In an effort to reduces barriers to the expansion of X-ray and E-beam facilities for irradiation sterilization, Team Nablo was formed in 2018. The team has conducted several studies on the comparison of polymer effects between gamma-ray, X-ray, and E-beam. The present study is dedicated to evaluate the dose rate effects on polymers. We believe that the dose rate cannot be considered individually, as dose remains the first-order effect. Moreover, the temperature elevation under irradiation, especially at high dose and dose rate, proves that dose rate and temperature are intrinsically linked. Thus, the goal of this study is to evaluate the influence of dose rate on the effects on polymers and to better understand the combination of treatment parameters (dose, dose rate and temperature) for radiation sterilization.

Irradiations were conducted at the Aerial Feerix® plant using 7 MV X-rays and 10 MeV electrons in 26 different irradiation conditions. A dedicated design of experiment was constructed with different dose levels (15 to 85 kGy), dose rates (0.003 to 12 kGy/s) temperatures (-5 to 60°C) relevant for the radiation sterilization industry.  LDPE, PP, POE and CIIR were provided by BD, and irradiations were conducted in air. The following post-irradiation analysis were conducted:  Colorimetry, FTIR, Tensile, DSC, Chemical extraction, SEC and NMR.

Interesting combinations of factors were observed, but the main influence on every modification remains the absorbed dose. The secondary and most impacting effect is the irradiation temperature, but thermal properties of each polymer must be considered (Tg, Tm). Dose rate generally exhibited only a small effect on conducted analysis. An on-going study will consider the influence of oxidative environments during irradiation.