Plasticized poly(vinyl chloride) (PVC) used for biomedical disposable devices was studied in the nonsterilized state after different exposure times to soft x-ray irradiation in a commercial photoelectron spectrometer (Al Ka, 15 kV/300 W; Mg Ka, 12 kV/240 W) by XPS surface analysis. The detailed spectra of C 1s, Cl 2p and O 1s have been recorded and processed. Irradiation with soft x-rays induces a clear decrease of the total Cl 2p intensity, an increase of total C 1s intensity and a doubling of the O 1s intensity after 45 min of irradiation with Al Ka (300 W). Irradiation with Mg Ka (240 W) is slightly less damaging. These results can be interpreted with the classical PVC degradation model, e.g. bond cleavage with the formation of HCl gas, although the Cl 2p high-resolution spectra reveal the formation of an additional side-product, probably CaCl 2 . For further studies of plasticized PVC using XPS surface analysis it can be concluded that a complete analysis of a polymer sample should not take >10 min of x-ray exposure in order to avoid notable polymer degradation.

Two different types of plasticized poly(vinyl chloride) (PVC) used for biomedical disposable devices -extruded and injection moulded -were studied in the non-sterilized condition and after 25 and 50 kGy of beta irradiation. The polymer surfaces were analysed by scanning electron microscopy (SEM) equipped with an x-ray energy-dispersive spectroscopy (XEDS) and by atomic force microscopy (AFM). The inner surface of two parts of a venous line showed a different morphology according to their original formulation (for extrusion or injection moulding process) and reacted differently on sterilization with beta irradiation. Moulded parts were affected only slightly by the radiation step, whereas the variations were bigger for the extruded parts. In order to gain the best performances for the medical devices studied, the utmost care must be taken in the sterilization step, which should be optimized as well as the other steps of the manufacturing process.

Extruded parts of non-sterilized and b-irradiated (25 and 50 kGy) plasticized poly(vinyl chloride) (PVC) used for disposable medical devices have been studied to investigate the effect of sterilization on surface chemical composition. The polymer surfaces were analysed using angle-resolved x-ray photoelectron spectroscopy. The inner surface of the blood tubing lines showed a fairly smooth surface both before and after sterilization, so a laterally homogeneous surface can be assumed for XPS analysis. The XPS survey spectra exhibited no signals besides carbon, chlorine, oxygen and calcium. Detailed analysis of the regions showed the C 1s, Cl 2p and O 1s signals to be multi-component, presenting signals of the PVC, the plasticizer and the other additives. Binding energies remained constant irrespective of b-radiation dosage, but the amount of chlorine component at 198.4 ± 0.1 eV (associated with modified PVC) decreased with sterilization dosage. Angle-resolved XPS revealed that this component is located at the outermost surface of the polymer. It can be hypothesized that the production processes themselves (extrusion and/or injection molded) already induce modifications of the polymer surface and also lead to surface segregation of the plasticizer. During the subsequent thermal sterilization of the polymer dehydrochlorination continues but, because of the very short time required by the b-irradiation technology to sterilize devices, the atmospheric oxygen is unable to diffuse into the irradiated material, thus inhibiting further side-degradation of the materials, such as thermo-oxidative degradation.