Team Nablo, an international collaborative team, was formed in 2018 to reduce barriers to the expansion of X-rays and e-beams for radiation processing applications including product sterilization.  Several studies have been initiated on the comparison of irradiation technologies (gamma, X-ray, and e-beam) on over 30 polymers. [1]

The impact of radiation on polymers can generally refer to dose rate effects, but dose rate cannot be considered individually. Temperature increase, especially at high dose and high dose rate, proves that dose, dose rate and temperature are intrinsically linked. Moreover, dose rate effects can be due to oxygen exhaustion mechanisms which cannot occur in inert atmosphere. Thus, the goal of this study is to evaluate the combined effects on several polymers. Knowing that free radicals are the seeds of every modification occurring during irradiation of polymers, EPR spectroscopy was performed for the post-irradiation analyses to monitor radical nature and concentration. A focus will be given on the understanding of the combination of these effects on radical evolution.

Irradiations have been conducted on the Aerial feerix® plant at 7 MV X-rays and 10 MeV e-beam at 42 irradiation conditions. Single layer LDPE, PP, POE, CIIR, and PVC samples, as well as multi-layer films (S71 and S80), were provided by manufacturers. A design of experiment was constructed with dose (15 to 85 kGy), dose rates (0.003 kGy/s to 12 kGy/s), irradiation temperatures (-5°C to 60°C) and irradiation atmosphere (0 to 100% of oxygen). This approach was chosen to permit multi-factorial analysis.

Combinations of factors have been analyzed and are discussed. Dose rate alone generally exhibits only a limited effect on radical generation.

[1] Fifield et al, Rad. Phys. Chem, 180 (2021)