to prevent or remove these gels, and those methods are typically proprietary.

PEEK also has a tendency to harden quickly when temperatures drop just a bit, and this can affect costs and conversion times. If too much material is left in the extruder once it cools, it will be difficult to remove it, adding to processing times. That material must also be disposed of, so if a converter isn’t running its processes efficiently, conversion will be much more expensive.

PEEK’s final properties are also affected by how long it is allowed to cool, or if it is allowed to anneal. During annealing, the polymer must be kept in its glass transition phase, which starts at 289 degrees Fahrenheit. Precise processes must also be in place to maintain this.

Custom extrusion of medical plastics like PEEK is complicated, with many potential pitfalls. That’s why medical facilities often look to experienced, certified converters to do the job.

What certifications are important for a PEEK converter?

Medical plastics and devices are covered under several standards, including standards published by the International Organization for Standardization (ISO) and the FDA. Some of those standards and processes relevant to medical device manufacturers and polymer converters include:

  • FDA registration – Every year, medical device manufacturers must register their facilities with the FDA. To maintain FDA registration, the manufacturer must pay a fee and provide relevant FDA premarket submission numbers for any products that require premarket approval. Nearly all implantable devices require premarket approval, so PEEK converters are required to verify their product and process quality and safety every year.

    Device manufacturers are also required to list all medical devices produced at their facilities, so if there are public health emergencies that require immediate attention, the FDA knows where devices are being made.

  • ISO 9001-2015 certification – The ISO 9001 standard is ISO’s general standard for process and quality management. It isn’t specific to the medical device industry, but it is widely adopted because it adds needed accountability, management involvement and regulatory compliance. To attain 9001 certification, a manufacturer must implement a Quality Management System (QMS) that details the above, as well as processes used to continuously improve the QMS. The goal, then, is to put into place a system for steady, responsible process improvement that allows for rapid corrections should they be necessary.

    ISO 9001-2015 is the newest iteration of the standard and streamlines the language and structure for easier compliance with other standards.

  • ISO 13485 certification – ISO 13485 certification addresses medical device manufacturers in particular, making it an extremely important certification for the industry. ISO 13485 builds on ISO 9001, adding requirements for design control, inspection, traceability and risk management. Further, ISO 13485 addresses work environment controls, as well as the use of preventative and corrective actions.

    For example, ISO 13485 contains standards on proper device sterilizing, proper device handling (to prevent contamination) and how to validate the process. Process validation is particularly important, as it is generally impossible to test a device’s properties without destroying that device. A validated process is one that accounts for both the material’s properties and the manufacturing processes that material is subjected to. If a process is validated, that means it produces a device or component that consistently meets safety and quality standards. PEEK converters must be able to verify these validated processes when necessary.

Custom extrusions of medical plastics is an involved process that requires experience, esoteric knowledge and constant improvement. If a PEEK extruder can offer those, they can also offer medical components that meet the industry’s most demanding standards.