The pains and pitfalls of polymers in medical devices

Anja Flossbach, Velox. explains what is at stake when it comes to the right material choice for the development of medical and pharmaceutical devices.

The use of polymers in medical devices has been growing steadily over the last years, replacing glass, metal and other conventional materials. However, when it comes to the right choice of polymer, some pains and pitfalls have to be taken into consideration.

“The development of medical and pharmaceutical devices takes time and money and is strictly regulated”, says Anja Flossbach, mechanical engineer and business development manager, medical plastics, at Velox. “Therefore, the right choice of material is crucial for developers to succeed when it comes to compliance regulations, certification processes and, most importantly, providing a high-quality product.”

There are at least five criteria that have to be evaluated thoroughly when selecting materials for specific medical or pharmaceutical applications. “On the one hand, of course, one has to consider the manufacturer’s design and application specifications”, says Flossbach. “On the other hand, the material properties are key aspects to be scrutinised with regard to these specifications. And last but not least, pricing as well as regulatory and handling aspects are critical for the products’ successful realisation and market entry.”

Preventing colour change and breakage

Housings for diagnostic and monitoring equipment for hospitals, for instance, often have to withstand highly aggressive and concentrated cleaning agents. This can cause stress cracking in the plastics, which may lead to fluids penetrating into the medical device, damaging the often expensive electronics. Hence, it is crucial to use the right material.

 “Upon examining the application specifications, we might introduce a polycarbonate/polyethylene terephthalate (PC/PET) for hospital equipment, whereas acrylonitrile butadiene styrene (ABS) or PC/ABS

could be considered for homecare devices, where less aggressive cleaning agents are typically used,” explains Flossbach.

Similarly, different polymers may react differently when it comes to the sterilisation of medical devices. To avoid colour change or loss of mechanical properties in processes like steam sterilisation, materials have to be particularly resistant, notably to high temperatures.

The right TPU for medical implants

Another example are implantable materials. Many medical-grade polymer suppliers do not allow the implantation of their materials into the body, or restrict it to particular time limits, typically 24 hours or 30 days. Nevertheless, there are material options for long-term implant applications (medical device classification 2a or higher).

“Our partner Lubrizol does not restrict the use of their TPUs to 30 day implants. Device designers are free to select from a wide TPU portfolio the most suitable grades to be tested and considered for each specific application,” she says.

Medical compounds: what’s in them?

Regulatory approval of customised compounds is another issue that can be difficult to handle if the device manufacturer does not have full transparency on the compound. Therefore, it is appreciated if the compounder provides full transparency about the formula of the compound. Velox’s partner IPC, for instance, who develops tailored compounds for medical applications, discloses compound formulae on the certificate of analysis.

Cooperation from the early design stage

“To really add value for our customers and help them choose the right material for their specific application, at Velox focus on technical assistance and engineering support by working with our customers from a very early design stage,” highlights Flossbach.