• Lindvold, Lars René
• Skowyra, Magdalena Maria
• Miller, Arne
• Ankjærgaard, Christina
• Skov, Anne Ladegaard
• Yu, Liyun

Abstract

Full-color development and stability of measured absorbance of thecommercially used Risø B3 radiochromic film dosimeter can be achieved byapplying a post-irradiation heat treatment procedure, typically at60 °C for 10 min. However, the choice of post-irradiation heatingduration and temperature has only been based on a trial and errormethod, and thus, the thermal stability of the material has not beenfully studied before. We show that B3 film undergoes a rapid thermaldecomposition of the PVB polymer base at 400 °C, with an initiation ofthe process at 70 °C. It means that higher irradiation temperatures,which can occur e.g. at high-dose electron beam irradiation, may causepolymer degradation. We also show that the post-irradiation heatingtemperature agrees with the polymer material's glass transitiontemperature as measured by differential scanning calorimetry (DSC). Thepost-irradiation heating procedure successfully removes the film'sthermal history. This can be seen as an endothermic peak in the firstheating cycle, which becomes smaller for higher irradiation doses. Glasstransition temperatures of irradiated and post-irradiation heated B3film are lower than those of the non-irradiated film, and decrease withincreasing the dose. That implies a probable chain scission ordegradation of the base polymer upon irradiation using high dose rateswith no irradiation temperature control.

Topics

• polymer
• glass
• glass
• glass transition temperature
• differential scanning calorimetry
• thermal decomposition