Image courtesy of Covestro

A naturally transparent and durable thermoplastic, polycarbonate is a versatile material used to produce a variety of commercial and consumer goods, including parts for automobiles and electronic products, camera lenses, and safety equipment. It also has multiple applications in medical technology, from neonatal care equipment to dialysis machines. Despite its universality, however, the polymer remains a somewhat controversial product, especially in the medical space, because of the presence of bisphenol A (BPA), a chemical used in the production of polycarbonate.  

Long road to commercialization

Initially discovered by German scientist Alfred Einhorn in 1898 at the University of Munich, polycarbonate went uncommercialized for decades. Breakthroughs came in the 1950s, thanks largely to Hermann Schnell at Bayer, where polycarbonate was registered under the brand name Makrolon, and General Electric’s Daniel Fox, often called the “father of Lexan.” They were instrumental in commercializing the material in the United States and Europe.

According to Len Czuba, president of Czuba Enterprises Inc., a product development organization that specializes in plastics and medical devices, polycarbonate was one of the first two polymers to offer superior engineering properties in a transparent melt-processable material. The other is polymethyl methacrylate (PMMA), better known by the trade names Plexiglas and Lucite.

The most significant advantage of polycarbonate is its solvent resistance and ductility, which ranks it as stronger than glass as well as PMMA, said Czuba. “Since its discovery, polycarbonate has been found to be an excellent injection moldable polymer that’s compatible for parts connecting to flexible PVC tubing with an easy solvent-bondable method in the medical device industry. Polycarbonate can be made into connectors, manifolds, housings for kidney dialysis filters, and facemask shields. It offers superior solvent resistance and resistance to solvent crazing,” said Czuba. Polycarbonate can meet all the biological and chemical requirements of medical device components, satisfying all safety and biocompatibility requirements, added Czuba.

Strength, clarity, and toughness

At Covestro, a manufacturer based in Germany that produces polyurethane and polycarbonate products including foams, coatings, and adhesives, polycarbonate plays a major role in developing next-generation, life-saving technology. “Used in applications where strength, clarity, and toughness are necessary, polycarbonates from Covestro exemplify the innovation, safety, and biocompatibility that healthcare and life sciences designers and manufacturers across the world have come to know and trust,” said Emily Shaffer, healthcare market manager at Covestro.

Covestro’s portfolio includes its suite of Makrolon resins, including low-friction and glass-filled formulations and the recently launched Apec 2045. (Covestro is a Bayer spin off, formed in 2015.) A new heat-resistant medical-grade co-polycarbonate, Apec 2045 is designed for use in medical devices, such as respiratory masks with molded-in seals, and products that require hot-air sterilization up to 180°C (356°F).

“Apec 2045 is enabling molders and medical original equipment manufacturers to significantly reduce production time and cost, without sacrificing quality, performance, or appearance as a replacement for the commonly used method of overmolding polycarbonate with liquid silicone rubber to produce masks and other devices requiring molded-in seals,” said Shaffer. “Apec 2045 co-polycarbonate boosts productivity in silicone overmolding applications, as it is made for the highest curing temperatures, which helps to more than double production volumes in the same amount of time due to shorter cycle times.” Shaffer added that using the new Apec material could also contribute to manufacturing sustainability goals, with the possibility of a lower carbon footprint as evidenced by its ISCC Plus certification and bio-circular content.

“Apec 2045 can also enable circular business models by supporting closed- and open-loop recycling by maintaining key mechanical properties across recycle loops,” said Shaffer.

Other important benefits include durability, transparency, sterilizability, and overall processability.

BPA fears are greatly exaggerated

Although opinions vary on the significance of BPA, the issue continues to plague the production and use of polycarbonates. First identified as a concern in 2008 in a report by the National Institutes of Health’s National Toxicology Program, BPA has appeared in headlines for years, up to and including 2024, when officials in France placed a ban on water bottles during the summer Olympics due to reported unsafe levels of the chemical.

As Czuba sees it, fears regarding BPA have always been exaggerated. “When the issue of BPA was first mentioned, it was related to the common practice by mothers of new-born children of sterilizing bottles in boiling water for a period of time before filling the bottles with formula or breast milk,” he explained. “Researchers found elevated amounts of BPA and speculated that this would pose a hazard to babies. This concern was then elevated and, in my opinion, blown out of proportion by the common press, and world consumers became unnecessarily frightened. Calls began to rise for regulators to take action against BPA.”

The current perspective by US FDA, based on its most recent safety assessment, holds that BPA is considered safe to be used in food packaging at the current levels that it occurs in foods. Similarly, the American Dental Association (ADA) issued a professional product review of BPA in 2016, restating its safe use with dental sealants that are frequently used in pediatric patients.

“BPA has been evaluated more than any other industrial chemical,” Czuba said. “It took years for the concern to be calmed, but it seems to finally have been put in the rear-view mirror [in the United States]. Polycarbonate is still one of the main engineering materials used in medical devices, and its use continues to grow. The amount of BPA formed during the heating of polycarbonate is extremely low — in the parts per billion.”

Czuba also stressed that if BPA is absorbed by the human body, studies have shown that it’s typically eliminated by urination within 24 hours. “This chemical does not accumulate in the tissue like other contaminants have been shown to do,” he said.

Pertaining to the physical structure of polycarbonate when heat is applied, there are certain limitations to navigate. According to Shaffer, medical devices and components that incorporate medical-grade Makrolon can be sterilized by common methods, but the temperature should not exceed 125°C (257°F) when utilizing steam sterilization because it may cause deformation of the molded parts. Covestro’s Apec high-heat polycarbonate has comparatively higher heat resistance and is compatible with high-heat steam autoclaving at temperatures up to 143°C (289°F).

A $15 billion market, and growing

The global polycarbonate market was valued at $15.1 billion in 2023 and is projected to achieve a 5.4% compound annual growth rate, reaching a value of $24.3 billion by 2032, according to Fortune Business Insights. Medical applications account for a fairly small percentage of global sales — it was around $1.2 billion in 2023 and is expected to reach $1.5 billion by 2031, according to a report from Transparency Market research. The material punches above its weight in the medical market, however, because of the margins it commands in this heavily regulated industry.

The market for bio-based polycarbonate is also expected to grow, with one recent report projecting revenue to reach nearly $140 million by 2032.

New medical polycarbonate films are reportedly gaining traction among physicians, as it helps them visually inspect the appearance of breast implants prior to implantation without opening the packaging.

Because polycarbonate has long been demonstrated to be safe and effective with all the major methods of medical device production and sterilization, there is no limitation related to its use as a medical device component, stressed Czuba.

“There has been significant research in polycarbonate to tailor it to many different applications in the medical device industry,” said Czuba. “I believe that this tried-and-true material will continue to serve those of us designing medical products and selecting the best materials for those products — polycarbonate often gives the best performance for these applications.”

Article source: MDDI