Designing with Plastics: The material of choice for today's applications

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This issue of
Designing with Plastics
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An ePublication of the International Association of Plastics Distribution

June 2009 | Focus: Medical

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Extruded thermoplastics
in the operating room


High performance thermoplastics extruded by Westlake Plastics Company.

When you mention plastics in the medical industry, most think of injection molded plastics or disposable plastics (i.e., items meant for one use and then discarded). However, extruded stock shape thermoplastics have earned their place within the industry maintaining a highly visible position in one distinct area of this field, the operating room.

The first consideration is the issue of risk assessment and product liability. Recent laws enacted by Congress have increased the awareness of polymers used as biomaterials. It is important to understand all the information regarding the device, including material requirements as they relate to size, color, resin-type and stock shape. Many devices have material specifications or standards associated with the material. These come from such organizations as the American Society for Testing and Materials (ASTM) or the International Standards Organization (ISO). Other pertinent information relates to the specific application, the method of sterilization, degree of patient contact or implant into the body. Recommendations and material selection can be based on these criteria.

Most plastic products in the hands of surgeons require USP (United States Pharmacopeia) Class VI approval that tests material for contact with human tissue. FDA Tripartite Guidelines and ISO 10993-1 modified matrix are also helpful for medical device approval depending on the country of origin. Pigment package/colorants are typically required to be FDA approved as well. Resins and raw materials meeting these parameters are readily available.

One of the most important aspects of plastic for medical devices is the ability to withstand repeated sterilization, the most common being steam in autoclaving. Cold/plasma, ethylene oxide (EtO) gas, dry heat, and radiation are other methods of sterilization. Devices can be sterilized and used several times in one day. Resistance to the sterilization process will often determine the life of the device in the field, and material compatibility is critical in this respect.

This article was written by Westlake Plastics Company.

In This Issue:
Extruded thermoplastics in the operating room
Extruded stock shapes have proven their viability in operating rooms for more than 50 years.

High-performance materials mean high-tech applications
Thermoplastic materials offer different advantages in medical applications.

Test your knowledge
What do you know about plastic materials used in medical applications?

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About IAPD
The International Association of Plastics Distribution, founded in 1956, is an international trade association comprised of companies engaged in the distribution and manufacture of plastics materials.

Members include plastics distributors, processors, manufacturers, resin manufacturers, manufacturers’ representatives and associated products and services, all of whom are dedicated to the distribution channel.

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High-performance materials mean high-tech applications

REPRINTED FROM THE IAPD MAGAZINE


The sophisticated mechanism of the MDPI Novolizer® powder inhaler from Asta Medica (now Sofotec GmbH, a subsidiary of Zentaris AG) relies on functional parts made of Hostaform® (POM) type C 9021 TF natural and Celanex® (PBT) type 2002-2 green from Ticona.

High-performance polymers have opened up many high-tech administration devices made of featherweight plastics that permit them to take over responsibility for administering medication, thus enhancing their quality of life.

Various materials have made this possible, and their properties are critical for use in medicine. There are different advantages that make a material suitable for a particular medical application:

POM and PBT offer excellent slip/frictional properties, resistance to wear-and-tear, good resistance to hydrolysis and chemicals and outstanding long-term stability.
Polyphenylene sulfide (PPS) is particularly suitable for functional parts with its extraordinary dimensional stability. In addition, it can be repeatedly sterilized in all known processes.
Liquid crystal polymer (LCP) exhibits a stable mechanical profile. It can be used to replace molded parts in medical devices and surgical instruments that have been made of light-metal alloys to date. These instruments can be subjected to repeated sterilization cycles as well without loss of their mechanical properties.
Cyclic olefin copolymer (COC) reduces the risk of biocontamination, exhibits a glass-like clarity, and offers a high moisture barrier and shatter resistance. These properties make it advantageous to replace glass for diagnostic tubes.
Ultra-high molecular weight polyethylene (UHMW-PE) offers exceptional impact strength, low wear, good slip properties and high stress cracking resistance — properties required for endoprostheses (artificial joints), orthopedic implants and ortheses. UHMW-PE also has biocompatibility in contact with skin, blood and tissue. UHMW-PE is used for the highly stressed socket and the joint head in artificial hip, knee and shoulder joints.