The effect of electron beam sterilization on Eastman Tritan™

Sterilizing medical devices helps reduce the bioburden to a safe level with minimal effects on the physical and optical properties of its polymers. Some of the most widely used sterilization methods in the medical industry today include gamma radiation, ethylene oxide (EtO), autoclave, and low-temperature hydrogen peroxide gas plasma. Another method gaining in popularity is electron beam (e-beam) radiation. It's a safe, reliable source of energy thanks to recent advancements in operating efficiency.
 
Compared to gamma radiation, e-beam radiation typically costs less due to higher dose rates that reduce the time of exposure at the same target dose. The shorter exposure time also minimizes the oxidation reactions that can occur at the polymer surface, resulting in less effect on resin properties than with gamma radiation.

To determine the effects of e-beam radiation on Tritan and other transparent medical polymers, Eastman conducted a series of studies that measured color shifting and physical property retention. Specific products tested are shown here:
Optical properties
Samples were exposed to e-beam radiation (25 and 50 kGy) and then stored in darkness. Their color was measured at days 3, 7, 14, and 42 using HunterLab UltraScan Sphere 8000 and the CIE L*, a*, b* color scale. (Samples were stored in darkness and only exposed to light for color measurement.)
 
 
Figure 2 shows the difference in b* color values between unexposed samples and sterilized samples at day 42—after e-beam radiation at both 25 and 50 kGy. 
 
Figure 2. Change in b* color 42 days after e-beam radiation—25 and 50 kGy  

Physical properties were measured before and after e-beam sterilization at 25 and 50 kGy. No physical property degradation was noted for Tritan MX711 or the other resins tested. The polyesters and copolyesters in the study showed no statistical change in molecular weight, although Tenite propionate 360 did show a loss of molecular weight, as expected from an aliphatic polymer.


Read the complete details of these studies here