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Although medical devices are sterilized in Argentina using ionizing radiation, electrons beams sterilization is of great interest. This is partly due to the lack of knowledge regarding their comparative effects on materials (primarily polymers). Thus, the objective of this work is to study the effect of both radiation sources: gamma rays (60Co) and electrons beams on the polymers acrylonitrile-butadiene-styrene (ABS) and polypropylene (PP) irradiated under different atmospheric conditions.
ABS and PP were irradiated at 60 kGy using a 10 MeV electron accelerator (Aerial CRT, France) and a 60Co source at the Semi Industrial Irradiation Plant (CNEA, Argentina). Polymer test specimens were cut according to the ASTM D 638 standard and packaged in polyethylene bags in the presence of air and vacuum. The polymers were characterized using differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and mechanical tests. Additionally, simulation of the dose uniform distribution (DUR) using PUFFIn software was studied. The utilized variables were: beam energy, width and height 10 MeV, 10 cm and 10 cm, respectively; number of particles 1e7; and irradiation distance to the source 100 cm.
The results obtained showed a 90 % reduction of the PP strain irradiated with gamma rays under atmospheric and vacuum conditions and a 70% reduction with electrons beams for both conditions. The elastic modulus of the gamma irradiated samples decreased by 9% and 4% and the electrons beam treated samples showed a decrease of 17 % and 18% when irradiated under air and vacuum conditions, respectively. The yield stress remained at 21 MPa for all conditions analyzed. The FTIR assay showed a change in the PP at the 1745 cm−1 wavenumber, associated with the appearance of C=O groups in aldehydes, ketones or carboxylic acids due to oxidation of the polymers after irradiation. There were no significant differences in the melting temperature of the polymer after irradiation.
In ABS irradiated under vacuum and atmospheric conditions, there were no significant changes in the elastic limit, yield stress and deformation. The FTIR technique did not show any notable change in the ABS chemical structure. The glass transition temperatures of the ABS were around 104ºC and 201ºC in all cases for the conditions analyzed.
The simulated DUR of the PP and ABS samples irradiated with electrons beams using PUFFIn was 1.13, more studies must be carried out on biomedical products and their packaging conditions.
In conclusion, in PP some modifications on the chemical and physical properties are observed at 60 kGy with both: gamma rays and electron beams. On the other hand, ABS seems to be a radio-resistant polymer that can be treated with both irradiation technologies without major modification at 60 kGy.
