Engineering plastics are a $8.4 billion industry in the U.S., and are projected to grow 3.5% annually through 2010, according to market researchers Freedonia Group, Cleveland, Ohio, (www.freedoniagroup.com). Typically, the materials are chosen for their high impact resistance, high heat resistance, mechanical strength, rigidity, and chemical stability. For medical applications, additives such as impact modifiers, and hydrophobic and conductive materials, are often added to these plastics. Recent trends in healthcare also make engineering plastics a good choice of material.

Devices in the home

A big trend in the medical market involves devices that are increasingly used outside of doctors' offices and hospitals. Home-based care might include devices for remote monitoring and diagnosing, such as glucose monitors that test blood and give a reading. A recent report from the University of Texas Medical Branch found that telehealth, or long-distance health services, could save the U.S. healthcare system $4.28 billion by reducing patient transfers and visits to physician offices. “We're seeing a big trend for anything that can help people stay at home,” says Josh Blackmore, RTP Company, Minn., (rtpcompany.com). “More devices are able to diagnose and treat patients at home by themselves.”

As more devices go home with patients, users are also demanding products with a friendly and pleasant look and feel. “Next generation glucose meters, insulin pens, patient-monitoring systems, and drug-delivery devices are starting to look more like consumer devices,” Blackmore adds. “Engineers are starting to pay more attention to the design, handling, ergonomics, shelf appeal, color, and branding. I frequently get calls from drug-delivery device makers who want something with more style.” Style could mean something as simple as different colors or more elaborate such as from a two-shot elastomer molding.

No substitutions

Another trend in plastics unique to medical devices is the rule of no substitutions. That is, once a formula is selected, tested, and given 510k approval, the manufacturer cannot make changes. “It has hit our industry like a ton of bricks,” says Blackmore. “You can't substitute brands, even if they're chemically equivalent. We have customers who want to know when personnel change, if the machines change, if the environment changes. We're seeing more and more audits asking these things.”

To help deal with this industry need, RTP created a no-subs designation. “We put ‘NS’ on the back of our formula and if anything changes, for example, our supplier is shut down by a natural disaster or goes bankrupt, we have to let our customer know how much material we have left, why it's going to change, and the alternatives. But we will not make substitutions on our own. This differs from the rest of the plastics industry, particularly in compounding, where it is common to substitute one resin with a particular flow for another resin with equal flow, for example. But for the medical industry this is unacceptable,” Blackmore adds.

Device companies play it safe

“No device OEM has ever asked me for the latest and greatest plastic material,” says Blackmore. Especially if they have a 510k to fill out, they're not likely to take chances. “There is a tendency to stick with proven new technology. If a company failed a biocompatibility test because of a new material, it could set the design cycle back months,” he says.

An example would be elastomer development which has been used successfully for a long time in the medical industry on traditional substrates like polypropylene. “Also, I'm seeing OEMs increasingly comfortable having us add additional performance properties to a TPE like lubrication or other fillers to enhance performance.

Spotlight on antimicrobial plastics

A study by the Centers for Disease Control and Prevention estimates there were 4.5 hospital infections for every 100 patient admissions and nearly 100,000 deaths from hospital infection in 2002. Recent studies indicate the rate is increasing due to antibiotic resistance. In response to these alarming statistics, Bayer MaterialScience LLC (BMS), Pittsburgh, (www.bayermaterialsciencenafta.com) developed two grades of antimicrobial Makrolon polycarbonate resin for medical devices.

Silver-based inorganic antimicrobials are used in engineering thermoplastics to control the growth of bacteria on the surface of medical devices. Incorporating these antimicrobials into BMS thermoplastics provides the potential to reduce the growth of bacteria on a medical device.