One of the major themes at Medical Design and Manufacturing West last week (Anaheim, CA) was the growing focus on extractables in healthcare applications. This is not a new issue, of course, but there are many signs the rubber is starting to hit the road.
The first indication of a shifting landscape came last month when California-based Kaiser Permanente announced it will no longer use PVC in tubing or bags because of concerns about plasticizers and dioxins. The
|Some blood management equipment is converting to copolyester.|
PC, PVC and more
There are signs that other large health care organizations and medical device manufacturers are also investigating alternatives for PVC, polycarbonate, and even other materials, based on interviews at MD&M.
One example is blood therapy and management equipment where Tritan copolyester from Eastman Chemical is making inroads.
"Tritan copolyester has good clarity, chemical resistance, processability, and eliminates annealing that is required for polycarbonate," Gopal R. Saraiya, marketing manager-medical devices for Eastman Chemical, said in an interview with Plastics Today. "There is also the potential to reduce wall thickness." And it's BPA free.
One expert who asked not to be named said in his opinion that the switch to copolyester for blood management products is taking place because it can be done with no sacrifice. "It's a virtual drop-in. Even the same molds can be used," he said.
It's a big application. There are more than one million treatments annually in North America, Asia and Japan. In some cases, the single-use systems involve four or five molded components.
In another example, a manufacturer of orthopedic cutting guides used for knee surgery is switching from polycarbonate to ABS or Ixef, a 50% glass-filled specialty nylon produced by Solvay Specialty Polymers. Another PC substitute is polyphenylsulfone , which can be used in the same molds, according to Christopher Wartinger , product manager of medical at Mack Mold, who spoke to Plastics Today in an interview at MD&M West. He said one customer even had concerns about formaldehyde extractables in a certain type of polyacetal.
Another extractables' issue is heavy metals in silicone and nitryl rubber, according to Terry Freeman, product manager-medical at Kraiburg TPE Corp. Kraiburg and several other companies are positioning elastomers as replacements for PVC as well. Teknor Apex has introduced Medalist MD-500 Series elastomers as a PVC replacement in medical tubing.
One outcome of the focus on extractables is growing use of high-purity cyclic olefin copolyomers (COC) in medical applications. At NPE 2012 (Orlando, FL; April 1-5), Sodick Plustech will mold a medical syringe made of cyclic olefin copolymer (COC) in a mold built by Nypro.
'Science is on our side'
Larry Johnson, global marketing director, Healthcare, PolyOne Corp., told Plastics Today:
"The healthcare industry is very risk adverse. Polyvinyl chloride and polycarbonate have been tried-and-true products for years and years. To switch to other products based on concerns that cannot be substantiated could be very risky." PolyOne produces PVC and also compounds a wide variety of plastics including elastomers that are potential replacements. Johnson said that PVC, probably the mostly widely used plastic in medical applications, is expected to continue to grow at 3% annually.
Sam Stewart, vice president of sales for Bayer MaterialScience makes a similarly strong case for polycarbonate. "We believe very strongly in the safety of polycarbonate. We would not sell it and the FDA would not allow us to sell it if it weren't safe. The science supports the safety of polycarbonate."
Meanwhile, polycarbonate and PVC producers are announcing new applications for their materials.
In an area also involving knee replacements, Bayer MaterialScience announced that OrthoSensor is using polycarbonate for a Knee Balancer device that provides precise, quantitative intraoperative data on soft tissue balancing during total knee replacement surgery. Until now, surgeons had to subjectively determine the amount of pressure to apply to a knee implant. The Knee Balancer uses sensors and wireless technology to provide real-time, evidenced-based data to the surgeon to optimize the positioning and balance of implants.
PolyOne introduced an addition to the Geon PVC line for medical device housings. "Hospitals and medical professionals are increasingly concerned about the transmission of hospital-acquired infections, which has resulted in increased use of stronger chemical disinfectants," said Rob Rosenau, president, Performance Products & Solutions. "This has led to an increase in medical device failures due to polymer cracking and crazing... Independent testing indicates that Geon HC for medical device housings has superior chemical resistance compared to many engineering thermoplastic alternatives for medical housings."
It would appear that use of PVC and polycarbonate will continue to grow in medical applications because of their property profiles and significant value. It would also appear that their growth rates may be slowed somewhat by concerns about extractables--whether valid or not.
|How safe are thermoset elastomers for medical?|
In a press release issued at MD&M West, Kraiburg TPE (Duluth, GA) made this statement: "The entire family (THERMOPLAST M) was designed to replace materials where heavy metal extractables could be a concern."
That statement caught my attention because I had thought that heavy metals were largely removed from plastics compounds as a result of ROHS and other initiatives several years ago.
I asked the company to explain the comment and received this reply today:
"SEBS-based TPEs are not cross linked therefore they do not have the potential to discharge vulcanization accelerators also known as curing agents which can be found in some thermoset elastomers. These derivatives could be, for example 2-Benzathiazalethiol or Mercaptobenzothiazole and Nitrosamine. Under certain conditions these could be extracted and be grounds for concern. (Nitrosamine is known to be a human carcinogen.)
"Consequently, SEBS-based TPE can also be used to substitute to polyisoprene and butyl rubber used in medical applications like cap liners, stoppers, gaskets and IV line port seals where extracables are of critical concern. Finally, some urethane elastomer systems can contain 4,4'-Methylenebis(2-Chloroaniline) (MbOCA) or even heavy metal catalysts."
The elaboration is from Keith Dunlap, director of sales and marketing at Kraiburg TPE. SEBS TPE refers to styrene-ethylene-butylene-styrene-based thermoplastic elastomer. The THERMOLAST M materials were formulated in Germany where concerns about extractables are even greater than they are in the United States.