Effects of ionizing radiation on country made poly(vinyl chloride)

PVC is one of the most used polymers aas medical supplies that needs some sterilization before its use. The radiosterilization has been used as an alternative process for the conventional process with ETO, due to its carcinogenic and mutagenic nature besides the difficult to control the operational parameters. Wherever the polymers irradiation can promotes changes in the material properties due to the structural modifications that occurs by the main chain scission and/or crosslinking. Some experiments were done to determine the changes that takes place in the irradiated PVC using pure PVC (PVC-P) and compounded PVC (PVC-C) samples, that were irradiated with gamma rays from a 60 Co source with doses between 0-215 kGy and dose rate of 0,5-50 kGy/h. The irradiations took place in the presence of air and in the vacuum at room temperature. The irradiation effects were investigated by infrared spectroscopy, electron paramagnetic resonance, numerical average molecular weight (M-barn), glass transition temperature (Tg) and tensile strength (Ts). The experiments showed the PVC suffers radiolytic oxidation when irradiated in air forming peroxydic, ketonic and alcohol structures. These structures take place from the formation of paramagnetic species like peroxy and alkoxy radicals present in both PVC although the intensity of the effects had been most pronounced in the PVC-P. The decreasing of the M-barn and Tg of PVC-P showed that the main chain scission reactions are predominant however in the PVC-C the crosslinking reactions are predominantly although no changes were observed in the Tg or Ts in doses up to 100 kGy. These facts showed that the antioxidants and stabilizers used in the PVC-C are protecting the polymer against radiosterilization (∼ 25 kGy) sufficiently. It was observed that the PVC-P became yellow when the dose increased which could be seem at doses below 50 kGy. Moreover no experiments had been done to determine the optical properties of PVC. The PVC-C did not show any yellowness at the radiosterilization doses. (author)