電子線滅菌はイーストマンTritan™コポリエステルにどのような影響を与えますか?

医療機器の滅菌は、透明ポリマーの光学特性や物性に悪影響を及ぼす場合があります。
 
電子線(電子ビーム)放射は、医療機器の滅菌方法として、ガンマ線、酸化エチレン(EtO)、オートクレーブ、過酸化水素低温プラズマにならび、最もよく利用されている方法のひとつです。
 
イーストマンでは、電子線放射がイーストマンTritanコポリエステルやその他の透明医療ポリマーの光学特性や物性に与える影響を調べるための研究を行いました。
 
Formula Resin type
Eastman Tritan copolyester MX711 コポリエステル
Eastar polyester MN052 polyester
Eastar copolyester MN211 コポリエステル
Eastar copolyester MN006 コポリエステル
DuraStar polymer MN611 コポリエステル
Tenite propionate 360A40012 Cellulose acetate propionate (CAP)
Lipid resistant PC polycarbonate
TABS Transparent ABS
Medical grade acrylic Acrylic (PMMA)

The objective of sterilizing medical devices is to reduce the bioburden to a safe level with minimal effects on the desired properties of its constituent polymers.
 
Technology advances have improved the performance of e-beam radiation, making it a safe, efficient, and reliable source of energy for sterilization. High dose rates reduce the time of exposure, which can make e-beam a less costly alternative to gamma radiation.
 
To study the effect of e-beam radiation on Tritan MX711, Eastman measured color shifting and physical property retention after e-beam radiation.   

Optical properties
Samples were exposed to e-beam radiation (25 and 50 kGy), then stored in darkness and their color 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 1 shows the changes in b* value, which measures the blue to yellow scale after e-beam exposure at 50 kGy. Photos of the molded samples before and after exposure are available upon request.

Figure 1. Eastman Tritan copolyester and other transparent resins after e-beam exposure at 50 kGY—b* color measurements




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. 

For complete details of these studies or more information about the advantages of Eastman Tritan copolyesters, email Eastman today.