Medical Plastics Keep Getting Better

by Johnathan Greene Mechanical Engineer

Demand for medical plastics is on the rise—BCC Research forecasts a 4.9 percent compound annual growth rate for medical plastics in the U.S. through 2015. This is in part driven by the approximate 30 million previously uninsured Americans that will gain insurance coverage through the Affordable Care Act, increasingly innovative medical device designs, and the huge baby boomer generation that will require an unprecedented number of joint replacements in the coming years.

As a result, plastics manufacturers continue to turn out new and improved medical plastics that have enhanced characteristics to meet specific applications such as strength, temperature resistance, chemical resistance, stiffness, electrical properties, flexibility, bioresorbability, and antimicrobial properties. These expanded characteristics also give medical device engineers new latitude in designing innovative products that are smaller, more complex, and multi-functional.

Medical-grade plastics should be biocompatible, chemically resistant to disinfectants and cleansers, able to withstand sterilization by hot steam, ethylene oxide, plasma, and gamma rays, and meet FDA requirements.

Plastics producers continue to engineer new resins to meet specific medical-device needs.

For example, Boston Scientific recently announced a new bioresorbable polymer polyglycolic lactic acid-coated (PLGA) drug-eluting stent. The PLGA polymer and drug coating dissipate within three months, which improves post-implant vessel healing and eliminates longer-term polymer exposure—a possible cause of post-surgical adverse events.

Ypsomed AG in Germany is using a new, ultra low-friction grade of Delrin® (an acetal resin) for its disposable, variable-dose injector pen. The low-friction qualities make it easier for diabetes patients to administer daily injections of insulin. This new grade of resin was specifically developed for parts requiring high-precision molding in the health-care industry.

Another slippery resin is Duke Empirical’s PebaSlix™, which has low-friction properties due to a proprietary patent-pending process that combines certain additives to the polyether block amide (PEBA)-based resin.

“This increases the level of product performance, while lowering costs by allowing production processing and sterilization options that haven't been available previously with traditional materials used for low-friction catheter applications,” says Robert LaDuca, CEO for Duke Empirical, a medical device manufacturer in Santa Cruz, California. “These newly available catheter materials are now finding their way into several products that will be on the market soon.”

Researchers continue to find new ways to use PEEK (polyetheretherketone), a high-temperature thermoplastic that is a good replacement for metallic implants due to its superior mechanical properties. PEEK is so strong that machine guidelines are essentially the same as those for metal. Antimicrobial agents have also been added to PEEK implants to decrease the risk of post-surgery infection; the plastic can also be engineered to enhance bone growth.

As reported in the October 2012 issue of Medical Product Outsourcing, manufacturers and resin suppliers continue to work together to develop new lines of materials that increase performance and extrusion efficiencies. One example is the use of nanofilled clay additives that can give traditional resins such as PEBA increased mechanical properties.

“The nano-sized particles interact at the molecular level to lock in with the polymer’s molecular chains and prevent slipping,” says LaDuca. “This results in a stiffer material with less elongation under equivalent stress, which ultimately results in higher-performing, thinner-walled catheter products that enable the next generation of medical therapies.”

The author of this article about medical plastics and how the medical industry will be relying on custom injection molding in the future has been a longtime student of practitioner of medical writing and the industry.