VICTREX® PEEK™ Polymer for the Medical Industry

Traditionally, components for medical devices have been constructed from glass, stainless steel and other valuable metals. In recent times, thermoplastics have replaced many of these applications as they offer freedom of design, increased versatility and a reduction in cost. However, sterilization of such components often results in a deterioration of the physical properties of the material. A critical selection parameter for many short-term in vivo medical components is the ability to be repeatedly sterilized over a useful service life. Most medical devices are sterilized by using either low-dose ionizing-radiation, thermal, chemical or steam treatments.

PEEK™ polymer, a polyaryletherketone resin, is extensively used in medical applications. It combines strength, purity, chemical resistance and ease of processing with superb sterilization resistance and a lack of interaction with biological systems. Although sustained in vivo applications of PEEK™ polymer are not recommended, components for medical devices and analytical equipment are commonplace.

Radiation-Sterlization

Due to the incredibly stable chemical structure of PEEK™ polymer, it is widely regarded as the only thermoplastic material capable of withstanding high doses of ionizing-radiation. It has been estimated that a component which is regularly sterilized over a 15-year lifetime may experience 1000 Mrads of radiation. Independent studies have shown that PEEK™ polymer undergoes slight deterioration after exposure to doses of ionizing- radiation in excess of 5000 Mrads.

Thermal or Steam-Sterlization

Dry-heat (338-356°F, (170-180°C)) or pressurized steam (248°F (120°C), 14.5 psi) sterilization of materials used for medical applications have been shown by bacteriological testing indicators (Bacillus stearothermophilus) to remove harmful pathogens and microorganisms. However, these temperatures and pressures exclude most thermoplastic materials for device construction, especially when considered over a reasonable service life. PEEK™ polymer has been shown to withstand such sterilization treatments for continuous periods pertaining to several service lifetimes. The data shown in Figure 1 were obtained from heat-aging experiments and represent the time at a given temperature for which the sample retains half of its original tensile strength.

Figure 1 The half lifetime of heat aged PEEK™ polymer samples. The dashed lines represent extrapolation from an Arrhenius fit to experimentally determined data.

Analytical Equipment

PEEK™ polymer is often used to form tubing and connection units used in analytical equipment for the chemical and medical industries. These applications are based upon the ability of PEEK™ polymer to carry fluids (especially biological systems) without interaction or the adsorption of protein structures.

Often these fluids are transported under high pressure over a wide temperature range which may result in sample loss through leakage at junction points. PEEK™ polymer is the natural choice for such applications as it has the ability to form components with fine tolerances and has a low value of the coefficient of linear thermal expansion (2.6 x 10-5 °F-1 by ASTM D696) up to the high glass transition temperature of 289°F (143°C) (Tg by DSC).

The FDA currently holds a Victrex device master file to support future medical applications.

PEEK™ polymer 450G, 450G Black 903 and and 450GL30 hold USP class VI rating for plastic materials.

NOTE: Due to the unpredictable long-term effects of implanted materials with biological systems, Victrex does not recommend PEEK™ polymer for sustained in vivo applications.

Medical Cont...